Vasa Vasorum and Coronary Atherosclerosis

VASA VASORUM AND CORONARY ATHEROSCLEROSIS FRANK D. MANN* Frequently, at the autopsy of a man dying in his prime with no disease except coronary atherosclerosis, the pathologist asks himself, Why does atherosclerosis so often strike this vital site so early? There have been various answers; I wish to explore a very old lead, the coronary vasa vasorum. In 1875 Professor W. Koester gave three oral presentations before the Medical Society of the Lower Rhine on what he termed endarteritis. These observations, apparently based on extensive studies with serial histopathologic sections, were recorded in only a few brief paragraphs in the minutes of one of the meetings [I]. Koester found that "inflammatory intimai thickenings," by which he had to mean atheromata, always showed proliferation of capillaries, which were connected to the vasa vasorum of the adventitia. He emphasized the morphologic interpretation that the vascular proliferation proceeded from the adventitial vasa vasorum, not from the endothelial surface. He further observed that the intimai thickenings were always in contact with areas of nuclear proliferation in the adjacent smooth muscle of the media. Thus Koester can reasonably be held to have anticipated by many decades the presently accepted principle that the atheroma originates by proliferation of smooth muscle [2]. It is not surprising that this very old and brief report has received only a little recent attention [3]. Wartman, in the course of extensive studies on hemorrhage into coronary atheromata, showed these lesions to be richly vascularized and was able to trace these intimai vessels to the adventitial vasa vasorum [4]. Recently, Barger et al. demonstrated by a beautiful photographic technique the connections of the vessels of coronary plaques to the adventitial vasa vasorum [5]. Unlike Koester, however, they regarded the vascular proliferation as probably a response to intimai injury. The extent of *Address: 5316 East Roadrunner Road, Scottsdale, Arizona 85253.© 1985 by The University of Chicago. All rights reserved. 003 1-5982/85/2803-0443$0 1 .00 Perspectives in Biology and Medicine 28, 3 ¦ Spring 1985 \ 367 penetration of the vasa vasorum into the walls of normal arteries has apparently not been firmly established. Song et al., employing scanning electron microscopy and microinjection, have recently reported that in the normal aorta of the dog and the pig the vasa vasorum extend to the intima [6]. Thus it seems at least not ruled out that the vasa vasorum may provide a route through which injurious agents might initiate disease in the intima, as Koester claimed. I shall point out that the coronary vasa vasorum may have unusual access to possible injurious agents, the adrenal medullary hormones. In 1930 Robertson found that the fat pads that surround the origins of the great vessels and continue around the main coronary arteries are extremely vascular. Within these fat pads the vasa vasorum of the coronarles and those of the aorta and pulmonary artery are extensively interconnected [7]. These same vascular interconnections are demonstrated in Spalteholz's beautifully sharp photographs of injected and cleared human hearts [8, p. 34]. In times of stress a burst of catecholamines from the adrenals could conceivably be injected into this rich vascular sponge via the pulmonary artery. Then the vascular sponge could be squeezed by the aortic pulse and the catecholamines could enter the coronary vasa vasorum. Thus, at least an anatomic pathway exists whereby adrenal hormones could bypass the lungs and reach the coronary vasa vasorum rapidly and in relatively high concentration. There is a little physiologic evidence that such a bypass may be functional . In some old recordings a marked pressor response followed intravenous injection of epinephrine almost immediately, within three heartbeats [9, p. 402]. These recordings were made on dogs, which have the same anatomic relationships of the coronary vasa vasorum as does man [7, 8]. Such a bypass route might actually be advantageous to an animal in urgent need of intense physical exertion to escape danger. On the other hand, the physically quiescent occupant of an executive chair might experience coronary spasm. Recently, the role of spasm in coronary insufficiency has been emphasized [10]. Any concept of atherosclerosis must take into account the finding of Benditi and Benditt that the fibrous atherosclerotic plaque originates in man by...