Long-term evaluation of the behavior of a polytetrafluoroethylene microprosthesis in the rat iliac artery: Myointimal regression.

The present study represents a long-term investigation of polytetrafluoroethylene (PTFE) vascular microprostheses implanted in the right common iliac artery of rats, with the aim of evaluating the degree of intimal hyperplasia and the changes produced in the vascular prosthesis. A follow-up study was performed between 3 months and 1 year post-implantation, using immunohistochemical techniques, light, and electron microscopy. Three months after implantation, the PTFE segment appeared sandwiched between two cell layers. A general endothelialization was observed on the luminal surface. The underlying myointima appeared as an irregular lining of decreasing thickness, from the distal anastomosis with the receptor artery to the proximal suture. A large number of white blood cells were found adherent to and infiltrating the endothelium. A neoformed adventitia covered the prosthesis on the external surface. At 4 months post-implantation, a destabilization of the luminal surface was observed induced by white blood cells. A progressive reduction in the thickness of the myointimal layer was also apparent, so that 1 year after implantation, the luminal surface of the PTFE prosthesis was fully lined by a thin cell covering. There is good long-term tolerance to implanted PTFE microprostheses. The white blood cells present in the implant region appeared to play an important role in the long-term regression of intimal hyperplasia.