Acute Thrombogenicity of Fluoropolymer-Coated Versus Biodegradable and Polymer Free Stents.

AIMS: Durable-fluoropolymer coated everolimus-eluting stents (FP-EES) have shown lower rates of stent thrombosis (ST) versus bare-metal stents (BMS) and 1st-generation bioabsorbable-polymer (BP) DES. However, the specific role of the FP in thromboresistance has not been explored.

METHODS AND RESULTS: A total of 57 stents were assessed in 3 separate ex-vivo swine arterio-venous shunt-model experiments [1st-shunt-experiment, custom-made fluoropolymer-coated BMS (FP-only) vs. BMS (n=8 each); 2nd-shunt-experiment, FP-EES vs. abluminally-coated biodegradable-polymer sirolimus-eluting stents (BP-SES) vs. BMS (n=8 each); and 3rd-shunt-experiment, FP-EES vs. polymer-free BiolimusA9-coated stents (PF-BCS) vs. BMS (n=6 each)]. After 1h of circulation, stents were bisected, and each half was dual-immunostained using platelet cocktail and a marker for inflammation. Antibody staining was visualized by confocal microscopy. In addition, stents were evaluated by scanning electron microscopy. FP-only stents showed significantly lower platelet adherence compared with BMS (% fluorescence-positive area: FP-only=1.8%, BMS=5.6%, p=0.047) with similar inflammatory cell density. FP-EES also demonstrated the lowest platelet adherence compared with BP-SES (p=0.056), PF-BCS (p=0.013) and BMS (p=0.003) with the significantly lowest inflammatory cell density.

CONCLUSIONS: Fluoropolymer coating imparts greater thromboresistance relative to BMS and to polymer-free-DES designs, which reflects an unique phenomenon known as fluoropassivation, representing one proposed mechanism for clinically observed low ST rates in FP-EES.