UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Cerebral blood flow in heart transplant recipients at rest and during incremental exercise Smirl, Jonathan David 2011

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
24-ubc_2011_fall_smirl_jonathan.pdf [ 2.09MB ]
Metadata
JSON: 24-1.0072554.json
JSON-LD: 24-1.0072554-ld.json
RDF/XML (Pretty): 24-1.0072554-rdf.xml
RDF/JSON: 24-1.0072554-rdf.json
Turtle: 24-1.0072554-turtle.txt
N-Triples: 24-1.0072554-rdf-ntriples.txt
Original Record: 24-1.0072554-source.json
Full Text
24-1.0072554-fulltext.txt
Citation
24-1.0072554.ris

Full Text

CEREBRAL BLOOD FLOW IN HEART TRANSPLANT RECIPIENTS AT REST AND DURING INCREMENTAL EXERCISE  by  JONATHAN DAVID SMIRL  B.Sc., The University of Victoria, 2004  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF SCIENCE  in  College of Graduate Studies  (Interdisciplinary Studies)  [Health and Exercise Sciences]  THE UNIVERSITY OF BRITISH COLUMBIA (Okanagan)  September 2011  © Jonathan David Smirl, 2011 i  Abstract  Pathological impairments to cardiac output may impact cerebral blood flow (CBF). Prior studies on heart transplant recipients (HTR) have reported increases of 25-53% in CBF, 1-6 months following transplant. It is currently unknown if CBF is chronically altered in the years following transplant or during progressive exercise stress, when compared with agedmatched controls (AM). Donor population controls (DC) were included to determine if the responses observed in HTR are related to the age of the donor rather than the individual. The aim of this thesis was to examine the influence of long-term heart transplantation on the regulation of CBF velocity (CBFv) at rest and during incremental exercise. Two hypotheses were tested: 1) CBFv would be similar in HTR when compared to AM, but lower than DC; 2) that during incremental exercise, the HTR would have reduced elevations in CBFv compared with AM and DC. To address these hypotheses, HTR were tested who have a reported inability to acutely increase cardiac output during exercise. Seven male clinically stable HTR (62 ± 9 yrs of age, 9 ± 7 yrs post-transplant), seven male AM (62 ± 7 yrs), and seven male DC (22 ± 3 yrs) were recruited for this study. Bilateral middle cerebral arteries were insonated using transcranial Doppler ultrasound to obtain an index of CBFv. Data were obtained while seated and during an incremental cycling test to volitional exhaustion. A repeated measures ANOVA was applied to identify differences across exercise intensity. Comparisons between groups were performed with Fisher‟s LSD post hoc test. The main findings were: 1) Rest: CBFv was comparable between HTR and AM (40 vs. 41 cm/s), as expected, CBFv was 68% higher in the DC compared with the HTR and AM  ii  groups (P<0.05).  2) Incremental exercise: mean CBFv was not significantly different  between the HTR and AM groups across any of the exercise intensities. In conclusion, the CBFv of long-term HTR are comparable to AM both at rest and during incremental exercise that despite a suppressed VO2 Peak (and likely Q) CBFv is well maintained during incremental exercise in long – term HTR.  iii  Preface  This study was approved by the University of British Columbia Clinical Research Ethics Board (H11-02576 – CBF in HTR) and the University of Alberta Clinical Research Ethics Board. (Pro00011560). Chapters three, four and five are based on data collected in the Mazankowski Alberta Heart Institute at the University of Alberta by Dr. Philip Ainslie, Dr. Mark Haykowsky, Dr. Luis Altamirino-Diaz, Dr. Helen Jones, Kit Marsden, Mike Nelson and Jonathan Smirl. The data were analyzed in the cardiovascular physiology laboratory at the University of British Columbia by Jonathan Smirl. Dr. Ainslie and Dr. Haykowsky were responsible for the overall design and concept of the study, technical assistance, data collection, equipment acquisition, subject recruitment, and funding for the study.  Dr. Altamirino-Diaz was  responsible for the collection and analysis of the echocardiograph images. Dr. Jones, Kit Marsden and Mike Nelson assisted in the collection of the data.  Jonathan Smirl was  responsible for assisting in the overall study design and study concept. Jonathan coordinated the data collection involved in this study, and analyzed all of the data, including statistical analyses and writing. There has been a version of chapters three, four and five accepted for an oral presentation at Physiological 2011 (annual scientific meeting of the Physiological Society). Jonathan D. Smirl, Mark J. Haykowsky, Katelyn R. Marsden, Helen Jones, Michael D. Nelson, Luis A. Altamirano-Diaz, and Philip N. Ainslie. (2011) Cerebral blood flow in heart transplant recipients: rest and during exercise. Jonathan Smirl was responsible for the data collection, data analysis, writing, and formatting of the abstract.  iv  Table of Contents  Abstract…….. ........................................................................................................................... ii Preface…………… .................................................................................................................. iv Table of Contents ..................................................................................................................... v List of Tables .......................................................................................................................... vii List of Figures ........................................................................................................................ viii List of Abbreviations ............................................................................................................... ix Acknowledgements .................................................................................................................. xi Dedication ............................................................................................................................... xii Chapter One: Introduction and Review of the Literature ...................................................... 1 1.1. Brief Background on Heart Transplantation .........................................................1 1.2. Regulation of CBF ...............................................................................................3 1.2.1. Neurogenic Control of CBF............................................................................4 1.2.2. Influences of Cardiac Function on CBF ..........................................................6 1.2.3. Autoregulatory Control of CBF ......................................................................9 1.2.4. Regulation of CBF by PaCO2 ....................................................................... 10 1.2.5. Effects of Cerebral Metabolism on CBF at Rest and During Exercise ........... 11 1.3. Cognitive Impairment in CHF ............................................................................ 12 1.4. Influences of Cardiac Disease on CBF ............................................................... 13 1.4.1. Congestive Heart Failure .............................................................................. 13 1.4.2. Ischemic Heart Disease ................................................................................ 14 1.5. Changes in CBF in HTR .................................................................................... 15 Chapter Two: Purpose, Aims and Hypotheses .......................................................................22 2.1. 2.2. 2.3.  Purpose of Thesis ............................................................................................... 22 Aims .................................................................................................................. 22 Hypotheses ........................................................................................................ 23  Chapter Three: Methods.........................................................................................................24 3.1. Participants ........................................................................................................ 24 3.2. Instrumentation .................................................................................................. 27 3.3. Transcranial Doppler Ultrasound........................................................................ 29 3.3.1. Validity of TCD ........................................................................................... 31 3.3.2. Principle of TCD .......................................................................................... 31 3.3.3. Technique of TCD........................................................................................ 32 3.4. Incremental Cycling Exercise Protocol ............................................................... 33 3.5. Statistical Data Analysis..................................................................................... 34  v  Chapter Four: Results .............................................................................................................35 4.1. 4.2. 4.3. 4.4. 4.5. 4.6.  Participant Characteristics .................................................................................. 35 Incremental Exercise Test .................................................................................. 35 Rest.................................................................................................................... 38 VO2peak ............................................................................................................... 40 HRreserve Relationships ........................................................................................ 43 Mild, Moderate and Intense Exercise ................................................................. 45  Chapter Five: Discussion and Conclusion ..............................................................................49 5.1. Principle Findings .............................................................................................. 49 5.2. Influence of HT on CBF at Rest - Comparison with Previous Studies................. 49 5.3. Young Heart, Old Brain: Influence of Aging on CBF ......................................... 50 5.4. Influence of HTR on CBF Alterations During Exercise ...................................... 51 5.5. Influence of Aging on End-Tidal PCO2 .............................................................. 52 5.6. Differential Changes in Systolic MCA Velocity and Pulsatility Index ................ 53 5.7. Limitations ........................................................................................................ 55 5.7.1. TCD Ultrasound ........................................................................................... 55 5.7.2. Activity Matching ........................................................................................ 56 5.8. Implications ....................................................................................................... 56 5.8.1. MCAv at Rest .............................................................................................. 56 5.8.2. MCAv During Incremental Exercise............................................................. 56 5.8.3. MCAv in HTR With and Without Subject #02 ............................................. 57 5.9. Future Studies .................................................................................................... 57 5.9.1. Effects of Long-Term Endurance Training on CBF in HTR .......................... 57 5.9.2. Longitudinal Study of CBF in HTR .............................................................. 58 5.9.3. Effects of Incremental Exercise on CBF in End-Stage Heart Failure Patients 58 5.10. Conclusion ......................................................................................................... 58 Bibliography ............................................................................................................................59 Appendices ...............................................................................................................................83 Appendix I: Participant Information Sheet ....................................................................... 83 Appendix II: Participant Consent Form............................................................................ 86 Appendix III: Literature Review of Cardiac Output on Cerebral Blood Flow ................... 87 Appendix IV: Raw Data – Output from LabChart .......................................................... 102  vi  List of Tables  Table 3.1. Participant Characteristics (all subjects) ....................................................................25 Table 3.2. Participant Characteristics (subject #02 excluded) .....................................................26 Table 4.1. Cardiovascular, Pulmonary and Cerebrovascular responses at rest and during the incremental exercise test at 50%, 70%, 90% and Peak VO2 Consumption (all subjects) ..............................................................................................................36 Table 4.2. Cardiovascular, Pulmonary and Cerebrovascular responses at rest and during the incremental exercise test at 50%, 70%, 90% and Peak VO2 Consumption (subject #02 excluded) ...............................................................................................37  vii  List of Figures  Figure 1.1. Factors and pathways that regulate CBF control........................................................ 5 Figure 1.2. The de-innervated donor heart is being sutured in the recipient during cardiac transplantation surgery. ............................................................................................ 7 Figure 1.3. Summary of the percent change in pre- and post-transplant CBF observed in studies of HTR. .......................................................................................................17 Figure 1.4. Summary of pre- and post-transplant and control/normal CBF values in the studies with HTR.. ..................................................................................................18 Figure 3.1. Instrumentation on subject during the incremental exercise protocol. .......................28 Figure 3.2. Image of (A) the TCD probe in place with the headband, (B) a frontal view of the MCA insoniation, (C) MCA velocity waveform and envelope .............30 Figure 4.1. Resting values for (A) MCAv, (B) HR and (C) BP for HTR, AM and DC. ..............39 Figure 4.2. Relative VO2peak values for HTR, AM and DC. ........................................................41 Figure 4.3. (A) HRpeak and (B) HRreserve for HTR, AM and DC. .................................................42 Figure 4.4. (A) Overall relationship between HRreserve and age for all subjects, (B) the relationship between HRreserve and years post transplant. ..........................................44 Figure 4.5. (A) MCAv, (B) Mean BP, (C) PET CO2, and (D) CVR for HTR, AM and DC throughout the incremental exercise test. ...........................................................47 Figure 4.6. (A) Systolic MCAv, (B) Diastolic MCAv, and (C) PI for HTR, AM and DC throughout the incremental exercise test. ...........................................................48  viii  List of Abbreviations  ACA  -  Anterior Cerebral Artery  ACE  -  Angiotension-Converting Enzyme  AM  -  Age-Matched Control  BP  -  Blood Pressure  BPM  -  Beats Per Minute  BMI  -  Body Mass Index  CA  -  Cerebral Autoregulation  CBF  -  Cerebral Blood Flow  CHF  -  Congestive Heart Failure  CO2  -  Carbon Dioxide  CPP  -  Cerebral Perfusion Pressure  CVP  -  Central Venous Pressure  CVR  -  Cerebrovascular Resistance  DC  -  Donor Population Control  ECG  -  Electrocardiogram  PET CO2 -  Partial Pressure of End Tidal Carbon Dioxide  HF  -  Heart Failure  HR  -  Heart Rate  HRpeak  -  Heart Rate Peak  HRreserve -  Heart Rate Reserve  HT  -  Heart Transplant  HTR  -  Heart Transplant Recipient  ix  ICP  -  Intra-cranial Perfusion Pressure  IHD  -  Ischaemic Heart Disease  LVEF  -  Left Ventricular Ejection Fraction  MABP  -  Mean Arterial Blood Pressure  MCA  -  Middle Cerebral Artery  MCAv  -  Middle Cerebral Artery Velocity  O2  -  Oxygen  PCA  -  Posterior Cerebral Artery  PaCO2  -  Partial Pressure of Arterial Carbon Dioxide  PI  -  Pulsitility Index  PNS  -  Parasympathetic Nervous System  Q  -  Cardiac Output  SNS  -  Sympathetic Nervous System  SV  -  Stroke Volume  TOR  -  Target of Rapamycin  VO2peak  -  Peak Oxygen Consumption  x  Acknowledgements  I would like to thank Dr. Philip Ainslie for his support, vast knowledge and guidance during my M.Sc. Throughout the process he has taught me more than just many valuable research skills and techniques but, also social and interpersonal skills that extend far beyond the research lab. A large thank you also goes to Dr. Mark Haykowsky from the University of Alberta and all of the subjects who participated in this study. I would especially like to acknowledge the tremendous performances of the heart transplant recipients. Without their efforts, this study would have never been able to occur. Dr. Shieak Tzeng from the University of Otago, the time that you spent advising on the data analysis was much appreciated. Kurt Smith and Chris Willie, thank you for the informal discussions throughout the writing process. Thanks to my committee members Dr. Neil Eves, Dr. Gord Binsted and Dr. Gareth Jones. I appreciated your contributions and feedback. The efforts of Kit Marsden and Dr. Helen Jones were much appreciated during the data collection. I would also like to thank my peers on the many informal physiological discussions that take place around the Human Kinetics lab at UBCO. These talks have helped shape my ideas and philosophy on what it takes to be a researcher. Last but not least, I would like to thank all of my friends and family for their support and encouragement.  xi  Dedication “The only place where success comes before work is in the dictionary.” ~Vince Lombardi  xii  Chapter One: Introduction and Review of the Literature  The heart transplant recipient (HTR) population represents a unique opportunity to observe the effects of cardiac output (Q) on cerebral blood flow (CBF) because the cerebrovasculature and cardiovasculature systems differ in chronological age. The cerebrovasculature is left intact and is therefore the same age as the HTR, where as the donor heart will typically be younger. This unique population provides an opportunity to examine some of the conflicting results in the Q and CBF literature (refer to section 1.2.2.) Namely, studying this population should enable the determination as to which is the key component of CBF: is it the age of the brain and its cerebrovasculature or is it the age of the heart and its cardiovasculature? The following literature review describes a brief background on heart transplantation (HT) along with the factors associated with the regulation of CBF. The influences of cardiac function, aging and cardiac disease on CBF as it relates to the healthy human, congestive heart failure (CHF) and HTR populations are also considered. Thereafter, there is also a brief summary of the sparse literature that has directly assessed CBF in HTR.  1.1.  Brief Background on Heart Transplantation  The first successful heart transplant was performed by Christiaan Barnard in 1967. The initial survival outcome was not very promising; the recipient, Louis Washkansky, survived for just 18 days1. However, the 2 nd heart transplant recipient (HTR) had a much better outcome and survived for 19 months1. With improved surgical techniques and better medications, survival rates have continued to improve. During the 1980s the median survival  1  was up to 8.3 years; by the 2000s it had increased to approximately 10.5 years 2. With improved survival rates, heart transplantation has moved beyond being an experimental medical procedure and is now an accepted therapy for extending end-stage heart failure patients‟ lives3. Coinciding with the improved survival rates of HTR, there is an increased desire by the patients to return to a functional lifestyle and experience a good quality of life. However, pre-operatively many of the HTR have CHF and, because of this, undergo extended pre-transplant hospitalization. During this time of bed-rest, their cardiovascular parameters - such as peak oxygen consumption (VO2  - decrease approximately 26%3,  peak)  typically ranging from 10 to 14 mL/kg/min4, 5. Yet, after HT, ventricular systolic function is improved to normal levels  6,7  as a result of the donor heart. Furthermore, through regular  endurance training, peak heart rate (HRpeak) and VO2 peak can improve to 95% of age-matched norms3. As extreme examples; there has been a case of a HTR who completed Ironman™ Canada8; and a group of 14 HTR successfully competing in a 4-day 600km running relay from Paris to La Plagne9. Despite this potential for improvement, many HTR experience VO2  peak  values approximately 50-70% of their predicted age-matched counterparts3,  Possible reasons for the reduced VO2 vascular function17, therapy3,  18  peak  .  include; depression11-14, fatigue12, 14-16, abnormal  , diastolic dysfunction19,  21, 22  10  , cardiac allograft de-innervation5,  20  , post-transplant immunosuppressive  7, 10, 23  , skeletal muscle dysfunction24  associated with the pre-transplant/post-transplant de-conditioning 3, 21, and physical pain12-14. The increased longevity after successful heart transplantation2 has led to a change in the long-term outcomes of HTR.  For example, neurological complications eventually  develop in approximately 60-80% of all HTR14, 25, 26. Tung et al.12, have reported that this may be due to side effects from the life-long post-operative use of anti-rejection  2  immunosuppressant therapies. Over the course the post-transplant survival period, there is approximately a 14-18% occurrence rate of a cerebrovascular event, such as cerebral haemorrhage or ischaemic stroke occuring14,  26, 27  . Zierer et al.28, have suggested another  possible reason for the cerebrovascular events that are experienced in the HTR populations that the cerebrovasculature in HTR may have a limited range of tolerance for changes in systemic blood pressure (BP). This risk of a cerebrovascular events may be due to cerebral vessel remodeling in the face of chronic cerebral hypoperfusion that has been associated with heart failure (HF)25, 26, 28, 29. However, with the possible increase in CBF associated with cardiac transplantation30-32 (refer to section 1.5.) there is a trade-off; an increased risk of hyper-perfusion related complications occurring over the short-term post-transplant28, 30. In addition over the long-term, there is an increased likelihood that an ischaemic stroke will occur as a complication of cardiac transplantation25-27. The end result for HTR is that they ultimately require extremely sensitive hemodynamic management and it is suggested they should be cautious of both hypo- and hyper-tensive episodes28. This avoidance is troublesome, since changes in BP occur in a myriad of everyday activities; postural change, coughing, laughing, defecation, exercise, and sexual activity, etc...  1.2.  