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Outcomes following percutaneous coronary intervention and coronary artery bypass grafting surgery in… Gasevic, Danijela; Khan, Nadia A; Qian, Hong; Karim, Shahzad; Simkus, Gerald; Quan, Hude; Mackay, Martha H; O’Neill, Blair J; Ayyobi, Amir F Dec 26, 2013

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RESEARCH ARTICLE Open AccessOutcomes following percutaneous coronaryintervention and coronary artery bypass graftingsurgery in Chinese, South Asian and whitepatients with acute myocardial infarction:administrative data analysisDanijela Gasevic1, Nadia A Khan2,3*, Hong Qian3, Shahzad Karim1, Gerald Simkus1, Hude Quan4,Martha H Mackay5,6, Blair J O’Neill7 and Amir F Ayyobi1AbstractBackground: Little is known on whether there are ethnic differences in outcomes following percutaneous coronaryintervention (PCI) and coronary artery bypass grafting surgery (CABG) after acute myocardial infarction (AMI). Wecompared 30-day and long-term mortality, recurrent AMI, and congestive heart failure in South Asian, Chinese andWhite patients with AMI who underwent PCI and CABG.Methods: Hospital administrative data in British Columbia (BC), Canada were linked to the BC Cardiac Registry toidentify all patients with AMI who underwent PCI (n = 4729) or CABG (n = 1687) (1999–2003). Ethnicity wasdetermined from validated surname algorithms. Logistic regression for 30-day mortality and Cox proportional-hazardsmodels were adjusted for age, sex, socio-economic status, severity of coronary disease, comorbid conditions, time fromAMI to a revascularization procedure and distance to the nearest hospital.Results: Following PCI, Chinese had higher short-term mortality (Odds Ratio (OR): 2.36, 95% CI: 1.12-5.00; p = 0.02), andSouth Asians had a higher risk for recurrent AMI (OR: 1.34, 95% CI: 1.08-1.67, p = 0.007) and heart failure (OR 1.81, 95% CI:1.00-3.29, p = 0.05) compared to White patients. Risk of heart failure was higher in South Asian patients who underwentCABG compared to White patients (OR (95% CI) = 2.06 (0.92-4.61), p = 0.08). There were no significant differences inmortality following CABG between groups.Conclusions: Chinese and South Asian patients with AMI and PCI or CABG had worse outcomes compared to theirWhite counterparts. Further studies are needed to confirm these findings and investigate potential underlying causes.Keywords: PCI, CABG, Ethnicity, AMI, OutcomesBackgroundCoronary revascularization including percutaneous coron-ary intervention (PCI) and coronary artery bypass graft(CABG) surgery, is among the most common and mostexpensive major medical procedures provided in NorthAmerica [1], and is recommended by national guidelinebodies for the management of selected patients with acutemyocardial infarction (AMI) [2,3]. Percutaneous coronaryintervention has been shown to be more effective thanthrombolytic therapy for reperfusion [2,4]. In patients withAMI whose coronary anatomy appears unsuitable for PCI,CABG [3] or conservative treatment is indicated.As burden of coronary heart disease has been increasingin developing countries such as India and China [5,6], useof coronary revascularization technology will likely riseglobally. However, there is little evidence on the effective-ness of these procedures in South Asian and Chinese* Correspondence: nakhanubc@gmail.com2Division of General Internal Medicine, St. Paul’s Hospital, Vancouver,BC, Canada3Centre for Health Evaluation and Outcome Sciences, St. Paul’s Hospital, 1081Burrard Street, room 620-B, Vancouver, BC V6Z 1Y6, CanadaFull list of author information is available at the end of the article© 2013 Gasevic et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the CreativeCommons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, andreproduction in any medium, provided the original work is properly cited.Gasevic