THE HISTOLOGIC CHARACTERISTICS OF PRIMARY AND RESTENOTIC CAROTID PLAQUE

Background. Although smooth muscle cell proliferation is a prominent f eature of restenosis in experimental models, the role of cellular prol iferation in the initiation and progression of carotid restenosis is n ot well documented. Methods. Between 1985 and 1995, 35 carotid endarte rectomies (CEA) in 34 patients were performed for restenosis. Patient risk factors, cerebrovascular symptoms, and operative findings were re corded. Tissue specimens from 29 of these cases and 14 original specim ens from the same patient were examined by light microscopy (H&E, tric hrome, elastochrome, and Alcian blue) and immunohistochemistry (alpha actin, CD 68, vWF, and proliferating nuclear cell antigen (PCNA)) in o rder to determine the morphologic characteristics and cellular prolife rative activity of the plaque. Results. Hemodynamically significant re current stenosis occurred in the 29 patients (69% symptomatic) between 2 months and 30 years after their initial CEAs, Eleven of 29 (38%) le sions were removed early (<3 years). Recurrent lesions were characteri zed based on their components as neointimal thickening, 24% (7/29), ne ointimal thickening and atherosclerosis, 55% (16/29), or atherosclerot ic, 21% (6/29), Nineteen of 29 (66%) plaques were complicated by mural thrombus or intraplaque hemorrhage. An inflammatory cell infiltrate c onsisting of macrophages and T lymphocytes was observed adjacent to ar eas of recurrent atherosclerosis and macrophages in regions of intimal thickening. Although infrequently present (generally 1-3% of cells) P CNA-positive cells were detected in 41% (12 of 29) of recurrent and 14 % (2 of 14) of primary plaques. No PCNA-positive cells were detected i n the remaining 67% (29 of 43) of specimens. There was no statistical difference in the number of PCNA-positive cells in early recurrent les ions compared to those recurring after 3 years (36% vs 44%). PCNA immu noreactivity when present was most commonly noted in macrophages assoc iated with thrombus or atheroma rather than smooth muscle cells. Concl usions. Although evidence of cellular proliferation was observed in 40 % of recurrent carotid endarterectomy lesions, the proliferation rate was low (1-3%) and unrelated to the time interval of recurrence. Proli ferative activity was most pronounced in macrophages associated with i ntraplaque hemorrhage or atheroma, The contribution of inflammatory ce lls to the biologic behavior of restenotic lesions requires further in vestigation. (C) 1998 Academic Press.