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Outcomes following percutaneous coronary revascularization among South Asian and Chinese Canadians Mackay, Martha H; Singh, Robinder; Boone, Robert H; Park, Julie E; Humphries, Karin H Apr 19, 2017

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RESEARCH ARTICLE Open AccessOutcomes following percutaneous coronaryrevascularization among South Asian andChinese CanadiansMartha H. Mackay1*, Robinder Singh2, Robert H. Boone3, Julie E. Park4 and Karin H. Humphries5AbstractBackground: Previous data suggest significant ethnic differences in outcomes following percutaneous coronaryrevascularization (PCI), though previous studies have focused on subgroups of PCI patients or used administrativedata only. We sought to compare outcomes in a population-based cohort of men and women of South Asian (SA),Chinese and “Other” ethnicity.Methods: Using a population-based registry, we identified 41,792 patients who underwent first revascularization viaPCI in British Columbia, Canada, between 2001 and 2010. We defined three ethnic groups (SA, 3904 [9.3%]; Chinese,1345 [3.2%]; and all “Others” 36,543 [87.4%]). Differences in mortality, repeat revascularization (RRV) and target vesselrevascularization (TVR), at 30 days and from 31 days to 2 years were examined.Results: Adjusted mortality from 31 days to 2 years was lower in Chinese patients than in “Others” (hazard ratio[HR] 0.72; 95% confidence interval [CI] 0.53-0.97), but not different between SAs and “Others”. SA patients hadhigher RRV at 30 days (adjusted odds ratio [OR] 1.30; 95% CI: 1.12-1.51) and from 31 days to 2 years (adjustedhazard ratio [HR] 1.17; 95% CI: 1.06-1.30) compared to “Others”. In contrast, Chinese patients had a lower rate of RRVfrom 31 days to 2 years (adjusted HR 0.79; 95% CI: 0.64-0.96) versus “Others”. SA patients also had higher rates of TVR at30 days (adjusted OR 1.35; 95% CI: 1.10-1.66) and from 31 days to 2 years (adjusted HR 1.19; 95% CI: 1.06-1.34) comparedto “Others”. Chinese patients had a lower rate of TVR from 31 days to 2 years (adjusted HR 0.76; 95% CI: 0.60-0.96).Conclusions: SA had higher RRV and TVR rates while Chinese Canadians had lower rates of long-term RRV, compared tothose of “Other” ethnicity. Further research to elucidate the reasons for these differences could inform targeted strategiesto improve outcomes.Keywords: Coronary artery disease, Percutaneous coronary intervention, Ethnicity, OutcomesBackgroundIn Canada, the largest visible minority is South Asian(25%), followed by Chinese [1]. South Asians (SAs) areyounger at presentation, and have higher rates of diffusecoronary artery disease (CAD) compared to non-SAs[2–7]. Differences in outcomes have been noted andmay be explained by their higher prevalence of type-2diabetes and modifiable risk factors such as smoking andobesity, or smaller coronary diameter and novel riskfactors for CAD [7–10]. Conversely, Chinese have lowerrates of atherosclerosis compared to others [11–13], butthe prevalence among Chinese is increasing, attributedto increased dyslipidemia and other environmentalinfluences [14]. A review of over 10 million deaths fromthe United States found Asian Indian men to have thehighest proportional mortality ratio, followed by AsianIndian women and Filipino men, respectively [15]. InCanada, SA patients have paradoxically lower mortalityrates following myocardial infarction (MI), despite ahigher overall disease burden [16], whereas Chinese hadhigher short-term mortality following MI in one largecohort study [17].Revascularization (coronary artery bypass grafting[CABG] or PCI) remains the mainstay of treatment for* Correspondence: mmackay@providencehealth.bc.ca1School of Nursing, University of British Columbia, and St. Paul’s Hospital,1081 Burrard St, Vancouver, BC V6Z 1Y6, CanadaFull list of author information is available at the end of the article© The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link tothe Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Mackay