Open Access Research BMJ Open: first published as 10.1136/bmjopen-2014-006920 on 6 May 2015. Downloaded from Genome-wide association study of perioperative myocardial infarction after coronary artery bypass surgery Miklos D Kertai,1 Yi-Ju Li,2,3 Yen-Wei Li,2 Yunqi Ji,2 John Alexander,4,5 Mark F Newman,1,5 Peter K Smith,6 Diane Joseph,5 Joseph P Mathew,1 Mihai V Podgoreanu,1,5 for the Duke Perioperative Genetics and Safety Outcomes (PEGASUS) Investigative Team To cite: Kertai MD, Li Y-J, ABSTRACT et al Strengths and limitations of this study Li Y-W, . Genome-wide Objectives: Identification of patient subpopulations association study susceptible to develop myocardial infarction (MI) or, ▪ of perioperative myocardial This is the first genome-wide association study conversely, those displaying either intrinsic infarction after coronary of perioperative myocardial infarction, using pro- artery bypass surgery. BMJ cardioprotective phenotypes or highly responsive to spective cohorts of cardiac surgical patients, Open 2015;5:e006920. protective interventions remain high-priority knowledge standard definitions of the primary phenotype doi:10.1136/bmjopen-2014- gaps. We sought to identify novel common genetic and full adjustment for non-genetic risk factors. 006920 variants associated with perioperative MI in patients ▪ We conducted comprehensive and complemen- undergoing coronary artery bypass grafting using tary single marker and pathway-based genome- ▸ Prepublication history and genome-wide association methodology. wide association analyses. supplementary files are Setting: 107 secondary and tertiary cardiac surgery ▪ The study is powered to detect relatively large available. To view please visit centres across the USA. effect sizes. the journal (http://dx.doi.org/ Participants: We conducted a stage I genome-wide ▪ Rare genetic variant effects not analysed. 10.1136/bmjopen-2014- association study (GWAS) in 1433 ethnically diverse ▪ Predominantly Caucasian cohort, thus findings 006920). patients of both genders (112 cases/1321 controls) cannot be generalised to other populations. from the Genetics of Myocardial Adverse Outcomes and Received 14 October 2014 Graft Failure (GeneMAGIC) study, and a stage II analysis Revised 10 March 2015 http://bmjopen.bmj.com/ Accepted 12 March 2015 in an expanded population of 2055 patients (225 cases/ Conclusions: Using a two-stage GWAS and pathway 1830 controls) combined from the GeneMAGIC and analysis, we identified and prioritised several potential Duke Perioperative Genetics and Safety Outcomes susceptibility loci for perioperative MI. (PEGASUS) studies. Patients undergoing primary non- emergent coronary bypass grafting were included. Primary and secondary outcome measures: INTRODUCTION The primary outcome variable was perioperative MI, Despite advances in surgical techniques and defined as creatine kinase MB isoenzyme (CK-MB) pharmacological therapy, the incidence of values ≥10× upper limit of normal during the first on September 26, 2021 by guest. Protected copyright. postoperative day, and not attributable to preoperative myocardial infarction (MI) after coronary MI. Secondary outcomes included postoperative CK-MB artery bypass grafting (CABG) remains as as a quantitative trait, or a dichotomised phenotype high as 19%, and is associated with increased 1 based on extreme quartiles of the mortality and long-term morbidity. Strategies CK-MB distribution. to identify subpopulations of patients at risk Results: Following quality control and adjustment for for developing large myocardial infarcts on clinical covariates, we identified 521 single nucleotide the one hand, or those displaying an intrinsic polymorphisms in the stage I GWAS analysis. Among cardioprotective state on the other hand, these, 8 common variants in 3 genes or intergenic remain high-priority knowledge gaps and −5 regions met p<10 in stage II. A secondary analysis could inform selection of more specificpro- using CK-MB as a quantitative trait (minimum tective agents.2 p=1.26×10−3 for rs609418), or a dichotomised The evidence for heritability of MI is strik- phenotype based on extreme CK-MB values (minimum −6 ing, supported both by family studies and, For numbered affiliations see p=7.72×10 for rs4834703) supported these findings. end of article. Pathway analysis revealed that genes harbouring top- recently, by a number of well powered and scoring variants cluster in pathways of biological replicated genome-wide association studies Correspondence to relevance to extracellular matrix remodelling, (GWAS), which primarily implicate common Dr Mihai V Podgoreanu; endoplasmic reticulum-to-Golgi transport and genetic variants at the 9p21 locus in multiple 3–6 [email protected] inflammation. racial groups. However, although family- Kertai