et al. BMC Cardiovascular Disorders 2013, 13:121http://www.biomedcentral.com/1471-2261/13/121populations with AMI and how it compares to Whitepopulation. Although no studies explored the ethnic differ-ences in outcomes in the post-AMI post-revascularizationsetting, in patients with coronary artery disease who haveundergone revascularization procedures, studies yieldedconflicting results. Namely, while some studies reported nodifference in mortality rates following PCI between SouthAsian and White patients [7,8], other observed lower mor-tality among Asian patients compared to their WesternEuropean counterparts [9]. Similarly, among studies explor-ing the ethnic differences in fatal cardiac outcomes follow-ing CABG, some studies reported higher mortality in SouthAsian compared to White patients [10-12], while others ob-served no such difference [13]. However, these studies arelimited by lack of adjustment for differences in baselineprognostic characteristics, some by small sample sizes, andthe effectiveness of revascularization is known to differ be-tween AMI populations and those with stable coronary ar-tery disease [2,14]. Therefore, the objective of this analysiswas to evaluate ethnic differences in fatal and non-fatal out-comes following PCI and CABG in Chinese, South Asian,and White patients who have suffered acute myocardial in-farction (AMI) while controlling the analyses for potentialconfounders such as socio-demographics, severity of coron-ary artery disease, and presence of comorbid conditions.MethodsData sourcesFor this retrospective cohort study, data were derivedfrom the hospital administrative data collected in theprovince of British Columbia (BC), Canada, and the BCCardiac Registry from April 1999 to March 2003. The hos-pital administrative data include demographics, admissionand discharge dates, and most responsible diagnosis foradmission along with comorbid conditions for all patientsadmitted to hospital in BC. The BC Cardiac Registry datainclude the type, date and clinical details of the revascular-ization procedure performed, data on the indication forthe procedure, extent of coronary artery disease, complica-tions and other outcomes. The Registry includes all suchprocedures performed in the province. The Vital Statisticsfile contains the date of death for all patients with legis-lated mandatory reporting and is updated daily. Data werelinked using a unique identifier common to all databases.Study populationAll patients with AMI diagnosed 1999–2003 in BC wereidentified using a validated coding algorithm in the hospitaladministrative database [15] based on the most responsiblediagnosis code (International Classification of Diseases,ninth revision [ICD 9], 410.x). This coding algorithm has apositive predictive value of 95% (91% to 98%) identifyingthe physician’s diagnosis of acute myocardial infarctionfrom hospital charts [16]. Patients younger than 20 years ofage and those who were discharged from hospitalized forless than one day were excluded from the study to reducethe risk of false-positive diagnosis of AMI.Revascularization and outcomesFor the study primary end-points, short (30-day) and long-term mortality, date of death was obtained from the BCVital Statistics file. The secondary end-points included firstrecurrence of AMI and readmission to the hospital forheart failure (ICD 9, 428.x), and these were derived fromhospital administrative data. For the study end-points, pa-tients were followed-up for a maximum of 4 years.Other prognostic variablesTo adjust for baseline prognostic differences betweengroups, we used the mortality prediction rule followingAMI [17] that was validated for 30-day and 1-year mortalitydisplaying reasonable accuracy (areas under the curve was0.78 and 0.79 for 30-day and 1-year mortality, respectively).The variables included age (dichotomized into 20–64 and65 