Effect of elevated HbA1c on outcomes in on-pump versus off-pump coronary artery bypass grafting

Background Diabetic patients are at an increased risk of cardiovascular morbidities. We aimed to examine if elevated pre-operative glycosylated hemoglobin (HbA1c) levels are associated with higher likelihood of experiencing adverse events in on-pump (ONCAB) versus off-pump (OPCAB) coronary artery bypass graft (CABG) procedures. We examined characteristics of patients undergoing CABG using our institutional STS Adult Cardiac Surgery Database (ACSD) from 2014 to 2020. Descriptive statistics and univariate analyses were used to compare postoperative outcomes between ONCAB and OPCAB based on preoperative HbA1c levels: (1) HbA1c ≤ 6.0%, (2) 6.0% < HbA1c ≤ 7.0%, (3) 7.0% < HbA1c ≤ 8.5%, (4) HbA1c > 8.5%. Multivariable models were built to assess risk factors associated with adverse events. Primary outcomes were operative mortality and stroke. Results For ONCAB, statistically significant associations were found between increasing HbA1c and new post-operative dialysis ( p= 0.01), rates of readmission ( p= 0.003) and greater lengths of stay ( p= 0.002). For OPCAB, statistically significant associations were found between increasing HbA1c and rates of operative mortality ( p= 0.04), post-operative renal failure ( p= 0.0001), new post-operative dialysis ( p= 0.0001), sternal wound infection ( p= 0.01), and greater lengths of stay ( p= 0.03). No significant relationship was noted between HbA1c and stroke, reoperation due to bleeding, or post-operative transfusion. Conclusions Increasing HbA1c positively correlated with numerous adverse patient outcomes in both ONCAB and OPCAB, and differences were noted in which outcomes were most impacted between the two techniques. Pre-operative medical optimization from a diabetes standpoint is paramount to improve CABG outcomes in both on-pump or off-pump techniques.