Regulation of CBF  The human brain has a mass of approximately 1400g which equates to ~2% of the total mass of an average 70kg male33. At rest, normal cerebral oxygen (O2) consumption is 3.5mL/100g brain tissue per minute34 equating to ~49mL O2 per min, or approximately 20% of the ~250mL O2 per min the body consumes at rest. Thus, the brain has placed itself very prominently in the hierarchical positioning of organ demands35. With particular emphasis on  3  the integrative perspective, the following section provides an overview of the factors that regulate of CBF in humans.  1.2.1. Neurogenic Control of CBF  Neurogenic control refers to the influence on CBF of the sympathetic nervous system (SNS) [Figure 1.1. (1)] and parasympathetic nervous system (PNS) [Figure 1.1. (2)]. The cerebral vasculature is extensively innervated by sensory and autonomic neurons 36-38. Sensory neurons have been implicated in the transmission of afferent activity produced by the nociceptors to the central nervous system; however, their role in cerebral vasomotor control is unclear39. Autonomic neurons from the SNS and PNS nervous systems innervate the cerebral vasculature. The SNS innervations arise from the superior cervical ganglia 40; PNS innervations arise from the sphenopalatine and otic nerves41. The functional role for SNS and PNS control of the cerebral vasculature is controversial42-47. The SNS contribution to CBF regulation is dependant on the rate of change in arterial blood pressure42, a response that has an important role in dynamic cerebral autoregulation (CA)48, 49. As BP can surge during REM sleep, it has been suggested that elevations in SNS activity may act in a shielding/protective role and prevent cerebral hyperperfusion during the periods of increased BP50-52. Although SNS control of CBF is not fully understood, it appears it may have a functional role during extreme hypo and hypertension. The role of the PNS in CBF regulation is also still largely unknown, especially in humans.  However, a recent study; has implied that the PNS may have a role in  4  cerebrovascular system regulation during exercise 53, a finding that was further discussed in a companion editorial41.  Figure 1.1.  Factors and pathways that regulate CBF control. Control of cerebrovascular tone through neurogenic means is controversial, however sympathetic (1) and parasympathetic (2) inputs have been implicated. The quotient of cardiac output (Q; 3) and total peripheral resistance (TPR; 4) of the circulatory system is mean arterial blood pressure (MABP; 5). The peripheral vasculature has an impact on CBF regulation by way of MABP. Cerebral perfusion pressure (CPP; 6) is the pressure gradient difference between MABP and intra-cranial pressure (ICP) under conditions where the central venous pressure (CVP), as measured at the jugular vein (7), is lower than ICP and is the driving force behind cerebral perfusion. Cerebral autoregulation is under the influence of modulating factors such as CO2 and brain metabolism (8). (adapted from47).  5  1.2.2. Influences of Cardiac Function on CBF  The primary function of the heart is to adequately perfuse the organs of the body with blood. The heart provides this function by contracting its muscular walls, increasing the pressure in the closed chamber (i.e. ventricle), when the internal pressure is greater than that of the attached artery (pulmonary or aorta), the blood is expelled through the valve and into the circulatory system. The intrinsic rate of the sino-atrial node of the heart is approximately 100 beats per minute (bpm). In healthy humans the sino-atrial node is also extrinsically regulated by the PNS and SNS54. Increased parasympathetic tone slows the heart rate (HR) below the basal rate whereas enhanced sympathetic tone increases HR towards peak levels with the secondary assistance of catecholamines54. Heart transplant recipients represent a unique population to study the effects of cardiac function because, during the transplantation process, the nerve fibres to the heart are transected, resulting axonal degeneration and complete denervation of the heart (Figure 1.2) 55, 56. Surgical denervation results in the heart having increased sensitivity to the neurotransmitters that were lost, resulting in the transplanted heart being highly sensitive to norepinephrine and epinephrine55. The end result is that the transplanted heart is, at least initially, completely denervated and dependent upon hormones (e.g. catecholamines) to control increases in HR.  This hormone dependence  following transplant results in a delayed and blunted HR response and creates a greater reliance upon the pre-load to increase stroke volume (SV) and thus Q, especially during exercise7, 10, 57. However, over time, re-growth of transected nerves can take place and result in some re-innervation of the heart 56. More rapid and complete re-innervation of the heart can occur if the allograft heart comes from a younger donor and if the transplantation procedure is fast and uncomplicated56.  6  Figure 1.2.  The de-innervated donor heart (red) is being sutured in the recipient (blue) during cardiac transplantation surgery. The major blood vessels of the pulmonary and systemic circuits are labeled for identification and orientation.  7  Cardiac output [Figure 1.1. (3)] is the total volume of blood expelled per minute and is determined by the quotient of HR and SV5, 58. At rest in the healthy human population, SV is approximately 70-80 mL and is influenced by 3 main factors: diastolic stretch, contractility and BP58. Diastolic stretch and contractility are influenced by the total peripheral resistance (TPR) [Figure 1.1. (4)] which is the sum of the vascular resistance across the entire circulatory system and as such has an impact on SV by way of the diastolic stretch 58. Alterations in BP influence venous return and thus will also have an affect on SV58, for example: an increase in TPR will lead to an increase in diastolic stretch. The relationship between Q and CBF is unclear in the current literature (Table 1.1. – Appendix IV). From the 31 studies reviewed in Table 1.1., 9 studies showed no Q-CBF relationship, 9 studies showed a Q-CBF relationship and 5 studies showed conflicting results. The Q-CBF relationship occurs under certain conditions [e.g., changes in body temperature, blood volume or alterations in BP and venous return due to increases in lower body negative pressure or medications] while other conditions do not show a relationship at all. A possible reason for some of this confusion in the literature on the Q-CBF relationship is the counterintuitive nature of this concept. For example, neither of the mechanisms that mediate Q [SV or heart rate] are represented in Poiseuille‟s law. Poiseuille‟s law is a major concept in the determination of CBF and is represented in the following equation:  F = (P1-P2)πr4/8μL  Equation 1.  Where: F=flow, P1=inflow pressure, P2=outflow pressure, r=radius, μ= viscosity of the fluid, L=length  8  The inflow pressure is BP; out flow pressure is the pressure in the internal jugular vein [Figure 1.1. (7)]. The length of the cerebral vasculature is not a physiological variable that changes or can be altered as it is consistent within each individual87. So if those are not responsible for the observed changes in Q and CBF, what does and is there a population we could observe that may better assist us in understanding this relationship?  1.2.3. Autoregulatory Control of CBF  A critical intrinsic response of the mammalian brain is known as cerebral autoregulation (CA) – the process by which adjustments are made to the cerebrovascular resistance to ensure that the CBF levels are matched to metabolic needs 88. There are two main components to CA: static and dynamic. Static CA describes the tendency of CBF to be chronically maintained over a wide range of BP changes89 [Figure 1.1. (5)]; and dynamic CA describes the ability of the cerebral vasculature to resist acute changes in perfusion pressure, due to changes in BP over a short time-course of less than five seconds48. If CA fails, the brain is put at risk of ischaemic damage (during low blood pressures) and of haemorrhage (during high blood pressure). Impairment of CA has been associated to the risk of stroke90. The classic description by Lassen91, and further re-emphasized in a review by Paulson et al.92, was that CBF has an autoregulatory range that is maintained over a wide range of BP (50-150 mmHg); however, this has been challenged by recent evidence that CBF is also dependant upon alterations to BP89. Lucus et al. 89 have reported that MCAv changes ~8% per 10 mmHg shift in BP across both hypo- and hypertension, suggesting that arterial baroreflex regulation of BP [Figure 1.1. (4)] may have a greater role in CBF control than traditionally thought.  Moreover, an inverse relationship between cardiac baroreflex  9  sensitivity and dynamic CA, suggests the presence of compensatory interactions between peripheral blood pressure and central CBF control mechanisms, that optimize CBF control has been reported93. Such interactions may account for the divergent changes in CA and baroreflex sensitivity seen with normal aging, and in clinical conditions such as spontaneous hypertension94, autonomic failure95, and chronic hypotension96. alterations in heart rate variability97,  98  Because of related  and baroreceptor sensitivity99 following heart  transplantation, unstable control of blood pressure may ensue. Thus, dynamic CA may be a particularly important mechanism to protect the brain from alterations in BP. However, to date no studies have assessed CBF or dynamic CA over the longer term (i.e. years) in HTR.  1.2.4. Regulation of CBF by PaCO2 The downstream cerebral arterioles [Figure 1.1. (8)] are highly sensitive to changes in the partial pressure of arterial CO2 (PaCO2)100. Respiratory-induced changes in PaCO2 are tightly coupled with CBF and therefore play an important role in the regulation of CBF 101, 102. Cerebrovascular reactivity is the CBF response to changes in PaCO 2 and is of vital homeostatic importance as it helps regulate, influence and maintain central pH  33, 101, 103, 104  .  When there is an elevation in PaCO2 (hypercapnia) there is a corresponding increase in the CBF as a result of the vasodilation of the cerebral arteriole bed [Figure 1.1. (8)]33. Conversely, when there is a reduction in PaCO2 (hypocapnia), vasoconstriction of the cerebral arteriole bed occurs and there is a subsequent reduction in the CBF 33. However, there are differences in the amplitude of CBF response to hyper- and hypocapnic events100, with hypercapnic events demonstrating a larger response over a wider array of CO 2  10  challenges105.  This is possibly due to a large release of nitric oxide in the brain that  coincides with hypercapnia, where as this response is not present in hypocapnia 106. Studies have shown that there is a link between cerebrovascular endothelial dysfunction and impairment in the reactivity of cerebral vascualture 107-109 as well as cognitive decline109-111. These findings suggest that alterations in the peripheral vasculature, may also affect cerebrovascular function, including cognitive outcomes.  Congestive heart failure  (CHF), which is one of the primary precursors to heart transplantation, is characterized by decreasing cardiac function112,  113  .  This reduction in cardiac function along with  cerebrovascular endothelium dysfunction and impaired reactivity may relate to the observed cognitive declines associated with this population114, 115.  1.2.5. Effects of Cerebral Metabolism on CBF at Rest and During Exercise  Oxygen delivery to the brain is reliant upon the arterial O 2 content and CBF. Resting cerebral O2 consumption is maintained throughout a variety of PaCO2 alterations, as typically experienced during cerebrovascular reactivity challenges116-118, via increases in O2 extraction33. It has been well- reported that CBF is elevated by 10-20% during sub-maximal exercise (reviewed in: 100, 119). These increases in CBF are likely driven via the increased O2 requirements of the brain100,  120  . After the aerobic threshold (60-70% of VO2Peak), CBF  returns toward baseline (and possibly lower) values due to hyperventilation-induced hypocapnia, regardless of increasing O2 demands within the brain120, 121. Exercise-induced hyperventilation (and related hypocapnia) therefore appears to be a stronger regulator of CBF than cerebral metabolism at exercise intensities above aerobic threshold (~70% VO 2max)122.  11  1.3.  Cognitive Impairment in CHF  Clinical populations with severe cardiovascular disease and end-stage heart failure have also been shown to have impaired cognitive function30, 31, 114, 123-128. Approximately 2550% of CHF patients experience cognitive impairment, which is associated with a 5-fold increase in mortality among older adult hospitalized patients114, 129. Structural and functional brain changes, including discrete losses in gray matter, brain volume, areas of silent stroke, and decreased CBF31,  130-133  , have also been observed in CHF patients.  End-stage HF  patients who have undergone heart transplantation have shown significant rapid improvements in cognitive functioning soon after transplants that were stable within 3 months127,  134, 135  . These studies indicate that a higher stroke volume, higher cardiac and  lower right atrial pressure are all correlated with better cognitive function135. Gruhn et al.31, argued that the neurological impairment in the CHF patients was due cerebral hypoperfusion associated with a CBF 30% below normal resting values 31. These conclusions are hindered, as there were no neuropsychological testing pre- or posttransplant31. The 30% reductions in CBF are above the aggregate experimental and human study data, which showed that non-human primates have a 22 mL/100g per min (40% below normal resting values) threshold before neuronal function is impaired 136.  In humans,  electroencephalography activity decreases if mean CBF falls below 23 mL/100g per min (54% below normal resting values) during carotid clamping137. Ackerman noted clinical cognitive dysfunction is not necessarily related to a CBF threshold. Rather, these studies support the notion that the brain may be more tolerant to hypoperfusion than early investigators had implied138.  However, a review paper by Roman139 concluded that  circulatory conditions, such as cerebral hypoperfusion due to CHF, result in localized brain  12  injuries that lead to undiagnosed forms of cognitive decline in older adults. Thus, further research with prospective studies and experimental models are still needed to determine the pathogenesis of cognitive dysfunction in end-stage HF patients and HTR.  1.4.  Influences of Cardiac Disease on CBF  According to the 2008 cardiac transplant update from the Canadian Cardiovascular Society Consensus Conference140: Cardiac transplantation is the treatment of choice for patients who have severe end-stage heart failure despite maximal medical therapy and/or complex congenital heart disease not amenable to surgical palliation at reasonable risk. In the 27th official adult heart transplant report by the Registry of the International Society for Heart and Lung Transplantation2, CHF represents 51.4% of all pre-transplant diagnosis, Ischaemic heart disease (IHD) 39.9%, re-transplant 2.4% and other causes making up the remaining diagnosis2.  1.4.1. Congestive Heart Failure  The major reductions in deaths from cardiovascular diseases (hypertension, coronary diseases and damage to the cardiac valves) have led to more and more people living with HF112, 113. There are an estimated 5.7 million people living with HF and almost 300 000 annual deaths from HF complications in the United States of America alone 113. End-stage HF occurs after the myocardium has exhausted all of its reserve capacity and compensatory  13  mechanisms, leaving the possibility for salvage limited leading to terminal CHF112. The greatest survival outcome for end-stage HF patients is a cardiac transplant. However, the supply of donor hearts is limited, with only 3000-5000 heart transplants take place worldwide each year 2, 113. Reduced CBF has been reported in older adult males with CHF32, 141-144. However, there are conflicting opinions in the literature on the root cause of the reduced CBF. Loncar et al.141 reported that older adult males with mild to moderate CHF have reduced CBF values independently associated with reduced left ventricular ejection fraction (LVEF). Conversely, Choi et al.32 have shown that in cases of severe HF there is no correlation between LVEF and CBF. This discrepancy could be due to experimental differences in the assessment of CBF and related complications associated with the functional classification of CHF, such as neurohormonal activation, having an influence on CBF141. Regardless of the cause of the reduced CBF, both groups acknowledge a myriad of negative outcomes associated with reduction in CBF. For instance, the authors speculated that the reduced CBF may result in structural changes occurring within the brain32, 141, 144; this effect could manifest in negative outcomes such as impaired cognitive function (as previously described), and autonomic nervous system dysfunction141. Whilst speculative, these outcomes might be the reason for the increased risk of CHF patients also developing cognitive disorders such as Alzheimer disease or dementia141.  1.4.2. Ischemic Heart Disease  Ischemic heart disease (IHD) is one of the major causes of death in the western world and will result in over 150 000 deaths in the United Kingdom in the next year 145, 146. IHD  14  involves a complex interaction between haematological, biochemical, immunological and physiological factors145, 146. All of these combine to elevate certain clotting factors, such as fibrinogen, which result in paralyzing the heart due to the blocking blood flow to one or more of the major coronary arteries eventually resulting in coronary artery thrombosis and resultant myocardial ischemia146, 147. Over time, the blockages build-up and lead to cellular death of the localized myocardial tissue resulting in a reduced ejection fraction and possible rupture of the myocardial wall147. The two most effective and viable long-term treatments for end-stage IHD are cardiac surgery and heart transplantation146, 147. Reduced CBF has been observed in approximately 75% of IHD patients148, 149, which may possibly explain why one of the major complications of cardiac surgery is ischemic stroke148,  149  . With the increased risk of ischemic stroke associated with cardiac surgery,  Kawabori et al.148, have recommended that IHD patients should be preoperatively screened for MCA and internal carotid artery occlusion.  1.5.  Changes in CBF in HTR  Heart transplantation is a life saving surgical intervention for select individuals with end-stage HF. Despite normal resting left ventricular systolic function after surgery, HTR have reduced Q during exercise6, impairment in Q reserve  6, 10  10  .  The mechanism responsible for post-transplant  is attributed to surgical denervation of the transplanted heart 10,  diastolic dysfunction10, and peripheral vascular dysfunction10. A consequence of a blunted Q reserve is that it may result in decreased CBF (refer to section 1.2.2.). Currently, there have been only three studies that have examined CBF at rest in HTR30-32. Moreover, to date, no studies have reported how CBF might be altered during exercise. The following section will  15  provide an overview of the salient methodological and experimental findings from these three studies. It was reported150 that CBF might be reduced in patients with CHF, resulting in cognitive impairments, memory problems, confusion, lethargy and dizziness. Many of these conditions were improved after heart transplantation127.  On this basis, Gruhn et al.  31  reasoned that CBF alterations may be occurring in patients with CHF who undergo heart transplantation. In their study, CHF patients had reported CBF baseline values of 35 ± 3 mL/min per 100g rising to 50 ± 3 mL/min per 100g using Xenon gas inhalation (Figure 1.3.) one month after undergoing successful heart transplantation (P<0.05), and the after transplantation the HTR were not significantly different from the control values 52 ± 5 mL/min per 100g (Figure 1.4.). Thus, leading to the conclusion that CBF rapidly normalizes after heart transplantation. A small subset of the HTR were re-examined at 6 months post transplant and it was reported that the CBF and MCAv values did not differ from those at one month31.  16  Massaro et al. Choi et al. Gruhn et al.  100 80  Change (%)  60 40 *  20  *  * 0 -20 -40 Pre  Post  Pre- and Post- Transplant CBF  Figure 1.3.  Summary of the percent change in pre- and post-transplant cerebral blood flow (CBF) observed in studies of heart transplant recipients (HTR). All three HTR studies30-32 reported statistically significant CBF increases posttransplant of between 25 and 53% (*denotes, P < 0.05).  17  Cerebral Blood Flow (mL/min/100g or cm/s)  100  Pre-Transplant Post-Transplant Control-Normal  * *  80 * 60  *  *  *  40  20  0 Gruhn et al.  Massaro et al.  Choi et al.  HTR Study  Figure 1.4.  