et al. BMC Cardiovascular Disorders  (2017) 17:101 DOI 10.1186/s12872-017-0535-0most patients with symptomatic CAD. Studies haveshown that Canadian, British and Indian SAs experiencepoorer outcomes than non-SAs following CABG [18–22],especially those with diabetes [20]. British researchers haveshown higher rates of re-stenosis, target lesion revasculari-zation and CABG post-PCI among SAs versus non-SAs,but no differences in mortality [23, 24]. Canadian studiesexamining outcomes following acute MI among SA,Chinese and Caucasian patients have had conflictingfindings regarding short-term mortality and recurrentMI [17, 21, 25] although a recent study demonstratedlonger survival amongst acute coronary syndromepatients who received revascularization [26]. We aimedto compare the outcomes among men and women ofSA, Chinese and “Other” ethnicity, following PCI.MethodsStudy designThis retrospective observational cohort study usedprospectively collected data from the Cardiac ServicesBritish Columbia (CSBC) Cardiac Registry [27], a databaseincluding demographic, clinical and procedural outcomedetails (excluding mortality) of all patients undergoingcardiac procedures in the Canadian province of BritishColumbia. This included patients with elective (stablecoronary disease), urgent (acute coronary syndrome) andemergent (ST-elevation MI) urgency ratings. Mortalitydata was obtained from the Vital Statistics Agency ofBritish Columbia [28]. We included all patients over20 years who had undergone PCI in British Columbiaas their first revascularization, from April 1, 2001 toOctober 31, 2010.Patients with a prior PCI or CABG were excluded foraccurate identification of those who required any repeatrevascularization (RRV) or target vessel revascularization(TVR). The study received approval from the institution’sResearch Ethics Board.MeasuresDemographic data and procedural details were obtainedfrom the CSBCCR. Ethnicity was assigned by CSBCusing the Nam Pechan surname analysis program for SAethnicity (Bradford Health Authority, Bradford, UK),(86–92% sensitivity; greater than 95% specificity) [29, 30]and Quan’s List for Chinese ethnicity [31] (78% sensitivity;99.7% specificity; 81% positive predictive value; 99.6%negative predictive value). Patients whose names were notidentified as either SA or Chinese were classified as“Other”; Canadian census data indicate that approximately97% of Canadians who do not report SA or Chineseethnicity are of European ancestry [1]. After surname ana-lysis, the dataset was stripped of all patient identifiers.Three endpoints (mortality, RRV and TVR) weredetermined at two time points (30 days and 31 days to2 years). If a patient experienced more than one RRV,the first procedure was taken as the event. Staged PCIwas not considered a RRV. We defined staged PCI as anelective procedure performed within 60 days after theindex PCI on a different vessel than that of the indexPCI. Furthermore, TVR was defined as a RRV on thesame vessel as the index PCI. Four coronary arteries (leftmain, left anterior descending, left circumflex and right)were used to define staged PCI and TVR.StatisticsGroup differences were assessed using Chi-squaredtests for categorical variables and analysis of variancefor continuous variables after log transformation,since neither age nor body mass index (BMI) werenormally distributed. For 30-day event rates, propor-tions were calculated, whereas Kaplan-Meier estimateswere used to calculate 31-day to 2-year event rates,due to different lengths of follow-up.Since the hazard ratios (HR) for ethnicity in the early(first 30-days) compared to the late (31 days to 2 years)differed, two separate analyses were performed tofurther examine ethnicity-based differences in theprimary outcomes: logistic regression analysis (up to30 days) and Cox proportional hazard models (after30 days), with “Others” as the reference group. Whenexamining repeat revascularization and TVR, patientswere censored at the time