years of age and older), sex, area-level socio-economicstatus (assessed from area-level median household incomebased on the 2001 Canadian Census), and presence of co-morbid conditions such as heart failure, cardiogenic shock,arrhythmia (any atrial or ventricular arrhythmia), diabetesmellitus, cerebrovascular disease, cancer, and acute orchronic renal disease. We also determined distance to thenearest hospital (defined as distance between the postalcode centroids of the residential area and the nearest hos-pital), duration from diagnosis of AMI to revascularizationprocedure examined in the model, and severity of coronaryartery disease based on Duke Criteria [18,19].Defining ethnicityEthnicity data were not available in administrative data.The Nam Pehchan computer program [20] and Chinesesurname list [21] were used to identify study participantsof South Asian and Chinese ethnicity, respectively. Accord-ing to the 2006 Canadian Census, in British ColumbiaCanadian province, South Asians and Chinese were thetwo largest visible minority groups, while the remainingpopulation was predominantly White [22]. Consequently,the rest of the study non-South Asian and non-Chineseparticipants were classified as White. Nam Pehchan pro-gram has been shown to classify South Asian names with90.5% sensitivity and 99.4% specificity, while a positive pre-dictive value of the program was 63.2% [20]. Sensitivity,specificity and a positive predictive value of the Chinesesurname list are 77.7%, 99.7%, and 80.5% respectively [21].In the event of changing surnames following an interracialmarriage, misclassification may occur; however, usingChinese surname list, there was only a small drop in sensi-tivity when married females (Sensitivity = 73.2%) werecompared to never-married ones (76.7%). In addition,Gasevic et al. BMC Cardiovascular Disorders 2013, 13:121 Page 2 of 7http://www.biomedcentral.com/1471-2261/13/121validation of Nam Pehchan program revealed only 0.05%of the 356,555 names to have mixed components of SouthAsian and non-South Asian origins [20].Statistical analysisEthnic differences in baseline characteristics were testedusing Chi-square test or Fisher’s exact test, where appro-priate. Ethnic differences in short-term mortality (up to30 days after AMI) were modeled using logistic regression.Furthermore, ethnic differences in long-term mortality(30 days to a maximum of 4 years after index AMI), timeto the first recurrent AMI, and hospitalization for heart fail-ure were evaluated using Cox proportional-hazards model-ing. The proportional hazard assumption was assessedusing the methods based on cumulative sums of martingaleresiduals [23]. Firth correction methods were applied in theregression models in case of monotone likelihood with in-finite estimates [24,25]. All regression models wereadjusted for age, sex, socio-economic status, distance tothe nearest hospital, duration from the diagnosis ofAMI to a revascularization procedure examined in themodel, severity of coronary disease and presence ofcomorbid conditions (congestive heart failure, cardio-genic shock, arrhythmia, diabetes mellitus, cerebrovascu-lar disease, cancer, and acute or chronic renal disease)based on the Ontario AMI mortality prediction rule [17].Analyses were performed using SAS statistical softwareversion 9.1 (SAS Institute Inc., Cary, NC). The Universityof British Columbia institutional research ethics boardapproved the study.ResultsBaseline characteristicsOut of 6416 patients with AMI who underwent revascu-larization, 2.8% were Chinese, 8% were South Asian and89.2% were White patients. By the revascularizationTable 1 Characteristics of Chinese, South Asian and White patients who underwent percutaneous coronary interventionCharacteristics Chinese South Asian White pN = 4729 n = 139 n = 371 n = 4219Female 35 (25.2) 74 (20.0) 1153 (27.3) 0.008Age (years) < 0.0001< 