The impact of coronary artery bypass on late myocardial infarction

Two hundred consecutive patients undergoing coronary artery bypass for stable and unstable angina pectoris were followed clinically 3 to 53 months (mean 27) and with serial electrocardiograms (ECG's) 3 to 43 months (mean 18.5) postoperatively. Complete (twelve lead) resting ECG data including preoperative, early postoperative (in hospital), and late (post hospital) studies were available in 98 per cent (196/199) of hospital survivors. A total of 2,304 ECG's were examined by two cardiologists for a total follow-up of 3,629 patient months. Myocardial infarction was defined as the appearance of a new, significant (Minnesota Code) Q wave. Fifty-four per cent (108/200) had triple vessel disease and 24 per cent (47/200) preinfarction angina pectoris by strict criteria. There was one hospital death for an operative mortality of 0.5 per cent (1/200). There was one late fatal and three late nonfatal myocardial infarctions. Seventeen patients developed new Q waves in the early postoperative period, a perioperative infarction rate of 8.5 per cent (17/200). The 43 month cumulative myocardial infarction rate, including all early and late postoperative new Q waves and three late deaths from cardiac disease, was 14 per cent. Twenty-two per cent (20/91) showed disappearance of Q waves present at the time of hospital discharge. These data suggest that the late myocardial infarction rate is low in surgically managed patients.