Fibrin content of carotid thrombi alters the production of embolic stroke in the rat.

BACKGROUND AND PURPOSE Mechanical denudation of the endothelium of the carotid artery in animals produces a nonocclusive thrombus, but the brains of these animals have not been examined for the presence of embolic stroke. METHODS The endothelium of the right carotid artery of 16 Wistar rats was denuded using a balloon catheter. Phosphotungstic acid hematoxylin (PTAH) staining and scanning electron micrographs of the nonocclusive thrombi in the carotid arteries were compared with those produced by photochemical methods, and brains were examined for infarcts. RESULTS Although nonocclusive thrombi were present in the carotid arteries of 4 of 4 rats killed at 4 hours and in 8 of 12 killed at 24 hours, neither cerebral infarcts nor emboli were seen in the 14 brains evaluated by light microscopy. PTAH demonstrated a high fibrin content in the thrombus produced by the endothelial denudation, with almost no fibrin seen in photochemically induced thrombi. Scanning electron microscopy confirmed dense networks of fibrin in the thrombi produced by balloon denudation. CONCLUSIONS The composition of a nonocclusive thrombus may determine the embolic potential of this thrombus. A low fibrin content in a nonocclusive platelet thrombus may enhance the embolic potential. This suggests that platelet inhibition may also be indicated in patients with carotid artery disease who are being treated with anticoagulant.