Natural history of coronary artery disease based on coronary angiography
Coronary angiography has long been recognized as the most accurate means of predicting the natural course of coronary artery disease. Several prerequisites, however, must be fulfilled to make such follow-up studies statistically and clinically acceptable. (1) The number or patients included in the follow-up must be high enough to allow easy statistical handling; 200 cases seem to be a minimum. (2) The follow-up should continue at least 5 years after angiography in order to demonstrate reliably the differences in mortality between the normal population and patients with coronary artery disease, not only in cases of triple-vessel disease, but especially in cases of single- and double-vessel disease. (3) The patients should be as homogeneous as possible, including single-vessel disease, double-vessel disease, and triple-vessel disease in equally representative groups. Hence, the number of patients selected for surgery during the sampling period must be small (preferably below one third of the cases studied) in order not to overweigh unduly the study with respect to the more severe cases with the worst prognosis. Only a few studies fulfill these strict criteria: the studies of Bruschke et al,1 comprising 590 cases, and Burggraf and Parker,2 comprising 259 patients although incomplete, including only 94% of cases in the third year, 88% in the fourth year, and 73% in the fifth year, and our study in Zurich (Lichtlen-Stein-brunn),3 comprising 244 patients who underwent coronary angiography between 1966 and 1971. These three studies comprise 1093 cases. They show differences with regard to overall cumulative 5-year survival as well . . .