Differences in histopathologic findings in restenotic lesions after directional coronary atherectomy or balloon angioplasty

BACKGROUND Directional coronary atherectomy (DCA) and balloon angioplasty (percutaneous transluminal coronary angioplasty, PTCA) differ in their method of dilating stenotic vessels. It is not known whether there is any morphologic difference between restenotic lesions that occur after DCA and those occurring after PTCA. METHODS To evaluate histopathologic differences between restenotic lesions after DCA or PTCA, we reviewed coronary atherectomy specimens excised from 37 patients with stable angina. Patients were classified into three groups: those with restenotic lesions after DCA (n = 8), those with restenotic lesions after PTCA (n = 14), and those with primary lesions (n = 15). Specimens were analyzed immunohistochemically using monoclonal antibodies specific for smooth muscle cells (HHF35), endothelial cells (CD31), macrophage-derived foam cells (CD6B) and cell replication activity (Ki-67). In seven patients undergoing repeat DCA, de novo plaques and restenotic plaques were compared. RESULTS Stellate smooth muscle cell (S-SMC) content in restenotic lesions after DCA (87%) was significantly greater than that in primary lesions (40%; P = 0.032) and that in restenotic lesions after PTCA (43%; P = 0.045). Foam cells tended to be more prevalent in primary lesions (67%) than in restenotic lesions after DCA (25%; P = 0.062) or after PTCA (36%; P = 0.10). Restenotic lesions after DCA had more S-SMC proliferation and fewer foam cells than did primary lesions. There were no differences in the presence of thrombus, calcification, cholesterin, hemosiderin, the percentage of HHF35-positive cells or Ki-67-positive cells, or neovascularization among the three groups. CONCLUSIONS Smooth muscle cell proliferation may have an important role in the development of restenosis after DCA. Fewer foam cells are present in restenotic lesions after DCA or PTCA than are present in primary lesions.