Summary of pre- and post-transplant and control/normal cerebral blood flow (CBF) values in the studies with heart transplant recipients (HTR). CBF values were reported as mL/min/100g brain mass (Xenon inhalation) by Gruhn et al.31 and Choi et al.32, and as cm/s (transcranial Doppler) by Massaro et al.30. Gruhn et al.31, and Choi et al.32, reported age-matched (AM) control values, Massaro et al.30, did not provide this information, instead AM normal values were obtained from Ainslie et al. 151. All studies reported statistically significant differences pre- and post-transplant as well as between HTR and AM comparison groups. No statistically significant differences were reported between post-transplant and AM comparison groups. (*denotes, P < 0.05)  18  One difference noted was the end-stage HF patients had significantly (P<0.05) lower end tidal carbon dioxide (PET CO2) concentrations (34.5 ± 1.5 mmHg) than their control groups (39.0 ± 0.8 mmHg)  31  . Assuming normal cerebrovascular CO2 reactivity33, the 4.5  mmHg reduction in PET CO2 would account for approximately 18% of the observed 30% reduction in CBF. Hypocapnia is a well known condition associated with congestive heart failure (CHF) patients152-155, and chronic hypocapnic exposure can result in cerebral hemodynamic maladaptation  156  . Gruhn et al.31 reported that the increase in CBF following  HT being strictly caused by the marked hypercapnia was questionable. Therefore, they concluded that the decreases in CBF for patients with severe CHF may contribute to the neurological symptoms they experience31. Another possibility to explain Gruhn‟s findings was noted in a companion Editorial138. This editorial suggested that the reported 30% increase in CBF following HT was perhaps due to a perisurgical fall in hematocrit, as well as putting forth the notion that the pre-surgery reduction in CBF may not be sufficient to cause neurological impairment. Although Gruhn et al.  31  did not provide the hematocrit data for their subjects, it was  estimated that net hematocrit levels fell by 8.3% 30 days post transplant 138. A reduction in hematocrit levels from 0.57 to 0.24 can result in an increase in red blood cell velocity of more than 50% due to the reduction in red blood cell viscosity157. Such changes may explain the CBF changes found by Gruhn et al.  31  could have occurred due to blood viscosity  changes as noted in Poiseuille‟s law (Equation 1.) 138. In the second study, Massaro et al.30 reported changes in CBF velocity (as index by transcranial Doppler - TCD) in CHF patients before and after heart transplantation in order to evaluate the intracranial hemodynamic features that are associated with the improvement of  19  cardiac output. Twenty-six patients were preoperatively selected for their study. Upon completion of neuroimaging examinations (cranial CT or MRI), 4 patients were excluded because of silent ischaemic brain lesions and 20 for signs of cerebral atrophy30. The twentytwo patients included in the study had a mean age of 45.3 years, MCAv of 45.1 ± 10.6 cm/s (Figure 1.3.), and a mean hematocrit of 38.8 ± 5.5% 30.  Fourteen patients underwent  successful heart transplantation. Findings showed a 53.3% increase in MCAv (P<0.0001) in MCAv of 53.3% (Figure 1.2.) and a lower mean hematocrit levels (31.2 ± 2.0%) was observed30.  Pre-operative and post-operative neuropsychological evaluations were not  performed during the study30. When evaluating their data for the 53.3% improvement in MCAv the authors were unable to observe any MCAv-hematocrit correlation138. The lack of correlational data in the pre- and post-transplant measures of MCAv and hematocrit, led Massaro et al. 30 to conclude that the CBF increases observed in their studies were probably not due to the changes in hematocrit levels.  Overall, these findings allowed the authors to report that the main  mechanism for the increase in MCAv after successful heart transplantation was most likely due to the improved Q. In support, Baufreton et al.158 have recently confirmed in healthy humans there is no MCAv - hematocrit relationship. The focus of the final study by Choi et al.  32  was to investigate factors that represent  the chronicity and level of severity of HF, but not associated with exercise capacity or the LVEF, in respect to global CBF changes observed in CHF patients, rather than the effects of heart transplantation on CBF. Overall, fifty-two CHF patients took part in their study, four of which underwent heart transplantation. In these four, it was noted that global CBF at rest increased (35.5 ± 1.6 to 44 ± 3.2 mL/100g per min: Figure 1.3.) and left ventricular ejection  20  fraction (LVEF) normalized (19.8 ± 6.8% to 66.8 ± 3.3%) for these subjects 32. However, the authors did not expand upon or make any reference to these findings in their discussion. These results, in conjunction with the findings by Gruhn et al.  31  , support the conclusion by  Massaro et al. 30, in that the main mechanism for the increase in CBF post-transplant is likely due to the increased Q that the „new‟ heart provides.  21  Chapter Two: Purpose, Aims and Hypotheses  2.1.  Purpose of Thesis A limitation of the prior studies of CBF in HTR30-32, is that CBF was only examined  at rest during the acute post-transplant time period (up to 6 months), and was also not examined during exercise stress, when Q reserve is challenged 6, 21. The HTR population has a reported inability to increase Q during exercise due to cardiac denervation159-161.  However, it has also been reported that the exercise HR response  will vary with the length of time after transplant and this may be due to the possible reinnervation of the heart 6. Furthermore, the role that this possible cardiac re-innervation and concomitant improvement in exercise Q associated with heart transplantation has on CBF is unknown100. How these possible alterations in the long-term HTR (cardiac re-innervation and improvements in exercise Q) will affect CBF at rest and during exercise stress is currently unknown.  2.2.  Aims  The aim of this thesis was enhance the current literature of CBF in HTR by being the first study to examine the influence of long-term heart transplantation on the regulation of CBF at rest as well as being the first study to assess the effects of exercise stress on CBF in HTR.  22  2.3.  Hypotheses  1.  That CBF (indexed using TCD) would be similar in HTR when compared to age and activity-matched controls, but CBF would be attenuated relative to donor population controls.  2.  During incremental cycling exercise, to exhaustion, HTR would have reduced elevations in CBF compared with age and activity-matched controls (AM) and donor population controls (DC).  23  Chapter Three: Methods  3.1.  Participants  Seven male clinically stable HTR (62 ± 9 yrs), years post transplant (9 ± 7 yrs), from the University of Alberta Heart Transplant Clinic, seven male AM (62 ± 7 yrs), and seven male DC (22 ± 3 yrs) were recruited for this study (Table 3.1). All of the HTR subjects were clinically stable and had no clinical or biopsy evidence of rejection. The AM were recruited to match with the HTR on an individual basis for both age and activity level, as there is a decrease in MCAv of approximately 1% per year across the aging spectrum, and a 17% increase in MCAv that is associated with long-term endurance training, irrespective of aging151. The DC were included in the study to offset a study limitation of Kao et al.10, which indicated that the exercise response observed in HTR may be more closely related to the age of the donor rather than the age of the individual. The age of the DC group was chosen to represent the most common heart transplant donor group. For example, in North America over 50% of all donors are between the ages of 18-342. All subjects were asked to abstain from caffeine, smoking and alcoholic beverages for a period of 12 hours prior to the study and all medications were maintained for the study. Each subject underwent a familiarization of the laboratory and testing protocols before the initiation of the incremental peak exercise protocol. This study and was approved by the University of Alberta Health Research Ethics Board (Pro00011560), and all participants provided written informed consent before the experiment.  24  Included in the study was the only HTR to have successfully completed the Ironman™ endurance race (subject #02)8. This subject was also the only HTR participant to have a non-ischemic pre-surgery etiology. Statistical analysis were performed with and without HTR subject #02 in order to establish if the increased fitness and training levels associated with completion of an Ironman Triathlon and/or the effects of the non-ischemic pre-surgery etiology influenced the main findings of the study (Table 3.2).  Table 3.1. Participant Characteristics (all subjects)  Age (years) Body Mass Index (kg/m2) Resting BP (mmHg) Resting Mean MCAv (cm/s) Resting Cerebrovascular Resistance (mmHg/cm/s) Resting Pulsitility Index (AU) Peak O2 Consumption (ml/kg/min) Years after transplantation Medications Corticosteroid Antiproliferative agent Calcinerurin inhibitor mTOR inhibitor Ca2+ channel blocker (diltiazem) ACE inhibitor Diuretic Aspirin Lipid –lowering agent  HTR (n=7)  AM (n=7)  DC (n=7)  62 ± 9 27 ± 5 99 ± 4 40 ± 12  62 ± 7 26 ± 4 99 ± 15 41 ± 7  22 ± 3 †‡ 25 ± 3 91 ± 6 69 ± 9 †‡  2.6 ± 0.7 0.9 ± 0.2 25 ± 10  2.5 ± 0.5 1.1 ± 0.3 35 ± 9  1.3 ± 0.2 †‡ 1.1 ± 0.2 51 ± 7 †‡  9±7 2 4 4 4 5 4 3 6 4  1 1 1 1  Values are means ± SD. All subjects were ischemic pre-surgery etiology except HTR subject #02 who was non-ischemic etiology. Heart transplant recipient (HTR); age-matched (AM); donor population control (DC); blood pressure (BP); target of rapamycin (TOR); angiotensin-converting enzyme (ACE). Statistical significance was set at P < 0.05, †denotes significance between HTR vs. DC, ‡denotes significance between AM vs. DC.  25  Table 3.2. Participant Characteristics (without HTR subject #02 and matched controls)  Age (years) Body Mass Index (kg/m2) Resting BP (mmHg) Resting Mean MCAv (cm/s) Resting Cerebrovascular Resistance (mmHg/cm/s) Resting Pulsitility Index (AU) Peak O2 Consumption (ml/kg/min) Years after transplantation Medications Corticosteroid Antiproliferative agent Calcinerurin inhibitor mTOR inhibitor Ca2+ channel blocker (diltiazem) ACE inhibitor Diuretic Aspirin Lipid –lowering agent  HTR (n=6)  AM (n=6)  DC (n=6)  64 ± 8 28 ± 4 98 ± 3 41 ± 13  63 ± 7 26 ± 4 98 ± 16 42 ± 8  21 ± 2 †‡ 26 ± 2 90 ± 7 67 ± 7 †‡  2.6 ± 0.7 0.9 ± 0.3 22 ± 4  2.5 ± 0.4 1.1 ± 0.3 33 ± 8*  1.4 ± 0.3 †‡ 1.0 ± 0.2 50 ± 7 †‡  7±4 2 4 4 4 4 4 3 6 4  1 1 1 1  Values are means ± SD. All subjects were ischemic pre-surgery etiology. Heart transplant recipient (HTR); age-matched (AM); donor population control (DC); blood pressure (BP); target of rapamycin (TOR); angiotensin-converting enzyme (ACE). Statistical significance was set at P < 0.05, *denotes significance between HTR vs. AM, †denotes significance between HTR vs. DC, ‡denotes significance between AM vs. DC.  26  3.2.  Instrumentation  Whenever possible, both the right and left middle cerebral arteries were insonated by placing a 2-MHz Doppler probe (Spencer Technologies, Seattle, WA, USA) to obtain bilateral CBF velocity and are securely locked in place with an adjustable head-band (Spencer Technologies, Seattle, WA, USA), enabling continuous measures of CBFv throughout the incremental cycling test. electrocardiogram  (ECG).  Blood  Heart rate was recorded with a three-lead  pressure  was  monitored  in  the  arm  by  electrosphygmomanometry (SunTech Medical, Morrisville, NC, USA), with a microphone placed over the brachial artery and the Korotkoff sounds gated to the ECG. Expired O2 and CO2 gases were measured by an online gas analyzer (Sensormedics Metabolic Cart, 2900BZB, Sensormedics Corporation, Homestead, FL, USA and Vmax Encore VIASYS Healthcare Inc. Yorba Linda, CA, USA) and were calibrated with standard gas of a known concentration before each exercise test. All data were recorded and stored for subsequent analysis using commercially available software (LabChart version 7.0, ADInstruments, Colorado Springs, CO, USA). Echocardiograph images (Vivid-i, GE Healthcare, USA) were recorded and assesed by a cardiologist in order to directly compare the Q with the CBFv. Unfortunately upon assessment of the recorded images, the data were deemed unacceptable for valid measurement due to subject movement during the incremental exercise test. An example of the instrumentation setup for the incremental exercise protocol is shown in Figure 3.1.  27  TCD Gas Exchange ECG Sphygmomanometer Echocardiograph Imaging  Figure 3.1.  Instrumentation setup on subject during the incremental cycling exercise protocol. Transcranial Doppler ultrasound (TCD), Electrocardiograph (ECG).  28  3.3.  Transcranial Doppler Ultrasound  Transcranial Doppler ultrasound (TCD) was first introduced into the clinical and research areas by Aaslid162 in 1982.  This technique has several advantages for the  assessment of measuring CBF velocities in humans; it is non-invasive, has high resolution, allows for continuous monitoring, and repeated measures101,  163  .  Transcranial Doppler  ultrasound functions are based on the principle of Doppler shift; as such, TCD is able to detect the red blood cell flow velocities in a variety of cerebral vessels (MCA, anterior cerebral artery, posterior cerebral artery). This study utilized the MCA as it is readily available through the temporal acoustic window, has a trajectory that is parallel with the insonation probe101, 162 (Figure 3.2.) and has been shown to carry approximately 70-80% of the blood volume into the respective hemisphere164. It is key to be aware that TCD gives a measure of blood flow velocity (cm/s) and not blood flow (mL/min/100g) per se. However, provided that the insonated vessel remains constant in diameter, these two principles are closely related as shown by the following equation163:  Cerebral blood flow velocity = blood flow volume / blood vessel diameter  Equation 2.  29  A  B  C  Figure 3.2.  Image of the transcranial Doppler ultrasound (TCD) probe being held in place with the headband (A), a frontal view of the insonation of the middle cerebral artery (MCA) (B), image of the MCA velocity waveform and envelope (C).  30  3.3.1. Validity of TCD  In the literature it has been shown that the diameter of the MCA remains relatively unchanged over a range of 23-60 mmHg for PaCO2163, 165-167. Additionally, there have been several studies on humans that have compared TCD estimates of MCAv with several other measures of CBF: Kety-Schmidt method168, magnetic resonance imaging  167  and the Fick  principle169. All of these studies have shown a good correlation between the measures of CBF with the assessment of MCAv via TCD; as such the findings of these studies collectively support the use and validity of MCAv as an indirect measure of CBF.  3.3.2. Principle of TCD  The basic principle of TCD is that a transmitter inside a Doppler probe emits a 2 MHz pulsed-Doppler ultrasound beam through the thin bone acoustic window to a given target vessel. Some of the ultrasound beam is then reflected off of the red blood cells and recorded by the receiver in the Doppler probe. The Doppler shift is the difference between the transmitted and received signals and determines the velocity of the red blood cells in the target vessel and is calculated in the following equation170:  Doppler frequency shift = 2 x V x Ft x cosθ/C  Equation 3.  Where: V=velocity of the reflector (red blood cells), Ft=transmitted frequency (2 MHz), cosθ=correction factor based on the angle of insoniation, and C=speed of sound in the blood (1540m/s)  31  In TCD, since both the transmitted frequency and speed of sound in the blood are constants, the frequency of the Doppler shift is ultimately dependant upon the velocity of the red blood cells and the angle of insonation of the Doppler probe170. The angle of insonation is vital to the accuracy of the measure. It is recommended that the angle of insonation is kept less than 30°; as the cosine will vary between 1 and 0.86 in this range, thus giving a maximum error of less than 15%162. An advantage to measuring the MCA, as opposed to other cerebral vessels is that the angle of insonation is that the flow of the vessel is parallel to the probe (Figure 3.2.-B), thus resulting in a lower insonation angle and therefore less error170. The final Doppler signal is the summation of all of the signals reflected from the velocity of each of the red blood cells within the sample volume of the target vessel 170. The processing unit in the TCD uses spectral analysis to extract the 3-dimensional Doppler data into a 2-dimensional Doppler waveform (Figure 3.2.-C)170.  This waveform and its  subsequent spectral envelope are used to determine the MCAv, which is recorded for future analysis.  3.3.3. Technique of TCD The approach to insonating a cerebral vessel has been described in detail elsewhere101, 162, 170  and is summarized as follows. First, acoustic gel is placed on the probe and temporal  window, this aids in signal conduction. Second, the Doppler probe is positioned over the acoustic window and held in place with an adjustable headband. Lastly, the MCAv signal is obtained and secured by an experienced research technician using search methods that have been previously described101, 162.  32  The flow-volume MCAv waveform was obtained from the spectral envelope and displayed in LabChart in real time. From the flow-volume waveform, systolic and diastolic MCAv were obtained. Mean MCAv was calculated as follows:  Mean MCAv = 1/3 Systolic MCAv + 2/3 Diastolic MCAv  Equation 4.  Where: Mean MCAv = mean middle cerebral artery velocity (cm/s), Systolic MCAv = systolic middle cerebral artery velocity (cm/s), Diastolic MCAv = diastolic middle cerebral artery velocity (cm/s).  In addition, Cerebrovascular Resistance (CVR) was calculated as: MAP/MCAv. MCAv Pulsitility Index (PI) was calculated as: (Systolic MCAv-Diastolic MCAv)/Mean MCAv.  3.4.  Incremental Cycling Exercise Protocol  An electrically braked cycle ergometer (Monark 894E, Varberg, Sweden) was utilized for the incremental cycling exercise test.  Baseline measures were recorded in a seated  position on the cycle ergometer, after the subjects began the exercise protocol. The first stage was begun at 50 watts (W) and the workload for all subsequent stages was increased 25W every 2 min until the respiratory exchange ratio exceeded 1.00, subsequently the workload increased 25W every minute until volitional exhaustion. Upon completion of the protocol VO2peak was determined from the highest 20-second average expired O2 value. This protocol was modified for the HTR to begin at 25W due to the lower expected VO2peak values as described by Scott et al.6.  33  The criteria for completing the exercise protocol were: leveling off of VO2, respiratory exchange ratio greater than 1.15, a rate of perceived exertion of 20 (on the 6-20 Borg scale), or heart rate at age-predicted maximal values.  3.5.  Statistical Data Analysis  Statistical analyses were performed using PASW version 18.0 for Windows (PASW, Inc. Chicago, Illinois). A one-way repeated measures ANOVA with group by intensity comparisons was applied to identify differences across intensity. Upon establishing the normality of the data using a skewness-kurtosis normality test, comparisons between groups were performed with Fisher‟s LSD post hoc test. Linear Regression was used to determine the relationship between heart rate reserve (HRreserve) and age, and years post transplant. Data are presented as means ± standard deviation (SD), and significance was set at P < 0.05. All statistical tests were run with and without HTR subject #02.  34  Chapter Four: Results  4.1.  Participant Characteristics  Participant characteristics are shown in Table 3.1.  There were no statistical  significances in body mass index (BMI), resting BP or resting pulsitility index (PI). By design the DC were younger than the HTR and AM groups. Differences were observed between the HTR and DC as well as the AM and DC groups for resting MCAv and cerebrovascular resistance (CVR). The HTR (inclusive of subject #02) had a lower VO 2peak than the AM and DC comparison groups by 27% and 50% respectively (Table 3.1.). When subject #02 and matched controls were excluded, the HTR had a lower VO 2peak than the AM and DC comparison groups by 34% and 56% respectively (Table 3.2.). Removal of this subject, however, did not influence any other variables.  4.2.  Incremental Exercise Test  Cerebrovascular, cardiovascular and pulmonary responses at rest and during the incremental exercise test are summarized in Table 3.3. (all subjects) and Table 3.4. (without HTR subject #02 and matched controls).  35  Table 4.1. Cardiovascular, Pulmonary and Cerebrovascular responses at rest and during the incremental exercise test at 50%, 70%, 90% and peak VO2 (all subjects) MCAvmean (cm/s) Rest HTR 40 ± 12 AM 41 ± 7 DC 69 ± 9†‡ 50% VO2peak HTR 46 ± 10 AM 52 ± 10 DC 84 ± 11†‡ 70% VO2peak HTR 47 ± 11 AM 54 ± 8 DC 84 ± 11†‡ 90% VO2peak HTR 46 ± 11 AM 54 ± 6 DC 75 ± 8†‡ 100% VO2peak HTR 45 ± 11 AM 53 ± 8 DC 63 ± 9†  MCAvsys (cm/s)  MCAvdia (cm/s)  HR (bpm)  HRreserve (bpm)  BPmean (mmHg)  BPsys (mmHg)  BPdia (mmHg)  PET CO2 (mmHg)  CVR (mmHg/cm/s)  PI (AU)  63 ± 20 70 ± 12 119 ± 18†‡  28 ± 10 27 ± 7 45 ± 7†‡  93 ± 9 74 ± 10* 72 ± 13†  0±0 0±0 0±0  99 ± 4 104 ± 19 91 ± 6  123 ± 5 134 ± 26 117 ± 11  87 ± 7 82 ± 12 78 ± 8  28 ± 5 29 ± 3 37 ± 4†‡  2.7 ± 0.7 2.6 ± 0.6 1.3 ± 0.2†‡  0.9 ± 0.2 1.0 ± 0.3 1.0 ± 0.2  80 ± 19 97 ± 16 159 ± 23†‡  28 ± 7 29 ± 9 47 ± 9†‡  107 ± 8 100 ± 10 122 ± 19†‡  14 ± 5 26 ± 19 51 ± 7†‡  107 ± 6 110 ± 12 99 ± 6‡  149 ± 12 169 ± 21* 143 ± 11‡  86 ± 7 81 ± 10 77 ± 8  33 ± 3 37 ± 3 43 ± 4†‡  2.5 ± 0.6 2.2 ± 0.3 1.2 ± 0.2†‡  1.1 ± 0.2 1.3 ± 0.3 1.3 ± 0.2  87 ± 22 107 ± 12* 162 ± 18†‡  28 ± 7 27 ± 8 45 ± 10†‡  125 ± 3 125 ± 19 164 ± 13†‡  32 ± 11 51 ± 28 92 ± 7†‡  118 ± 12 120 ± 13 105 ± 6†‡  176 ± 24 197 ± 28 163 ± 13‡  88 ± 10 81 ± 10 76 ± 8†  34 ± 2 37 ± 2* 44 ± 4†‡  2.6 ± 0.8 2.2 ± 0.4 1.3 ± 0.3†‡  1.2 ± 0.2 1.5 ± 0.3* 1.4 ± 0.2  88 ± 24 112 ± 8* 148 ± 20†‡  25 ± 7 25 ± 8 38 ± 6†‡  142 ± 7 143 ± 19 185 ± 8†‡  49 ± 11 69 ± 28 113 ± 15†‡  126 ± 11 127 ± 11 109 ± 7†‡  196 ± 17 214 ± 20 178 ± 9†‡  91 ± 12 83 ± 10 74 ± 8†  32 ± 2 35 ± 5 36 ± 4†  3.0 ± 1.0 2.4 ± 0.4 1.5 ± 0.2†‡  1.4 ± 0.3 1.6 ± 0.3 1.5 ± 0.2  88 ± 25 109 ± 13 132 ± 24†  23 ± 7 24 ± 7 28 ± 8  152 ± 10 154 ± 18 196 ± 5†‡  60 ± 15 80 ± 28 124 ± 12†‡  128 ± 9 129 ± 13 111 ± 7†‡  202 ± 16 221 ± 17* 187 ± 12‡  91 ± 13 84 ± 17 73 ± 8†  28 ± 3 32 ± 4 28 ± 5  3.1 ± 1.0 2.5 ± 0.5 1.8 ± 0.2†  1.4 ± 0.3 1.6 ± 0.2 1.7 ± 0.3  Values are means ± SD. Heart transplant recipient (HTR); age-matched (AM); donor population control (DC); middle cerebral artery velocity (MCAv); heart rate (HR); blood pressure (BP); end tidal CO 2 (PET CO2); cerebrovascular resistance (CVR) and pulsitility index (PI). Statistical significance was set at P < 0.05, *denotes significance between HTR vs. AM, †denotes significance between HTR vs. DC, ‡denotes significance between AM vs. DC.  36  Table 4.2. Cardiovascular, Pulmonary and Cerebrovascular responses at rest and during the incremental exercise test at 50%, 70%, 90% and peak VO2 (without HTR subject #02 and matched controls) MCAvmean (cm/s) Rest HTR 41 ± 13 AM 42 ± 8 DC 67 ± 7†‡ 50% VO2peak HTR 46 ± 11 AM 51 ± 11 DC 82 ± 10†‡ 70% VO2peak HTR 47 ± 12 AM 54 ± 9 DC 82 ± 11†‡ 90% VO2peak HTR 46 ± 13 AM 55 ± 7 DC 75 ± 9†‡ 100% VO2peak HTR 45 ± 12 AM 53 ± 8 DC 64 ± 9†  MCAvsys (cm/s)  MCAvdia (cm/s)  HR (bpm)  HRreserve (bpm)  BPmean (mmHg)  BPsys (mmHg)  BPdia (mmHg)  PET CO2 (mmHg)  CVR (mmHg/cm/s)  PI (AU)  64 ± 22 71 ± 12 113 ± 13†‡  29 ± 10 27 ± 8 44 ± 7†‡  93 ± 10 76 ± 10* 71 ± 14†  0±0 0±0 0±0  98 ± 3 98 ± 16 90 ± 7  124 ± 5 133 ± 28 117 ± 12  85 ± 6 80 ± 12 77 ± 9  27 ± 5 29 ± 3 37 ± 4†‡  2.6 ± 0.7 2.5 ± 0.4 1.4 ± 0.3†‡  0.9 ± 0.3 1.1 ± 0.3 1.0 ± 0.2  79 ± 21 97 ± 18 154 ± 20†‡  28 ± 8 28 ± 9 46 ± 9†‡  106 ± 9 99 ± 10 120 ± 20‡  13 ± 5 24 ± 19 50 ± 7†‡  106 ± 7 106 ± 7 98 ± 6  150 ± 13 165 ± 20 143 ± 12‡  84 ± 7 78 ± 5 76 ± 8†  33 ± 3 36 ± 3 43 ± 4†‡  2.5 ± 0.7 2.1 ± 0.4 1.2 ± 0.2†‡  1.1 ± 0.2 1.4 ± 0.3 1.3 ± 0.2  85 ± 24 107 ± 13* 159 ± 17†‡  28 ± 7 27 ± 8 44 ± 11†‡  125 ± 3 123 ± 20 163 ± 14†‡  32 ± 12 48 ± 30 92 ± 8†‡  117 ± 13 118 ± 13 104 ± 6  174 ± 25 195 ± 30 163 ± 14‡  90 ± 10 79 ± 7* 75 ± 8†  33 ± 2 37 ± 2 43± 4†‡  2.7 ± 0.8 2.2 ± 0.4 1.3 ± 0.3†‡  1.2 ± 0.2 1.5 ± 0.3* 1.4 ± 0.2  86 ± 26 113 ± 8* 149 ± 22†‡  25 ± 7 25 ± 8 38 ± 7†‡  142 ± 8 143 ± 21 186 ± 9†‡  49 ± 12 66 ± 30 115 ± 15†‡  125 ± 12 127 ± 12 109 ± 7†‡  203 ± 18 218 ± 17 179 ± 10‡  92 ± 12 83 ± 11 74 ± 9†  32 ± 2 34 ± 5 36 ± 4  3.0 ± 1.1 2.3 ± 0.4 1.5 ± 0.3†‡  1.3 ± 0.2 1.6 ± 0.3* 1.5 ± 0.2  85 ± 26 111 ± 14 136 ± 25†  24 ± 7 24 ± 7 28 ± 8  151 ± 10 152 ± 20 195 ± 6†‡  59 ± 16 77 ± 29 125 ± 13†‡  130 ± 8 124 ± 6 111 ± 8†‡  203 ± 17 218 ± 17 187 ± 14‡  94 ± 12 78 ± 8* 73 ± 8†  28 ± 2 32 ± 5 29 ± 5  3.2 ± 1.1 2.4 ± 0.3 1.8 ± 0.2†  1.4 ± 0.2 1.6 ± 0.2 1.7 ± 0.3†  Values are means ± SD. Heart transplant recipient (HTR); age-matched (AM); donor population control (DC); middle cerebral artery velocity (MCAv); heart rate (HR); blood pressure (BP); end tidal CO 2 (PET CO2); cerebrovascular resistance (CVR) and pulsitility index (PI). Statistical significance was set at P < 0.05, *denotes significance between HTR vs. AM, †denotes significance between HTR vs. DC, ‡denotes significance between AM vs. DC.  37  4.3.  