Vascular Response of a Polymer-free, Paclitaxel-coated Stent (Zilver PTX®) Versus a Polymer-coated, Paclitaxel-eluting Stent (Eluvia®) in Healthy Swine Femoropopliteal Arteries

Abstract Purpose The purpose of this study was to compare the long-term vascular healing responses of healthy swine iliofemoral arteries treated with polymer-free, paclitaxel-eluting stent (Z-PES, Zilver PTX®) or fluoropolymer-based, paclitaxel-eluting stent (FP-PES, Eluvia®). Methods Bilateral iliofemoral arteries were treated with Z-PES (n=16) or FP-PES (n=24) in 20 swine and were examined histologically at 1-, 3-, 6- and 12-months. Results Morphometric analysis revealed larger external and internal elastic lamina, stent expansion, and lumen area in FP-PES versus Z-PES at all timepoints. Luminal narrowing was similar in the two groups at 1-month, however, greater stenosis was observed in Z-PES at 3-month with significant regression thereafter resulting in equivalent stenosis at 6- and 12-months. Greater drug effect and less complete vessel healing were found in FP-PES at all timepoints, including greater numbers of malapposed struts with excessive fibrin deposition at 1- and 3-months versus Z-PES. Three (3/12) FP-PESs from the 6- and 12-month cohorts also showed circumferential medial disruption with peri-strut inflammation, while no abnormal findings were observed in contra-lateral Z-PESs. Conclusion Prolonged paclitaxel release with the presence of a permanent polymer may contribute to the differential vascular responses seen for Z-PES and FP-PES, including medial layer disruption and aneurysmal vessel degeneration sometimes observed in FP-PES. These distinct features should be confirmed by pathology and in vivo imaging of human superficial femoral arteries to determine their clinical significance.