Surface healing and histologic maturation of patent polytetrafluoroethylene grafts implanted in patients for up to 60 months.

Histologic, transmission, and scanning electron microscopic observations were made of 26 biopsy specimens from patent polytetrafluoroethylene grafts that had been implanted as arterial bypasses for up to 60 months. The results showed the rarity of host connective tissue ingrowth, the absence of neovascularization, and the limited neointimal proliferation. The defect of staining for factor VIII-related antigen by immunohistochemistry confirmed the absence of true endothelial cells at a distance from the anastomoses. Under electron microscopy the thin neointimal layer consisted mainly of fibrin, platelets, blood cells, and cellular debris. Even in prostheses implanted for the longest periods, mature collagen and elastin were not found. Tubular microfibrils (9- to 12-nm thick) could be observed. The source of such microfibrils, probably glycoproteins, remains under investigation.