50 18 (12.9) 70 (18.9) 593 (14.1)50 − 64 42 (30.2) 164 (44.2) 1587 (37.6)65 − 74 54 (38.9) 88 (23.7) 1152 (27.3)> 75 25 (18.0) 49 (13.2) 887 (21.0)Distance to nearest hospital ≥ 50 km 5 (3.6) 42 (11.3) 1306 (31.0) < 0.0001Income quintile* < 0.00011 (low) 39 (28.3) 85 (23.22) 902 (22.5)2 34 (24.6) 106 (29.0) 830 (20.7)3 25 (18.1) 85 (23.2) 771 (19.3)4 15 (10.9) 52 (14.2) 774 (19.4)5 (high) 25 (18.1) 38 (10.4) 724 (18.1)Diabetes mellitus 26 (18.7) 92 (24.8) 641 (15.2) < 0.0001Heart failure 18 (13.0) 30 (8.1) 330 (7.8) 0.09Hypertension 52 (37.4) 92 (24.8) 1041 (24.7) 0.003Cerebrovascular disease 5 (3.6) 0 (0.0) 43 (1.0) 0.0015Renal disease 5 (3.6) 5 (1.4) 63 (1.5) 0.13Cardiogenic shock 3 (2.2) 4 (1.1) 44 (1.0) 0.46Cardiac dysrhythmia 18 (13.0) 24 (6.5) 431 (10.2) 0.04Severity of coronary disease† 0.6Single-vessel 51 (37.8) 135 (37.1) 1481 (36.2)2-vessel 39 (28.9) 119 (32.7) 1341 (32.8)3-vessel 38 (28.1) 98 (26.9) 1126 (27.5)Left main 7 (5.2) 9 (2.5) 130 (3.2)Normal 0 (0) 3 (0.8) 12 (0.3)Variables presented as n (%); Analyses: comparing categories across ethnic groups using a Chi-square test (2-df). *Data are missing for 224 patients (Chinese 0.7%,South Asians 1.3%, and White 5.2%). †Data are missing for 140 patients (Chinese 2.9%, South Asians 1.9%, White 3.1%).Gasevic et al. BMC Cardiovascular Disorders 2013, 13:121 Page 3 of 7http://www.biomedcentral.com/1471-2261/13/121procedure, out of 4729 patients with AMI who under-went PCI, 3% were Chinese, 7.8% were South Asian and89.2% were White patients. Furthermore, 1687 patientsunderwent CABG within one year of AMI out of which2.6% were Chinese, 8.1% South Asian and 89.3% wereWhite patients. Among those who underwent PCI(Table 1), South Asian patients were younger at the timeof AMI presentation compared to Chinese and Whitepatients. Diabetes mellitus was more prevalent amongSouth Asian patients, followed by Chinese and Whitepatients. Chinese were more likely to have hypertensioncompared to their South Asian and White counterparts.Further, the prevalence of cerebrovascular disease andcardiac dysrhythmias was highest among Chinese andlowest among South Asian patients.As outlined in Table 2, similar to the PCI population,among patients who underwent CABG, South Asian pa-tients were younger at AMI presentation and more likelyto have diabetes mellitus compared to their Chinese andWhite counterparts. However, the prevalence of cardio-genic shock was highest among Chinese patients, followedby South Asian and White patients. The highest preva-lence of 3-vessel coronary artery disease was among SouthAsians, followed by White and Chinese patients.OutcomesOne hundred and sixteen patients died within 30 daysfrom PCI (6.5% of Chinese patients (n = 9), 3.0% of SouthAsian (n = 11), and 2.3% of White patients (n = 96)).Within a year from PCI, there were 23, 16, and 23 fatalitiesTable 2 Characteristics of Chinese, South Asian and White patients who underwent coronary artery bypass graftingsurgery within one year of AMICharacteristics Chinese South Asian White p valueN = 1687 n = 43 n =137 n =1507Female 8 (18.6) 25 (18.3) 319 (21.2) 0.68Age (years) 0.0717< 50 3 (7.0) 15 (11.0) 111 (7.4)50 − 64 16 (37.2) 62 (45.2) 518 (34.4)65 − 74 16 (37.2) 40 (29.2) 545 (36.1)> 75 8 (18.6) 20 (14.6) 333 (22.10)Distance to the nearest hospital≥ 50 km 2 (4.7) 15 (11.0) 514 (34.1) < 0.0001Income quintile* 0.521 (low) 11 (26.8) 38 (28.6) 328 (23.0)2 9 (22.0) 34 (25.6) 289 (20.3)3 7 (17.1) 23 (17.3) 259 (18.2)4 8 (19.5) 20 (15.0) 275 (19.3)5 (high) 6 (14.6) 18 (13.5) 273 (19.2)Diabetes mellitus 12 (27.9) 44 (32.1) 321 (21.3) 0.0098Heart failure 10 (23.3) 22 (16.1) 233 (15.5) 0.38Hypertension 11 (25.6) 47 (34.3) 423 (28.1) 0.27Cerebrovascular disease 1 (2.3) 0 (0.0) 39 (2.6) 0.16Renal disease 0 (0.0) 6 (4.4) 35 (2.3) 0.19Cardiogenic shock 2 (4.7) 5 (3.7) 19 (1.3) 0.0231Cardiac dysrrhythmia 6 (14.0) 19 (13.9) 208 (13.8) 0.99Severity of coronary disease† 0.49Single vessel 1 (2.5) 6 (4.8) 73 (5.3)2 vessel 8 (19.5) 14 (11.2) 229 (16.8)3 vessel 21 (51.2) 85 (68.0) 795 (58.4)Left main 11 (26.8) 20 (16.0) 264 (19.4)Normal 0 (0.0) 0 (0.0) 1 (0.1)Variables presented as n (%); Analyses: comparing categories across ethnic groups using a Chi-square test (2-df). *Data are missing for 89 patients (Chinese = 4.7%,South Asians 3%, and White 5.5.