of death or at the end of twoyears, whichever came first.The following clinical covariates were included inthe adjusted models: age, BMI, smoking status(current, former, never), prior infarction, history ofhypertension, dyslipidemia, cerebrovascular disease,congestive heart disease, diabetes mellitus, peripheralvascular disease, pulmonary disease, liver/gastrointes-tinal disease, malignancy, dialysis, left ventricularejection fraction, use of ASA, ACE inhibitor or statinin 24 h before the procedure, as well as peri-proceduralvariables, including indication (acute coronary syn-drome, stable angina vs. other), procedure urgency(elective vs. non-elective), disease severity (3-vessel orleft main vs. rest). Due to high missing rates of stenttype and cardiogenic shock, additional analysis wasperformed, including these variables in the adjustedmodel. Sex was included in the final model regardlessof its significance. When the sex effect was signifi-cant, sex by ethnicity interaction was then added tosee if the effect of ethnicity on outcomes wasmodified by sex. When a covariate violated theproportional hazard assumption, it was used as astratifying variable or an interaction term with a timevariable was added. We used SAS version 9.3 (SASInstitute Inc., Cary, NC) for all analyses.Mackay et al. BMC Cardiovascular Disorders  (2017) 17:101 Page 2 of 7ResultsClinical and demographic characteristics41,792 patients who underwent PCI as a first revascu-larization were included, of which 3904 (9.3%) wereof SA, 1345 (3.2%) Chinese, and 36,543 (87.4%)“Other” ethnicity. There were many statisticallysignificant differences among the three groups (seeTable 1), though not all are clinically significant. Interms of the urgency of the PCI, Chinese patientswere most likely to undergo an elective procedure,whereas patients of “Other” ethnicity were least likely.MortalityPatients of Chinese ethnicity had higher crude rates of30-day mortality (n = 48, rate = 3.6%; 95% CI: 2.6-4.6)compared to both the SA group (n = 83, rate = 2.1%; 95%CI: 1.7-2.6) and “Others” (n = 799, 2.2%; 95% CI: 2.0-2.3).There was no difference after adjustment in 30-daymortality between Chinese and “Others” (OR 1.18; 95%CI: 0.84-1.66), or SAs and “Others” (OR 0.88; 95%CI: 0.68-1.13) (see Table 2). There were no sex differ-ences in 30-day mortality (OR 1.02; 95% CI 0.88-1.20).Unadjusted 31-day to 2-year mortality was lower in SATable 1 Demographic and pre-procedure clinical characteristicsVariablea All Ethnicity p-valueSA (n = 3904) Chinese (n = 1345) Other (n = 36,543)Male 30047 (71.9) 2741 (70.2) 1018 (75.7) 26288 (71.9) <0.001Age 64 (56, 73) 62 (53.5, 71) 65 (56, 74) 64 (56, 74) <0.001BMI, kg/m2 27.3 (24.6, 30.5) 26.2 (23.9, 29.1) 24.5 (22.4, 26.7) 27.5 (24.9, 30.8) <0.001Elective 9534 (22.9) 900 (23.1) 362 (27.1) 8272 (22.7) <0.001IndicationACSStable anginaOther30115 (72.3)9877 (23.7)1662 (4.0)2780 (71.4)976 (25.1)140 (3.6)866 (64.5)416 (31.0)60 (4.5)26469 (72.7)8485 (23.3)1462 (4.0)<0.001Medications within 24 h prior to procedureASAACE-IStatins38030 (91.0)20294 (48.6)24910 (59.6)3543 (90.8)1735 (44.4)2306 (59.1)1156 (85.9)524 (39)751 (55.8)33331 (91.2)18035 (49.4)21853 (59.8)<0.001<0.0010.011Congestive heart failure 2320 (5.6) 232 (5.9) 84 (6.3) 2004 (5.5) 0.260Prior MI 7094 (17) 580 (14.9) 169 (12.6) 6345 (17.4) <0.001HTN 23744 (56.8) 2310 (59.2) 892 (66.3) 20542 (56.2) <0.001Dyslipidemia 22346 (53.5) 2281 (58.4) 751 (55.8) 19314 (52.9) <0.001CBVD 2762 (6.6) 203 (5.2) 85 (6.3) 2474 (6.8) 0.01Diabetes Mellitus 8817 (21.1) 1204 (30.8) 353 (26.2) 7260 (19.9) <0.001Dialysis 520 (1.2) 56 (1.4) 28 (2.1) 43 (1.2) 0.008LVEF> 50%30–50%< 30%Not entered20570 (49.2)15893 (38.0)1065 (2.6)4264 (10.2)2128 (54.5)1285 (32.9)129 (3.3)362 (9.3)715 (53.2)429 (31.9)36 (2.6)165 (12.3)17727 (48.5)14179 (38.8)900 (2.5)3737 (10.2)<0.001Smoking statusCurrent 9149 (21.9) 445 (11.4) 185 (13.8) 8519 (23.3) <0.001Former 15926 (38.1) 546 (14) 357 (26.5) 15023 (41.1)Never 16717 (40) 2913 (74.6) 803 (9.7) 13001 (35.6)PVD 