Endothelial cell damage and thrombus formation after partial arterial constriction: relevance to the role of coronary artery spasm in the pathogenesis of myocardial infarction.

The left anterior descending coronary artery of four dogs and the right common carotid artery of 15 rabbits were subjected to 40-60% reduction in transluminal diameter for 1 hour by partial ligation with suture thread. Scanning electron microscopic examination of the luminal surface of these vessels revealed endothelial craters and balloons, fragmentation and desquamation on the proximal slope of the constriction. Platelet attachment to exposed subendothelial tissues was clearly evident, and microthrombi were seen at the point of maximum constriction. Blood flow, as measured by electromagnetic flow probe, was virtually unchanged upon partial ligation. In control studies, where a second ligature was placed proximal to and before the first to reduce blood to the distal constriction site substantially or totally, endothelial desquamation was found in only one of 14 animals, and the number of craters and balloons was significantly reduced. We suggest that endothelial damage and thrombus formation may occur at the site of focal arterial constriction even when the reduction in transluminal diameter is insufficient to alter substantially the rate of flow.