Rest  Resting mean (Figure 4.1.-A), systolic and diastolic MCAv were not significantly different between the HTR and AM groups; however, these variables were lower in the HTR and AM groups when compared to DC (Table 4.1.). At rest, HR (Figure 4.1.-B) was significantly different for the HTR as compared to both the AM and DC. No significant differences were reported in any of the resting mean, systolic or diastolic BP (Figure 4.1.-C). The DC had higher (P<0.05) PET CO2 levels and lower CVR than both the HTR and AM. No other significant differences were found at rest between the groups (Table 4.1.). When subject #02 was excluded from the analysis, all of the previous findings were unchanged (Table 4.2.).  38  Heart Transplant Recipient Age-Matched Control Donor Population Control  A  120  *  B  130  * *  * 80  MABP (mmHg)  60  80  40  110 100 90  60 20  80 HTR  Figure 4.1.  C  120  100 HR (bpm)  Mean MCAv (cm/s)  100  AM  DC  HTR  AM  DC  HTR  AM  DC  Resting values for (A) mean middle cerebral artery velocity (MCAv), (B) heart rate (HR) and (C) mean arterial blood pressure (MABP) for the heart transplant recipient (HTR), age-matched (AM) and donor population control (DC) groups. Statistical significant differences between HTR vs. DC and AM vs. DC were observed in MCAv and HR, no statistical differences were noted between HTR vs. AM for any condition, nor between any of the HTR, AM or DC groups MABP. (Values are means ± SD. *denotes, P < 0.05)  39  4.4.  VO2peak Relative VO2peak for all subjects (Figure 4.2.-A; Table 3.1) values for the HTR (25.4 ±  10.4 mL/kg/min) and AM (35.0 ± 8.7 mL/kg/min) were significantly lower than the DC (50.6 ± 6.7 mL/kg/min) (Table 3.1.). The HRpeak (Figure 4.3.-A) and HRreserve (Figure 4.3.-B) for the DC were significantly higher than both the HTR and AM groups, and there was a trend toward lower relative VO2peak and HRreserve between HTR and AM (P = 0.055, and P = 0.071 respectively).  When subject #02 was excluded from the analysis, there was a significant  difference observed in the VO2peak between the HTR and AM groups (Figure 4.2.-B; Table 3.2.). At VO2peak, mean and systolic MCAv were significantly lower in the HTR as compared to the DC, but not significantly different from the AM. The DC had lower MABP than both the HTR and AM (P<0.05). Systolic BP was higher in the AM group, compared with both the HTR and DC. The only other significant difference in BP at VO 2peak was the lower diastolic BP for the DC when compared with the HTR. The DC also had lower (p<0.05) CVR when compared to the HTR. All other cerebrovascular, cardiovascular and cardiorespiratory VO2peak responses were not different between the HTR, AM and DC groups with all subjects included (Table 4.1.). The exclusion of subject #02 resulted in the same findings except the significant differences observed between the HTR and AM groups in BP did not occur in the mean BP; rather, they occurred in both diastolic BP at both 70%and 100% of VO2peak (Table 4.2.).  40  Relative Peak VO2 (mL/kg/min)  80  Heart Transplant Recipient Age-Matched Control Donor Population Control  AA * *  60  40  20  0 HTR  Relative Peak VO2 (mL/kg/min)  80  AM  BB  DC  * *  *  60  40  20  0 HTR  Figure 4.2.  AM  DC  Relative VO2peak for the heart transplant recipient (HTR), age-matched (AM) and donor population control (DC) groups. (A) Data shown with the inclusion of all subjects, (B) Data shown with the exclusion of HTR subject #02. Statistical significant differences were observed between HTR vs. DC and AM vs. DC. Values are means ± SD. *denotes, P < 0.05.  41  Heart Transplant Recipient Age-Matched Control Donor Population Control  A  200  *  B  220  * Heart Rate Reserve (bpm)  Peak Heart Rate (bpm)  * 200  180  160  *  150  100  50  140  120  0 HTR  Figure 4.3.  AM  DC  HTR  AM  DC  (A) Peak heart rate (HRpeak) and (B) heart rate reserve (HRreserve) for the heart transplant recipient (HTR), agematched (AM) and donor population control (DC) groups. Statistically significant differences observed between the HTR vs. DC and AM vs. DC in both HRpeak and HRreserve. Although there were no statistically significant differences for either condition between HTR vs. AM, a lower trend was observed in HRreserve (P = 0.071). Significance between the HTR vs. AM groups was not reached upon the exclusion of subject #02 (not shown). Values are means ± SD. *denotes, P < 0.05.  42  4.5.  HRreserve Relationships There was a significant negative relationship associated with HRreserve and age for the  life-span of the entire subject pool (Figure 4.4.-A). There was also a significant individual group relationship between HRreserve and age for the AM group (R2 = 0.79, P = 0.008; data not shown). There was no HRreserve relationship for either the HTR (R2 = 0.13, P = 0.429) or DC (R2 = 0.02, P = 0.778). The HRreserve for the DC were significantly higher than both the HTR and DC throughout the incremental exercise test (Table 4.1. and Table 4.2.). The HTR also showed a lower trend in HRreserve as compared to the AM during the test; however significance was never reached (mild, P = 0.080; moderate, P = 0.070; intense, P = 0.075). There was no evident relationship between HRreserve with years after transplant (Figure 4.4.B) with or without HTR subject #02.  43  Heart Transplant Recipient Age-Matched Control Donor Population Control  160  R2 = 0.73, P < 0.001  A  20  120  Years Post Transplant  Heart Rate Reserve (bpm)  140  R2 = 0.18, P = 0.341  B  25  100 80 60  15  10  5  0  40 20 20  40  60  Age (years)  Figure 4.4.  80  30  40  50  60  70  80  90  Heart Rate Reserve (bpm)  (A) Overall relationship between heart rate reserve (HRreserve) and age of all subjects - heart transplant recipients (HTR), age-matched (AM) and donor population controls (DC); and (B) the relationship between HRreserve and years post transplant. Although not plotted, the relationship between age and HRreserve for each group (A) are as follows: HTR (R2 = 0.13, P = 0.429), AM (R2 = 0.79, P = 0.008), DC (R2 = 0.02, P = 0.778). Red circle indicates subject #02.  44  4.6.  Mild, Moderate and Intense Exercise  During mild (50% of VO2peak), moderate (70% of VO2peak) and intense (90% of VO2peak) exercise, MCAvmean (Figure 4.5.-A) was higher (P<0.05) in the DC compared to both the HTR and AM. However, MCAvmean was not significantly different between the HTR and AM groups. From rest to mild exercise the MCAvmean for the DC demonstrated a large increase, plateaued as intensity increased to the moderate level, followed by a sharp decline as peak intensity was reached. The HTR and AM groups demonstrated a different trend; both groups had a steady increase in MCAvmean up to the moderate intensity level, after which a plateau was obtained that continued to the end of the test to VO 2Peak (Figure 4.5.-A). The HTR, AM and DC groups all demonstrated a trend of BP increasing with exercise intensity (Figure 4.5.-B). During mild exercise the AM was significantly higher than the DC; however, HTR was not significantly different from either the AM or the DC. In moderate exercise, intense and peak exercise the HTR and AM group were not different in BP; however, they were higher than the DC. The PET CO2 response (Figure 4.5.-C) for all three groups showed a similar trend to one another from rest to mild exercise, at which point the DC were significantly higher than both the HTR and AM. All three groups experienced a small increase during moderate exercise and were significantly different from each other with DC and HTR having the highest and lowest values respectively. The DC group experienced a sharper decline in PET CO2 during intense exercise than the HTR and AM groups; the only significant difference during intense exercise was between the HTR and DC. There were no differences in PET CO2 during peak exercise (Table 4.1. and Table 4.2.).  45  Across majority of the incremental exercise test spectrum, the CVR of the HTR and AM were higher than the DC (Figure 4.5.-D; P<0.05). Only at peak exercise intensity did this change, at which point only the CVR of the HTR was significantly higher than the DC; there were no differences between the HTR and AM groups. There where no significant changes to the results when subject #02 was excluded from the analysis (Table 4.2.). During mild exercise, systolic MCAv (Figure 4.6.-A) for the DC was significantly higher than the HTR and AM. All three groups were different during moderate and intense exercise; DC was higher than AM, and the HTR were lower than AM. There was a slightly different pattern demonstrated in the diastolic MCAv (Figure 4.6.-B). For example, throughout the entire incremental exercise test, there were no differences between HTR and AM; however, the diastolic MCAv for DC was higher (P<0.05). Only at peak exercise did the diastolic MCAv for the DC decrease enough that there was no longer any significant differences amongst the groups.  The only difference in PI throughout the incremental  exercise test occurred during moderate exercise.  At which point the HTR were lower  (P<0.05) than the AM (Figure 4.6-C; Table 4.1). When subject #02 was removed from the analysis, there were no significant changes in the systolic or diastolic MCAv data (Table 4.2.). However, during the analysis of the PI there were two changes to the significance findings: a difference between the HTR and AM at 90% VO2peak and between the HTR and DC at 100% of VO2peak.  46  Heart Transplant Recipient Age-Matched Control Donor Population Control  A  †‡  Mean MCAv (cm/s)  90  †  70 60 50 40  Base 50% 70% 90% Peak  End Tidal CO2 (mmHg)  †‡  †  40 35 30 25 20 Base 50% 70% 90% Peak  Cerebrovascular Resistance (mmHg/cm/s)  Base 50% 70% 90% Peak  45  ‡  100  80  *†‡  †‡  110  20  †‡  †‡  120  90  C C  †‡  130  30  50  BB  140  †‡  †‡  80  150  †‡ Mean BP (mmHg)  100  4.5  D D †‡  4.0 3.5  †‡  †‡  †  †‡  3.0 2.5 2.0 1.5 1.0 Base 50% 70% 90% Peak  Figure 4.5. (A) Mean middle cerebral artery velocity (MCAv), (B) mean blood pressure (BP), (C) end tidal CO2 (PET CO2), and (D) cerebrovascular resistance (CVR) values for the heart transplant recipient (HTR), age-matched (AM) and donor population control (DC) groups across the incremental exercise test. (Values are means ± SD. *denotes between HTR vs. AM, †denotes significance between HTR vs. DC, ‡denotes significance between AM vs. DC. Statistical significance was set at P < 0.05). Data shown is for all subjects.  47  Systolic MCAv (cm/s)  200  A  160  †‡  *†‡  *†‡  †  †‡  Heart Transplant Recipient Age-Matched Control Donor Population Control  120 80 40 0  Diastolic MCAv (cm/s)  Base 50% 70% 90% Peak 60  B  †‡  †‡  †‡  50  †‡  40 30 20 10  Pulsitility Index  Base 50% 70% 90% Peak  2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4  C *  Base 50% 70% 90% Peak Figure 4.6.  (A) Systolic middle cerebral artery velocity (MCAv), (B) Diastolic MCAv, and (C) Pulsatility Index (PI) values for the heart transplant recipient (HTR), agematched (AM) and donor population control (DC) groups across the incremental exercise test. (Values are means ± SD. *denotes between HTR vs. AM, †denotes significance between HTR vs. DC, ‡denotes significance between AM vs. DC. Statistical significance was set at P < 0.05). Data shown is for all subjects.  48  Chapter Five: Discussion and Conclusion  5.1.  Principle Findings  The two novel principle findings of this study were: 1) Although the general pattern of change in mean MCAv was comparable during exercise in HTR compared to AM, systolic MCAv was selectively reduced in the HTR during moderate and intense exercise; and 2) When compared to DC, a comparable „relative‟ elevation in mean MCAv was evident from rest to light intensity exercise; however, HTR and AM controls did not display comparable declines in MCAv at exercise intensities 70% of VO2peak and greater. At these higher intensities the HTR and AM MCAv declines were similar to each other but blunted when compared to the DC. These findings were unaltered with and without the inclusion of the highly trained HTR; subject #02 (Table 4.1. and 4.2.). Collectively, the similarities in the CBF response between HTR and AM during exercise are remarkable and highlights that a „younger‟ denervated donor heart does not adversely impact on CBF at rest or during exercise, even with the presence of immunosuppressive therapy and likely stiffer vasculature in HTR. Nevertheless, the influence of medication and/or arterial stiffness in the HTR may underpin the apparent differences in systolic MCA velocity and pulsation.  5.2.  Influence of HT on CBF at Rest - Comparison with Previous Studies To date, as mentioned, only three studies have quantified CBF following HT 30-32.  Gruhn et al.31 reported that CBF was reduced in patients with severe chronic heart failure by approximately 30% and that these levels were normalized with heart transplantation one month after transplant. When the patients were re-examined at six months post transplant,  49  the CBF values did not differ from those observed one-month post. Ackerman138 wrote an editorial in response to the 2001 Gruhn et al.31 study and criticized the lack of data on hematocrit levels, as they have observed that hematocrit levels are lower in HTR – it was suggested that the lower hematocrit levels would reduce the viscosity in the blood and be able to account for virtually all of the increase in CBF. Massaro et al.30 did report increases in CBF in all 14 of their subjects one month after receiving the HT; however, they were unable to correlate the 53% increase in CBF to the lower mean hematocrit levels. In the final study, Choi et al. 32 presented data on four patients with chronic heart failure that underwent heart transplantation; global CBF was raised by 25% two to four months post surgery. Our study is the first report of how CBF is altered over the longer term (i.e. years – 1 to 22 years) following HT. Our findings show that CBF (as indexed by TCD) in HTR is similar to agematched controls at rest (Table 4.1. and Table 4.2.). Based on the lack of correlational data between hematocrit and MCAv in the findings by Massaro et al.30 (HTR) and the confirmation by Baufreton et al.158 (healthy humans), we feel that MCAv values that were observed in the current study were not influenced by the hematocrit levels of either the HTR or their controls.  5.3.  Young Heart, Old Brain: Influence of Aging on CBF  Over the course of normal human aging, physiological and psychological changes occur that result in the structural and functional alterations of the cardiovascular and cerebrovascular systems171, 172. These alterations result in observed decreases in CBF over that possibly reflect a global decrease in cerebral perfusion151. Ainslie et al.151, quantified this decline in CBF as a decrease in MCAv of approximately 1% per year through a  50  comprehensive study of 307 healthy male subjects. Another key finding from this study was that regular endurance exercise training results in an increase in MCAv of approximately 17% across the aging spectrum151. It was speculated that the underlying mechanisms for these improvements in CBF were due to the numerous cardiovascular benefits that are associated with regular physical training151. These results also demonstrate that „normal‟ is really only a point of reference for comparison as living a healthy and active lifestyle can potentially delay pathological disorders that result in age-associated cerebrovascular related brain diseases151. With healthy aging, CBF declines 25-30% between 20 and 80 years of age151,  173  . Similarly, a longitudinal study by Fotenos et al.174 has shown there to be a  reduction of 0.45% per year in total brain volume after 30 years of age. As expected, resting MCAv (Figure 4.1.-A; Table 4.1. and Table 4.2.) was higher in the DC compared with the AM and HTR participants173. Interestingly, despite a „younger‟ heart, the HTR had comparable declines in CBF as the AM controlled (Figure 4.5.-A). Thus, this apparent reduction in resting MCAv with age is likely due to the reduction in brain volume174 and therefore metabolism and blood flow175 rather than age- and HTR-related differences in cardiac function. In other words, an „old brain‟ is the fundamental cause of cerebral hypoperfusion rather than a „young heart‟ as the CBF in the HTR are responding in a similar fashion to the AM, even though their heart is more similar in age to the DC.  5.4.  Influence of HTR on CBF Alterations During Exercise  MCAvmean was elevated ~20% in response to sub-maximal exercise in the young and older individuals with and without HT (Figure 4.5.-A). This magnitude of increase is similar to that observed by other authors in young participants100 and recently in old176. It is well  51  established, at least in healthy young humans, that MCAv is intensity dependent up until ~70% of VO2 max, after which it declines to near resting levels due to hyperventilationinduced hypocapnia120, 121. Below the ventilatory threshold the increase in CBF with exercise is likely driven by increases in PaCO2 and cerebral metabolism, as a result of increased functional activation with motor activity100; however, above this intensity, the large disproportional increase in ventilation results in a reduction in PaCO 2 and concomitant reductions in CBF despite progressive elevations in the cerebral metabolism. In contrast, in both HTR and age matched controls, we did not observe comparable declines in MCAv at maximal exercise intensity as evident in the AM (Figure 4.5.-A, Table 4.1. and Table 4.2.); thus, this influence seems to be due to age per se rather than related autonomic and vascular changes associated with HT. The mechanisms by which older adults are less able to exhibit comparable levels of hypocapnia (mediated via exercise-induced hyperventilation) are not clear, but may be as a result of factors such as reduced lung and chest wall compliance177,  178  , respiratory muscle fatigue179, and differences in age-related  chemosensitivity180, 181.  5.5.  Influence of Aging on End-Tidal PCO2 A number of factors may explain the apparently age-related reductions in PET CO2  (Table 4.1. and Table 4.2.). Fundamentally, arterial PCO2 can be altered via respiratory mechanisms (alveolar ventilation) and renal (or acid-base) mechanisms (bicarbonate filtration/reabsorbtion). In the respiratory system, arterial PCO 2 diffuses from the blood stream into the alveoli where it can be expelled directly from the body. In the renal system, bicarbonate is filtered by the glomeruli into the renal tubules, when bicarbonate levels are  52  below 24 mM/L, virtually all of the bicarbonate is reabsorbed, when bicarbonate levels exceed 28 mM/L, the excess above this value is expelled in the urine182. With aging, there is decrease in the steady-state bicarbonate ion concentration and an increase in steady-state blood proton concentration183. Decreases in PaCO2 with aging can be attributed to the progressive metabolic acidosis occurring due to the normal decline in renal function: reduction in size and number of glomeruli, impairments in electrolyte transfer in the renal tubules, and a decrease in renal blood flow184 which result in less bicarbonate filtration occurring. As well as the subsequent respiratory adaptations: less compliant chest wall, decrease in strength of respiratory muscles, alveoli dilatation, enlargement of airspaces, decrease in exchange surface area which combine to result in a decrease in air exchange within the lungs185. These myriad of factors, alone or in combination, would seems to explain the higher baseline PET CO2 in DC as compared with the HTR and AM populations (Figure 4.5-C).  5.6.  Differential Changes in Systolic MCA Velocity and Pulsatility Index  The superior location of the brain with respect to the heart means that a higher pressure, pulsatile flow may be more effective at overcoming the effect of gravity and maintaining CBF186. Systolic MCAv was generally lower in the HTR across all exercise intensities but only reached statistical significance with the AM at 70% and 90% of the VO2peak (Table 4.1. and Table 4.2.; Figure 4.6.