Effect of Aortic Cross-Clamp Time on Myocardial Infarction after Coronary Bypass Surgery

Univariate and multivariate statistical analyses were applied to 1200 consecutive patients undergoing first-time myocardial revascularization. Forty-three patients (3.6%) developed evidence of myocardial infarction as judged by serial electrocardiograms and release of enzymes. Out of 23 preoperative and intraoperative potential risk factors for perioperative myocardial infarction, multivariate regression analysis revealed that duration of aortic cross-clamping was a powerful continuous variable risk factor. The relative risk increased twofold at 44 minutes compared to 17 minutes, approached three times the risk at 53 minutes, and reached more than six times the risk after 84 minutes of aortic cross-clamping. Two other independent predictors for perioperative myocardial infarction were identified: the presence of preoperative arterial hypertension and significant (> 75%) left main coronary artery stenosis. Left ventricular impairment, gender, age, severity of angina, and the number of distal anastomoses were not identified as risk factors for perioperative myocardial infarction. Our data indicate that the incidence of perioperative myocardial infarction may be reduced by consistent efforts to minimize aortic cross-clamp time without compromising the adequacy of myocardial revascularization.