2847 (6.8) 120 (3.1) 46 (3.4) 2681 (7.3) <0.001Pulmonary disease 4190 (10) 304 (7.8) 82 (6.1) 3804 (10.4) <.0001Liver-GI 3492 (8.4) 305 (7.8) 105 (7.8) 3082 (8.4) 0.3126Malignancy 2898 (6.9) 126 (3.2) 63 (4.7) 2709 (7.4) <.00013-vessel or left main disease 9445 (22.7) 1009 (26.1) 356 (26.7) 8080 (22.4) <0.001SA South Asian, BMI body mass index, ACS acute coronary syndrome, MI myocardial infarction, HTN hypertension, CBVD cerebrovascular disease, LVEF leftventricular ejection fraction, PVD peripheral vascular disease, GI gastrointestinalaFor age and BMI, median and interquartile ranges are reported; for other variables frequency and percentages are reportedMackay et al. BMC Cardiovascular Disorders  (2017) 17:101 Page 3 of 7Canadians as compared to Chinese patients or Others;however, in adjusted models there was no statisticallysignificant difference in 31-day to 2-year mortality betweenSA patients and “Others” (HR 0.96; 95% CI: 0.79-1.16), butChinese patients had lower mortality compared with“Others” (HR 0.72; 95% CI: 0.53-0.97). There were nosignificant sex differences found in mortality during thisperiod, after adjustment (HR 1.02; 95% CI: 0.91-1.13).Repeat revascularizationPatients of SA ethnicity had higher crude rates of30-day repeat revascularization (n = 258, rate = 6.6%;95% CI: 5.8-7.4) compared to both the Chinese group(n = 58, rate = 4.3%; 95% CI: 3.2-5.4) and “Others”(n = 1698, rate = 4.6%; 95% CI: 4.4-4.9). With adjust-ment, SA patients rate of RRV remained 30% higher at30 days (OR 1.30; 95% CI: 1.12-1.51), compared to“Others” (see Table 3). There was no difference in rates of30-day RRV between Chinese and “Others”.Although women had lower rates of 30-day RRVcompared to men on multivariate analysis (OR 0.85;95% CI 0.76-0.95), there was no significant sex-by-ethnicity interaction on RRV (p interaction = 0.91).SA patients also had significantly higher crude rates ofRRV from 31 days to 2 years, as compared to “Others”or Chinese patients. On multivariate analysis, SApatients’ RRV remained significantly higher (HR 1.17;95% CI: 1.06-1.30); in contrast, Chinese patients had a 21%lower adjusted rate of RRV (HR 0.79; 95% CI: 0.64-0.96).There was no sex difference in RRV from 31 days to 2 yearspost-procedure.Target vessel revascularizationSA patients (n = 127, rate = 3.3%; 95% CI: 2.8-3.9) hadsignificantly higher rates of TVR at 30 days compared toboth the Chinese (n = 27, rate = 2.1%; 95% CI: 1.3-2.8)and Other patients (n = 836, rate = 2.3%; 95% CI: 2.2-2.5).After adjustment, SA patients had a 35% higher rate of30-day TVR compared to “Others” (OR 1.35; 95% CI:1.10-1.66), but no difference in 30-day TVR betweenChinese patients and “Others” (see Table 4). There was nosex difference in TVR for the first 30 days.Table 2 Unadjusted and adjusted odd ratios and hazard ratios of mortality, by ethnicity and sexCharacteristic Mortality30-Daya 31 Days to 2 YearsUnadjusted OR (95% CI) Adjustedd OR (95% CI) Unadjusted HR (95% CI) Adjustedd HR (95% CI)Ethnicityb SAn = 39040.96 (0.75,1.22) 0.88 (0.68, 1.13) 0.76 (0.63, 0.92) 0.96 (0.79, 1.16)Chinesen = 13451.64 (1.20, 2.23) 1.18 (0.84, 1.66) 0.85 (0.63, 1.14) 0.72 (0.53, 0.97)Sexc 1.48 (1.29, 1.71) 1.02 (0.88,1.20) 1.44 (1.31, 1.60) 1.02 (0.91, 1.13)OR odds ratio, CI confidence interval, SA South AsianaFor 30-day repeat revascularization, odds ratio (OR) and its CI are reported; for 31-day to 2-year outcomes, hazard ratio (HR) and its CI are reportedb Referent : “Others” (n = 36,543)c Referent: MaledAdjusted for urgency (elective vs. non-elective), indication (acute coronary syndrome, stable angina vs. other), ASA, ACE-inhibitor, statin use within 24 h prior toprocedure, smoking status (current, former vs. never), prior infarction, hypertension, dyslipidemia, cerebrovascular disease, diabetes mellitus, peripheral vasculardisease, pulmonary disease, liver-gastrointestinal disease, malignancy number of diseased vessel (3 or left main vs. rest), dialysis, left ventricular ejection fraction(>50% 