-A) i.e., a intensity close to or above the aerobic threshold. However, when subject #02 was removed from the analysis, the PI of the AM controls was also significantly higher than the HTR at 70% and 90% (Table 4.2.). The higher trends shown systolic BP for the AM (Table 4.1. and Table 4.2.) in conjunction with  53  the PI and systolic MCAv indicate that there may be a stiffening of the vasculature that is responsible for these changes. Alternatively, the related reductions in BP at the higher exercise intensities in HTR were similar to the findings of Braith et al.3. These reductions may be explained by the structural alternations experienced in the HTR during their low-flow state of CHF3; such changes may have led to an impairment in peripheral vasoconstrictor responsiveness post transplant 3. Recently, Laurent et al.187, when observing the effects of systolic blood pressures in the circulatory system it is best to utilize propagative models (i.e. the Moens-Korteweg equation) as they assume the velocity at which the pulse wave travels along the vessel will have a finite value. Laurent et al.187 suggested that applying propagative models will represent a more realistic approach to how the arterial tree functions as a propagative model that is composed of a simple distensible vessel that terminates at the peripheral resistance and has elastic properties, which allow for the generation of pressure waves. Using this notion, it is possible to understand how the increase in arterial stiffness would increase the cerebral perfusion pressure, and result in an increase in the systolic BP which would most likely influence the systolic MCAv and PI as noted in Table 4.1. and Table 4.2. Furthermore, the PI (Figure 4.6.-C) was increased in response to exercise in the all of the groups (HTR, AM and DC). These increases in PI may be a result of changes in vascular tone that are due to the increased systolic BP and/or alterations in PET CO 2 which indirectly influences this variable (Table 4.1. and Table 4.2.).  A decreased resistance/higher  compliance system is beneficial, reducing the capacity of the vascular bed to respond to transient alterations in blood flow. It appears as though the HTR are well adapted to maintain  54  cerebral perfusion during exercise as well as both the AM and DC (Table 3.3.). This is a novel finding and warrants further investigation.  5.7.  Limitations  5.7.1. TCD Ultrasound  A limitation of TCD ultrasound is that it only measures CBF velocity (cm/s) and is not a measure of true CBF volume (mL/min/100g). However, numerous studies have shown that the cross-sectional area of the conduit vessels in the brain remain constant 163, 165-167 and as such the changes that are observed in CBFv are directly proportional to the global CBF both at rest and during exercise100,101. It is recognized that changes in vessel diameter will significantly alter blood flow (radius to the fourth power, Equation 1.). However, several studies have measured vessel diameter directly measured in humans, over a wide range of mean arterial pressures and PET CO2, with diameter remaining relatively stable163, 165-167. The quality of the TCD ultrasound signal is also dependant upon sufficient penetration of the temporal acoustic window. As we age, there is a general reduction in the quality of the acoustic window, Marinoni et al.188 have suggested that over time there may be changes to the reflection, scattering and absorption qualities, due to the effects of osteoporosis resulting in an increase in the amount of inadequate windows from 3.0% of males younger than 30 to 7.6% of males over 60 years old 188.  55  5.7.2. Activity Matching  The HTR and AM controls were matched for BMI and activity levels; however, the young controls were recruited from a university based population and were not matched based on activity; they were only matched with BMI. This may have resulted in a slight portion of the elevated MCAv values reported for the DC, as previous studies have shown that there can be up to a 17% increase in MCAv associated with long-term endurance training, irrespective of age151. However, subject #02 did not show an increased MCAv as compared with the rest of the HTR and AM which is probably due to a sample size issue as a larger N (>45) is typically needed to show a fitness influence on CBF189.  5.8.  Implications  5.8.1. MCAv at Rest  The MCAv at rest in the HTR is comparable with their age and activity matched controls. When compared with the DC, the MCAv in both the HTR and AM groups were significantly lower, suggesting that the „older‟ brain and cerebrovasculature of the HTR plays a greater role than that of the „younger‟ heart.  5.8.2. MCAv During Incremental Exercise  During the incremental exercise test, the MCAv in HTR responded in a similar fashion as that of the AM, with and without the inclusion of subject #02.  56  The MCAv responses in both the HTR and AM did not decrease at the same rate as the DC during the higher exercise intensities (90% and 100% of VO 2peak). During the incremental exercise test there was very little variation in the PET CO 2 and MCAv for both the HTR and AM. However, the DC responded in a similar fashion up to aerobic threshold; at higher exercise intensities, the DC experienced a dramatic decrease in both the PET CO 2 and MCAv (Figure 4.5.; Table 4.1. and Table 4.2.). This finding highlights the powerful role of PaCO2 on MCAv, irrespective of the age of the brain or heart.  5.8.3. MCAv in HTR With and Without Subject #02 The removal of the „fit‟ HTR did not alter any of the main MCAv findings of this study. Unfortunately, with only one highly fit HTR, it is not possible to examine the longterm training effects on MCAv in HTR as there was simply not a large enough sample size (n>45; 189) to show the training effects on MCAv. A further study should be conducted with a much larger n to determine the effects of long-term training in HTR on MCAv.  5.9.  Future Studies  To further understand the relationship between CBF and HTR, the following studies are proposed:  5.9.1. Effects of Long-Term Endurance Training on CBF in HTR  This study is proposed because the removal of the long-term trained HTR did not alter any of the main MCAv findings of this study.  This was most likely due to the  57  extremely low n (1) and a larger sample (n>45) would be most likely to show the training effects of HTR on MCAv.  5.9.2. Longitudinal Study of CBF in HTR  This study only provides a cross-sectional insight in the effects of long-term HT on CBF. A study that follows a group of HTR throughout their post-transplant experience would enable a broader picture of the true long-term effects of HT on CBF regulation.  5.9.3. Effects of Incremental Exercise on CBF in End-Stage Heart Failure Patients  This study is proposed because the literature has shown that there is a known decrease in CBF in patients with end-stage heart failure32, 141-144. Also, a VO2peak of less than 15.0 mL/kg/min is one of the criteria for receiving a HT. It would be interesting to compare the CBF results of a population with a greatly reduced VO2peak to the HTR individuals in this study. This could provide more insight into the benefits of HT on CBF.  5.10. Conclusion  During both rest and throughout the incremental exercise test, the HTR and AM had similar responses in their CBF, and these responses were different from DC. These findings held true with and without the inclusion of subject #02. Thus leading to the conclusion, that despite a suppressed VO2 Peak (and likely Q) cerebral blood flow is well maintained during incremental exercise in long – term heart transplant recipients.  58  Bibliography  1. Toledo-Pereyra LH. Heart transplantation. J Invest Surg. 2010; 23: 1-5. 2. Stehlik J, Edwards LB, Kucheryavaya AY, Aurora P, Christie JD, Kirk R, Dobbels F, Rahmel AO, Hertz MI. The Registry of the International Society for Heart and Lung Transplantation: twenty-seventh official adult heart transplant report--2010. J Heart Lung Transplant. 2010; 29: 1089-1103. 3. Braith RW, Edwards DG. Exercise following heart transplantation. Sports Med. 2000; 30: 171-192. 4. Myers J, Geiran O, Simonsen S, Ghuyoumi A, Gullestad L. Clinical and exercise test determinants of survival after cardiac transplantation. Chest. 2003; 124: 2000-2005. 5. Opasich C, Pinna GD, Bobbio M, Sisti M, Demichelis B, Febo O, Forni G, Riccardi R, Riccardi PG, Capomolla S, Cobelli F, Tavazzi L. Peak exercise oxygen consumption in chronic heart failure: toward efficient use in the individual patient. J Am Coll Cardiol. 1998; 31: 766-775. 6. Scott JM, Esch BT, Haykowsky MJ, Warburton DE, Toma M, Jelani A, Taylor D, Paterson I, Poppe D, Liang Y, Thompson R. Cardiovascular responses to incremental and sustained submaximal exercise in heart transplant recipients. Am J Physiol Heart Circ Physiol. 2009; 296: H350-8. 7. Hosenpud JD, Morton MJ, Wilson RA, Pantely GA, Norman DJ, Cobanoglu MA, Starr A. Abnormal exercise hemodynamics in cardiac allograft recipients 1 year after cardiac transplantation. Relation to preload reserve. Circulation. 1989; 80: 525-532.  59  8. Haykowsky MJ, Riess K, Burton I, Jones L, Tymchak W. Heart transplant recipient completes ironman triathlon 22 years after surgery. J Heart Lung Transplant. 2009; 28: 415. 9. Richard R, Verdier JC, Duvallet A, Rosier SP, Leger P, Nignan A, Rieu M. Chronotropic competence in endurance trained heart transplant recipients: heart rate is not a limiting factor for exercise capacity. J Am Coll Cardiol. 1999; 33: 192-197. 10. Kao AC, Van Trigt P 3rd, Shaeffer-McCall GS, Shaw JP, Kuzil BB, Page RD, Higginbotham MB. Central and peripheral limitations to upright exercise in untrained cardiac transplant recipients. Circulation. 1994; 89: 2605-2615. 11. Grandi S, Sirri L, Tossani E, Fava GA. Psychological characterization of demoralization in the setting of heart transplantation. J Clin Psychiatry. 2010; . 12. Tung HH, Chen HL, Wei J, Tsay SL. Predictors of quality of life in heart-transplant recipients in Taiwan. Heart Lung. 2010; . 13. Ulubay G, Ulasli SS, Sezgin A, Haberal M. Assessing exercise performance after heart transplantation. Clin Transplant. 2007; 21: 398-404. 14. van de Beek D, Kremers W, Daly RC, Edwards BS, Clavell AL, McGregor CG, Wijdicks EF. Effect of neurologic complications on outcome after heart transplant. Arch Neurol. 2008; 65: 226-231. 15. Martinelli V, Fusar-Poli P, Emanuele E, Klersy C, Campana C, Barale F, Vigano M, Politi P. Getting old with a new heart: impact of age on depression and quality of life in long-term heart transplant recipients. J Heart Lung Transplant. 2007; 26: 544-548.  60  16. Reyes CJ, Evangelista LS, Doering L, Dracup K, Cesario DA, Kobashigawa J. Physical and psychological attributes of fatigue in female heart transplant recipients. J Heart Lung Transplant. 2004; 23: 614-619. 17. Calo L, Semplicini A, Davis PA, Bonvicini P, Cantaro S, Rigotti P, D'Angelo A, Livi U, Antonello A. Cyclosporin-induced endothelial dysfunction and hypertension: are nitric oxide system abnormality and oxidative stress involved? Transpl Int. 2000; 13 Suppl 1: S413-8. 18. Andreassen AK, Kvernebo K, Jorgensen B, Simonsen S, Kjekshus J, Gullestad L. Exercise capacity in heart transplant recipients: relation to impaired endotheliumdependent vasodilation of the peripheral microcirculation. Am Heart J. 1998; 136: 320328. 19. Pope SE, Stinson EB, Daughters GT 2nd, Schroeder JS, Ingels NB Jr, Alderman EL. Exercise response of the denervated heart in long-term cardiac transplant recipients. Am J Cardiol. 1980; 46: 213-218. 20. Paulus WJ, Bronzwaer JG, Felice H, Kishan N, Wellens F. Deficient acceleration of left ventricular relaxation during exercise after heart transplantation. Circulation. 1992; 86: 1175-1185. 21. Haykowsky M, Eves N, Figgures L, McLean A, Koller M, Taylor D, Tymchak W. Effect of exercise training on VO2peak and left ventricular systolic function in recent cardiac transplant recipients. Am J Cardiol. 2005; 95: 1002-1004. 22. Sanchez H, Bigard X, Veksler V, Mettauer B, Lampert E, Lonsdorfer J, Ventura-Clapier R. Immunosuppressive treatment affects cardiac and skeletal muscle mitochondria by the toxic effect of vehicle. J Mol Cell Cardiol. 2000; 32: 323-331.  61  23. Marconi C. Pathophysiology of cardiac transplantation and the challenge of exercise. Int J Sports Med. 2000; 21 Suppl 2: S106-8. 24. Zoll J, N'Guessan B, Ribera F, Lampert E, Fortin D, Veksler V, Bigard X, Geny B, Lonsdorfer J, Ventura-Clapier R, Mettauer B. Preserved response of mitochondrial function to short-term endurance training in skeletal muscle of heart transplant recipients. J Am Coll Cardiol. 2003; 42: 126-132. 25. Montero CG, Martinez AJ. Neuropathology of heart transplantation: 23 cases. Neurology. 1986; 36: 1149-1154. 26. Mayer TO, Biller J, O'Donnell J, Meschia JF, Sokol DK. Contrasting the neurologic complications of cardiac transplantation in adults and children. J Child Neurol. 2002; 17: 195-199. 27. Belvis R, Marti-Fabregas J, Cocho D, Garcia-Bargo MD, Franquet E, Agudo R, Brosa V, Camprecios M, Puig M, Marti-Vilalta JL. Cerebrovascular disease as a complication of cardiac transplantation. Cerebrovasc Dis. 2005; 19: 267-271. 28. Zierer A, Melby SJ, Voeller RK, Guthrie TJ, Al-Dadah AS, Meyers BF, Pasque MK, Ewald GA, Moon MR, Moazami N. Significance of neurologic complications in the modern era of cardiac transplantation. Ann Thorac Surg. 2007; 83: 1684-1690. 29. Inoue K, Luth JU, Pottkamper D, Strauss KM, Minami K, Reichelt W. Incidence and risk factors of perioperative cerebral complications. Heart transplantation compared to coronary artery bypass grafting and valve surgery. J Cardiovasc Surg (Torino). 1998; 39: 201-208.  62  30. Massaro AR, Dutra AP, Almeida DR, Diniz RV, Malheiros SM. Transcranial Doppler assessment of cerebral blood flow: effect of cardiac transplantation. Neurology. 2006; 66: 124-126. 31. Gruhn N, Larsen FS, Boesgaard S, Knudsen GM, Mortensen SA, Thomsen G, Aldershvile J. Cerebral blood flow in patients with chronic heart failure before and after heart transplantation. Stroke. 2001; 32: 2530-2533. 32. Choi BR, Kim JS, Yang YJ, Park KM, Lee CW, Kim YH, Hong MK, Song JK, Park SW, Park SJ, Kim JJ. Factors associated with decreased cerebral blood flow in congestive heart failure secondary to idiopathic dilated cardiomyopathy. Am J Cardiol. 2006; 97: 13651369. 33. Ainslie PN, Duffin J. Integration of cerebrovascular CO 2 reactivity and chemoreflex control of breathing: mechanisms of regulation, measurement, and interpretation. Am J Physiol Regul Integr Comp Physiol. 2009; 296: R1473-95. 34. Rowell LB. Control of regional blood flow during dynamic exercise. In: Rowell LB, ed. Human Cardiovascular Control. New York: Oxford University Press; 1993: 204-254. 35. Peters A, Schweiger U, Pellerin L, Hubold C, Oltmanns KM, Conrad M, Schultes B, Born J, Fehm HL. The selfish brain: competition for energy resources. Neurosci Biobehav Rev. 2004; 28: 143-180. 36. Edvinsson L. Neurogenic mechanisms in the cerebrovascular bed. Autonomic nerves, amine receptors and their effects on cerebral blood flow. Acta Physiol Scand Suppl. 1975; 427: 1-35. 37. Moore CI, Cao R. The hemo-neural hypothesis: on the role of blood flow in information processing. J Neurophysiol. 2008; 99: 2035-2047.  63  38. Sandor P. Nervous control of the cerebrovascular system: doubts and facts. Neurochem Int. 1999; 35: 237-259. 39. Edvinsson L, Uddman R, Juul R. Peptidergic innervation of the cerebral circulation. Role in subarachnoid hemorrhage in man. Neurosurg Rev. 1990; 13: 265-272. 40. Bonica JJ. Autonomic innervation of the viscera in relation to nerve block. Anesthesiology. 1968; 29: 793-813. 41. Truijen J, van Lieshout JJ. Parasympathetic control of blood flow to the activated human brain. Exp Physiol. 2010; 95: 980-981. 42. Levine BD, Zhang R. Comments on Point:Counterpoint: Sympathetic activity does/does not influence cerebral blood flow. Autonomic control of the cerebral circulation is most important for dynamic cerebral autoregulation. J Appl Physiol. 2008; 105: 1369-1373. 43. Strandgaard S, Sigurdsson ST. Last Word on Point:Counterpoint: Sympathetic nervous activity does/does not influence cerebral blood flow. J Appl Physiol. 2008; 105: 1375. 44. Strandgaard S, Sigurdsson ST. Point:Counterpoint: Sympathetic activity does/does not influence cerebral blood flow. Counterpoint: Sympathetic nerve activity does not influence cerebral blood flow. J Appl Physiol. 2008; 105: 1366-7; discussion 1367-8. 45. van Lieshout JJ, Secher NH. Last Word on Point:Counterpoint: Sympathetic activity does/does not influence cerebral blood flow. J Appl Physiol. 2008; 105: 1374. 46. van Lieshout JJ, Secher NH. Point:Counterpoint: Sympathetic activity does/does not influence cerebral blood flow. Point: Sympathetic activity does influence cerebral blood flow. J Appl Physiol. 2008; 105: 1364-1366. 47. Ainslie PN, Tzeng YC. On the regulation of the blood supply to the brain: old age concepts and new age ideas. J Appl Physiol. 2010; 108: 1447-1449.  64  48. Zhang R, Zuckerman JH, Giller CA, Levine BD. Transfer function analysis of dynamic cerebral autoregulation in humans. Am J Physiol. 1998; 274: H233-41. 49. Zhang R, Zuckerman JH, Iwasaki K, Wilson TE, Crandall CG, Levine BD. Autonomic neural control of dynamic cerebral autoregulation in humans. Circulation. 2002; 106: 1814-1820. 50. Ainslie PN. Have a safe night: intimate protection against cerebral hyperperfusion during REM sleep. J Appl Physiol. 2009; 106: 1031-1033. 51. Tzeng YC, Willie CK, Atkinson G, Lucas SJ, Wong A, Ainslie PN. Cerebrovascular regulation during transient hypotension and hypertension in humans. Hypertension. 2010; 56: 268-273. 52. Cassaglia PA, Griffiths RI, Walker AM. Cerebral sympathetic nerve activity has a major regulatory role in the cerebral circulation in REM sleep. J Appl Physiol. 2009; 106: 10501056. 53. Seifert T, Fisher JP, Young CN, Hartwich D, Ogoh S, Raven PB, Fadel PJ, Secher NH. Glycopyrrolate abolishes the exercise-induced increase in cerebral perfusion in humans. Exp Physiol. 2010; . 54. Paton JF, Boscan P, Pickering AE, Nalivaiko E. The yin and yang of cardiac autonomic control: vago-sympathetic interactions revisited. Brain Res Brain Res Rev. 2005; 49: 555565. 55. Bristow MR. The surgically denervated, transplanted human heart. Circulation. 1990; 82: 658-660.  65  56. Bengel FM, Ueberfuhr P, Hesse T, Schiepel N, Ziegler SI, Scholz S, Nekolla SG, Reichart B, Schwaiger M. Clinical determinants of ventricular sympathetic reinnervation after orthotopic heart transplantation. Circulation. 2002; 106: 831-835. 57. Kao AC, Van Trigt P 3rd, Shaeffer-McCall GS, Shaw JP, Kuzil BB, Page RD, Higginbotham MB. Allograft diastolic dysfunction and chronotropic incompetence limit cardiac output response to exercise two to six years after heart transplantation. J Heart Lung Transplant. 1995; 14: 11-22. 58. Levick JR. An introduction to cardiovascular physiology. London: Arnold; 2003. 59. Scheinberg P. Cerebral circulation in heart failure. Am J Med. 1950; 8: 148-152. 60. Kety SS, Schmidt CF. The determination of cerebral blood flow in man by use of nitrous oxide in low concentrations. Am J Physiol. 1945; 53-66. 61. Schieve JF, Scheinberg P, Wilson WP. The effect of adrenocorticotrophic hormone (ACTH) on cerebral blood flow and metabolism. J Clin Invest. 1951; 30: 1527-1529. 62. Sensenbach W, Madison L, Eisenberg S. Cerebral hemodynamic and metabolic studies in patients with congestive heart failure. I. Observations in lucid subjects. Circulation. 1960; 21: 697-703. 63. Eisenberg S, Madison L, Sensenbach W. Cerebral hemodynamic and metabolic studies in patients with congestive heart failure. II. Observations in confused subjects. Circulation. 1960; 21: 704-709. 64. Andrews PM, Panuska JA, Felicetti CL, Joyce RA. Cardiovascular responses of the unanesthetized and unrestrained hypothermic rat. J Appl Physiol. 1969; 27: 539-543. 65. Shapiro W, Chawla NP. Observations on the regulation of cerebral blood flow in complete heart block. Circulation. 1969; 40: 863-870.  66  66. Davis DH, Sundt TM Jr. Relationship of cerebral blood flow to cardiac output, mean arterial pressure, blood volume, and alpha and beta blockade in cats. J Neurosurg. 1980; 52: 745-754. 67. Moustafa HF, Hopewell JW. Age-related changes in cardiac output, cephalic and cerebral blood flow in the rat. Int J Appl Radiat Isot. 1981; 32: 309-312. 68. Cook PJ, Maidment CG, Dandona P, Hutton RA, James IM. The effect of intravenous epoprostenol (prostacyclin, PGI2) on cerebral blood flow and cardiac output in man. Br J Clin Pharmacol. 1983; 16: 707-711. 69. Hermansen MC, Kotagal UR, Kleinman LI. The effect of metabolic acidosis upon autoregulation of cerebral blood flow in newborn dogs. Brain Res. 1984; 324: 101-105. 70. Barrington KJ, Ryan CA, Peliowski A, Nosko M, Finer NN. The effects of negative pressure external high frequency oscillation on cerebral blood flow and cardiac output of the monkey. Pediatr Res. 1987; 21: 166-169. 71. Mutch WA, Patel PM, Ruta TS. A comparison of the cerebral pressure-flow relationship for halothane and isoflurane at haemodynamically equivalent end-tidal concentrations in the rabbit. Can J Anaesth. 1990; 37: 223-230. 72. van der Giessen WJ, Duncker DJ, Saxena PR, Verdouw PD. Nimodipine has no effect on the cerebral circulation in conscious pigs, despite an increase in cardiac output. Br J Pharmacol. 1990; 100: 277-282. 73. Bouma GJ, Muizelaar JP. Relationship between cardiac output and cerebral blood flow in patients with intact and with impaired autoregulation. J Neurosurg. 1990; 73: 368-374.  67  74. Levine BD, Giller CA, Lane LD, Buckey JC, Blomqvist CG. Cerebral versus systemic hemodynamics during graded orthostatic stress in humans. Circulation. 1994; 90: 298306. 75. Ide K, Pott F, Van Lieshout JJ, Secher NH. Middle cerebral artery blood velocity depends on cardiac output during exercise with a large muscle mass. Acta Physiol Scand. 1998; 162: 13-20. 76. Larsen FS, Strauss G, Knudsen GM, Herzog TM, Hansen BA, Secher NH. Cerebral perfusion, cardiac output, and arterial pressure in patients with fulminant hepatic failure. Crit Care Med. 2000; 28: 996-1000. 77. Wilson TE, Cui J, Zhang R, Witkowski S, Crandall CG. Skin cooling maintains cerebral blood flow velocity and orthostatic tolerance during tilting in heated humans. J Appl Physiol. 2002; 93: 85-91. 78. Joseph M, Ziadi S, Nates J, Dannenbaum M, Malkoff M. Increases in cardiac output can reverse flow deficits from vasospasm independent of blood pressure: a study using xenon computed tomographic measurement of cerebral blood flow. Neurosurgery. 2003; 53: 1044-51; discussion 1051-2. 79. Brown CM, Dutsch M, Hecht MJ, Neundorfer B, Hilz MJ. Assessment of cerebrovascular and cardiovascular responses to lower body negative pressure as a test of cerebral autoregulation. J Neurol Sci. 2003; 208: 71-78. 80. Kusaka T, Okubo K, Nagano K, Isobe K, Itoh S. Cerebral distribution of cardiac output in newborn infants. Arch Dis Child Fetal Neonatal Ed. 2005; 90: F77-8.  68  81. Ogoh S, Brothers RM, Barnes Q, Eubank WL, Hawkins MN, Purkayastha S, O-Yurvati A, Raven PB. The effect of changes in cardiac output on middle cerebral artery mean blood velocity at rest and during exercise. J Physiol. 2005; 569: 697-704. 