Purpose: To evaluate polyethylene terephthalate and polyurethane as coatings of vascular endoprostheses in the treatment of experimental arteriovenous fistulas (AVFs).
Materials and methods: Nineteen bilateral carotid artery-to-external jugular vein AVFs were created in 10 adult dogs. Fourteen polyethylene terephthalate-coated and five polyurethane-coated self-expandable nitinol stents were placed with a transfemoral approach. Angiography was performed immediately after placement, after 1 and 3 weeks, and at months 3, 6, 9, and 12. All grafts were examined histopathologically.
Results: The AVF was successfully occluded with all but one of the polyethylene terephthalate-coated stents. Graft patency was seen with 12 polyethylene terephthalate-coated stents, while acute vessel occlusion was evident with two polyethylene terephthalate-coated stents following percutaneous transluminal angioplasty immediately after implantation. In the group with polyurethane-coated stents, three graft dislocations and two delayed vessel occlusions were observed. In both groups, histologic examination disclosed a mild foreign body reaction with a few macro-phages. No inflammatory reactions were seen. An unorganized fibrin layer was found adjacent to the polyurethane coating.
Conclusion: Polyethylene terephthalate-coated nitinol stents showed good biocompatibility and a high rate of occlusion of experimental AVFs. The mechanical properties of the polyethylene terephthalate coating were similar to those of the nitinol stents, which facilitated handling. Polyurethane-coated stents showed frequent dislocation.