Abstract
The author investigated the sequential morphological changes at the site of carotid endarterectomy (CE) in cats with light microscope and scanning electron microscope (SEM).
Adult cats were anesthetized with ketamine-HCl and the right common carotid artery was exposed. After an intravenous administration of 1, 000 units heparin-Na, arterial wall was incised linearly and CE was completed by removing the endothelium, internal elastic laminae (IEL) and a part of muscle layers of the media for a distance of approximately 0.5 cm under surgical microscope. The artery was closed with 10-0 monofilament nylon. Animals were sacrificed at the acute phase (5, 10, 15, 30 min. and 1, 4, 5 days), reparative phase (1, 2, 3 weeks) and mature phase (4, 8 weeks).
1) Acute phase—At the earliest interval, the luminal surface of endarterectomized lesion was covered with small thrombi, but with the lapse of time small thrombi were decreased in number and a thin layer of adherent platelets without development of a thrombus was observed. 2) Reparative phase—The regeneration of the endothelium took place from the unendarterectomized border of the induced lesion. The central portion of CE had not yet completed the protrusions which were formed by the new endothelial cells, showing an amorphous smooth surface. At the center of the lesion, luminal surface was also covered with blood cells except areas of the smooth surface. The smooth surface appeared as the result of fusion of flattened platelets. Similar structures were seen at the advancing front of sheets of the regenerated endothelium. These findings seemed to suggest that the regeneration of the endothelium was influenced by preceded fusion of the platelets and that regeneration of endothelium took place not only from the each end of unendarterectomized vascular wall but also from islands of endothelium appeared at a number of different places over luminal surface. Under light microscopic observation, no IEL was identified by observations in reparative phase. There was poorly stained layer of amorphous material underneath the regenerated endothelial cells. 3) Mature phase—Endarterectomized area was covered completely with new endothelial cells and blood cells were not seen on the luminal surface. However, linings of the new endothelial cells were irregular and different from normal ones.
