Increased glucose variability is associated with atrial fibrillation after coronary artery bypass

Background: Elevated preoperative hemoglobin A1c (HbA1c) is a predictor of poor outcomes following coronary artery bypass grafting (CABG), but the role of increased postoperative glucose variability (GV) is unknown. We hypothesized that short-term postoperative GV is associated with an increased risk of postoperative atrial fibrillation following isolated CABG. Methods: Multicenter retrospective study of 2073 patients who underwent isolated CABG from January 2012 to March 2018. Postoperative GV in the first 24 hours was measured by standard deviation, coefficient of variation, and mean amplitude of glycemic excursions. Multivariate logistic regression assessed the independent association of GV with postoperative atrial fibrillation. Results: A total of 2073 patients met the study criteria, and 446 patients (21.5%) developed postoperative atrial fibrillation. Using multivariate logistic regression to adjust for covariates, postoperative atrial fibrillation was associated with increased 24-hour GV (odds ratio [OR] = 1.16, 95% confidence interval [CI], 1.05-1.27, P < 0.01) and increased 24-hour mean glucose (OR = 1.14, 95% CI, 1.08-1.21, P < 0.01). Thus, for every 10% increase in 24-hour GV or 10 mg/dL increase in mean glucose, there was a 16% or 14% increased risk of postoperative atrial fibrillation respectively. Conclusions: Increased 24-hour GV and mean glucose are predictors of atrial fibrillation after CABG. Preoperative HbA1c is not a risk factor for postoperative atrial fibrillation after adjusting for postoperative mean glucose and GV. Further investigation is needed to determine the relationship between adherence to strict glucose control and adverse events following CABG.