30–50%, <30%, vs. not entered), age and BMITable 3 Unadjusted and adjusted odd ratios and hazard ratios of repeat revascularization, by ethnicity and sexCharacteristic Repeat Revascularization30-Daya 31 Days to 2 YearsUnadjusted OR (95% CI) Adjustedd OR (95% CI) Unadjusted HR (95% CI) Adjustedd HR (95% CI)Ethnicityb SAn = 39041.44 (1.25, 1.66) 1.30 (1.12, 1.51) 1.24 (1.13, 1.37) 1.17 (1.06, 1.30)Chinesen = 13450.98 (0.75, 1.27) 0.88 (0.67, 1.16) 0.83 (0.68, 1.00) 0.79 (0.64, 0.96)Sexc 1.44 (1.25, 1.65) 0.85 (0.76, 0.95) 0.96 (0.90, 1.03) 0.99 (0.92, 1.07)OR odds ratio, CI confidence interval, SA South AsianaFor 30-day repeat revascularization, odds ratio (OR) and CI are reported. For post 30-day 2-year outcomes, hazard ratio (HR) and CI are reportedb Referent: “Others” (n = 36,543)c Referent: Maled Adjusted for urgency (elective vs. non-elective), indication (acute coronary syndrome, stable angina vs. other), ASA, ACE-inhibitor, statin use within 24 h prior toprocedure, smoking status (current, former vs. never), prior infarction, hypertension, dyslipidemia, cerebrovascular disease, diabetes mellitus, peripheral vasculardisease, pulmonary disease, liver-gastrointestinal disease, malignancy number of diseased vessel (3 or left main vs. rest), dialysis, left ventricular ejection fraction(>50% 30–50%, <30%, vs. not entered), age and BMIMackay et al. BMC Cardiovascular Disorders  (2017) 17:101 Page 4 of 7SA patients also had higher crude rates of TVRbetween 31 days to 2 years than Chinese patients or“Others”. Following adjustment, SA patients also had asignificantly higher rate of TVR from 31 days to 2 years(HR 1.19; 95% CI: 1.06-1.34). However, Chinese patientswere found to have a lower adjusted rate of TVR,compared to “Others” (HR 0.76; 95% CI: 0.60-0.96).There were no sex differences in TVR between 31 daysand 2 years.DiscussionTo our knowledge, this is the largest Canadian cohortstudy investigating the association of ethnicity withoutcomes of all patients who have undergone PCI (i.e.,of elective, urgent and emergent urgency). Due to thelarge sample size, we found many statistically significantdifferences in baseline characteristics. Many of thesedifferences were small and their clinical relevance isunclear. The younger age of SAs at presentation for initialPCI and the higher rate of diabetes are consistent withprevious reports [11, 14, 16–19, 22–24]. Interestingly, the“Other” ethnicity cohort had the lowest rates of diabetes,hypertension and dyslipidemia, yet had the highest ratesof vascular disease. This might be explained by theirhaving the highest rates of current and former smoking.Finding no sex differences in any of the specified PCIoutcomes in our overall sample is consistent with someother researchers’ findings [23, 24, 32]. However, othershave shown that, among patients undergoing angiogramfor either stable angina or ACS, women have worseoutcomes, even after adjusting for revascularization[33, 34]. Identifying other factors (e.g. microvasculardysfunction, diffuse distal disease, higher rate ofdepression) that might explain these conflicting findingsdemands further study.There were higher rates of RRV and TVR between30 days and 2-years among SA patients, and loweramong Chinese. British and other investigators havesimilarly found significantly higher rates of TVR in SApatients [18–20, 22–24]. Given our adjustment fortraditional risk factors and relevant covariates, novel riskfactors and smaller coronary diameters may explainthese differences [7–10]. However, Anand et al. haveshown SA Canadians have higher atherosclerosis andcardiovascular event rates, compared to those of Europeanand Chinese background [14], despite adjusting fortraditional risk factors, Framingham risk and novel factors(fibrinogen, plasminogen activator inhibitor- 1, lipoprotein(a), homocysteine). These findings, taken with ours,suggest the possibility of an unknown pathophysiologicalmechanism of accelerated atherosclerotic disease inpatients of SA ethnicity. Our