Abstract 3442: Pattern and Time Path of Neonintimal Healing in Drug Eluting versus Bare Metal Stents in the Rat Aortic Stent Model

Abstract

Purpose:to determine if the neointima of drug-eluting stents is histological different from their bare metal controls. Neointimal formation in stented aortas was evaluated quantatively and qualitatively at two time points. Methods:male Wistar rats were randomized to one of four groups: Express 2 stent , Taxus Express 2 stent , Bx Velocity stent and Cypher stent. Stents were implanted in the abdominal aorta. Histological analyses were performed after 1 and 4 weeks. After 1 week the inflammation score and neointimal cell density was measured. Stented aortas were also examined for acellularity of neointima and /or the presence of a hemorrhage in the neointima. After 4 weeks the same measurements were performed plus the neointimal area and neointimal thickness. Results:no differences were observed after 1 week between bare metal stents and drug-eluting stents. At 4 weeks neointimal cell density was lower and inflammation-score was higher in the drug eluting stents. Furthermore in less than 10% of the bare metal stents acellularity of neointima and/or hemorrhage was found. On the contrary, in more than 90% of the drug eluting stents acellularity of neointima and/or hemorrhage was seen. Neointima area and neointimal thickness was reduced in the drug-eluting stents. No histological differences were found between the paclitaxel and the sirolimus eluting stent. Conclusions:Both drug eluting stents are effective in reducing neointimal formation however in both drug eluting stents acellular areas were observed in the neointima of almost every single stent. This is likely to be a reflection of incomplete healing which persists after neointimal formation has peaked. Table 1. Histological measurements: results in the 4 week groups.