82. Dombrowski SM, Schenk S, Leichliter A, Leibson Z, Fukamachi K, Luciano MG. Chronic hydrocephalus-induced changes in cerebral blood flow: mediation through cardiac effects. J Cereb Blood Flow Metab. 2006; 26: 1298-1310. 83. Ogoh S, Dalsgaard MK, Secher NH, Raven PB. Dynamic blood pressure control and middle cerebral artery mean blood velocity variability at rest and during exercise in humans. Acta Physiol (Oxf). 2007; 191: 3-14. 84. Ogawa Y, Iwasaki K, Aoki K, Shibata S, Kato J, Ogawa S. Central hypervolemia with hemodilution impairs dynamic cerebral autoregulation. Anesth Analg. 2007; 105: 1389-96, table of contents. 85. Ogoh S, Tzeng YC, Lucas SJ, Galvin SD, Ainslie PN. Influence of baroreflex-mediated tachycardia on the regulation of dynamic cerebral perfusion during acute hypotension in humans. J Physiol. 2010; 588: 365-371. 86. Deegan BM, Devine ER, Geraghty MC, Jones E, Olaighin G, Serrador JM. The relationship between cardiac output and dynamic cerebral autoregulation in humans. J Appl Physiol. 2010; . 87. Malkoff M. Cerebral blood flow physiology and metabolism. In: Torbey MT, ed. Neurocritical Care. New York: Cambridge University Press; 2009: 1-10. 88. Tiecks FP, Lam AM, Aaslid R, Newell DW. Comparison of static and dynamic cerebral autoregulation measurements. Stroke. 1995; 26: 1014-1019.  69  89. Lucas SJ, Tzeng YC, Galvin SD, Thomas KN, Ogoh S, Ainslie PN. Influence of changes in blood pressure on cerebral perfusion and oxygenation. Hypertension. 2010; 55: 698705. 90. Aries MJ, Elting JW, De Keyser J, Kremer BP, Vroomen PC. Cerebral autoregulation in stroke: a review of transcranial Doppler studies. Stroke. 2010; 41: 2697-2704. 91. Lassen NA. Cerebral blood flow and oxygen consumption in man. Physiol Rev. 1959; 39: 183-238. 92. Paulson OB, Strandgaard S, Edvinsson L. Cerebral autoregulation. Cerebrovasc Brain Metab Rev. 1990; 2: 161-192. 93. Tzeng YC, Lucas SJ, Atkinson G, Willie CK, Ainslie PN. Fundamental relationships between arterial baroreflex sensitivity and dynamic cerebral autoregulation in humans. J Appl Physiol. 2010; 108: 1162-1168. 94. Serrador JM, Sorond FA, Vyas M, Gagnon M, Iloputaife ID, Lipsitz LA. Cerebral pressure-flow relations in hypertensive elderly humans: transfer gain in different frequency domains. J Appl Physiol. 2005; 98: 151-159. 95. Hetzel A, Reinhard M, Guschlbauer B, Braune S. Challenging cerebral autoregulation in patients with preganglionic autonomic failure. Clin Auton Res. 2003; 13: 27-35. 96. Duschek S, Hadjamu M, Schandry R. Enhancement of cerebral blood flow and cognitive performance following pharmacological blood pressure elevation in chronic hypotension. Psychophysiol. 2007; 44: 145-153. 97. Koskinen P, Virolainen J, Koskinen PK, Hayry P, Kupari M. Evolution of heart rate variability in cardiac transplant recipients: a clinical study. J Intern Med. 1996; 239: 443449.  70  98. van de Borne P, Montano N, Narkiewicz K, Degaute JP, Oren R, Pagani M, Somers VK. Sympathetic rhythmicity in cardiac transplant recipients. Circulation. 1999; 99: 16061610. 99. Hughson RL, Maillet A, Dureau G, Yamamoto Y, Gharib C. Spectral analysis of blood pressure variability in heart transplant patients. Hypertension. 1995; 25: 643-650. 100. Ogoh S, Ainslie PN. Cerebral blood flow during exercise: mechanisms of regulation. J Appl Physiol. 2009; 107: 1370-1380. 101. Willie CK, Colino FL, Tzeng YC, Binstead G, Jones LW, Haykowsky MJ, Bellapart J, Ogoh S, Smith KJ, Smirl JD, Ainslie PN. Utility of transcranial Doppler ultrasound for the integrative assessment of cerebrovascular function. Journal of Neuroscience Methods. 2011; 196(2): 221-37. 102. Brian JE Jr, Faraci FM, Heistad DD. Recent insights into the regulation of cerebral circulation. Clin Exp Pharmacol Physiol. 1996; 23: 449-457. 103. Busija DW, Heistad DD. Factors involved in the physiological regulation of the cerebral circulation. Rev Physiol Biochem Pharmacol. 1984; 101: 161-211. 104. Atkinson JL, Anderson RE, Sundt TM Jr. The effect of carbon dioxide on the diameter of brain capillaries. Brain Res. 1990; 517: 333-340. 105. Ogoh S, Hayashi N, Inagaki M, Ainslie PN, Miyamoto T. Interaction between the ventilatory and cerebrovascular responses to hypo- and hypercapnia at rest and during exercise. J Physiol. 2008; 586: 4327-4338. 106. Peebles KC, Richards AM, Celi L, McGrattan K, Murrell CJ, Ainslie PN. Human cerebral arteriovenous vasoactive exchange during alterations in arterial blood gases. J Appl Physiol. 2008; 105: 1060-1068.  71  107. Ainslie PN, Murrell C, Peebles K, Swart M, Skinner MA, Williams MJ, Taylor RD. Early morning impairment in cerebral autoregulation and cerebrovascular CO2 reactivity in healthy humans: relation to endothelial function. Exp Physiol. 2007; 92: 769-777. 108. Lavi S, Gaitini D, Milloul V, Jacob G. Impaired cerebral CO2 vasoreactivity: association with endothelial dysfunction. Am J Physiol Heart Circ Physiol. 2006; 291: H1856-61. 109. Hoth KF, Tate DF, Poppas A, Forman DE, Gunstad J, Moser DJ, Paul RH, Jefferson AL, Haley AP, Cohen RA. Endothelial function and white matter hyperintensities in older adults with cardiovascular disease. Stroke. 2007; 38: 308-312. 110. Markus H, Cullinane M. Severely impaired cerebrovascular reactivity predicts stroke and TIA risk in patients with carotid artery stenosis and occlusion. Brain. 2001; 124: 457467. 111. Markus HS, Boland M. "Cognitive activity" monitored by non-invasive measurement of cerebral blood flow velocity and its application to the investigation of cerebral dominance. Cortex. 1992; 28: 575-581. 112. Kannel WB, Belanger AJ. Epidemiology of heart failure. Am Heart J. 1991; 121: 951957. 113. Boilson BA, Raichlin E, Park SJ, Kushwaha SS. Device therapy and cardiac transplantation for end-stage heart failure. Curr Probl Cardiol. 2010; 35: 8-64. 114. Pressler SJ. Cognitive functioning and chronic heart failure: a review of the literature (2002-July 2007). J Cardiovasc Nurs. 2008; 23: 239-249.  72  115. Zuccala G, Pedone C, Cesari M, Onder G, Pahor M, Marzetti E, Lo Monaco MR, Cocchi A, Carbonin P, Bernabei R. The effects of cognitive impairment on mortality among hospitalized patients with heart failure. Am J Med. 2003; 115: 97-103. 116. Wasserman AJ, Patterson JL Jr. The cerebral vascular response to reduction in arterial carbon dioxide tension. J Clin Invest. 1961; 40: 1297-1303. 117. Kety SS, Schmidt CF. The effects of altered arterial tensions of carbon dioxide and oxygen on cerebral blood flow and cerebral oxygen consumption of normal young men. J Clin Invest. 1948; 27: 484-492. 118. Mandell DM, Han JS, Poublanc J, Crawley AP, Kassner A, Fisher JA, Mikulis DJ. Selective reduction of blood flow to white matter during hypercapnia corresponds with leukoaraiosis. Stroke. 2008; 39: 1993-1998. 119. Secher NH, Seifert T, Van Lieshout JJ. Cerebral blood flow and metabolism during exercise: implications for fatigue. J Appl Physiol. 2008; 104: 306-314. 120. Moraine JJ, Lamotte M, Berre J, Niset G, Leduc A, Naeije R. Relationship of middle cerebral artery blood flow velocity to intensity during dynamic exercise in normal subjects. Eur J Appl Physiol Occup Physiol. 1993; 67: 35-38. 121. Hellstrom G, Fischer-Colbrie W, Wahlgren NG, Jogestrand T. Carotid artery blood flow and middle cerebral artery blood flow velocity during physical exercise. J Appl Physiol. 1996; 81: 413-418. 122. Ogoh S, Dalsgaard MK, Yoshiga CC, Dawson EA, Keller DM, Raven PB, Secher NH. Dynamic cerebral autoregulation during exhaustive exercise in humans. Am J Physiol Heart Circ Physiol. 2005; 288: H1461-7.  73  123. Burra P, Senzolo M, Pizzolato G, Tursi V, Livi U, Chierichetti F, Dam M. Frontal cerebral blood flow is impaired in patients with heart transplantation. Transpl Int. 2002; 15: 459-462. 124. Hoth KF, Poppas A, Moser DJ, Paul RH, Cohen RA. Cardiac dysfunction and cognition in older adults with heart failure. Cogn Behav Neurol. 2008; 21: 65-72. 125. Schall RR, Petrucci RJ, Brozena SC, Cavarocchi NC, Jessup M. Cognitive function in patients with symptomatic dilated cardiomyopathy before and after cardiac transplantation. J Am Coll Cardiol. 1989; 14: 1666-1672. 126. Bornstein RA, Starling RC, Myerowitz PD, Haas GJ. Neuropsychological function in patients with end-stage heart failure before and after cardiac transplantation. Acta Neurol Scand. 1995; 91: 260-265. 127. Roman DD, Kubo SH, Ormaza S, Francis GS, Bank AJ, Shumway SJ. Memory improvement following cardiac transplantation. J Clin Exp Neuropsychol. 1997; 19: 692697. 128. Zuccala G, Onder G, Pedone C, Carosella L, Pahor M, Bernabei R, Cocchi A, GIFAONLUS Study Group [Grupo Italiano di Farmacoepidemiologia nell'Anzanio]. Hypotension and cognitive impairment: Selective association in patients with heart failure. Neurology. 2001; 57: 1986-1992. 129. Almeida OP, Flicker L. The mind of a failing heart: a systematic review of the association between congestive heart failure and cognitive functioning. Intern Med J. 2001; 31: 290-295. 130. Sila CA. Cognitive impairment in chronic heart failure. Cleve Clin J Med. 2007; 74 Suppl 1: S132-7.  74  131. Alves TC, Rays J, Fraguas R Jr, Wajngarten M, Meneghetti JC, Prando S, Busatto GF. Localized cerebral blood flow reductions in patients with heart failure: a study using 99mTc-HMPAO SPECT. J Neuroimaging. 2005; 15: 150-156. 132. Siachos T, Vanbakel A, Feldman DS, Uber W, Simpson KN, Pereira NL. Silent strokes in patients with heart failure. J Card Fail. 2005; 11: 485-489. 133. Woo MA, Macey PM, Fonarow GC, Hamilton MA, Harper RM. Regional brain gray matter loss in heart failure. J Appl Physiol. 2003; 95: 677-684. 134. Almenar-Pertejo M, Almenar L, Martinez-Dolz L, Campos J, Galan J, Girones P, Ortega F, Ortega T, Rebollo P, Salvador A. Study on health-related quality of life in patients with advanced heart failure before and after transplantation. Transplant Proc. 2006; 38: 2524-2526. 135. Bornstein RA, Starling RC, Myerowitz PD, Haas GJ. Neuropsychological function in patients with end-stage heart failure before and after cardiac transplantation. Acta Neurol Scand. 1995; 91: 260-265. 136. Baron JC. Perfusion thresholds in human cerebral ischemia: historical perspective and therapeutic implications. Cerebrovasc Dis. 2001; 11 Suppl 1: 2-8. 137. Sundt TM Jr, Sharbrough FW, Anderson RE, Michenfelder JD. Cerebral blood flow measurements and electroencephalograms during carotid endarterectomy. J Neurosurg. 2007; 107: 887-897. 138. Ackerman RH. Cerebral blood flow and neurological change in chronic heart failure. Stroke. 2001; 32: 2462-2464. 139. Roman GC. Brain hypoperfusion: a critical factor in vascular dementia. Neurol Res. 2004; 26: 454-458.  75  140. Haddad H, Isaac D, Legare JF, Pflugfelder P, Hendry P, Chan M, Cantin B, Giannetti N, Zieroth S, White M, Warnica W, Doucette K, Rao V, Dipchand A, Cantarovich M, Kostuk W, Cecere R, Charbonneau E, Ross H, Poirier N. Canadian Cardiovascular Society Consensus Conference update on cardiac transplantation 2008: Executive Summary. Can J Cardiol. 2009; 25: 197-205. 141. Loncar G, Bozic B, Lepic T, Dimkovic S, Prodanovic N, Radojicic Z, Cvorovic V, Markovic N, Brajovic M, Despotovic N, Putnikovic B, Popovic-Brkic V. Relationship of reduced cerebral blood flow and heart failure severity in elderly males. Aging Male. 2011; 14: 59-65. 142. Paulson OB, Jarden JO, Godtfredsen J, Vorstrup S. Cerebral blood flow in patients with congestive heart failure treated with captopril. Am J Med. 1984; 76: 91-95. 143. Paulson OB, Jarden JO, Vorstrup S, Holm S, Godtfredsen J. Effect of captopril on the cerebral circulation in chronic heart failure. Eur J Clin Invest. 1986; 16: 124-132. 144. Furuang L, Siennicki-Lantz A, Elmstahl S. Reduced cerebral perfusion in elderly men with silent myocardial ischaemia and nocturnal blood pressure dipping. Atherosclerosis. 2011; 214: 231-236. 145. Crossman D. The future of the management of ischaemic heart disease. BMJ. 1997; 314: 356-359. 146. Marshall DP. Ischaemic heart disease, cardiac surgery and heart/heart-lung transplantation reviewed from a haematological perspective. Br J Biomed Sci. 1993; 50: 212-220.  76  147. Hildebrandt A, Reichenspurner H, Reichart B. Heart transplantation--the treatment of choice for patients with end-stage ischaemic heart disease. Thorac Cardiovasc Surg. 1989; 37: 37-41. 148. Kawabori M, Kuroda S, Terasaka S, Nakayama N, Matsui Y, Kubota S, Nakamura M, Nakanishi K, Okamoto F, Iwasaki Y. Therapeutic strategies for patients with internal carotid or middle cerebral artery occlusion complicated by severe coronary artery disease. World Neurosurg. 2010; 73: 345-350. 149. Moraca R, Lin E, Holmes JH,4th, Fordyce D, Campbell W, Ditkoff M, Hill M, Guyton S, Paull D, Hall RA. Impaired baseline regional cerebral perfusion in patients referred for coronary artery bypass. J Thorac Cardiovasc Surg. 2006; 131: 540-546. 150. Rajagopalan B, Raine AE, Cooper R, Ledingham JG. Changes in cerebral blood flow in patients with severe congestive cardiac failure before and after captopril treatment. Am J Med. 1984; 76: 86-90. 151. Ainslie PN, Cotter JD, George KP, Lucas S, Murrell C, Shave R, Thomas KN, Williams MJ, Atkinson G. Elevation in cerebral blood flow velocity with aerobic fitness throughout healthy human ageing. J Physiol. 2008; 586: 4005-4010. 152. Hachamovitch R, Brown HV, Rubin SA. Respiratory and circulatory analysis of CO2 output during exercise in chronic heart failure. Circulation. 1991; 84: 605-612. 153. Hanly P, Zuberi N, Gray R. Pathogenesis of Cheyne-Stokes respiration in patients with congestive heart failure. Relationship to arterial PCO2. Chest. 1993; 104: 1079-1084. 154. Hanly PJ, Millar TW, Steljes DG, Baert R, Frais MA, Kryger MH. Respiration and abnormal sleep in patients with congestive heart failure. Chest. 1989; 96: 480-488.  77  155. Bradley TD, Takasaki Y, Orr D, Popkin J, Liu P, Rutherford R. Sleep apnea in patients with left ventricular dysfunction: beneficial effects of nasal CPAP. Prog Clin Biol Res. 1990; 345: 363-70. 156. Jansen GF, Krins A, Basnyat B. Cerebral vasomotor reactivity at high altitude in humans. J Appl Physiol. 1999; 86: 681-686. 157. Gidaspow D, Huang J. Kinetic theory based model for blood flow and its viscosity. Ann Biomed Eng. 2009; 37: 1534-1545. 158. Baufreton C, Pinaud F, Corbeau JJ, Chevailler A, Jolivot D, Ter Minassian A, Henrion D, De Brux JL. Increased cerebral blood flow velocities assessed by transcranial doppler examination is associated with complement activation after cardiopulmonary bypass. Perfusion. 2010; 26(2): 91-98. 159. Toledo E, Pinhas I, Aravot D, Almog Y, Akselrod S. Functional restitution of cardiac control in heart transplant patients. Am J Physiol Regul Integr Comp Physiol. 2002; 282: R900-908. 160. Kavanagh T. Exercise rehabilitation in cardiac transplantation patients: a comprehensive review. Eura Medicophys. 2005; 41: 67-74. 161. Hayman MA, Nativi JN, Stehlik J, McDaniel J, Fjeldstad AS, Ives SJ, Wray DW, Bader F, Gilbert EM, Richardson RS. Understanding Exercise-induced Hyperemia: Central and Peripheral Hemodynamic Responses to Passive Limb Movement in Heart Transplant Recipients. Am J Physiol Heart Circ Physiol. 2010; 299(5): H1653-9. 162. Aaslid R, Markwalder TM, Nornes H. Noninvasive transcranial Doppler ultrasound recording of flow velocity in basal cerebral arteries. J Neurosurg. 1982; 57: 769-774.  78  163. Giller CA, Hatab MR, Giller AM. Estimation of vessel flow and diameter during cerebral vasospasm using transcranial Doppler indices. Neurosurgery. 1998; 42: 1076-82. 164. Lindegaard KF, Lundar T, Wiberg J, Sjoberg D, Aaslid R, Nornes H. Variations in middle cerebral artery blood flow investigated with noninvasive transcranial blood velocity measurements. Stroke. 1987; 18: 1025-1030. 165. Poulin MJ, Robbins PA. Indexes of flow and cross-sectional area of the middle cerebral artery using doppler ultrasound during hypoxia and hypercapnia in humans. Stroke. 1996; 27: 2244-2250. 166. Serrador JM, Picot PA, Rutt BK, Shoemaker JK, Bondar RL. MRI measures of middle cerebral artery diameter in conscious humans during simulated orthostasis. Stroke. 2000; 31: 1672-1678. 167. Valdueza JM, Balzer JO, Villringer A, Vogl TJ, Kutter R, Einhaupl KM. Changes in blood flow velocity and diameter of the middle cerebral artery during hyperventilation: assessment with MR and transcranial Doppler sonography. Am J Neuroradiol. 1997; 18: 1929-1934. 168. Nuttall GA, Cook DJ, Fulgham JR, Oliver WC Jr, Proper JA. The relationship between cerebral blood flow and transcranial Doppler blood flow velocity during hypothermic cardiopulmonary bypass in adults. Anesth Analg. 1996; 82: 1146-1151. 169. ter Minassian A, Melon E, Leguerinel C, Lodi CA, Bonnet F, Beydon L. Changes in cerebral blood flow during PaCO2 variations in patients with severe closed head injury: comparison between the Fick and transcranial Doppler methods. J Neurosurg. 1998; 88: 996-1001.  79  170. Moppett IK, Mahajan RP. Transcranial Doppler ultrasonography in anaesthesia and intensive care. Br J Anaesth. 2004; 93: 710-724. 171. Matteis M, Troisi E, Monaldo BC, Caltagirone C, Silvestrini M. Age and sex differences in cerebral hemodynamics: a transcranial Doppler study. Stroke. 1998; 29: 963-967. 172. Niehaus L, Lehmann R, Roricht S, Meyer BU. Age-related reduction in visually evoked cerebral blood flow responses. Neurobiol Aging. 2001; 22: 35-38. 173. Buijs PC, Krabbe-Hartkamp MJ, Bakker CJ, de Lange EE, Ramos LM, Breteler MM, Mali WP. Effect of age on cerebral blood flow: measurement with ungated twodimensional phase-contrast MR angiography in 250 adults. Radiology. 1998; 209: 667674. 174. Fotenos AF, Snyder AZ, Girton LE, Morris JC, Buckner RL. Normative estimates of cross-sectional and longitudinal brain volume decline in aging and Alzheimer's Disease. Neurology. 2005; 64: 1032-1039. 175. Pantano P, Baron JC, Lebrun-Grandie P, Duquesnoy N, Bousser MG, Comar D. Regional cerebral blood flow and oxygen consumption in human aging. Stroke. 1984; 15: 635-641. 176. Marsden KR, Haykowsky MJ, Smirl JD, Jones H, Nelson MD, Altamirano-Diaz LA, Gelinas JC, Tzeng YC, Smith KJ, Willie CK, Bailey DM, Ainslie PN. Aging blunts hyperventilation-induced hypocapnia and reduction in cerebral blood flow velocity during maximal exercise. Age (Dordr). 2011; [Epub ahead of print]. 177. Edelman NH, Mittman C, Norris AH, Shock NW. Effects of respiratory pattern on age differences in ventilation uniformity. J Appl Physiol. 1968; 24: 49-53.  80  178. Turner JM, Mead J, Wohl ME. Elasticity of human lungs in relation to age. J Appl Physiol. 1968; 25: 664-671. 179. Chen HI, Kuo CS. Relationship between respiratory muscle function and age, sex, and other factors. J Appl Physiol. 1989; 66: 943-948. 180. Kronenberg RS, Drage CW. Attenuation of the ventilatory and heart rate responses to hypoxia and hypercapnia with aging in normal men. J Clin Invest. 1973; 52: 1812-1819. 181. Peterson DD, Pack AI, Silage DA, Fishman AP. Effects of aging on ventilatory and occlusion pressure responses to hypoxia and hypercapnia. Am Rev Respir Dis. 1981; 124: 387-391. 182. Pitts RF, Ayer JL, Schiess WA, Miner P. The Renal Regulation of Acid-Base Balance in Man. Iii. the Reabsorption and Excretion of Bicarbonate. J Clin Invest. 1949; 28: 35-44. 183. Frassetto L, Sebastian A. Age and systemic acid-base equilibrium: analysis of published data. J Gerontol A Biol Sci Med Sci. 1996; 51: B91-9. 184. Colloca G, Santoro M, Gambassi G. Age-related physiologic changes and perioperative management of elderly patients. Surg Oncol. 2010; 19: 124-130. 185. Janssens JP, Pache JC, Nicod LP. Physiological changes in respiratory function associated with ageing. Eur Respir J. 1999; 13: 197-205. 186. Rowell LB, Blackmon JR. Human cardiovascular adjustments to acute hypoxaemia. Clin Physiol. 1987; 7: 349-376. 187. Laurent S, Cockcroft J, Van Bortel L, Boutouyrie P, Giannattasio C, Hayoz D, Pannier B, Vlachopoulos C, Wilkinson I, Struijker-Boudier H, European Network for Noninvasive Investigation of Large Arteries. Expert consensus document on arterial stiffness: methodological issues and clinical applications. Eur Heart J. 2006; 27: 2588-2605.  81  188. Marinoni M, Ginanneschi A, Forleo P, Amaducci L. Technical limits in transcranial Doppler recording: inadequate acoustic windows. Ultrasound Med Biol. 1997; 23: 12751277. 189. Ogoh S, Ainslie PN. Cerebral blood flow during exercise: mechanisms of regulation. J Appl Physiol. 2009; 107: 1370-1380.  82  Appendices  Appendix I: Participant Information Sheet  INFORMATION SHEET CARDIAC FUNCTION, CEREBRAL BLOOD FLOW AND ARTERIAL BLOOD PRESSURE DURING VENTILATORY CHALLENGE, CARDIAC UNLOADING AND CYCLE EXERCISE, IN HEART TRANSPLANT RECIPIENTS INVESTIGATORS M. Haykowsky, Ph.D. W. Tymchak, MD, FRCPC I. Paterson, MD, FRCPC R. Thompson, Ph.D. P. Ainslie, Ph.D.  U of A, Dept. of Physical Therapy U of A, Division of Cardiology U of A, Division of Cardiology U of A, Dept. of Biomedical Engineering UBCO, Human kinetics  (780) 492-5970 (780) 407-1574 (780) 407-7729 (780) 492-8665 (250) 807-8089  BACKGROUND AND PURPOSE Heart transplant recipients have reduced cardiac output (pumping capacity of the heart) during exercise or cardiac (un)loading (as occurs when going from lying to standing position quickly). The effect that reduced cardiac output reserve has on blood flow to the brain (called cerebral blood flow) has not been studied in heart transplant recipients. The aim of this study is to assess the acute effect of a ventilator challenge, cardiac unloading, and cycle exercise on cardiac function, cerebral blood flow and arterial blood pressure in heart transplant recipients and age-matched healthy individuals. DESCRIPTION OF THE STUDY If you decide to participate in this study, the total time commitment will be one extra visit (4 hours) at the Alberta Cardiovascular and Stroke Research Centre in the Mazankowski Alberta Heart Institute. Refusal to participate in this study will not affect your treatment at the University of Alberta Hospital. RESEARCH PROCEDURES Assessment of cardiac function, cerebral blood flow and arterial blood pressure during ventilatroy challenge. Prior to this test, we will measure your height and weight. A number of electrodes (electrical contacts) will be placed on your chest and connected to a computer to measure your heart rate. A small cuff will be placed on your finger to measure your blood pressure. A special headpiece with an ultrasound probed attached to it that will be positioned on your head to measure the blood flow to your brain. Some gel and an ultrasound probe will be placed on your chest to measure your cardiac function. You will also be fitted with a nose clip and will breathe through a special mask that will be attached to a computer that will analyze your oxygen uptake and carbon dioxide (CO 2) production. After resting measures are obtained, you will breathe a gas mixture (5% CO2 in 21% O2) for 3 min, followed by a brief recovery. You will then be asked to increase your breathing rate and depth for 3 minutes.  