population-based findingsindicate no difference in post-PCI mortality among thethree groups, which is similar to other reports [32]. Wefound a non-significant trend toward higher short-termmortality in Chinese patients, which others have found[17, 21]. King et al. reported a tendency among Chinesepatients toward atypical symptoms and delayed treatment-seeking for symptoms of ACS, which may explain the trendtoward higher short-term mortality [35]. Other explana-tions may include higher procedural complications orbleeding rates [36]. Chinese patients in our study hadsignificantly lower rates of RRV and TVR from 30 days to2 years. A prior study examined variations in outcomesamong Chinese, Indian Asian and Malay patients followingPCI [12] and found Chinese patients had significantly lowerrates of MI, RRV and mortality compared to SA patients.Previous Canadian studies have found similarly lowerrates of MI and recurrent events among Chinese MIpatients, but higher short-term mortality [17, 37]. Wewere unable to find any literature comparing post-PCIoutcomes of Chinese patients to a cohort of patients ofEuropean ancestry.Our study has limitations. Although we used validatedsurname analysis tools to identify ethnicity [29–31], self-report remains the gold standard [38, 39]. MisclassificationTable 4 Unadjusted and adjusted odd ratios and hazard ratios of target vessel revascularization, by ethnicity and sexCharacteristic Target Vessel Revascularization30-Daya 31 Days to 2 YearsUnadjusted OR (95% CI) Adjustedd OR (95% CI) Unadjusted HR (95% CI) Adjustedd HR (95% CI)Ethnicityb SAn = 39041.46 (1.20, 1.77) 1.36 (1.10, 1.66) 1.25 (1.12, 1.40) 1.10 (1.06, 1.34)Chinesen = 13450.92 (0.63, 1.36) 0.83 (0.56, 1.23) 0.80 (0.64, 1.01) 0.76 (0.60, 0.96)Sexc 0.81 (0.70, 0.94) 0.86 (0.73, 1.00) 1.00 (0.93, 1.09) 1.03 (0.95, 1.12)aFor 30-day repeat revascularization, odds ratio (OR) and confidence intervals (CI) are reported; for post-30-day 2-year outcomes, hazard ratio (HR) and CI are reportedb Referent: “Others” (n = 36,543)c Referent: Maled Adjusted for urgency (elective vs. non-elective), indication (acute coronary syndrome, stable angina vs. other), ASA, ACE-inhibitor, statin use within 24 h prior toprocedure, smoking status (current, former vs. never), prior infarction, hypertension, dyslipidemia, cerebrovascular disease, diabetes mellitus, peripheral vasculardisease, pulmonary disease, liver-gastrointestinal disease, malignancy number of diseased vessel (3 or left main vs. rest), dialysis, left ventricular ejection fraction(>50% 30–50%, <30%, vs. not entered), age and BMIMackay et al. BMC Cardiovascular Disorders  (2017) 17:101 Page 5 of 7of ethnicity could lead to a bias towards the null. Someperi-procedural factors were not available for inclusion inthe model including ST-elevation MI as the specificindication for PCI and ejection fraction. We also did nothave data on socioeconomic status, or post-PCI medicaltherapy and risk factor control, any of which might havehad an effect on outcomes.ConclusionsAlthough mortality rates following PCI are similaramong ethnic groups, SAs have higher rates of RRV andTVR as compared to those of “Other” ethnicity.Conversely, Chinese patients had lower rates of RRV andTVR compared to those of “Other” ethnicity. Furtherinvestigation of ethnicity-based variability in PCIoutcomes is warranted.AbbreviationsBMI: body mass index; CABG: coronary artery bypass graft; CAD: coronaryartery disease; CI: confidence interval; HR: hazard ratio; MI: myocardialinfarction; OR: odds ratio; PCI: percutaneous coronary intervention;RRV: repeat revascularization; SA: South Asian; TVR: target vesselrevascularizationAcknowledgmentThe authors acknowledge the statistical support of the BC Centre forImproved Cardiovascular Health (iCVHealth).FundingDr. Mackay was supported by a Cardiac Services of British ColumbiaFellowship award and a Michael Smith Foundation for Health ResearchScholar Award during this work. Neither of these agencies had any role