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The first 153 cases of saphenous vein aortocoronary bypass surgery performed at The Johns Hopkins Hospital were reviewed. Eighty-eight percent of the 140 late survivors reported significant symptomatic improvement. Seventy-one unselected patients consented to complete reevaluation at a mean interval of 6.1 months postoperatively. Vein bypass patency in this group was 66 percent. Eighty-two percent of these 71 patients had improved performance on electrocardiographic stress testing. There were no significant differences between hemodynamic status on pre- and postoperative studies regardless of the status of vein bypass patency. Repeat coronary angiography revealed a 30 percent incidence of new total occlusions of the intrinsic coronary circulation. Segmental wall motion on ventriculography was improved in 12 percent, unchanged in 50 percent and decreased in 38 percent of the segments analyzed. Localized electrocardiographic changes compatible with myocardial damage developed in the immediate postoperative period in 45 of these patients (63 percent); in 38 of the 45, these changes corresponded to new angiographic abnormalities. Physiologic mechanisms underlying symptomatic improvement were sought by identification of an "angina-producing" myocardial segment. In most instances, alleviation of angina could be related to either: (1) a patent bypass graft into an unchanged intrinsic coronary artery with presumed increased blood flow to the distal coronary segment, or (2) occlusion of the bypass graft and the corresponding coronary artery with probable infarction of previously ischemic myocardium. Current criteria for the selection of patients undergoing coronary bypass surgery are reviewed in the light of these findings. It is concluded that relief of disabling angina is the major indication for surgery. Prevention of myocardial infarction and improvement in left ventricular function are at present less reliable objectives.

The studies on natural history of ischemic heart disease are reviewed and the major predictors of mortality identified. The severity of the coronary atherosclerosis and the status of ventricular function are found to be more important predictors of survival than the clinical presentation. The objectives of therapy in patients with ischemic heart disease are (1) to improve the quality of life by reducing symptoms, (2) to improve ventricular function, and (3) to increase survival time. The results of surgical therapy are examined in relation to these three objectives. Symptomatic improvement is present in 85 to 95 percent of patients after surgery, but convincing evidence for improved ventricular function is lacking and controlled studies of natural history have failed to show that surgery increases survival time. Analysis of the mechanism of symptomatic improvement after surgery suggests that increased blood flow to the ischemic area as well as infarction of ischemic myocardium and the nonspecific effects of surgery may account for the improvement. The prevention of coronary atherosclerosis is viewed as an attainable long-term solution to the problem of ischemic heart disease.