Preoperative Glycosylated Hemoglobin: A Risk Factor for Patients Undergoing Coronary Artery Bypass

Abstract

Background: The prevalence of diabetes in the population of patients presenting with coronary artery disease continues to rise. The aim of this study was to assess whether high Glycosylated hemoglobin (HbA1c) was associated with adverse outcomes in patients undergoing elective coronary artery bypass grafting.

Methods: A retrospective observational study on prospectively collected data in 4,678 patients undergoing elective, isolated coronary artery bypass graft procedures in a single institution over a 4-year period was conducted. Patients were grouped into those with adequate preoperative control of hyperglycemia (HbA1c <6.5%) and those with suboptimal control (HbA1c ≥6.5%). Multivariable analysis using HbA1c as a binary independent variable was undertaken in the whole group. A subgroup analysis in diabetic patients and in nondiabetic patients was performed. The effect of HbA1c on outcomes at higher levels (HbA1c ≥8.0% and HbA1c ≥9.0%) was also assessed.

Results: A total of 4,678 patients (mean age, 58.8; male, 4,254) were included in the study. HbA1c was less than 6.5% in 2,476 (52.93%) patients and 6.5% or higher in 2,202 (47.07%) patients. On multivariate analysis, there was no difference in mortality rates between the groups (odds ratio, 1.36; 95% confidence interval [CI], 0.95 to 1.953; p = 0.08). Overall, an HbA1c of 6.5% or higher was an independent risk factor for respiratory complications (odds ratio, 1.05; 95% CI, 1.008 to 4.631; p = 0.01) and sternal dehiscence (odds ratio, 2.161; 95% CI, 1.008 to 4.63; p = 0.04). An association between HbA1c levels and adverse outcomes was not seen in nondiabetic patients. No additional adverse postoperative complications were seen with increasing HbA1c levels (HbA1c ≥8.0% and HbA1c ≥9.0%).

Conclusions: An HbA1c level of 6.5% or higher in patients presenting for coronary artery bypass grafting was associated with a significant increase in the incidence of deep sternal wound infection and respiratory complications.