Platelet deposition in rabbit common carotid arteries promoted by arterial stenosis and spasm

Coronary arteriograhy in patients with ischemic heart disease often shows spasm of the coronary arteries. The question is whether spasm is a triggering factor for thrombosis in a stenotic artery. If so, what are the mechanisms for this? A stenosing teflon ring was applied to the right common carotid artery of anesthetized rabbits and 1-nor-epinephrine was dripped over the outer surface of both carotid arteries, causing spasm. In control animals an indifferent solution did not cause spasm. Nineteen rabbits were killed 30 min or 24 h after treatment. Microscopically, arteries with stenosis and spasm contained thrombi nearby the stenosis significantly more often than arteries in control animals. In another 14 rabbits, killed at 30 min, the number of platelets on the intimal surface away from the stenosis was quantified. In arteries with both stenosis and spasm the counts were significantly greater than in arteries with no treatment. The intimal surface in stenotic and spastic arteries showed assumed imprints of eddying flow and endothelial injury downstream and upstream of the stenosis. Spastic arteries showed increased folding of the internal elastic membrane, altered endothelial cells, and adhering platelets. Spasm in a rabbit artery with a preformed stenosis facilitates thrombosis probably by creating increased flow disturbances. Spasm may induce endothelial injury, causing adherence of platelets.