83  Assessment of cardiac function, cerebral blood flow and arterial blood pressure during cardiac unloading tests. After a 10-15 minute rest period of lying flat on your back, you will be instructed to sit up and stand as quickly as possible (within 3 seconds) during which time your heart rate, blood pressure and cerebral blood flow will be measured. After a brief rest period, you to lie on your back in a comfortable, relaxed position with your legs inside a custom built lower body pressure chamber. The chamber will be sealed snuggly around your waist. During the test, the pressure inside the chamber will be reduced with a household vacuum to alter the amount of blood returning to the heart. After a 5-miunte rest period, you will undergo three (-10 mmHg, -20mmHg and -40 mmHg for 10 minutes at each stage) levels of decreased pressure during which time your heart rate, blood pressure, heart function and cerebral blood flow will be measured. If you become lightheaded, dizzy, or your blood pressure begins to drop the test will be stopped. Assessment of cardiac function, cerebral blood flow and arterial blood pressure, during cycle exercise. After resting measures of your heart rate, blood pressure, cardiac function, cerebral blood flow and oxygen uptake (using a special mouthpiece and collection tube attached to a computer that measures your O2 consumption) are obtained, you will begin cycling at a comfortable speed and the resistance that you will pedal against will become more difficult every two minutes until you feel you are no longer able to continue cycling. This test will be test will be completed in 10-15 minutes. A specially trained health care worker will supervise the above tests. POSSIBLE BENEFITS This study will determine your heart function, cerebral blood flow and blood pressure during a ventilatory challenge, cardiac unloading and during cycle exercise. POSSIBLE RISKS During the lying to stand test you may feel lightheaded. During the lower body negative pressure test you may feel lightheaded or become unconscious, however, your heart rate, blood pressure, cardiac function and cerebral blood flow will be carefully monitored to prevent this from occurring. In addition, the pressure will be returned to normal immediately to reduce the feeling of light-headedness. The inflated finger cuff used to measure your blood pressure may result in a numb feeling that will disappear when the cuff is removed. The exercise that you will perform is considered safe. All testing and exercise sessions will be performed under appropriate supervision. Data from individuals with/without heart disease suggests that the likelihood of having a heart attack or dying during an exercise test is 1 in 10,000 tests. The mouthpiece that is used during the exercise test may make your mouth feel dry. You may also experience temporary muscle soreness after exercising. There are no adverse effects associated with cardiac or cerebral ultrasound. COSTS You will not have to pay for the tests that you will perform in this study. However, you may be coming to the University of Alberta more often than if you were not participating in this study. You will be reimbursed for your parking and food costs associated with participating in the study. CONTACTS Please contact the investigators listed below if you have any questions or concerns: M. Haykowsky, PhD at (780) 492-5970 W. Tymchak, MD FRCPC (780) 407-1574  84  CONFIDENTIALITY Personal records will be kept confidential. Only the persons listed above will have access to your data. Any report published as a result of this study will not identify you by name. For this study, the researchers will need to access your personal health records for health information such as medical history and test results. The health information collected as part of this study will be kept confidential unless release is required by law, and will be used only for the purpose of the research study. By signing the consent form you give permission to the study staff to access any personally identifiable health information which is under the custody of other health care professionals as deemed necessary for the conduct of the research. In addition to the investigators listed, the Health Research Ethics Board may have access to your personal health records to monitor the research and verify the accuracy of study data. By signing the consent form you give permission for the collection, use and disclosure of your medical records. Study information is required to be kept for 7 years. Even if you withdraw from the study, the medical information which is obtained from you for study purposes will not be destroyed. You have a right to check your health records and request changes if your personal information is incorrect. VOLUNTARY PARTICIPATION You are free to withdraw from this study at any time without giving a reason. If knowledge gained from this study or any other study becomes available which could influence your decision to continue, you will be promptly informed. If you have any questions or concerns about any aspect this study, you may contact the Health Research Ethics Board at 492-9724. This office has no affiliation with the study investigators.  85  Appendix II: Participant Consent Form CONSENT FORM CARDIAC FUNCTION, CEREBRAL BLOOD FLOW AND ARTERIAL BLOOD PRESSURE DURING VENTILATORY CHALLENGE, CARDIAC UNLOADING AND CYCLE EXERCISE, IN HEART TRANSPLANT RECIPIENTS  INVESTIGATORS M. Haykowsky, Ph.D. W. Tymchak, MD FRCPC I. Paterson, MD, FRCPC R. Thompson, Ph.D. P. Ainslie, Ph.D.  U of A, Dept. of Physical Therapy U of A, Division of Cardiology U of A, Division of Cardiology U of A, Dept. of Biomedical Engineering UBCO, Human kinetics  (780) 492-5970 (780) 407-1574 (780) 407-7729 (780) 492-8665 (250) 807-8089  Please answer the following questions: Do you understand that you are being asked to be in a research study?  Yes ___  No ___  Have you read and received a copy of an attached information sheet?  ___  ___  Do you understand the benefits and risks in taking part in this research study?  ___  ___  Have you had an opportunity to ask questions and discuss this study?  ___  ___  Do you understand that you are free to withdraw from the study at any time without having to give a reason and without affecting your future medical care?  ___  ___  Has the issue of confidentiality been explained to you, and do you understand who will have access to your medical records?  ___  ___  Do you want the investigators to inform you family doctor that you are participating in this study?  ___  ___  Who explained this study to you? I agree to take part in this study:  _______________________________________________ Yes No ___ ___  ________________________________________________ Signature of Participant  _________________ Date  ________________________________________________ Printed Name of Participant ________________________________________________ Signature of Witness  __________________ Date  I believe that the person signing this form understands what is involved in the study and voluntarily agrees to participate. ________________________________________________ __________________ Signature of Investigator or Designee Date  86  Appendix III: Literature Review of Cardiac Output on Cerebral Blood Flow Table 1.1. Summary of the current literature observing effects of cardiac output on cerebral blood flow Studya  Population (n)  CBF Technique  Intervention (n)  Schienber g 195059  CHF (14) (patients with anaemia were excluded)  Kety and Schmidt60 N2O technique  General observations  CBF ↓ 39% (40 vs 65 mL/min/100g), a-v O2 difference ↑ 41% (8.6 vs 6.1 volumes per cent). The Author noted: the means may not be directly comparable as the CHF mean age was 40 Male and female and normal were all under 30 and healthy males.  Schieve et al. 195161  Human subjects of varying health (14)  Kety and Schmidt 60 N2O technique  Adrenocorto -tropic Hormone intake  With Adrenocortotropic Hormone intake:  Kety and Schmidt60 N2O technique  Observation of CBF as compared to CHF classification state in lucid patients  CHF patients as compared to normal data:  Sensenbach et al. 196062  CHF (37): mild to moderate (24), severe (13) (patients with anaemia, pulmonary disease, renal disease or cerebral arterioscleros is were excluded)  Findings  Q-CBF Relationship  CHF patients when compared with normal population showed:  CBF ↓ 18% (61 to 50 mL/min/100g), MABP ↑ 9% (90 to 98 mmHg), CVR ↑ 32% (1.6 to 2.1 units).  Mild to moderate CHF: ↔ CBF (51 vs 48 mL/min/100g), MABP ↑ 30% (121 vs 94 mmHg), CVR ↔ (2.49 vs 2.35 units).  NF  NF  NF  Severe CHF: ↓ 21% CBF (39 vs 48 mL/min/100g), MABP ↔ (100 vs 94 mmHg), CVR ↑ 13% (2.66 vs 2.35 units).  87  Studya  Einsberg et al. 196063  Andrews et al. 196964  Shapiro and Chawla 196965  Population (n) Severe CHF (24) (patients with mental disease, pulmonary disease, renal disease or cerebral arteriosclerosis were excluded)  Unanesthetized Rats (14); Anesthetized Rats (14)  Human patients with complete heart block (5)  CBF Technique  Intervention (n)  Kety and Schmidt60 N2O technique  Observation of CBF as compared to CHF classification state in confused patients  Fractional uptake of Iodoantipryrine -133I  Temperature change  Kety and Schmidt60 N2O technique  Cardiac pacemaker controlled HR set at 3040, 60, 70, 90 and 100 beats per minute  Findings  Q-CBF Relationship  Confused severe CHF patients as compared to; normal controls and lucid severe CHF patients: CHF vs normal: ↓ 46% CBF (26 vs 48 mL/min/100g), MABP ↔ (98 vs 94 mmHg), CVR ↑ 54% (3.61 vs 2.35 units).  NF  Confused vs Lucid: ↓ 40% CBF (26 vs 43 mL/min/100g), MABP ↑ 15% (106 vs 92 mmHg), CVR ↑ 62% (3.54 vs 2.18 units).  Unanesthetized Rats showed a 50% ↓ in CBF with temperature ↓: 0.77 (37°C) to 0.38 mL/min (25°C), Hematocrit values were reported to ↑ from 0.45 (37°C) to 0.59 (25°C), Q ↓ 48% from 286 (37°C) to 149 mL/kg/min (25°C);  +  Anesthetized Rats showed a small ↓ in CBF with temperature ↓: CBF, Hematocrit and Q values were not reported.  HR 30-40: Q (2.8 L/min), CBF control (100%), CVR control (100%), PaCO2 (38 mmHg) HR 60: Q (3.6 L/min), CBF control (118%), CVR control (88%), PaCO2 (41 mmHg) HR 70: Q (3.4 L/min), CBF control (118%), CVR control (94%), PaCO2 (40 mmHg) HR 90: Q (3.4 L/min), CBF control (118%), CVR control (93%), PaCO2 (41 mmHg) HR 100: Q (3.6 L/min), CBF control (124%), CVR control (98%), PaCO2 (39 mmHg)  +  88  Studya  Davis and Sundt 198066  Moustafa and Hopewell 198167  Population (n)  CBF Technique  133  Cats (70)  Xenon washout  125  Female rats (28)  Iodoantipyrine extraction technique  Intervention (n) Hypovolumi c (10); Propanol (10); Isoproterenol (10); Hypervolumic (10); Angiotensio n (10); PropanololAngiotensio n (10); Phenoxybenzamineangiotension (10)  Age Changes: 6 months (6) 9 months (4) 12 months (6) 15 months (6) 18 months (6)  Findings  Q-CBF Relationship  Hypovolumic: Q ↓ 32%, CBF ↓ 24%, MABP ↓ slightly Propanol: HR ↓ 28%, Q ↓ 23%, CBF ↓ 30%, MABP not reported Isoproterenol: HR ↑ 20%, Q ↑ 38%, CBF ↔, MABP not reported Hypervolumic: HR ↓ slightly, Q ↓ 7%, CBF ↓ 22%, MABP ↓ slightly  +/-  Angiotension: induced changes in MABP had varied results in CBF, overall a slight ↑ in CBF and ↓ in Q with ↑ in MABP (changes less than 10%) Propanolol-Angiotension: MABP ↓ 6%, Q ↓ 26%, CBF ↓ 12% Phenoxybenzamine-angiotension: MABP ↓ 24%, Q ↔, CBF ↓ 15%  6 months (6): Q 257 mL/min/kg body weight, CBF 6.7 mL/min/kg body weight; 9 months (4): Q 183 mL/min/kg body weight, CBF 6.0 mL/min/kg body weight; 12 months (6): Q 208 mL/min/kg body weight, CBF 4.8 mL/min/kg body weight; 15 months (6): Q 163 mL/min/kg body weight, CBF 4.1 mL/min/kg body weight; 18 months (6): Q 157 mL/min/kg body weight, CBF 3.5 mL/min/kg body weight  +  89  Studya  Cook et al. 198368  Hermanse n et al. 198469  Barringto n et al. 198770  Population (n)  Healthy males (7)  Newborn dogs (13)  Adult monkeys (6)  CBF Technique  Intervention (n)  Findings  Q-CBF Relationship  Xenon inhalation  Intravenous administration of Epoprostenol  Pre infusion: ABPsys 123 mmHg, ABPdia 76 mmHg, HR 73 bpm, Q 4.2 L/min, CBF 46.0 mL/min/100g 15 minutes post: ABPsys 122 mmHg, ABPdia 73 mmHg, HR 79 bpm, Q 4.4 L/min, CBF 40.7 mL/min/100g 30 minutes post: ABPsys 123 mmHg, ABPdia 73 mmHg, HR 79 bpm, Q 4.1 L/min, CBF 38.9 mL/min/100g  -  Radioactiv e microspher e reference organ technique  Metabolic Acidosis  With increasing acidosis, there was a 27% ↓ in Q, ↔ in HR, ↔ in CBF. Concluded that decrease in Q due to ↓ in SV and had no effect on CBF.  -  133  133  Xenon clearance  Negative pressure ventilation via external high frequency oscillation  Control (mechanical ventilation) vs. external high frequency oscillation: ↔ Q (2.83 vs 3.03 L/min) ↔ CBF (43.9 vs 39.0 mL/min/100g) ↔ MABP (119 vs 113 mmHg)  NF  90  Studya  Population (n)  CBF Technique  Intervention (n)  Findings  Q-CBF Relationship  Isoflurane vs. Halothane at each injection stage:  Mutch et al. 199071  New Zealand white Rabbits (16)  Summing weighted flows in all brain regions and comparing to brain weight of the decapitated rabbit  van der Giessen et al. 199072  Conscious cross-breed pigs (14)  Inspection of the brain during dissection  Isoflurane injection (8); Halothane injection (8)  Nimodipine injection  Baseline: MABP (64.3 vs 67.2 mmHg), Q (472 vs 506 mL/min), CBF (0.7 vs 0.9 mL/g/min), PE injection (N/A), ICP (2.9 vs 2.1), CPP (61.4 vs 65.5) Flow 2: MABP (79.2 vs 81.5 mmHg), Q (385 vs 363 mL/min), CBF (0.9 vs 1.1 mL/g/min), PE injection (8.5 vs 15.3 μg/kg/min), ICP (3.1 vs 2.4 mmHg), CPP (76.1 vs 79.5 mmHg) Flow 3: MABP (89.6 vs 94.7 mmHg), Q (388 vs 263 mL/min), CBF (1.0 vs 1.8 mL/g/min), PE injection (12.8 vs 28.6 μg/kg/min), ICP (3.4 vs 3.6 mmHg), CPP (86.2 vs 91.5 mmHg) Flow 4: MABP (105.4 vs 106.6 mmHg), Q (341 vs 226 mL/min), CBF (1.2 vs 2.5 mL/g/min), PE injection (16.9 vs 63.5 μg/kg/min), ICP (3.7 vs 5.1 mmHg), CPP (101.7 vs 102.0 mmHg) Flow 5: MABP (116.6 vs 115.8 mmHg), Q (325 vs 150 mL/min), CBF (1.4 vs 3.8 mL/g/min), PE injection (21.1 vs 137.3 μg/kg/min), ICP (5.0 vs 6.7 mmHg), CPP (111.7 vs 109.8 mmHg)  -  Highest nimodipine dosage as compared to baseline data: HR ↑ 42%, Q ↑ 54%, CBF ↔, CVR ↔, MABP ↓ 9%  91  Studya  Population (n)  CBF Technique  Intervention (n)  Findings  Q-CBF Relationship  Pre-drug vs pos-drug comparison for intact and impaired cerebral autoregulation: (Absolute values not reported for Q) Intact cerebral autoregulation:  Bouma and Muizelaar 199073  Human patients with intact or impaired cerebral autoregulatio n (35)  133  Xenon inhalation or 133 Xenon injection  Phenylephrine, Arfonad and Mannitol administration  Phenylephrine: CBF (36 vs 35 mL/100g/min, ↓ 1%), MABP (96 vs 127 mmHg, ↑ 32%), ICP (18 vs 20 mmHg, ↑ 11%), Q (↑ 7%) Arfonad: CBF (41 vs 40 mL/100g/min, ↓ 2%), MABP (111 vs 86 mmHg, ↓ 23%), ICP (18 vs 21 mmHg, ↑ 17%), Q (↓ 10%) Mannitol: CBF (37 vs 37 mL/100g/min, ↔), MABP (101 vs 100 mmHg, ↓ 1%), ICP (18 vs 13 mmHg, ↓ 28%), Q (↑ 17%)  -  Impaired cerebral autoregulation: Phenylephrine: CBF (21 vs 32 mL/100g/min, ↑ 53%), MABP (92 vs 123 mmHg, ↑ 34%), ICP (18 vs 16 mmHg, ↓ 11%), Q (↑ 15%) Arfonad: CBF (66 vs 46 mL/100g/min, ↓ 31%), MABP (108 vs 77 mmHg, ↓ 29%), ICP (16 vs 18 mmHg, ↑ 13%), Q (↑ 22%) Mannitol: CBF (20 vs 27 mL/100g/min, ↑ 40%), MABP (94 vs 90 mmHg, ↓ 4%), ICP (17 vs 16 mmHg, ↓ 6%), Q (↑ 1%)  92  Studya  Population (n)  CBF Technique  Intervention (n)  Findings  Q-CBF Relationship  Arrows indicate changes from rest at –15, -30, -40 and –55 mmHg  Levine et al. 199474  Healthy males (13)  MCAv via TCD  Orthostatic challenge (lower body negative pressure)  Rest: Q (5.7 L/min), non-fainter MCAv (58 cm/s), fainter MCAv (52 cm/s), HR (58 bpm), SV (98 mL), MABP (82 mmHg) -15 mmHg: Q (5.7 L/min, ↔), non-fainter MCAv (61 cm/s, ↔), fainter MCAv (52 cm/s, ↔), HR (63 bpm, ↑ 9%), SV (90 mL, ↓ 9%), MABP (83 mmHg, ↔) -30 mmHg: Q (5.0 L/min, ↓ 12%), non-fainter MCAv (56 cm/s, ↔), fainter MCAv (50 cm/s, ↔), HR (68 bpm, ↑ 17%), SV (73 mL, ↓ 11%), MABP (83 mmHg, ↔) -40 mmHg: Q (4.2 L/min, ↓ 24%), non-fainter MCAv (55 cm/s, ↔), fainter MCAv (45 cm/s, ↓ 14%), HR (76 bpm, ↑ 31%), SV (55 mL, ↓ 33%), MABP (84 mmHg, ↔) -55 mmHg: Q (3.5 L/min, ↓ 39%), non-fainter MCAv (50 cm/s, ↓ 14%), fainter MCAv (N/A), HR (90 bpm, ↑ 55%), SV (90 mL, ↓ 57%), MABP (88 mmHg, ↑ 6%)  -  93  Studya  Population (n)  CBF Technique  Intervention (n)  Findings  Q-CBF Relationship  Control vs Metroprolol at rest and during Handgrip and cycling at (83, 113, 147, and 186 watts)  Ide et al. 199875  Healthy human volunteers (9)  MCAv via TCD  Effect of reducing the ability to change Q at rest, during handgrip and cycling exercise with metroprolol (β1 adrenergic blockade)  Larsen et al. 200076  Fulminant hepatic failure patients (9)  MCAv via TCD  Norepinephrine infusion  Rest: MCAv (59 vs 56 cm/s), percent change in Q (100 vs 92 %), HR (67 vs 65 bpm), MABP (94 vs 86 mmHg), PaCO2 (5.1 vs 4.9 kPa) Handgrip: MCAv (67 vs 63 cm/s), percent change in Q (116 vs 100 %), HR (77 vs 71 bpm), MABP (106 vs 100 mmHg), PaCO2 (5.1 vs 5.0 kPa) + 83 watts: MCAv (72 vs 64 cm/s), percent change in Q (218 vs 185 %), HR (113 vs 99 bpm), MABP (105 vs 96 mmHg), PaCO2 (5.2 vs 5.3 kPa) 113 watts: MCAv (72 vs 66 cm/s), percent change in Q (260 vs 222 %), HR (135 vs 114 bpm), MABP (112 vs 103 mmHg), PaCO2 (5.1 vs 5.2 kPa) 147 watts: MCAv (69 vs 64 cm/s), percent change in Q (315 vs 258 %), HR (158 vs 128 bpm), MABP (119 vs 106 mmHg), PaCO2 (4.9 vs 4.9 kPa) 186 watts: MCAv (66 vs 62 cm/s), percent change in Q (349 vs 293 %), HR (169 vs 130 bpm), MABP (122 vs 112 mmHg), PaCO2 (4.4 vs 4.6 kPa)  Measurements before and during Norepinephrine infusion: MCAv (49 vs 63 cm/s, ↑ 30%), Q (5.7 vs 7.1 L/min, ↑ 25%), MABP (75 vs 97 mmHg, ↑ 32%), SV (59 vs 71 mL, ↑ 20%)  +  94  Studya  Population (n)  Gruhn et al. 200131  Congestive heart failure (12); Heart transplant recipients (5)  Van Lieshout et al. 200145  Healthy young adult humans (10)  CBF Technique  Intervention (n)  Xenon inhalation  Pre- and post- heart transplantation  MCAv via TCD  5 minutes of Standing, followed by 2 minutes of leg tensing and 2 final minutes of standing  133  Findings  Q-CBF Relationship  Measurements taken pre- and post-transplant: CBF (36 vs 50 mL/min/100g, ↑ 39%), CI (2.5 vs 2.4 L/min/m2, ↔), MABP (76 vs 93 mmHg, ↑ 22%)  NF  Stand 1: Q (4.2 L/min), MCAv (58 cm/s), MABP (75 mmHg), PaCO2 (4.7 kPa) Tensing: Q (4.5 L/min), MCAv (64 cm/s), MABP (79 mmHg), PaCO2 (5.0 kPa)  +  Stand 2: Q (4.2 L/min), MCAv (58 cm/s), MABP (77 mmHg), PaCO2 (4.7 kPa)  Measures are pre and during experimental condition:  Wilson et al. 200277  Healthy humans (9)  MCAv via TCD  Normothermic tilt and whole body heating tilt (with and without precooling)  Normothermic – no cooling: MCAv (62 vs 54 cm/s), Q (6.5 vs 5.2 L/min), MABP (87 vs 82 mmHg), HR (57 vs 72 bpm) Normothermic – pre-cooling: MCAv (61 vs 60 cm/s), Q (6.3 vs 5.8 L/min), MABP (86 vs 93 mmHg), HR (57 vs 63 bpm) Heating – no cooling: MCAv (55 vs 43 cm/s), Q (8.0 vs 5.7 L/min), MABP (83 vs 71 mmHg), HR (88 vs 126 bpm) Heating – pre-cooling: MCAv (54 vs 59 cm/s), Q (8.2 vs 5.2 L/min), MABP (88 vs 93 mmHg), HR (87 vs 72 bpm)  +/-  95  Studya  Population (n)  Joseph et al. 200378  Human patients with vasoplasm after subarachnoid hemorrhage (16)  CBF Technique  Intervention (n)  Xenon CT system  Hypervolemia: Phenylephrine to ↑ MABP (5); Dobutamine to ↑ Q (5)  Findings  Q-CBF Relationship  Measures are pre and post treatment: Phenylephrine: CBF (19.2 vs 33.3 mL/100g/min, ↑ 73%), MABP (103.4 vs 132.0 mmHg, ↑ 28%)  +  Dobutamine: CBF (24.8 vs 35.7 mL/100g/min, ↑ 44%), CI (4.0 vs 6.0 L/min/m 2, ↑ 50%)  Lower body negative pressure settings of 0, -10, -20, -30, -40, -50 mmHg (% change to baseline measure)  Brown et al. 200379  Human Adults (13)  MCAv via TCD  Orthostatic challenge: Lower body negative pressure  Kusaka et al. 200580  Newborn infant humans (17)  Mulitchan nel Near infrared spectrosco py  Observational  0 mmHg: MCAvmean (71 cm/s), Q (6.86 L/min), SV (116 mL), HR (60 bpm), MABP (86 mmHg) -10 mmHg: MCAvmean (67 cm/s, ↓ 6%), Q (6.37 L/min, ↓ 7%), SV (109 mL, ↓ 6%), HR (59 bpm, ↔), MABP (90 mmHg, ↑ 5%) -20 mmHg: MCAvmean (70 cm/s, ↔), Q (5.60 L/min, ↓ 18%), SV (93 mL, ↓ 20%), HR (61 bpm, ↔), MABP (89 mmHg, ↔) -30 mmHg: MCAvmean (70 cm/s, ↔), Q (4.65 L/min, ↓ 32%), SV (74 mL, ↓ 36%), HR (65 bpm, ↑ 8%), MABP (86 mmHg, ↔) -40 mmHg: MCAvmean (61 cm/s, ↓ 14%), Q (4.19 L/min, ↓ 39%), SV (63 mL, ↓ 44%), HR (71 bpm, ↑ 18%), MABP (89 mmHg, ↑ 3%) -50 mmHg: MCAvmean (57 cm/s, ↓ 20%), Q (3.80 L/min, ↓ 45%), SV (48 mL, ↓ 59%), HR (83 bpm, ↑ 38%), MABP (91 mmHg, ↑ 6%)  +/-  Significant positive relation between Q and CBF: + Linear regression line equation: CBF = 0.03Q + 8.71, R2 = 0.70, P = 0.002  96  Studya  Population (n)  CBF Technique  Intervention (n)  Findings  Q-CBF Relationship  Rest and exercise values for: lower body negative pressures at 8 Torr and 16 Torr, albumin infusion 1 and 2. (% changes are to control values).  