The National Heart, Lung, and Blood Institute Coronary Artery Surgery Study (CASS)

The Coronary Artery Surgery Study (CASS) was organized in 1973 with the support of the National Heart, Lung, and Blood Institute. Enrollment of patients began 1974 and continued through May 1979; follow-up will continue through May 1983, CASS consists of a prospective, randomized study to compare the results of medical and surgical treatment in a subset of patients with anatomically proved coronary artery disease, and a registry of consecutive patients undergoing coronary arteriography at the 15 cooperating sites in the United States and Canada. By the end of the enrollment period, 24,959 patients had entered the registry and 780 patients were randomized. Clinical and objective data are gathered for each subject at entry and during follow-up. The coronary arteriograms are analyzed according to a common format. An angiographic committee reviewed the technical excellence and the quality of interpretation of angiograms in the study at regular intervals. The patients were randomized into three groups: (A) those with less than severely disabling angina and normal ventricular function, (B) those with less than severely disabling angina and reduced ventricular function, and (C) those who survived myocardial infarction. Specific end points for follow-up include mortality, rate of myocardial infarction and 'quality of life'. The cooperating investigators analyzed the data in the registry to describe the natural history of coronary artery disease, the clinical characteristics of the population enrolled and the choice of treatment in nonrandomized patients. The present report describes the protocol and selected clinical descriptions of the patients in the registry and randomized study.