inthe design of the study, analysis and interpretation of data or in writing themanuscript. Cardiac Services BC routinely collects the clinical data related toPCI procedures and provided those data for the necessary linkages to otherdatabases managed by the Ministry of Health, after all necessary approvalswere secured.Availability of data and materialsThe data that support the findings of this study are available from CardiacServices BC and BC Vital Statistics Agency (through Population Data BC), butrestrictions apply to the availability of these data. The data were used underthe Research Agreements for the current study, and so are not publiclyavailable. Data are, however, available by submitting a data access requestto the relevant data stewards.Disclaimer: All inferences, opinions, and conclusions drawn in this paperare those of the authors, and do not reflect the opinions or policies of theData Steward(s).Authors’ contributionsMHM led the research study, including oversight of data analysis andmanuscript preparation. RS drafted the manuscript and coordinated severalrevisions. RHB provided important clinical perspectives on the interpretationof the data and analysis plan, as well as critical review of the manuscript. JEPprovided advice about and conducted the statistical analysis, and providedcritical review of the statistical aspects of the manuscript. KHH providedpivotal advice about the analysis plan and critical review of the manuscript.All authors have read and approved the final version of this manuscript.Competing interestsWe have no conflicts of interest to disclose. J.E. Park is an employee of the BCCentre for Improved Cardiovascular Health, but since the Centre did notcontribute any financial support to this work, there was no conflict of interest.Consent for publicationNot applicable.Ethics approval and consent to participateThis study was approved by the Providence Health Care/University of BritishColumbia Research Ethics Board (reference number: H10-03050). As this wasa retrospective study and no personal identifiers were ever available to theresearchers, the requirement for written consent of participants was waivedby the Research Ethics Board.Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims inpublished maps and institutional affiliations.Author details1School of Nursing, University of British Columbia, and St. Paul’s Hospital,1081 Burrard St, Vancouver, BC V6Z 1Y6, Canada. 2Faculty of Medicine,University of Manitoba and St. Boniface Hospital, Winnipeg, Canada. 3Divisionof Cardiology, University of British Columbia and St. Paul’s Hospital,Vancouver, Canada. 4BC Centre for Improved Cardiovascular Health,Vancouver, Canada. 5Division of Cardiology, University of British Columbia,Vancouver, Canada.Received: 23 November 2016 Accepted: 12 April 2017References1. Statistics Canada. National Household Survey Profile, 2011 NationalHousehold Survey. 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Ethnic and sex differences in theincidence of hospitalized acute myocardial infarction: British Columbia, Canada1995-2002. BMC Cardiovasc Disord. 2010; doi:10.1186/1471-2261-10-38.38. Harding S, Dews H, Simpson SL. The potential to identify South Asians using acomputerised algorithm to classify names. Popul Trends. 1999;97:46–9.39. Mays VM, Ponce NA, Washington DL, Cochran SD. Classification of race andethnicity: Implications for public health. Ann Rev Public Health. 2003;24:83–110.•  We accept pre-submission inquiries •  Our selector tool helps you to find the most relevant journal•  We provide round the clock customer support •  Convenient online submission•  Thorough peer review•  Inclusion in PubMed and all major indexing services •  Maximum visibility for your researchSubmit your manuscript atwww.biomedcentral.com/submitSubmit your next manuscript to BioMed Central and we will help you at every step:Mackay et al. BMC Cardiovascular Disorders  (2017) 17:101 Page 7 of 7


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