Introduction: The optimal timing for coronary artery bypass grafting (CABG) following an acute myocardial infarction (MI) is a topic of controversy among cardiologists and cardiothoracic surgeons. We sought to perform a systematic review of the evidence.
Methods: PubMed was searched for studies that compared mortality between patients who underwent CABG, at different time points, following an acute MI. The quality of evidence was assessed using the National Institute of Health (NIH) quality assessment tool for observational cohort and cross-sectional studies. Mortality was compared between groups who had CABG performed <24 hours (acute), 24-72 hours (sub-acute), and >72 hours (delayed) following MI.
Results: Sixteen observational studies were identified (1 prospective, 15 retrospective) which included 94,841 patients. There were no randomized controlled trials (RCT). Five studies used data from official registries while 11 relied upon data from a single site. Two studies specified the MI type as NSTEMI, 2 as STEMI, and it was unspecified in 12. Mortality was assessed as ‘in-hospital’ in 10 studies, ‘perioperative’ in 5, and ‘one month’ in 1. Using the NIH quality assessment tool, we scored 12 domains on a dichotomous scale of ‘yes’, ‘no’, or ‘other’ and found the average number of ‘yes’ answers was 6.5/12 with a range of 4 to 8/12. A quantitative comparison of mortality risk between timing groups could not be performed due to heterogeneity between recorded baseline covariates across studies as well as heterogeneity between MI-type, timing cut-offs, and specific mortality endpoints across studies. Only 1 study used propensity-matching, most used some logistic regression but 4 did not adjust at all for baseline cofounders. Most studies found that mortality was increased when patients underwent CABG <24 hours following MI but there was no consistent difference in mortality between sub-acute versus delayed groups.
Conclusions: The current evidence base for timing of CABG post-MI is poor, being composed of low to fair quality observational studies and expert opinion. Selection bias is a major concern for all studies that were reviewed. Well-conducted RCTs are urgently needed to better inform this important clinical question.