Embolization of platelets after endothelial injury to the aorta in rabbits. Assessment with 111indium-labeled platelets and angiography.

This study exploits the ability of a collateral arterial network to trap platelet aggregates in order to document the frequency of macroembolization in rabbits after endothelial damage. Two weeks after ligation of the right superficial femoral artery, endothelial injury was induced in the distal aorta; within 3 hours the rabbits were studied using either angiography or 111indium-labeled (111In) platelet scintigraphy. Angiography indicated visible aggregates in the thigh region in eight of 19 and arterial occlusion in three of 19 rabbits. The collateral-dependent thigh also showed more 111In-labeled platelet activity than the contralateral side (P less than .001), whether platelets were injected before or 2 hours after injury. Radioactivity in the limbs of rabbits with no injury was distributed symmetrically. Blood pool volume, assessed with technetium-99m-labeled red blood cells, was the same in both thighs, and could not account for these observations. The findings indicate that platelet activation and aggregation after endothelial injury lead to microembolization much more frequently than it leads to macroaggregate formation and visible artery occlusion.