A new polymer concept for coating of vascular stents using PTFEP (poly(bis(trifluoroethoxy)phosphazene) to reduce thrombogenicity and late in-stent stenosis

Objectives: We sought to evaluate the new polymer PTFEP (poly-bis(trifluoroethoxy)phosphazene) for (1) its ability to reduce thrombogenicity and late in-stent stenosis and (2) its effect on endothelialization in a rabbit iliac artery model. Materials and Methods: Nanocoated (similar to 50 nm) and bare stainless-steel stents were implanted bilaterally in the iliac arteries of 30 New Zealand White rabbits (1, 4, 8, 12, and 16 weeks follow-up) and evaluated by angiography, light, and scanning electron microscopy. Results: Bilateral stent placement was successful in 27 of 30 rabbits. Thrombus depositions occurred in none of the 27 coated but in 4 of the 27 bare stents (P = 0.037). A normal angiogram was obtained in 18 of 22 coated stents at risk for restenosis (follow-up >= 4 weeks) but only in 13 of 22 bare stents (P = 0.023). Marked restenosis (luminal loss > 30%) was found in 6 bare stents (P = 0.011) but not in any coated stents. The neointima was 47.7-73.9 mu m on coated and 66.9-115.2 mu m on bare stents (statistically significant at 4, 8, and 16 weeks). Scanning electron microscopy detected full endothelialization in all stents from 4 weeks on (22 stents in both groups). Conclusion: PTFEP nanocoating successfully showed thromboresistance and reduced late in-stent stenosis. Endothelialization was equal in both stent types. Studies in more human-like models and human feasibility studies in human arteries are encouraged.