Risk factors for operative mortality and sternal wound infection in bilateral internal mammary artery grafting

To investigate risk factors for operative mortality and sternal infection in patients undergoing bilateral internal mammary artery grafting, we analyzed the data of 199 patients who underwent this procedure from January 1986 through June 1992. These patients were also compared with those who underwent only saphenous vein grafting (1664 cases) and those who underwent unilateral internal mammary artery grafting (3359 cases) during the same time frame. The operative mortality was 3.52% (7/199) in the patients having bilateral internal mammary artery grafting, 2.71% (91/3359) in those having unilateral internal mammary artery grafting, and 8.53% (142/1664) in the patients having saphenous vein grafting (p < 0.0001). The occurrence rate of sternal infections was 2.45% (5/199) for bilateral internal mammary artery grafting, 1.32% (13/1664) for saphenous vein grafting, and 1.19% (20/3359) for unilateral internal mammary artery grafting (p = 0.27). The univariate analysis revealed that age, history of congestive heart failure, emergency operation, ejection fraction, and aortic crossclamp time were significantly correlated with operative mortality and that obesity was correlated with sternal wound infection. Stepwise multiple logistic regression identified that old age (> or = 70 years) (p < 0.0001), long perfusion time (p < 0.0001), and emergency operation (p = 0.0004) are risk factors for operative mortality and that obesity (p = 0.0009) is the only significant risk factor for sternal wound infection. We conclude that bilateral internal mammary artery grafting does not increase operative mortality in properly selected patients. However, this procedure should be carefully chosen in elderly (> or = 70 years) patients and for emergency operation. Obese patients have a high risk for sternal infection after bilateral internal mammary artery grafting.