John D. Puskas, Michael E. Halkos, Vinod H. Thourani, Patrick D. Kilgo, Omar M. Lattouf, Robert A. Guyton.
Emory University, Atlanta, GA, USA.
OBJECTIVE: Bilateral internal thoracic artery (BITA) grafting during coronary artery bypass improves long-term and event-free survival, but may carry a higher risk of wound complications. It is unknown whether preoperative control of diabetes, manifested by hemoglobin A1c (HBA1C) levels, impacts the effect of BITA with respect to wound infection.
METHODS: 6673 consecutive patients (622 BITA) had isolated CABG between 1/1/2002--3/30/2007 and were retrospectively reviewed. A propensity score (PS) measured each patient’s probability of having BITA vs. single ITA (SITA) based on 51 risk factors. Measures of standardized glucose management (mean serum glucose on day of surgery (DOS) and postoperative days (POD) 1-3) were calculated for each patient. Endpoints were 30-day deep sternal wound infection (DSWI), superficial infection (SI), and their composite (WI). Multivariable logistic models examined the effect of HBA1C, BITA and their interaction on outcomes, adjusted for PS and glucose levels. Area under the receiver operating characteristic curve analyses identified HBA1C threshold values above which patients were at increased risk for wound infection. Adjusted odds ratios (AOR) measured increased risk per unit increase in HBA1C.
RESULTS: Mean glucose on DOS was 129.6 + SD 25.5 and on POD 1-3 was 133.0 + 33.7. During this period, BITA patients had a slightly lower mean glucose on DOS (124 vs. 130, p<0.001) and on POD 1-3 (129 vs. 133, p=0.004). HBA1C threshold values for each outcome ranged from 6.7-7.2. Patients undergoing BITA were at increased risk of DSWI (AOR=2.86, 95% CI 1.43-5.84) and WI (AOR=2.02, 95% CI 1.17-3.50). HBA1C was associated with increased risk of SI (AOR=1.34, 95% CI 1.16-1.56), DSWI (AOR=1.33, 95% CI 1.17-1.51) and WI (AOR=1.33, 95% CI 1.20-1.48) after multivariable adjustment. No interactions existed between BITA and HBA1C, meaning that BITA impacted all patients similarly, regardless of HBA1C value.
CONCLUSIONS: Despite uniform perioperative glucose management, preoperative HBA1C remained a predictor of wound infection, especially above a threshold value of 7-8. BITA grafting was associated with increased risk of DSWI irrespective of HBA1C level.Outcome Incidence BITA vs SITA AOR (p-value) HbA1C per unit AOR (p-value) Interaction p-value Maximizing HbA1C Threshold SI 65/6356 1.23 (0.630) 1.34 (<0.001) 0.91 6.9 DSWI 83/6356 2.86 (0.003) 1.33 (<0.001) 0.70 7.2 WI 145/6356 2.02 (0.012) 1.33 (<0.001) 0.73 6.7
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