Pathophysiology and Natural History Coronary Artery Disease

CASS includes a multicenter patient registry and a randomized controlled clinical trial. It is designed to assess the effect of coronary artery bypass surgery on mortality and selected nonfatal end points. From August 1975 to May 1979, 780 patients with stable ischemic heart disease were randomly assigned to receive surgical (n = 390) or nonsurgical (n = 390) treatment and were followed through April 15, 1983. At 5 years, the average annual mortality rate in patients assigned to surgical treatment was 1.1%. The annual mortality rate in those receiving medical therapy was 1.6%. Annual mortality rates in patients with single-, double-, and triple-vessel disease who were in the surgical group were 0.7%, 1.0%, and 1.5%; the corresponding rates in patients in the medical group were 1.4%, 1.2%, and 2.1%. The differences were not statistically significant. Nearly 75% of the patients had entry ejection fractions of at least 0.50. The annual mortality rates in patients in the surgical group in this subgroup with single-, double-, and triple-vessel disease were 0.8%, 0.8%, and 1.2% and corresponding rates in the medical group were 1.1%, 0.6%, and 1.2%. The annual rate of bypass surgery in patients who were initially assigned to receive medical treatment was 4.7%. The excellent survival rates observed both in CASS patients assigned to receive medical and those assigned to receive surgical therapy and the similarity of survival rates in the two groups of patients in this randomized trial lead to the conclusion that patients similar to those enrolled in this trial can safely defer bypass surgery until symptoms worsen to the point that surgical palliation is required. Circulation 68, No. 5, 939-950, 1983. CORONARY ARTERY DISEASE is a major cause of morbidity and mortality in the United States. In spite of encouraging decreases in age-adjusted mortality during the past decade,' in 1980 coronary artery disease was the cause of 566,000 deaths.2 Over 683,000 patients were admitted to hospitals in the United States that year with acute myocardial infarction.3 An estimated 5.4 million individuals have been diagnosed as having coronary artery disease as manifest by chronic angina or healed myocardial infarction.t Medical and surgical therapies for patients with coronary artery disease have changed considerably over the past 20 years. Medical management now includes aggressive modification of risk factors, liberal use of nitrates, administration of /3-adrenoceptorThis collaborative clinical trial was supported by the National Heart, Lung and Blood Institute. Address for reprints: Lloyd Fisher, Ph.D., CASS Coordinating Center, University of Washington, 1107 N.E. 45th St., Room 530, Seattle, WA 98105. Received June 2, 1983; revision accepted July 21, 1983. *Contributing investigators and participating clinical centers are listed before references. tThe Health Interview Survey, National Center for Health Statistics: Unpublished data. Vol. 68, No. 5, November 1983 blocking drugs, and more recently use of calcium antagonists. Current modes of medical therapy for coronary artery disease may favorably influence survival in selected patients. For example, results of three recent controlled trials support the premise that long-term administration of fl-blocking drugs reduces mortality in survivors of acute myocardial infarction.t Surgical treatment of patients with coronary artery disease has evolved from ineffective procedures such as thoracic sympathectomy, epicardial abrasion, and internal mammary artery ligation to the currently favored procedure, coronary artery bypass grafting with the use of either reversed saphenous vein or internal mammary artery grafts. Experienced surgical teams perform this procedure with low risk to the patient. Numerous reports attest to the fact that complete or partial relief of angina is accomplished in 60% to 90% of patients in the months and years after bypass.' 8 Coronary artery bypass surgery is often the treatment of choice for patients who have poorly controlled angina and coronary arterial anatomy making revascularization possible.9 The marked relief of angina after coronary bypass, the low operative risk, the increas939 by gest on A uust 7, 2017 http://ciajournals.org/ D ow nladed from