Acute Thrombogenicity of a Durable Polymer Everolimus-Eluting Stent Relative to Contemporary Drug-Eluting Stents With Biodegradable Polymer Coatings Assessed Ex Vivo in a Swine Shunt Model.

OBJECTIVES: This study sought to evaluate whether the permanent fluoropolymer-coated Xience Xpedition everolimus-eluting stent (Xience-EES) exhibits lower acute thrombogenicity compared with contemporary drug-eluting stents (DES) with biodegradable polymer coatings in an acute swine shunt model.

BACKGROUND: Previous pre-clinical and clinical experience suggests that several factors may influence the predisposition for acute thrombus formation of polymer-coated DES, including stent design and the polymer coating technology. It remains unclear whether relevant differences exist with respect to acute thrombogenicity, particularly between current commercial stent designs using permanent polymers and those using biodegradable polymers.

METHODS: An ex vivo carotid to jugular arteriovenous porcine shunt model involving a test circuit of 3 in-line stents, was used to test acute thrombogenicity, where Xience-EES (n = 24) was compared with 4 CE-marked DES with biodegradable polymer coatings (BioMatrix Flex, Synergy, Nobori, and Orsiro [n = 6 each]). After 1 h of circulation, platelet aggregation in whole mount stents was evaluated by confocal microscopy with immunofluorescent staining against dual platelet markers (CD61/CD42b) along with scanning electron microscopy.

RESULTS: Xience-EES showed the least percentage of thrombus-occupied area as compared with the biodegradable polymer-coated DES, with a significant difference compared with BioMatrix Flex and Synergy (mean differences: [BioMatrix Flex: 15.54, 95% confidence interval [CI]: 11.34 to 19.75, p < 0.001; Synergy: 8.64, 95% CI: 4.43 to 12.84, p < 0.001; Nobori: 4.22, 95% CI: -0.06 to 8.49, p = 0.055; Orsiro: 2.95, 95% CI: -1.26 to 7.15, p = 0.286). The number of cell nuclei on strut surfaces was also the least in Xience-EES, with a significant difference relative to BioMatrix Flex, Nobori, and Orsiro (mean ratios: BioMatrix Flex: 4.73, 95% CI: 2.46 to 9.08, p < 0.001; Synergy: 1.44, 95% CI: 0.75 to 2.76, p = 0.51; Nobori: 5.97, 95% CI: 3.11 to 11.44, p < 0.001; Orsiro: 5.16, 95% CI: 2.69 to 9.91, p < 0.001).

CONCLUSIONS: Xience-EES's overall design confers acute thromboresistance relative to contemporary DES with biodegradable coatings, with less platelet aggregation versus BioMatrix Flex and Synergy, and less inflammatory cell attachment versus BioMatrix Flex, Nobori, and Orsiro, in an ex vivo swine shunt model, which lends support to reported clinical findings of lower early stent thrombosis.