Purpose: To evaluate the healing characteristics of stents versus endovascular grafts in the porcine iliac artery.
Materials and methods: A total of 20 iliac arteries in 10 domestic swine were used to evaluate the healing characteristics of stents versus endovascular grafts. Each animal received one stent and one endovascular graft in opposite iliac arteries. The endovascular grafts were constructed with use of 6 cm of expanded polytetrafluoroethylene (ePTFE) (3 mm inner diameter, 30 microm internodal distance) and Palmaz stents (P204 or P188) secured at each end of the graft. A solitary Palmaz stent (P308 or P294) was used on the opposite side. The devices were explanted at 1, 5, and 12 weeks.
Results: One of three endovascular grafts and two of three stents were patent at 1 week. Two of three endovascular grafts and all three stents were patent at 5 weeks. All three endovascular grafts and stents were patent at 12 weeks. Gross examination, histologic, and scanning electron microscopy demonstrated differences in the healing response of the two devices. A marked abluminal inflammatory response to the graft material was observed. This resulted in neovascularization of the tissue along the abluminal surface of the graft. In addition, marked neointimal thickening at the unsupported section of the endovascular graft resulted in significant luminal narrowing.
Conclusion: The porcine model may be used for evaluating the healing characteristics of endovascular grafts. Intravascular placement of ePTFE prosthetic graft material dramatically alters the healing of this type of graft material. The graft material did not prevent the formation of a progressively thickening neointima.