Early vascular response to overlapped paclitaxel-eluting stents in swine coronary arteries.

ABSTRACT

BACKGROUND: The early response to the TAXUS Express2 paclitaxel-eluting stent (PES) system was compared to the response to the Express2 bare metal stent (BMS) system in porcine arteries. METHODS: Swine coronary arteries were implanted with overlapping PES or BMS and examined at 1, 2, 4, 10, and 20 days postimplantation using scanning electron microscopy or light microscopy. RESULTS: Vascular healing in terms of strut coverage, reendothelialization, degree of inflammation, and absence of thrombus was equivalent in both groups from 1 to 20 days. Interstrut member spaces were unaffected by stent deployment and remained covered with endothelium from Day 1. In both groups at 2 days, small patches of endothelial cells covered approximately 5-10% of the stent surface. At 4 days, endothelial cell coverage progressed to nearly 50% in both groups. After 10 days, endothelial cell strut coverage was nearly complete (>90%), with regions of incomplete coverage located primarily in strut overlap regions in both groups. BMS exhibited a fibrocellular neointima and no parastrut fibrin, whereas PES exhibited a developing but immature fibrocellular neointima and prominent parastrut fibrin. By Day 20, an endothelialized neointima was present in both groups, with comparable coverage of proximal and distal stented regions. The neointima of PES was more fibrocellular and parastrut fibrin was still comparable to that at 10 days. CONCLUSION: Early vascular response was comparable for both PES and BMS, with similar rates of reendothelialization, limited inflammatory response, and absence of thrombus, but differed parastrut fibrin clearance and neointimal maturation rate.