The influence of myocardial bridges on the wall of the coronary arteries during cholesterol-induced atherosclerosis in dogs

Abstract

In dogs, the influence of myocardial bridges of the coronary arteries on the development of coronary atherosclerosis was investigated under experimental conditions of early (6 months) and advanced (13 months) atherosclerosis. The adverse effect of myocardial bridges was shown in cholesterol-induced coronary atherosclerosis in dogs. In both early and advanced phases of coronary atherosclerosis the bridges caused unequal development of the sclerotic changes in the arterial wall which were most apparent in the subepicardial segments. In the early phases the atherosclerotic lesions occur mostly in the intima, in the advanced degree of atherosclerosis they occur throughout the arterial wall. In the subepicardial arterial portions of the anterior descending branch, mainly proximal to the bridge, the intima becomes thickened with advancing atherosclerosis; in the small branches ramifying before the bridge, this even leads to complete occlusion. In contrast, in the intra-myocardial portion below the bridge, the intima is thinnest. Evaluation of the estimated differences in area (evoked by the atherosclerosis) between the individual layers of the arterial wall in the subepicardial and those in intramyocardial segments, shows a statistically significant relation between the presence of myocardial bridges and certain structural changes in the arterial wall.