Abstract
Forty-five carotid artery plaques (27 symptomatic, 18 asymptomatic) were obtained from carotid endarterectomies (25 unilateral, 10 bilateral) in 35 patients and were evaluated pathologically. We investigated the relationship of morphologic characteristics to the presence of cerebral ischemic symptoms and to the degree of stenosis associated with the carotid plaques. Simple fibrous plaques were found in 18 of the 45 plaques (40.0%) and were more frequently observed among the asymptomatic plaques (55.6%) than among the symptomatic plaques (29.6%). Ulceration was observed in 14 of the 45 plaques (31.1%) and was more frequent in plaques from symptomatic cases (44.4%) than in those from asymptomatic cases (11.1%). Six of the 12 plaques with ulceration showed intraplaque hemorrhage in the symptomatic cases. Eight of the 12 plaques with ulceration showed intraluminal thrombus in the symptomatic cases. Intraplaque hemorrhage was found in 17 of the 45 plaques (37.8%) and was more frequent in the plaques of symptomatic cases (48.1%) than those of asymptomatic cases (22.2%). Six of the 13 plaques with intraplaque hemorrhage showed ulceration in the symptomatic cases. Intraluminal thrombus was observed in 10 of the 45 plaques (26.7%) and more frequently in the plaques of symptomatic cases (37.0%) than in those of asymptomatic cases (11.1%). All plaques were divided into three broad degrees of stenosis groups (40-69%, 70-89%, 90-99%) angiographically. The incidence of simple fibrous plaques were most frequent in the most stenotic group, both when all plaques were considered and when only symptomatic plaques were examined. Although ulceration occurred more commonly in the 70-89% stenosis group, it was also observed in 4 plaques with relatively mild stenosis, and observed in only one plaque with more than 90% stenosis. Intraplaque hemorrhage occurred more commonly in the stenotic groups with more than 70% stenosis, whether all plaques or only symptomatic plaques were examined. These findings indicate that: 1) when stenosis of the carotid artery is severe, simple fibrous plaque may cause cerebral ischemia due to flow restriction, but a critical or hemodynamically significant internal carotid artery stenosis may be of a higher grade than previously appreciated when the lesion is a simple plaque, 2) ulceration of a carotid plaque is seen at a smaller plaque size and induces cerebral ischemia due to embolic phenomena, 3) since intraplaque hemorrhage may contribute to the acute progression of carotid stenosis, hemorrhage may cause hemodynamic failure. Intraplaque hemorrhage may also play an important role in ulceration to cause embolic phenomena.
