Purpose: Does hirudin coating improve the patency of iliac artery endoprostheses in comparison to non-hirudin-coated endoprostheses?
Materials and methods: Nitinol stents and stentgrafts covered with polytetrafluoroethylene (PTFE) were coated with the polymer polyamino-p-xylylene-co-poly-p-xylylene using chemical vapor deposition (CVD) technique. Hirudin was covalently bound to the surface of the endoprostheses via the amino-group. External factors (mounting of the prosthesis, sterilization, storage time and temperature, release) affecting the hirudin activity were evaluated in vitro. Five types of prostheses were compared in vivo: (1) plain and (2) CVD- and hirudin-coated stents; (3) plain, (4) CVD-coated, and (5) CVD- and hirudin-coated PTFE-stentgrafts. In 20 sheep, 16 protheses of each type were inserted in arteries pretreated with a Fogarty maneuver. The animals were followed for either 1 (n = 10) or 6 (n = 10) months. Immediately after implantation and after 1, 3, and 6 months, intravascular ultrasound (IVUS) and angiography were performed. The vascular specimens were analyzed histologically.
Results: Within 10 weeks, the hirudin activity of coated stents dropped 60 % due to external factors; the activity of coated PTFE stentgrafts dropped 20 %. After 1, 3, and 6 months, IVUS and histology revealed a significantly reduced patency of the hirudin-coated stentgrafts compared to the other prostheses. Only IVUS showed a significantly reduced patency of hirudin coated stents after 1 and 3 months compared to plain and CVD-coated PTFE-stentgrafts. The reduced patency was caused by neointimal hyperplasia.
Conclusions: In an experimental setting, hirudin coating did not improve the patency of vascular endoprostheses.