ENDOTHELIALIZATION OF MICROPOROUS POLYTETRAFLUOROETHYLENE GRAFTS IN THE INFRARENAL AORTA AND CAVAL VEIN OF THE RAT

To study healing and endothelialization of vascular grafts, microporous polytetrafluoroethylene (PTFE) prostheses 2 mm in inner diameter and 5 mm long were implanted into the infrarenal aorta or caval vein of the rat. Patency was assessed in six rats from each group at days 3, 7, 14, 28, and 56 after implantation. Four grafts were occluded, two in the aorta (56 days) and two in the caval vein (3 and 14 days). The prostheses were examined via scanning electron and light microscopy for evaluation of endothelialization. At 3 days, the inner surface of the aortic grafts was covered by a plasma proteinaceous layer and that of the caval vein grafts by a thin mural thrombus. Endothelial cells then migrated from aorta/caval vein edges over the graft. At 14 days, the caval vein grafts were completely reendothelialized, and, at 28 days, the mural thrombus in these grafts was replaced by neointima. In contrast, endothelialization of the aortic grafts had advanced only 1 mm at about 56 days, never forming a complete endothelial layer. We conclude that endothelialization of microporous PTFE prostheses is more rapid and complete in the caval vein than in the aorta of the rat.