Morphogenesis and clinicopathologic characteristics of recurrent carotid disease.

The histopathologic characteristics of primary plaques and recurrent carotid disease were studied in 32 patients. These data were related to symptoms, recurrence interval (6 to 176 months), arteriographic anatomy, and in situ operative findings. A striking predilection was noted for recurrent lesions to be located in the internal carotid artery near the origin, but still within the confines, of the original endarterectomy site and suture line. Although recurrence was frequently associated with a long primary arteriotomy, evidence of technical faults or periarterial fibrosis was rare. Early recurrent lesions (recurrence interval less than 36 months, n = 13) had significantly more smooth muscle cells and proteoglycans (p less than 0.001) than late recurrent lesions (recurrence interval greater than 36 months, n = 19). As previously reported, features of atherosclerosis (abundant collagen, calcium deposits, and foam cells) were more pronounced in late recurrences (p less than 0.001). However, the histopathologic differentiation between early and late recurrent carotid disease was indistinct. A continuum was noted whereby characteristics of late recurrent lesions increased in proportion to recurrence interval. All recurrent lesions were easily distinguished from primary plaques in that recurrences had a less orderly arrangement of all elements and lacked the classic topographic features of advanced atherosclerosis. An important feature that differentiated primary and recurrent lesions was the presence of surface and intraplaque thrombus in 90% of recurrent lesions (p less than 0.001). In early recurrent disease, luminal surface thrombus was striking; this was frequently platelet-rich and showed organization devoid of neovascularity. Intraplaque thrombus was more common in late recurrent disease, consisted almost entirely of fibrin, and was often contiguous with luminal surface thrombus. No discernible relationships were noted between thrombus associated with recurrent lesions and the presence or absence of symptoms, treatment with antiplatelet agents, and hypertension. This finding suggests that thrombus was a continuous and intrinsic component of recurrent disease rather than a secondary, complicating feature. Recurrent carotid disease is a progressive lesion that stems from ongoing thrombogenesis occurring at the endarterectomy site. Organized thrombus and smooth muscle cell proliferation comprise the bulk of the lesion, which undergoes atherosclerotic change with time.