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: To compare the long-term vascular healing responses of healthy swine iliofemoral arteries treated with a polymer-free paclitaxel-eluting stent (Z-PES, Zilver PTX) or a fluoropolymer-based paclitaxel-eluting stent (FP-PES, Eluvia).

Materials and methods: Bilateral iliofemoral arteries in 20 swine were treated with a Z-PES (n = 16) or a FP-PES (n = 24) 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 the FP-PES than in the Z-PES at all timepoints. Luminal narrowing was similar in the 2 groups at 1 month; however, greater stenosis was observed in the Z-PES group at 3 months, with significant regression thereafter, resulting in equivalent stenosis at 6 and 12 months. Greater drug effect and less complete vessel healing were found in the FP-PES group at all timepoints, including greater numbers of malapposed struts with excessive fibrin deposition at 1 and 3 months, than in the Z-PES group. Three of 12 FP-PESs from the 6- and 12-month cohorts also showed circumferential medial disruption with peri-strut inflammation, whereas no abnormal findings were observed in contralateral Z-PESs.

Conclusions: Prolonged paclitaxel release with the presence of a permanent polymer may contribute to the differential vascular responses seen for the Z-PES and FP-PES groups, including medial layer disruption and aneurysmal vessel degeneration that was sometimes observed in the FP-PES group. These distinct features should be confirmed by pathology and in vivo imaging of human superficial femoral arteries to determine their clinical significance.