%).†Data are missing for 159 patients (Chinese 4.7%, South Asians 8.8%, White 9.6%).Gasevic et al. BMC Cardiovascular Disorders 2013, 13:121 Page 4 of 7http://www.biomedcentral.com/1471-2261/13/121per 1000-patient years in Chinese, South Asian and Whitepatients, respectively. Among those who underwent CABGwithin 30 days following AMI, 4.7% of Chinese (n = 2),2.2% of South Asians (n = 3), and 4.1% of White patients(n = 62) died. With regards to long-term mortality follow-ing CABG, there were 0, 30 and 21 events per 1000-patient years in Chinese, South Asian and White patients,respectively. After controlling for baseline characteristics,the odds of short-term mortality were significantly higheramong Chinese compared to White patients who under-went PCI (Table 3). In the adjusted analyses, the risk of re-current AMI and heart failure was found to be higheramong South Asian than in White patients following PCI.No other ethnic differences were noted among patientswho underwent PCI. Among patients who underwentCABG, there were no statistically significant ethnic differ-ences in mortality and risk of recurrent AMI, however, therisk of heart failure was significantly higher among SouthAsian patients than in White patients.DiscussionIn this observational study we found significantly worseprognosis in South Asian and Chinese patients with AMIfollowing revascularization compared to their White coun-terparts. These observed ethnic differences in mortality,risk of recurrent AMI, and heart failure were independentof age, sex, socio-economic status, distance to the nearesthospital, the duration from an AMI diagnosis to a revascu-larization procedure, severity of coronary disease and co-morbid conditions.Our findings of higher short-term mortality amongChinese patients following PCI are in contrast to thoseof a recent study where the rates of all-cause and car-diac mortality following PCI were lower in Asian pa-tients (Singapore, Hong Kong, and Malaysia) comparedto their counterparts from Western Europe [9]. Thisdifference may be due to the fact that our populationwas an AMI population compared to a lower risk unse-lected coronary disease population in the study above.Moreover, we directly compared outcomes in ethnicgroups within a single health care system whereasKlomp et al. indirectly compared patients in differinghealth care systems [9,26].Higher short-term mortality following PCI amongChinese patients compared with their White counter-parts may have occurred for several reasons. Chinesepatients may have had arrived later to the emergencydepartment [27,28] resulting in less effectiveness of theprocedures or more extensive myocardial damage attime of PCI [29]. However, in our study, we extensively ad-justed for differences in baseline prognostic characteristicsand extent of coronary disease. Chinese patients may alsohave had higher post procedural complications or differ-ences in coronary artery disease management. Chinese pa-tients have been shown to have a lower rate of filling theirprescriptions and for adhering to secondary preventionmedications [30,31]. Furthermore, they have a greater useof herbal medications [32]. In addition, there may be gen-etic differences in antiplatelet responsiveness between theethnic groups [33,34] placing Chinese patients at higherrisk of peri- and post procedural complications.While no difference between South Asian and White pa-tients was observed for