Preoperative hemoglobin A1c predicts sternal wound infection after coronary artery bypass surgery with bilateral versus single internal thoracic artery grafts

Objective: Bilateral internal thoracic artery (BITA) grafting during coronary artery bypass (CABG) improves long-term and event-free survival but may carry a higher risk of wound complications. It is unknown whether preoperative hemoglobin A1c (HbA1c), a measure of long-term glucose control, predicts deep sternal wound infection (DSWI) after BITA grafting. Methods: Of 6356 consecutive patients who underwent isolated CABG between January 1, 2002 and March 30, 2007 and received at least one internal thoracic artery graft, 5199 (81.8%) had preoperative HbA1c levels obtained. BITA grafting was performed in 622 (9.8%) patients. A propensity score measured each patient's probability of having BITA versus single ITA based on 52 risk factors. The primary endpoint was DSWI. Multivariable logistic models with adjusted odds ratios (AOR) examined the effect of HbA1c, BITA grafting, and their interaction on outcomes, adjusted for the propensity score and postoperative glucose levels. Results: Patients undergoing BITA grafting with HbA1c ≥ 7% had a higher incidence of DSWI compared with patients with HbA1c lt;7% (5.0% vs. 1.4%, P = 0.014). After multivariable adjustment, BITA was associated with an increased risk of DSWI (AOR = 2.84, 95% confidence interval 1.41-5.74) in all patients (P = 0.004). For each unit increase in HbA1c, there was a 31% increased risk of DSWI (AOR = 1.31, 95% CI 1.16 -1.49, P < 0.001). Patients with HbA1c < 7% had 2.88-fold increase in DSWI compared with patients with HbA1c < 7%. Conclusions: Elevated preoperative HbA1c and BITA grafting were significant predictors of DSWI after CABG. Elevated HbA1c level should be considered in the risk/benefit analysis when selecting patients for BITA grafting.