Do coronary artery bypass operations prolong life?

Abstract

Coronary artery bypass operations improve survival in patients with symptomatic left main coronary artery stenosis, but whether or not longevity is improved in other patients has been controversial. Small clinical studies, even when randomized, have not sufficiently controlled for the heterogeneous distribution of risk factors in patient cohorts treated medically and surgically. The first randomized study large enough to overcome such problems, the Veterans Administration Cooperative Study, showed that coronary artery bypass procedures prolonged survival only in the high-risk subgroup. The surgically treated patients suffered more perioperative morbidity and mortality and had worse long-term survival than similar patients operated on in more recent years. The European Coronary Surgery Study Group recently reported that the three-year to five-year survival of symptomatic patients with triple-vessel disease and normal left ventricular function was better if patients were randomly assigned to surgical therapy. The third and by far the largest randomized study, the Coronary Artery Surgery Study (CASS), has not yet reported long-term follow-up results. Large clinical studies, both randomized and nonrandomized, that have subgrouped patients by the number of diseased coronary arteries and by the degree of left ventricular dysfunction all show that survival with single-vessel disease is excellent and not improved by operation. Medically treated patients with double- and triple-vessel disease who have good left ventricular function generally now have a five-year survival greater than 85 percent and only two of the major studies suggest that it is improved by operation. The results of most studies, however, suggest that bypass operation prolongs survival in symptomatic patients when left ventricular dysfunction coexists with double- and triple-vessel disease. Continually improving surgical techniques may potentiate the small survival differences that are now apparent, but until then, because the survival differences are so small, it is recommended that limiting anginal symptoms remain the primary indication for a coronary bypass procedure for an individual patient.