Overlapping paclitaxel-eluting stents: Long-term effects in a porcine coronary artery model

Abstract

At 4-year follow-up, paclitaxel-eluting stents (PES, TAXUS) have demonstrated clinical effectiveness in reducing restenosis without increasing death or myocardial infarction. Concerns remain with all drug-eluting stents, however, regarding potential interference with long-term healing, particularly in zones with adjacent stent overlap due to theoretical doubling in both drug release and tissue contact with coating polymer. Therefore, we evaluated long-term healing of overlapped TAXUS stents in an accepted animal model. Seventy-one non-injured swine underwent coronary artery placement of 138 overlapping stent-pairs (91 PES TAXUS Liberté 1 microg/mm(2) slow release formulation, 3.0 or 3.5 mm diameter pairs and 47 control bare metal Liberté pairs) deployed at a 1.1:1 to 1.2:1 target stent-to-artery diameter ratio. Pathological analysis was performed at 30 (9 bare, 10 paclitaxel), 90 (9 bare, 10 paclitaxel), 180 (10 bare, 16 paclitaxel), 360 (10 bare, 21 paclitaxel), and 580 (9 bare, 22 paclitaxel) days. At all time intervals overlapped TAXUS stents were consistently endothelialized and free of luminal thrombus or vascular dilatation. Full healing, however, was delayed compared to control, with macrophage processed para-strut fibrin and cellular debris still present, but reduced and sequestered from blood flow by an endothelialized neointima at 360 and 580 days. While neointimal thickness in TAXUS overlap zones was significantly less than control at 30 days, greater neointima formation was observed with TAXUS at > or =90 days, but was stable and did not progress further from 90 to 580 days. In this porcine model TAXUS stents demonstrated safety and acceptable healing with prolonged time to resolution of para-strut deposits, and did not produce the sustained neointimal suppression seen clinically.