Association Between Hemoglobin A1c and Major Adverse Coronary Events in Patients with Diabetes Following Coronary Artery Bypass Surgery.

Abstract

Diabetes is associated with a higher risk of major adverse coronary events (MACE) following coronary artery bypass grafting (CABG). Guidelines recommend disparate targets for glycemic control of patients with diabetes who have undergone CABG, ranging from a target hemoglobin A1c (HbA1c) of <7.0% to 7.1-8.5%, based on data from non-CABG patients. To date, no study has evaluated the long-term impact of HbA1c concentrations on MACE post-CABG. To evaluate the association between HbA1c and MACE in CABG patients with diabetes. A secondary analysis of the Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI2D) trial, which enrolled patients with type 2 diabetes and coronary artery disease, restricted to participants who underwent CABG with ≥1 HbA1c measurement post-CABG, was performed. The index date was date of first post-CABG HbA1c measurement. The primary outcome was MACE (composite of death, myocardial infarction, unstable angina, or repeat revascularization). Secondary outcomes included MACE components and heart failure. Cox proportional hazards models treating HbA1c as a time-dependent exposure (reference group: HbA1c 6.1-7.0%) were used to derive hazard ratios (HRs) with 95% confidence intervals adjusting for age, sex and baseline characteristics selected by stepwise regression. A total of 549 patients were followed over a median 3.5years. The median age of the cohort was 64years, 25.1% were female, and median baseline HbA1c was 6.7%. Compared to achieving an HbA1c 6.1-7.0%, HbA1c >8.0% was associated with an increased risk of MACE (HR 1.77, 1.01-3.10). This association was strongest for unstable angina (HR 5.21, 1.03-26.39). Achieving an HbA1c ≤6.0% was associated with an increased risk of death (HR 2.41, 1.01-5.74). Other comparisons were not statistically significant. Among patients with type 2 diabetes who underwent CABG, achieving HbA1c 6.1-7.0% was associated with a lower risk of MACE and unstable angina versus achieving an HbA1c >8.0% and lower risk of death versus achieving an HbA1c ≤6.0%.