mortality, South Asian patientswere found to be at greater risk of non-fatal adverse car-diovascular events following PCI and CABG comparedwith White patients, even when examining survivors only.Other studies examining ethnic differences in outcomesfollowing PCI or CABG have reported conflicting results.While several studies of unselected coronary disease pa-tients have revealed no difference in fatal cardiac outcomesTable 3 Ethnic differences in outcomes among patients who underwent PCI and CABGOutcome Chinese vs. White South Asians vs. White Chinese vs. South AsianPCI30-day mortality OR (95% CI) [p] 2.36 (1.12-5.00) [p = 0.02] 1.63 (0.83-3.20) [p = 0.15] 1.45 (0.56-3.77) [p = 0.45]1-year mortality HR (95% CI) [p] 0.69 (0.30-1.57) [p = 0.37] 0.77 (0.43-1.40) [p = 0.39] 0.89 (0.33-2.40) [p = 0.82]Recurrent AMI* HR (95% CI) [p] 1.04 (0.71-1.51) [p = 0.86] 1.34 (1.08-1.67) [p = 0.007] 0.77 (0.51-1.17) [p = 0.22]Heart failure* HR (95% CI) [p] 1.72 (0.74-4.02) [p = 0.21] 1.81 (1.00-3.29) [p = 0.051] 0.95 (0.36-2.55) [p = 0.92]CABG30-day mortality OR (95% CI) [p] 0.91 (0.20-4.22), [p = 0.91] 0.64 (0.20-2.01) [p = 0.44] 1.43 (0.23-9.04) [p = 0.70]1-year mortality HR (95% CI) [p] 0.14 (0.001-1.05) [p = 0.18] 1.12 (0.50-2.25) [p = 0.76] 0.13 (0.01-2.43) [p = 0.17]Recurrent AMI** HR (95% CI) [p] 0.52 (0.07-3.80) [p = 0.52] 0.44 (0.10-1.85) [p = 0.26] 1.18 (0.11-13.24) [p = 0.90]Heart failure** HR (95% CI) [p] 1.72 (0.52-5.75) [p = 0.38] 2.06 (0.92-4.61) [p = 0.08] 0.84(0.21-3.32) [p = 0.80]Models are adjusted for age, sex, SES, distance to nearest hospital, time from diagnosis of AMI to a procedure (PCI/CABG), severity of coronary disease andcomorbid conditions.PCI: Chinese, n = 139; South Asians, n = 371; White, n = 4219.CABG: Chinese, n = 43; South Asians, n = 137; White, n = 1507.*among survivors only, Chinese, n = 123; South Asian, n = 347; White, n = 3879.**among survivors only, Chinese, n = 31; South Asian, n = 85; White, n = 1010.Gasevic et al. BMC Cardiovascular Disorders 2013, 13:121 Page 5 of 7http://www.biomedcentral.com/1471-2261/13/121between South Asian and White patients following PCI[7,8] and CABG [13], others have observed higher CABGpostoperative mortality in South Asian than in White pa-tients [10-12]. However, the latter studies did not adjust forprognostic factors that may have contributed to the con-flicting results and did not directly study AMI populations.Our study represents a direct comparison of ethnicdifferences of AMI patients in a single health care sys-tem using extensive adjustment for prognostic factorsincluding severity of coronary disease. However, severalstudy limitations should be noted. First, this study is anobservational study and the ideal study design for deter-mining efficacy of these procedures following AMI wouldbe a randomized trial. This study is thus susceptible totreatment-selection bias and bias from residual confound-ing. Although we did adjust for multiple potential con-founding factors, we were not able to control for riskbehaviors (such as smoking, physical activity or diet), dys-lipidemia or extent of infarct (non-ST elevation MI, orpeak cardiac enzyme level) that could explain the observeddifference in outcomes. Second, ethnicity was definedusing surname algorithms because self-reported ethnicitydata were not available. However, surname algorithms havebeen shown to have high sensitivity and specificity; how-ever, there is a possibility that some of the ethnic categorieswere misclassified that could potentially underestimateinter-ethnic differences in study outcomes. Additionally,we did not know generational status of patients, but likely,given the age of patients in the cohort, most patients wouldbe first generation immigrants.ConclusionsThis observational study found a worse prognosis in SouthAsian and Chinese patients following revascularizationcompared to their White