Clinical pathologic correlations in coronary artery disease.

T HE EXTENSIVE clinical utilization of coronary angiography and coronary artery surgery in recent years has heightened interest in the anatomy and pathology of the coronary arterial tree. Much new information has indeed been amassed concerning the patterns of distribution of the coronary arteries, the size and extent of interarterial coronary anastomoses, the nature, location, and extent of coronary artery narrowing and occlusion, and the correlation of these findings with pathologic changes in the myocardium and with clinical manifestations of coronary heart disease. Many years ago these matters were the subjects of extensive clinicopathologic studies based on the postmortem injection-plus-dissection technic developed by Schlesinger.' We are, therefore, interested here in reviewing these early findings as well as the recent observations and assessing their significance for the many difficult problems that arise in the clinical management of coronary artery disease today. Anastomoses The most effective protection against the otherwise dire effects of coronary occlusions is afforded by the interarterial collateral circulation of the heart. In 1669 Lower described the development of anastomoses following arterial occlusion, but he did not state whether he had observed interarterial anastomoses in the coronary arteries of the normal heart.2 In a prolonged controversy, anatomists have maintained that interarterial coronary connections are normally present in man. Since aqueous solutions injected into one coronary artery appear immediately in the others, they are evidently connected at least by arteriolar and capillary vessels. Physiologists, however, have insisted that functionally the coronary arteries are end arteries inasmuch as acute experimental ligation or clinical occlusion of a large artery always produces myocardial infarction. Anastomoses present in the normal heart, therefore, are not of sufficient size and number to be functionally significant since they do not prevent myocardial infarction. The development of larger, functionally important interarterial anastomoses has been demonstrated repeatedly following gradual experimental or atherosclerotic occlusion of a coronary artery.3-5 These collateral channels between coronary arteries serve to nourish myocardium beyond complete occlusions that would otherwise undergo necrosis, and they also serve as bypasses or detours to connect proximal and distal portions of occluded arteries. It has been shown experimentally that dogs and pigs may survive gradual complete occlusion of one or more main coronary arteries with little myocardial damage.6 The clinical counterpart of these experiments, i.e. the occasional complete absence of clinical symptoms and of myocardial infarction or fibrosis despite multiple, old coronary artery occlusions, emphasizes the functional significance of the …