# Impact of Previous Coronary Artery Bypass Grafting on Clinical Outcomes in Patients With Acute Myocardial Infarction: A Systematic Review and Meta-Analysis

## TL;DR

This study finds that prior heart bypass surgery may increase mortality risk in patients with a specific type of heart attack, but not overall.

## Contribution

A systematic review and meta-analysis revealing differential mortality risk in STEMI patients with prior CABG.

## Key findings

- Previous CABG was not significantly linked to overall AMI mortality but showed higher risk in STEMI patients.
- STEMI patients with prior CABG had 16% higher mortality compared to those without CABG history.
- No significant difference in major adverse cardiac events was found between CABG and non-CABG groups.

## Abstract

This systematic review and meta-analysis examined the impact of previous coronary artery bypass grafting (CABG) on clinical outcomes in patients presenting with acute myocardial infarction (AMI). A comprehensive literature search was conducted across PubMed/MEDLINE, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science from January 2010 to August 2025, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Observational studies comparing outcomes between patients with AMI with and without prior CABG history were included. Two independent reviewers performed study selection, data extraction, and quality assessment using the Newcastle-Ottawa Scale (NOS). Statistical analyses employed random-effects models using RevMan 5.4 (The Nordic Cochrane Centre, Copenhagen, Denmark) and R software (R Foundation for Statistical Computing, Vienna, Austria). Nine studies comprising patients with ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI) were included in the final analysis. The pooled analysis demonstrated that previous CABG history was not significantly associated with all-cause mortality in the overall AMI population (relative risk (RR): 1.06, 95% confidence interval (CI): 0.97-1.16), although considerable heterogeneity was observed (I² = 87%). Subgroup analysis revealed that patients with STEMI with prior CABG had a 16% higher mortality risk compared to CABG-naïve patients (RR: 1.16, 95% CI: 1.12-1.20), while patients with NSTEMI showed a non-significant 6% increase (RR: 1.06, 95% CI: 0.95-1.19). No significant difference was found in major adverse cardiac events (MACE) between groups (RR: 0.98, 95% CI: 0.85-1.12). Meta-regression identified age, hypertension prevalence, and CABG prevalence as significant contributors to between-study heterogeneity. These findings suggest that prior CABG may confer increased mortality risk specifically in patients with STEMI, although limited study numbers in subgroup analyses warrant cautious interpretation and highlight the need for larger targeted investigations.