Intensity of Glycemic Control Affects Long-Term Survival After Coronary Artery Bypass Graft Surgery

Background. A patient's hemoglobin (Hb) A(1c) level, regardless of diabetic status, is a measure of glycemic control. Studies have found it is an independent predictor of short-term death in patients undergoing coronary artery bypass grafting (CABG). In this study, we used preoperative HbA ic to assess whether levels are associated with short-term and long-term survival after CABG. Methods. From a regional registry of consecutive cases, we identified 6,415 patients undergoing on-pump isolated CABG from 2008 to 2015 with documented preoperative HbA(1c) level. We defined four HbA(1c) groups: less than 5.7% (n = 1,713), 5.7% to 6.4% (n = 2,505), 6.5% to 8.0% (n = 1,377), and more than 8% (n = 820). Relationship to in-hospital outcomes and long-term survival was assessed. Outcome rates and hazard ratios were adjusted for patient and disease risk factors using multivariable logistic regression and Cox models. Results. The study included 3,740 patients (58%) not diagnosed as having diabetes and 2,674 with diabetes. Prediabetes (HbA(1c) 5.7% to 6.4%) was documented in 52% (n = 1,933) of nondiabetic patients. Higher HbA(1c) values were associated with younger age, female sex, greater body mass index, more comorbid diseases, lower ejection fraction, more 3-vessel coronary disease, and recent myocardial infarction (p < 0.05 trend for all). After adjustment for patient risk, greater HbA(1c) values were not associated with higher rates of in-hospital death or morbidity. Long-term survival was significantly worse as HbA(1c) increased. Risk of death increased by 13% for every unit increase in HbA(1c) (adjusted hazard ratio, 1.13; 95% confidence interval, 1.07 to 1.19; p < 0.001). Conclusions. Preadmission glycemic control, as assessed by HbA(1c), is predictive of long-term survival, with higher levels associated with poorer prognosis. Whether this risk can be modified by better glycemic control postoperatively remains to be determined. (C) 2019 by The Society of Thoracic Surgeons