Ogoh et al. 200581  Massaro et al. 200630  Healthy human males (7)  Congestive heart failure humans (22), heart transplantatio n subset (14)  MCAv via TCD  MCAv via TCD  Rest and Exercise with: infusions of albumin to ↑ Q; lower body negative pressure to ↓ Q  A subset (14) under heart transplantation  Rest: 8 Torr: MCAv (63 cm/s, ↓ 5%), Q (5.8 L/min, ↓ 11%), HR (70 bpm, ↑ 6%), MABP (96 mmHg, ↔), PaCO2 (39 mmHg, ↔) 16 Torr: MCAv (62 cm/s, ↓ 6%), Q (5.3 L/min, ↓ 18%), HR (74 bpm, ↑ 12%), MABP (99 mmHg, ↔), PaCO2 (40 mmHg, ↔) Albumin 1: MCAv (71 cm/s, ↑ 8%), Q (8.2 L/min, ↑ 26%), HR (82 bpm, ↑ 24%), MABP (92 mmHg, ↓ 4%), PaCO2 (41 mmHg, ↔) Albumin 2: MCAv (73 cm/s, ↑ 11%), Q (8.5 L/min, ↑ 31%), HR (84 bpm, ↑ 27%), MABP (91 mmHg, ↓ 5%), PaCO2 (41 mmHg, ↔)  +/-  Exercise: 8 Torr: MCAv (70 cm/s, ↔), Q (14.1 L/min, ↔), HR (123 bpm, ↑ 8%), MABP (104 mmHg, ↓ 5%), PaCO2 (42 mmHg, ↔) 16 Torr: MCAv (68 cm/s, ↔), Q (13.7 L/min, ↔), HR (130 bpm, ↑ 14%), MABP (106 mmHg, ↔), PaCO2 (41 mmHg, ↔) Albumin 1: MCAv (74 cm/s, ↔), Q (16.5 L/min, ↑ 12%), HR (129 bpm, ↑ 13%), MABP (105 mmHg, ↓ 4%), PaCO2 (41 mmHg, ↔) Albumin 2: MCAv (74 cm/s, ↔), Q (18.5 L/min, ↑ 26%), HR (133 bpm, ↑ 17%), MABP (106 mmHg, ↔), PaCO2 (41 mmHg, ↔)  Pre and 2-4 month post transplant measures: CBF (45.1 vs 69.1 cm/s, ↑ 53%), MABP (75.2 vs 94.6 mmHg, ↑ 26%), hematocrit (38.8 vs 31.2 %, ↓ 20%)  NF  97  Studya  Population (n)  CBF Technique  Intervention (n)  Choi et al. 200632  Advanced heart failure humans (52), underwent heart transplantation (4)  Radionucli de angiograph y  small subset (4) under heart transplantation  Findings  Q-CBF Relationship  Pre and 2-4 month post transplant measures: CBF (35.5 vs 44.3 mL/100g/min, ↑ 25%) LVEF (19.8 vs 66.8 %, ↑ 237%)  NF  Average CBF and Q for baseline, 2 weeks, 4-6 weeks, 8-12 weeks and 16+ weeks (% change is in relation to current measure vs baseline)  Drombro wski et al. 200682  Adult male dogs (31)  Stable isotope labeled microspher es with post mortem tissue evaluation  Chronic Hydrocephalus: Induced chronic obstructive hydrocephalus  CBF (mL/min/g): base (0.587), 2 weeks (0.317, ↓ 46%), 4-6 weeks (0.298, ↓ 49%), 8-12 weeks (0.384, ↓ 34%), 16+ weeks (0.242, ↓ 59%) Q (mL/min): base (4.97), 2 weeks (3.52, ↓ 29%), 4-6 weeks (3.46, ↓ 30%), 8-12 weeks (3.91, ↓ 21%), 16+ weeks (3.06, ↓ 38%)  +  Surgical Control: CBF (mL/min/g): base (0.661), 2 weeks (0.312, ↓ 53%), 4-6 weeks (0.403, ↓ 39%), 8-12 weeks (0.408, ↓ 38%), 16+ weeks (0.582, ↓ 12%) Q (mL/min): base (4.10), 2 weeks (2.86, ↓ 30%), 4-6 weeks (2.62, ↓ 36%), 8-12 weeks (3.35, ↓ 18%), 16+ weeks (3.77, ↓ 8%)  98  Studya  Population (n)  CBF Technique  Intervention (n)  Findings  Q-CBF Relationship  Effects of rest, moderate and heavy exercise under control and metropolol conditions. (Q and SV data are presented as % change from control rest, other values are absolute measures) Control:  Ogoh et al. 200783  Healthy males (8)  MCAv via TCD  Moderate and heavy exercise before and after cardioselective β1adrenergic blockade (metroprolol)  Rest: MCAv (60 cm/s), Q (0 %), SV (0 %), HR (66 bpm), MABP (92 mmHg), PaCO2 (5.2 kPa) Moderate: MCAv (75 cm/s), Q (182 %), SV (40 %), HR (130 bpm), MABP (104 mmHg), PaCO2 (5.7 kPa) Heavy: MCAv (67 cm/s), Q (276 %), SV (46 %), HR (171 bpm), MABP (115 mmHg), PaCO2 (5.4 kPa)  -  Metropolol: Rest: MCAv (52 cm/s), Q (-5 %), SV (-6 %), HR (67 bpm), MABP (85 mmHg), PaCO2 (5.1 kPa) Moderate: MCAv (59 cm/s), Q (146 %), SV (35 %), HR (117 bpm), MABP (93 mmHg), PaCO2 (5.4 kPa) Heavy: MCAv (56 cm/s), Q (235 %), SV (46 %), HR (163 bpm), MABP (109 mmHg), PaCO2 (5.1 kPa)  99  Studya  Population (n)  CBF Technique  Intervention (n)  Findings  Q-CBF Relationship  Data for baseline, lower body negative pressure (-15 and –30 mmHg), saline injection (15 and 30 mL/kg), (% changes are to baseline):  Ogawa et al. 200784  Ogoh et al. 201085  Healthy human males (12)  Healthy human males (9)  MCAv via TCD  Orthostatic challenge: lower body negative pressure; ↑ central blood volume with saline injections  MCAv via TCD  Acute hypotension by releasing thigh cuffs before and after; metropolol and glycolpyruvate plus metropolol  Baseline: MCAv (67 cm/s), Q (4.16 L/min), SV (72.9 mL), HR (58 bpm), MABP (80 mmHg), PET CO2 (41 mmHg) -15 mmHg: MCAv (67 cm/s, ↔), Q (3.64 L/min, ↓ 12%), SV (64.3 mL, ↓ 12%), HR (61 bpm, ↔), MABP (80 mmHg, ↔), PET CO2 (40 mmHg, ↔) -30 mmHg: MCAv (68 cm/s, ↔), Q (2.80 L/min, ↓ 33%), SV (44.2 mL, ↓ 39%), HR (68 bpm, ↑ 17%), MABP (77 mmHg, ↔), PET CO2 (40 mmHg, ↔) 15 mL/kg: MCAv (72 cm/s, ↑ 7%), Q (4.73 L/min, ↑ 14%), SV (78.0 mL, ↔), HR (61 bpm, ↔), MABP (86 mmHg, ↔), PET CO2 (40 mmHg, ↔) 30 mL/kg: MCAv (73 cm/s, ↑ 9%), Q (5.08 L/min, ↑ 22%), SV (75.5 mL, ↔), HR (68 bpm, ↑ 17%), MABP (82 mmHg, ↔), PET CO2 (40 mmHg, ↔)  +/-  Data for control, metropolol, and glycopyruvate plus metropolol, (% changes are to control): Control: MCAv (73 cm/s), Q (6.8 L/min), SV (103 mL), HR (67 bpm), MABP (85 mmHg), PET CO2 (39.7 mmHg) Metropolol: MCAv (70 cm/s, ↔), Q (6.0 L/min, ↓ 12%), SV (105 mL, ↔), HR (58 bpm, ↓ 13%), MABP (85 mmHg, ↔), PET CO2 (39.8 mmHg, ↔) Glycopyruvate+: MCAv (72 cm/s, ↔), Q (8.6 L/min, ↑ 27%), SV (92, ↓ 11%), HR (95 bpm, ↑ 42%), MABP (86 mmHg, ↔), PET CO2 (39.1 mmHg, ↔)  -  100  Studya  Population (n)  CBF Technique  Intervention (n)  Findings  Q-CBF Relationship  Supine and Seated data (% changes are to condition baseline):  Deegan et al. 201086  a  Healthy human volunteers (19)  MCAv and ACAv via TCD  Transient systemic hypoperfusion induced by thigh cuff deflation (supine and seated)  Supine: Baseline: MCAv (81.7 cm/s), ACAv (62.2 cm/s), Cardiac Index (2.2 L/min/m2), HR (64 bpm), MABP (90 mmHg) Pre-release: MCAv (83.7 cm/s, ↑ 3%), ACAv (62.8 cm/s, ↑ 1%), Cardiac Index (2.7 L/min/m2, ↑ 17%), HR (73 bpm, ↑ 14%), MABP (101 mmHg, ↑ 12%) Post-release: MCAv (79.2 cm/s, ↓ 3%), ACAv (58.5 cm/s, ↓ 6%), Cardiac Index (3.0 L/min/m2, ↑ 36%), HR (78 bpm, ↑ 22%), MABP (84 mmHg, ↓ 7%)  -  Seated: Baseline: MCAv (75.2 cm/s), ACAv (59.7 cm/s), Cardiac Index (2.5 L/min/m2), HR (73 bpm), MABP (91 mmHg) Pre-release: MCAv (77.6 cm/s, ↑ 3%), ACAv (60.3 cm/s, ↑ 1%), Cardiac Index (3.0 L/min/m2, ↑ 20%), HR (78 bpm, ↑ 7%), MABP (98 mmHg, ↑ 8%) Post-release: MCAv (71.1 cm/s, ↓ 5%), ACAv (52.9 cm/s, ↓ 11%), Cardiac Index (3.2 L/min/m2, ↑ 28%), HR (88 bpm, ↑ 21%), MABP (79 mmHg, ↓ 13%)  Studies are in chronological order.  n = number; CHF = congestive heart failure; CBF = cerebral blood flow; a-v O2 = atrial-venous Oxygen difference; MABP = mean arterial blood pressure; ABP sys = systolic arterial blood pressure; ABPdia = diastolic arterial blood pressure; N2O = Nitrogen Oxide; CVR = cerebrovascular resistance; Q = cardiac output; HR = heart rate; SV = stroke volume; CI = cardiac index; PaCO2 = partial pressure of arterial Carbon Dioxide; ICP = intracranial pressure; LVEF = left ventricular ejection fraction; MCA = middle cerebral artery; MCAv = middle cerebral artery velocity; ACA = anterior cerebral artery; ACAv = anterior cerebral artery velocity; TCD = transcranial Doppler. ↑ indicates increase; ↓ indicates decrease; ↔ indicates no change. + indicates positive Q-CBF relationship; - indicates no Q-CBF relationship; NF = no findings for Q-CBF relationship.  101  Appendix IV: Raw Data – Output from LabChart  AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7 AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4  Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50%  Systolic Relative (cm/s) (%) 69.450 0.000 71.120 0.000 84.700 0.000 69.090 0.000 51.770 0.000 58.600 0.000 82.080 0.000 50.980 0.000 57.400 0.000 63.680 0.000 78.720 0.000 101.270 0.000 43.550 0.000 48.480 0.000 123.000 0.000 91.000 0.000 105.000 0.000 149.000 0.000 120.000 0.000 119.000 0.000 125.000 0.000 87.490 0.260 88.600 0.246 103.290 0.219 82.340 0.192 91.790 0.773 97.380 0.662 130.550 0.591 60.560 0.188 86.990 0.516 75.830 0.191 98.290 0.249 105.690 0.044 51.760 0.189 80.640 0.663 172.000 0.398 132.000 0.451 145.000 0.381 189.000 0.268  MCAv Diastolic Relative Mean Relative Change to (cm/s) (%) (cm/s) (%) Baseline 35.490 0.000 46.810 0.000 0.000 30.630 0.000 44.127 0.000 0.000 18.830 0.000 40.787 0.000 0.000 21.580 0.000 37.417 0.000 0.000 19.200 0.000 30.057 0.000 0.000 26.590 0.000 37.260 0.000 0.000 36.220 0.000 51.507 0.000 0.000 26.050 0.000 34.360 0.000 0.000 23.770 0.000 34.980 0.000 0.000 33.860 0.000 43.800 0.000 0.000 22.110 0.000 40.980 0.000 0.000 47.500 0.000 65.423 0.000 0.000 21.100 0.000 28.583 0.000 0.000 22.440 0.000 31.120 0.000 0.000 43.000 0.000 69.667 0.000 0.000 38.000 0.000 55.667 0.000 0.000 54.000 0.000 71.000 0.000 0.000 49.000 0.000 82.333 0.000 0.000 40.000 0.000 66.667 0.000 0.000 37.000 0.000 64.333 0.000 0.000 52.000 0.000 76.333 0.000 0.000 32.500 -0.084 50.830 0.086 4.020 27.160 -0.113 47.640 0.080 3.513 17.800 -0.055 46.297 0.135 5.510 21.160 -0.019 41.553 0.111 4.137 26.260 0.368 48.103 0.600 18.047 32.590 0.226 54.187 0.454 16.927 45.450 0.255 73.817 0.433 22.310 27.970 0.074 38.833 0.130 4.473 25.470 0.072 45.977 0.314 10.997 28.790 -0.150 44.470 0.015 0.670 25.670 0.161 49.877 0.217 8.897 41.330 -0.130 62.783 -0.040 -2.640 18.130 -0.141 29.340 0.026 0.757 31.510 0.404 47.887 0.539 16.767 48.000 0.116 89.333 0.282 19.667 36.000 -0.053 68.000 0.222 12.333 57.000 0.056 86.333 0.216 15.333 52.000 0.061 97.667 0.186 15.333  102  DC 5 DC 6 DC 7  AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7 AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4  50% 50% 50%  131.000 165.000 177.000  0.092 0.387 0.416  70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90%  Systolic Relative (cm/s) (%) 98.140 0.413 104.360 0.467 111.220 0.313 95.700 0.385 103.330 0.996 105.830 0.806 132.450 0.614 63.870 0.253 100.080 0.744 81.930 0.287 113.120 0.437 109.550 0.082 54.210 0.245 85.960 0.773 176.000 0.431 133.000 0.462 156.000 0.486 183.000 0.228 146.000 0.217 168.000 0.412 172.000 0.376 115.990 0.670 108.430 0.525 117.720 0.390 107.490 0.556 104.580 1.020 102.430 0.748 126.000 0.535 61.990 0.216 97.650 0.701 87.420 0.373 117.530 0.493 112.250 0.108 53.460 0.228 84.440 0.742 182.000 0.480 127.000 0.396 129.000 0.229 142.000 -0.047  46.000 0.150 74.333 0.115 7.667 35.000 -0.054 78.333 0.218 14.000 54.000 0.038 95.000 0.245 18.667 MCAv Diastolic Relative Mean Relative Change to (cm/s) (%) (cm/s) (%) Baseline 32.670 -0.079 54.493 0.164 7.683 24.550 -0.198 51.153 0.159 7.027 15.620 -0.170 47.487 0.164 6.700 21.820 0.011 46.447 0.241 9.030 24.950 0.299 51.077 0.699 21.020 30.490 0.147 55.603 0.492 18.343 39.790 0.099 70.677 0.372 19.170 26.980 0.036 39.277 0.143 4.917 25.590 0.077 50.420 0.441 15.440 27.590 -0.185 45.703 0.043 1.903 27.500 0.244 56.040 0.367 15.060 37.280 -0.215 61.370 -0.062 -4.053 15.660 -0.258 28.510 -0.003 -0.073 33.300 0.484 50.853 0.634 19.733 53.000 0.233 94.000 0.349 24.333 30.000 -0.211 64.333 0.156 8.667 54.000 0.000 88.000 0.239 17.000 48.000 -0.020 93.000 0.130 10.667 42.000 0.050 76.667 0.150 10.000 34.000 -0.081 78.667 0.223 14.333 53.000 0.019 92.667 0.214 16.333 37.290 0.051 63.523 0.357 16.713 19.450 -0.365 49.110 0.113 4.983 14.720 -0.218 49.053 0.203 8.267 22.450 0.040 50.797 0.358 13.380 25.100 0.307 51.593 0.717 21.537 26.990 0.015 52.137 0.399 14.877 31.830 -0.121 63.220 0.227 11.713 22.440 -0.139 35.623 0.037 1.263 18.520 -0.221 44.897 0.283 9.917 27.020 -0.202 47.153 0.077 3.353 25.960 0.174 56.483 0.378 15.503 33.800 -0.288 59.950 -0.084 -5.473 13.500 -0.360 26.820 -0.062 -1.763 32.540 0.450 49.840 0.602 18.720 41.000 -0.047 88.000 0.263 18.333 28.000 -0.263 61.000 0.096 5.333 47.000 -0.130 74.333 0.047 3.333 38.000 -0.224 72.667 -0.117 -9.667  103  DC 5 DC 6 DC 7  AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7  90% 90% 90%  147.000 168.000 143.000  0.225 0.412 0.144  Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak  Systolic Relative (cm/s) (%) 108.090 0.556 107.340 0.509 120.620 0.424 101.220 0.465 95.520 0.845 99.160 0.692 133.070 0.621 60.610 0.189 105.170 0.832 91.080 0.430 115.070 0.462 110.540 0.092 52.070 0.196 81.450 0.680 178.000 0.447 118.000 0.297 109.000 0.038 113.000 -0.242 127.000 0.058 147.000 0.235 134.000 0.072  38.000 -0.050 74.333 0.115 7.667 32.000 -0.135 77.333 0.202 13.000 41.000 -0.212 75.000 -0.017 -1.333 MCAv Diastolic Relative Mean Relative Change to (cm/s) (%) (cm/s) (%) Baseline 28.910 -0.185 55.303 0.181 8.493 21.720 -0.291 50.260 0.139 6.133 15.550 -0.174 50.573 0.240 9.787 22.460 0.041 48.713 0.302 11.297 20.520 0.069 45.520 0.514 15.463 23.860 -0.103 48.960 0.314 11.700 36.330 0.003 68.577 0.331 17.070 20.730 -0.204 34.023 -0.010 -0.337 15.390 -0.353 45.317 0.296 10.337 24.520 -0.276 46.707 0.066 2.907 25.900 0.171 55.623 0.357 14.643 32.260 -0.321 58.353 -0.108 -7.070 13.190 -0.375 26.150 -0.085 -2.433 31.100 0.386 47.883 0.539 16.763 32.000 -0.256 80.667 0.158 11.000 27.000 -0.289 57.333 0.030 1.667 41.000 -0.241 63.667 -0.103 -7.333 30.000 -0.388 57.667 -0.300 -24.667 17.000 -0.575 53.667 -0.195 -13.000 23.000 -0.378 64.333 0.000 0.000 26.000 -0.500 62.000 -0.188 -14.333  104  Pulsitility Index AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7 AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7  Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50%  0.725 0.918 1.615 1.270 1.084 0.859 0.890 0.726 0.961 0.681 1.381 0.822 0.785 0.837 1.148 0.952 0.718 1.215 1.200 1.275 0.956 1.082 1.290 1.847 1.472 1.362 1.196 1.153 0.839 1.338 1.058 1.456 1.025 1.146 1.026 1.388 1.412 1.019 1.403 1.143 1.660 1.295  MAP Systolic Relative Diastolic Relative Mean (mmHg) (%) (mmHg) (%) (mmHg) 120.000 0.000 80.000 0.000 99.000 129.000 0.000 87.000 0.000 101.000 183.000 0.000 92.000 0.000 122.333 104.000 0.000 62.000 0.000 76.000 117.000 0.000 70.000 0.000 85.667 140.000 0.000 95.000 0.000 110.000 143.000 0.000 87.000 0.000 105.667 121.000 0.000 88.000 0.000 99.000 120.000 0.000 97.000 0.000 104.667 120.000 0.000 92.000 0.000 101.333 129.000 0.000 76.000 0.000 93.667 131.000 0.000 83.000 0.000 99.000 120.000 0.000 90.000 0.000 100.000 120.000 0.000 83.000 0.000 95.333 124.000 0.000 78.000 0.000 93.333 129.000 0.000 89.000 0.000 102.333 106.000 0.000 74.000 0.000 84.667 117.000 0.000 83.000 0.000 94.333 109.000 0.000 80.000 0.000 89.667 103.000 0.000 78.000 0.000 86.333 131.000 0.000 62.000 0.000 85.000 150.000 -0.351 82.000 0.025 104.667 168.000 0.302 83.000 -0.046 111.333 195.000 0.066 78.000 -0.152 117.000 136.000 0.308 72.000 0.161 93.333 171.000 0.462 70.000 0.000 103.667 191.000 0.364 101.000 0.063 131.000 170.000 0.189 80.000 -0.080 110.000 154.000 0.273 93.000 0.057 113.333 140.000 0.167 95.000 -0.021 110.000 169.000 0.408 82.000 -0.109 111.000 135.000 0.047 74.000 -0.026 94.333 149.000 0.137 82.000 -0.012 104.333 138.000 0.150 89.000 -0.011 105.333 157.000 0.308 84.000 0.012 108.333 138.000 0.113 77.000 -0.013 97.333 159.000 0.233 86.000 -0.034 110.333 138.000 0.302 73.000 -0.014 94.667 143.000 0.222 84.000 0.012 103.667 137.000 0.257 79.000 -0.013 98.333 128.000 0.243 78.000 0.000 94.667 156.000 0.191 61.000 -0.016 92.667  Relative (%) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 -0.197 0.102 -0.044 0.228 0.210 0.191 0.041 0.145 0.051 0.095 0.007 0.054 0.053 0.136 0.043 0.078 0.118 0.099 0.097 0.097 0.090  105  Pulsitility Index AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7 AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7  70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90%  1.201 1.560 2.013 1.591 1.535 1.355 1.311 0.939 1.477 1.189 1.528 1.178 1.352 1.036 1.309 1.601 1.159 1.452 1.357 1.703 1.284 1.239 1.812 2.100 1.674 1.541 1.447 1.490 1.110 1.762 1.281 1.621 1.309 1.490 1.041 1.602 1.623 1.103 1.431 1.466 1.759 1.360  Systolic (mmHg) 176.000 208.000 205.000 156.000 241.000 211.000 182.000 170.000 193.000 162.000 141.000 213.000 166.000 189.000 167.000 178.000 152.000 165.000 145.000 156.000 179.000 193.000 221.000 209.000 206.000 244.000 233.000 190.000 185.000 193.000 180.000 181.000 226.000 199.000 211.000 183.000 191.000 167.000 172.000 169.000 176.000 187.000  MAP Relative Diastolic Relative Mean (%) (mmHg) (%) (mmHg) -0.238 85.000 0.063 115.333 0.612 83.000 -0.046 124.667 0.120 72.000 -0.217 116.333 0.500 69.000 0.113 98.000 1.060 83.000 0.186 135.667 0.507 98.000 0.032 135.667 0.273 79.000 -0.092 113.333 0.405 94.000 0.068 119.333 0.608 82.000 -0.155 119.000 0.350 82.000 -0.109 108.667 0.093 77.000 0.013 98.333 0.626 87.000 0.048 129.000 0.383 91.000 0.011 116.000 0.575 106.000 0.277 133.667 0.347 75.000 -0.038 105.667 0.380 85.000 -0.045 116.000 0.434 72.000 -0.027 98.667 0.410 82.000 -0.012 109.667 0.330 78.000 -0.025 100.333 0.515 77.000 -0.013 103.333 0.366 60.000 -0.032 99.667 -0.165 86.000 0.075 121.667 0.713 94.000 0.080 136.333 0.142 65.000 -0.293 113.000 0.981 75.000 0.210 118.667 1.085 92.000 0.314 142.667 0.664 87.000 -0.084 135.667 0.329 83.000 -0.046 118.667 0.529 97.000 0.102 126.333 0.608 82.000 -0.155 119.000 0.500 81.000 -0.120 114.000 0.403 80.000 0.053 113.667 0.725 87.000 0.048 133.333 0.658 96.000 0.067 130.333 0.758 112.000 0.349 145.000 0.476 76.000 -0.026 111.667 0.481 86.000 -0.034 121.000 0.575 70.000 -0.054 102.333 0.470 78.000 -0.060 109.333 0.550 76.000 -0.050 107.000 0.709 76.000 -0.026 109.333 0.427 59.000 -0.048 101.667  Relative (%) -0.115 0.234 -0.049 0.289 0.584 0.233 0.073 0.205 0.137 0.072 0.050 0.303 0.160 0.402 0.132 0.134 0.165 0.163 0.119 0.197 0.173 -0.066 0.350 -0.076 0.561 0.665 0.233 0.123 0.276 0.137 0.125 0.214 0.347 0.303 0.521 0.196 0.182 0.209 0.159 0.193 0.266 0.196  106  Pulsitility Index AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7  Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak  1.432 1.704 2.078 1.617 1.648 1.538 1.411 1.172 1.981 1.425 1.603 1.341 1.487 1.052 1.810 1.587 1.068 1.439 2.050 1.927 1.742  Systolic (mmHg) 212.000 220.000 225.000 206.000 247.000 235.000 200.000 183.000 199.000 203.000 190.000 234.000 204.000 203.000 202.000 200.000 172.000 189.000 173.000 180.000 194.000  MAP Relative Diastolic Relative Mean (%) (mmHg) (%) (mmHg) -0.082 83.000 0.038 126.000 0.705 89.500 0.029 133.000 0.230 68.000 -0.261 120.333 0.981 80.000 0.290 122.000 1.111 70.000 0.000 129.000 0.679 119.000 0.253 157.667 0.399 77.000 -0.115 118.000 0.512 97.000 0.102 125.667 0.658 76.000 -0.216 117.000 0.692 82.000 -0.109 122.333 0.473 88.000 0.158 122.000 0.786 83.000 0.000 133.333 0.700 99.000 0.100 134.000 0.692 114.000 0.373 143.667 0.629 79.000 0.013 120.000 0.550 82.000 -0.079 121.333 0.623 71.000 -0.041 104.667 0.615 76.000 -0.084 113.667 0.587 72.000 -0.100 105.667 0.748 74.000 -0.051 109.333 0.481 58.000 -0.065 103.333  Relative (%) -0.033 0.317 -0.016 0.605 0.506 0.433 0.117 0.269 0.118 0.207 0.302 0.347 0.340 0.507 0.286 0.186 0.236 0.205 0.178 0.266 0.216  107  AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7 AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7  Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50%  HR Et CO2 CVR Yrs Post Age Absolute Absol Relative Absolute Relative (bpm) (mmHg) (%) (mmHg/cm/s)) (%) 75.500 30.700 0.000 2.784 0.000 59.00 65.100 30.700 0.000 2.289 0.000 53.00 83.500 26.200 0.000 2.999 0.000 74.00 90.580 32.500 0.000 2.031 0.000 69.00 71.920 25.200 0.000 2.850 0.000 64.00 62.050 29.000 0.000 2.952 0.000 53.00 67.500 29.700 0.000 2.052 0.000 58.00 90.580 31.900 0.000 2.881 0.000 12.0 63.00 90.580 31.300 0.000 2.992 0.000 23.0 50.00 96.120 27.400 0.000 2.314 0.000 6.0 65.00 105.700 23.000 0.000 2.286 0.000 1.0 61.00 87.260 30.300 0.000 1.513 0.000 8.5 61.00 100.240 31.200 0.000 3.499 0.000 10.0 78.00 77.670 19.600 0.000 3.063 0.000 4.5 54.00 75.000 37.000 0.000 1.340 0.000 20.00 83.000 32.000 0.000 1.838 0.000 21.00 53.000 42.000 0.000 1.192 0.000 24.00 78.000 39.000 0.000 1.146 0.000 26.00 74.000 34.000 0.000 1.345 0.000 18.00 86.000 40.000 0.000 1.342 0.000 22.00 53.000 36.000 0.000 1.114 0.000 20.00 109.170 36.200 0.179 2.059 -0.260 59.00 109.170 36.400 0.186 2.337 0.021 53.00 93.550 32.400 0.237 2.527 -0.157 74.00 83.090 33.100 0.018 2.246 0.106 69.00 95.670 38.400 0.524 2.155 -0.244 64.00 105.070 39.900 0.376 2.418 -0.181 53.00 105.470 40.000 0.347 1.490 -0.274 58.00 103.790 36.200 0.135 2.918 0.013 12.0 63.00 111.060 36.100 0.153 2.393 -0.200 23.0 50.00 115.420 32.900 0.201 2.496 0.079 6.0 65.00 114.340 28.500 0.239 1.891 -0.173 1.0 61.00 95.300 32.100 0.059 1.662 0.098 8.5 61.00 111.490 33.500 0.074 3.590 0.026 10.0 78.00 97.620 34.900 0.781 2.262 -0.262 4.5 54.00 125.000 45.000 0.216 1.090 -0.187 20.00 142.000 38.000 0.188 1.623 -0.117 21.00 97.000 49.000 0.167 1.097 -0.080 24.00 135.000 46.000 0.179 1.061 -0.074 26.00 129.000 39.000 0.147 1.323 -0.016 18.00 134.000 46.000 0.150 1.209 -0.099 22.00 94.000 41.000 0.139 0.975 -0.124 20.00  108  HR Abs (bpm) AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7 AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7  70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 70% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90% 90%  122.50 151.54 100.35 100.80 128.48 132.20 136.01 126.48 122.41 124.03 124.80 123.21 122.69 130.49 171.00 181.00 154.00 174.00 160.00 167.00 142.00 138.00 167.23 111.31 130.43 140.05 147.80 164.54 155.30 142.39 134.31 138.97 137.37 146.98 138.84 189.00 192.00 194.00 182.00 187.00 180.00 171.00  Et CO2 Abs (mmHg) 37.200 34.900 34.000 36.500 39.000 39.500 40.100 36.600 36.300 32.000 33.600 32.000 32.800 33.500 46.000 41.000 47.000 46.000 38.000 48.000 40.000 33.500 25.700 33.300 35.600 39.000 36.700 38.800 34.200 32.200 30.800 32.300 30.500 28.600 33.500 36.000 33.000 40.000 38.000 32.000 42.000 32.000  CVR (%) 0.212 0.137 0.298 0.123 0.548 0.362 0.350 0.147 0.160 0.168 0.461 0.056 0.051 0.709 0.243 0.281 0.119 0.179 0.118 0.200 0.111 0.091 -0.163 0.271 0.095 0.548 0.266 0.306 0.072 0.029 0.124 0.404 0.007 -0.083 0.709 -0.027 0.031 -0.048 -0.026 -0.059 0.050 -0.111  Yrs Post Age Rel (mmHg/cm/s)) (%) 2.116 2.437 2.450 2.110 2.656 2.440 1.604 3.038 2.360 2.378 1.755 2.102 4.069 2.628 1.124 1.803 1.121 1.179 1.309 1.314 1.076 1.915 2.776 2.304 2.336 2.765 2.602 1.877 3.546 2.651 2.418 2.012 2.224 4.860 2.909 1.269 1.984 1.377 1.505 1.439 1.414 1.356  Abs -0.240 0.065 -0.183 0.039 -0.068 -0.174 -0.218 0.054 -0.211 0.028 -0.232 0.389 0.163 -0.142 -0.161 -0.019 -0.060 0.029 -0.027 -0.021 -0.034 -0.312 0.213 -0.232 0.150 -0.030 -0.119 -0.085 0.231 -0.114 0.045 -0.120 0.470 0.389 -0.050 -0.053 0.079 0.154 0.313 0.070 0.054 0.217  Rel  12.0 23.0 6.0 1.0 8.5 10.0 4.5  12.0 23.0 6.0 1.0 8.5 10.0 4.5  59.00 53.00 74.00 69.00 64.00 53.00 58.00 63.00 50.00 65.00 61.00 61.00 78.00 54.00 20.00 21.00 24.00 26.00 18.00 22.00 20.00 59.00 53.00 74.00 69.00 64.00 53.00 58.00 63.00 50.00 65.00 61.00 61.00 78.00 54.00 20.00 21.00 24.00 26.00 18.00 22.00 20.00  109  AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 HTR 1 HTR 2 HTR 3 HTR 4 HTR 6 HTR 7 HTR 8 DC 1 DC 2 DC 3 DC 4 DC 5 DC 6 DC 7  Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak Peak  Years Post HR Et CO2 CVR Transplant Age Absolute Absolute Relative Absolute Relative (bpm) (mmHg) (%) (mmHg/cm/s)) (%) 146.000 32.000 0.042 2.278 -0.182 59.00 171.750 23.400 -0.238 2.646 0.156 53.00 122.850 31.100 0.187 2.379 -0.207 74.00 138.900 35.100 0.080 2.504 0.233 69.00 159.180 31.700 0.258 2.834 -0.006 64.00 159.550 32.900 0.134 3.220 0.091 53.00 176.300 36.600 0.232 1.721 -0.161 58.00 163.140 31.400 -0.016 3.694 0.282 12.0 63.00 159.000 25.400 -0.188 2.582 -0.137 23.0 50.00 142.630 28.500 0.040 2.619 0.132 6.0 65.00 144.120 27.800 0.209 2.193 -0.040 1.0 61.00 139.260 29.400 -0.030 2.285 0.510 8.5 61.00 158.900 24.200 -0.224 5.124 0.465 10.0 78.00 159.100 27.800 0.418 3.000 -0.021 4.5 54.00 200.000 23.000 -0.378 1.488 0.110 20.00 204.000 26.000 -0.188 2.116 0.151 21.00 195.000 35.000 -0.167 1.644 0.379 24.00 199.000 27.000 -0.308 1.971 0.720 26.00 192.000 27.000 -0.206 1.969 0.464 18.00 192.000 35.000 -0.125 1.699 0.266 22.00 189.000 25.000 -0.306 1.667 0.497 20.00  AM – Age Matched, HTR – Heart Transplant Recipient, DC – Donor Population Control, MCAv – Middle Cerebral Artery Velocity, MAP - Blood Pressure, Et CO2 – End Tidal Carbon Dioxide, CVR – Cerebrovascular Resistance, YRS Post – Years Post Transplant Data is presented as raw data output from LabChart and recorded in Excel, subsequent analysis was preformed in PASW 18.0 and graphs were produced in Sigma Plot.  110  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.24.1-0072554/manifest

Comment

Related Items