Comparison of self-expanding polyethylene terephthalate and metallic stents implanted in porcine iliac arteries

Purpose: Comparison of the biocompatibility of self-expanding polyethylene terephthalate (PET) stents with self-expanding metallic stents (Wallstents). Methods: Diameter- and length-matched PET stents and Wallstents were symmetrically implanted in the paired iliac arteries of 13 crossbred domestic swine. Stent deployment was studied angiographically and with intravascular ultrasound immediately after stent implantation. The angiographic stented lumen diameter was measured using quantitative vessel analysis before, immediately after stenting, and at 6-week follow-up. Cross-section histopathology and area morphometry were performed. Results: Immediately poststenting, intravascular ultrasound revealed proximal dislocation of 5 of the 13 PET stents, whereas all metal stents were firmly embedded at the implantation site. At 6-week follow-up, three of the remaining PET stents were totally or subtotally occluded by organized thrombus, whereas all metal stents were patent. Compared with immediately poststenting, the angiographic lumen diameter within the five remaining PET stents was reduced by 30%, and that of the metallic stents was virtually unaltered (p<0.02). This observation was confirmed by postmortem morphometry, wherein the PET-stented vessel segments a diameter stenosis of 40% was measured vs only 9% in the metallic stents (p<0.0001). Conclusion: PET-stent deployment is difficult to control due to the lack of radiopacity of this stent. PET stents seem to be more thrombogenic and lead to significantly more neointimal proliferation than metallic stents.