Diseases of the heart, particularly those involving the coronary arteries, are the major medical problem facing us today. Estimates of the number of persons with heart disease in this country have varied up to eight million,1 and practically half of cardiac deaths are caused by coronary artery disease.2 We have estimated that one-half to one million attacks of coronary occlusion occur annually.3 Probably an equal number of acute coronary insufficiency occur.4 As the span of life has lengthened, the incidence of coronary artery disease has increased, and will continue to do so. It has been estimated that in 1980 there will be 42 million persons between the ages of 50 and 74—almost double the number in 1940.5 The importance of coronary artery disease in industry scarcely requires emphasis, considering that over 60 million persons are employed and that, although two-thirds of acute coronary attacks occur