Pathology of Chronic Total Occlusion in Bare-Metal Versus Drug-Eluting Stents: Implications for Revascularization

Objectives The aim of this study was to explore the pathology of in-stent chronic total occlusion (IS-CTO) in bare-metal (BMS) versus drug-eluting stents (DES). Background Despite a relatively high prevalence of IS-CTO, little is known about the underlying etiology and histopathologic characteristics of the occlusion. Methods From CVPath Institute's stent registry of human native coronary arteries, the authors identified 56 lesions (32 BMS and 24 DES) from 54 patients with IS-CTO. Sections of stented coronary arteries were examined for histological features of IS-CTO. The underlying mechanisms of IS-CTO were determined along with the histopathological characteristics. Results The pathological prevalence of IS-CTO was significantly higher in BMS versus DES cases at autopsy (11.7% vs. 5.9%; p = 0.01). The most frequent etiology of IS-CTO was acute thrombotic occlusion (51% in BMS vs. 67% in DES), followed by restenosis (31% vs. 8%) and neoatherosclerotic rupture (9% vs. 4%). The proximal lumen pattern was abrupt in 67% of BMS and in 57% of DES, whereas the distal lumen was tapered in 68% of BMS and in 74% of DES. BMS showed longer fibrous cap of IS-CTO than DES in both proximal (4.6 mm vs. 1.6 mm; p = 0.06) and distal (5.3 mm vs. 2.0 mm; p = 0.06). Conclusions At autopsy, IS-CTO was observed more frequently in BMS versus DES, with acute thrombotic occlusion being the most frequent cause, followed by restenosis (especially in BMS) and neoatherosclerotic rupture. Our findings shed new light upon the frequency, mechanisms, and pathology of IS-CTO.