Electron microscopy of the sequence of events in the atheroembolic occlusion of cerebral arteries in an animal model.

Atheromatous material was removed from human atheromas, suspended in sterile saline in the ratio of 1 g to 5 ml and ground to allow passage through a needle; 0-5 ml of this suspension was injected into the left common carotid artery of 16 rabbits. Six animals died after the injection. The remaining animals were killed after various time intervals and the occluded arteries studied by electron microscopy. The general pattern of the embolic event in the cerebral arteries was that there were 3 groups of changes. Firstly, an immediate period of atherothrombotic occlusion occurred, which was followed by some resolution of the obstruction so as to leave the cholesterol crystals of the embolus stuck in the vessel walls as the only remaining element of the embolus in some cases. Finally, there was a late period in which the cholesterol crystals were isolated from the lumen of the vessel and surrounded by macrophages, fibroblastic cells and collagen. Endothelial lined channels developed in the original obstruction.