Differential Response of Delayed Healing and Persistent Inflammation at Sites of Overlapping Sirolimus- or Paclitaxel-Eluting Stents

Abstract

Although effective coverage of challenging coronary lesions has warranted the use of overlapping drug-eluting stents, the histopathological response to stent overlap is unknown. The arterial reaction to overlapping Cypher or Taxus drug-eluting stents was examined in rabbits with bare metal stents, BxVelocity or Express, serving as controls. Single iliac artery balloon injury was followed by placement of 2 overlapping 3.0-mm-diameter drug-eluting stents or bare metal stents in 60 animals (mean length of overlap, 9.8+/-3.6 mm). Stented arteries were harvested at 28 and 90 days for histology. Overlapped segments exhibited delayed healing compared with proximal and distal nonoverlapping sites at 28 days. Overlapped segments in Taxus stents induced significantly more luminal heterophils/eosinophils and fibrin deposition than Cypher; peristrut giant cell infiltration, however, was more frequent in the latter. Overlapping bare metal stents also showed mild delayed healing compared with nonoverlapped segments, but not to the same extent as drug-eluting stents. Although neointimal thickness within the overlap was similar in 28- and 90-day Cypher stents, there was a significant increase with Taxus (P=0.03). Compared with bare metal stents, drug-eluting stents further delay arterial healing and promote inflammation at sites of overlap. Taxus stents induced greater fibrin deposition, medial cell loss, heterophils/eosinophils, and late neointimal hyperplasia. Patients receiving overlapping drug-eluting stents need more frequent follow-up than patients with nonoverlapping stents.