Light and electron microscopy of polytetrafluoroethylene arterial grafts in dogs

Reinforced expanded polytetrafluoroethylene grafts with fibril lengths of approximately 17 to 25 micrometers were inserted into the infrarenal aorta of dogs for periods ranging from 24 hours to eight months. The grafts were studied by light and electron microscopy, which showed that polytetrafluoroethylene consists of ridges or nodes connected by fibrils. Initially red blood cells passed down in the pores of the polytetrafluoroethylene, and then the surface was covered with fibrin. A new endothelium developed by the twelfth day. The new intimal lining became thicker owing to the appearance of smooth muscle cells deep to the endothelial cells, forming a neointima 120 micrometers thick by eight months. Fibroblasts and collagen penetrated the graft, but vasa vasorum did not, although they were present in the external connective tissue.