counterparts. Observed ethnicdisparities in outcomes were present despite adjustment fordemographic, socio-economic and clinical characteristics.We believe that the availability of interpretation and trans-lation services, the presence of education programs teach-ing the importance of adherence to secondary preventionmedication, the recognition of early signs of AMI andtimely seek of care, along with equitable access to healthcare, may help reduce ethnic disparities in postrevasculari-zation outcomes. In addition, given the inter-ethnic differ-ences in the response to clopidogrel antiplatelet therapy, afuture personalized approach to therapy may further reducethe disparity in postrevascularization outcomes.Competing interestsThe authors declare no competing interests.Authors’ contributionsDG participated in the design of the study, interpreted the data and drafted themanuscript. NAK made substantial contributions to design of the study anddata interpretation, helped to draft the manuscript, and she critically revised it.HQian performed statistical analyses and contributed to data interpretation.SK participated in the discussion and critically revised the manuscript. GScontributed to the conception of the study, participated in the discussion andcritically revised the manuscript. HQuan participated in the discussion and criticallyrevised the manuscript. MHM participated in the discussion and critically revisedthe manuscript. BJO participated in the discussion and critically revised themanuscript. AFA conceived the study, participated in its design, datainterpretation, the manuscript discussion and critically revised the manuscript.All authors read and approved the final manuscript.AcknowledgementsThis study was funded by the Canadian Institutes for Health Research.AFA receives salary support from the Cardiac Services of British Columbiaand Provincial Health Services Authority for a special grant for South Asiancardiovascular health initiative. NAK receives salary support from the MichaelSmith Foundation for Health Research Career Scientist Award. HQ receivessalary support from the Alberta Heritage Foundation for Medical ResearchSenior Population Investigator award. MM is supported by a Heart andStroke Foundation of Canada Research Scholarship. We thank the Ministry ofHealth for British Columbia and the British Columbia Cardiac RegistryServices for providing access to the research data.Author details1Cardiac Services, Royal Columbian Hospital, New Westminster, BC, Canada.2Division of General Internal Medicine, St. Paul’s Hospital, Vancouver,BC, Canada. 3Centre for Health Evaluation and Outcome Sciences, St. Paul’sHospital, 1081 Burrard Street, room 620-B, Vancouver, BC V6Z 1Y6, Canada.4Department of Medicine, University of Calgary, Calgary, AB, Canada. 5Schoolof Nursing, University of British Columbia, Vancouver, BC, Canada. 6HeartCentre, St. Paul’s Hospital, Vancouver, BC, Canada. 7Department of Medicine,Division of Cardiology, University of Alberta, Edmonton, Canada.Received: 13 March 2013 Accepted: 11 December 2013Published: 26 December 2013References1. Mark DB, Hlatky MA: Medical economics and the assessment of value incardiovascular medicine: part II. Circulation 2002, 106:626–630.2. 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BMC Cardiovascular Disorders2013 13:121.Submit your next manuscript to BioMed Centraland take full advantage of: • Convenient online submission• Thorough peer review• No space constraints or color figure charges• Immediate publication on acceptance• Inclusion in PubMed, CAS, Scopus and Google Scholar• Research which is freely available for redistributionSubmit your manuscript at www.biomedcentral.com/submitGasevic et al. BMC Cardiovascular Disorders 2013, 13:121 Page 7 of 7http://www.biomedcentral.com/1471-2261/13/121


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