MD, et al. BMJ Open 2015;5:e006920. doi:10.1136/bmjopen-2014-006920 1 Open Access BMJ Open: first published as 10.1136/bmjopen-2014-006920 on 6 May 2015. Downloaded from based methods are not practical for studying periopera- discovery data set, leading to a total of 2055 patients. tive MI (PMI), its genetic basis is strongly suggested by The additional patients underwent CABG with cardio- several observations, including wide variability in inci- pulmonary bypass between 1997 and 2006 as part of the dence and severity that is poorly explained by clinical Perioperative Genetics and Safety Outcomes Study, an and procedural risk factors, different racial susceptibility IRB-approved longitudinal study at the Duke University profiles and results from preclinical animal models. Medical Center.11 12 Indeed, extensive genetic variability has been found in biological pathways implicated in the pathophysiology of Definition of PMI postoperative MI, such as the complex acute inflamma- PMI was defined according to the universal definition of tory response to cardiac surgery. Mounting evidence for MI19 as an elevation in the plasma level of creatine heritability of a proinflammatory state suggests that indi- kinase MB isoenzyme (CK-MB) that was >10 times the vidual genetic history may also significantly modulate the upper limit of normal, as measured by a core laboratory magnitude of postoperative inflammatory response after within 24 h after surgery, and that was not attributable to cardiac surgery.7 Yet only a few studies have identified an intervening clinical event or preoperative MI (adjudi- allelic associations with altered susceptibility to myocardial cated by the PREVENT-IV Clinical Events Committee).18 ischaemia-reperfusion injury in cardiac surgical popula- tions, all based on a candidate gene association Genotyping and quality controls – approach.8 12 Thus, the overall influence of common Genomic DNA was isolated from whole blood or saliva genetic variation on the incidence of PMI remains poorly using standard procedures. Genotyping in both cohorts understood. was performed on the Illumina Human610-Quad Recently, integrated testing of genes involved in the BeadChip at the Duke Genomic Analysis Facility. Sample same biological pathway has emerged as an alternative and genotype quality control of data flow included strategy for evaluating the combined effects of multiple assessment of call rates, gender check, cryptic related- genetic variants with small effect size on a disease ness, SNP missingness and the Hardy-Weinberg equilib- – phenotype.13 15 Given the polygenic nature of disease rium, as previously described.20 We used principal susceptibility, this approach is increasingly being used to components derived from the EIGENSTRAT21 method identify groups of gene variants with shared cellular to control for population stratification (see online sup- function that are enriched for disease, while also improv- plementary methods). ing the statistical power of GWAS. In this study, we adopted this strategy by first employing genome-wide Statistical analysis association methodology to identify common genetic Univariate regression analysis was performed to test dif- variants associated with PMI after CABG, followed by ferences in demographic, clinical and procedural http://bmjopen.bmj.com/ pathway-based analyses to uncover biological mechan- characteristics between patients with and without post- isms of relevance to PMI. operative MI; statistically significant covariates were sub- sequently used to adjust genetic association tests. Genome-wide association analyses performed in the METHODS stage I cohort used multivariable logistic regression The study design and reporting of the results follow the models implemented in PLINK 1.07, assuming an addi- ‘ recommendations by Strengthening the Reporting of tive genetic model, and including significant clinical cov- ’ 16 Genetic Association Studies (STREGA). We per- ariates and the top 10 principal components to adjust on September 26, 2021 by guest. Protected copyright. 17 formed a joint two-stage GWAS combined with a for population stratification (see online supplementary pathway analysis approach. table S1). Statistical significance for stage I analyses was a priori arbitrarily defined as a two-tailed p<0.001, to Patient populations balance between the overly conservative Bonferroni cor- The stage I cohort (discovery cohort) comprised 1493 rection and type II error, given that we had an a priori ethnically diverse subjects who underwent an isolated defined replication data set to obviate type I error. In CABG with cardiopulmonary bypass for the first time stage II analyses, the same clinical covariate and princi- and were enrolled between 2002 and 2003 in the pal component