Myocardial infarction after aortocoronary bypass: etiologic factors

To ascertain the frequency and probable determinants of myocardial infarction after aortocoronary bypass, two groups of patients were studied: a group of 20 patients who underwent valve replacement of repair of congenital anomalies and a group of 24 patients who underwent aortocoronary bypass. Postoperative myocardial infarction was diagnosed by an increase in serum creatine phosphokinase concentration to a minimum of 1200 IU in two consecutive samples. The frequency of myocardial infarction differed between the groups, being only 5% in group 1 but 20.4% in group 2. In the patients undergoing coronary artery surgery, the duration of bypass, the aortic cross-clamp time and the vent site did not influence the rate of infarction. However, the incidence of myocardial necrosis did correlate with the number of vessels bypassed. In no case was the clinical course influenced by the infarction. Our results suggest that the frequency of perioperative infarction is higher in coronary artery surgery than in other adult cardiac surgery, and that the most important determining factor is the number of diseased vessels.