Comparison of vascular response between durable and biodegradable polymer-based drug-eluting stents in a porcine coronary artery model.

AIMS: Biodegradable polymer-based drug-eluting stents are thought to be safer than durable polymer-based stents. However, the long-term vascular response remains unclear. The aim of this study was to compare the biocompatibility of durable polymer-based sirolimus-eluting (SES) and everolimus-eluting (EES) stents with biodegradable polymer-based biolimus-eluting (BES) stents in a porcine coronary model. Stents were implanted in porcine coronaries. Acetylcholine challenge tests and optical coherence tomography (OCT) examination were performed at one month. Animals were sacrificed at three and six months (n=6 each), and the stents were analysed histologically. At one month, acetylcholine challenge tests revealed a trend towards greatest vasoconstriction in SES, less in BES, and least in EES, but the differences were not significant. OCT analysis demonstrated the highest incidence of uncovered struts in SES, followed by BES, while EES showed almost complete strut coverage (41.7±27.0%, 24.5±23.8%, 0.4±0.8%, respectively; p=0.004). Upon histological analysis at three months, SES showed a significantly higher inflammatory score than BES and EES (2.9±1.4, 0.8±0.9, 0.5±0.4, respectively; p=0.001), and this was maintained at six months (1.6±1.5, 0.3±0.3, 0.4±0.6, respectively; p=0.049). While SES showed an increased inflammatory reaction, EES and BES showed minimal inflammation. These results indicate that the late inflammatory reaction does not necessarily depend on degradability of the polymer, if the combination of the drug, metal, and polymer is biocompatible.