Continuing investigation of small-diameter vascular graft materials suggests that unacceptable graft complications continue and that the ideal material has not yet been found. We compared healing of xenogeneic small diameter grafts (3.5 to 5.0 mm diameter) made from porcine small intestine submucosa (SIS) implanted in the carotid artery to expanded polytetrafluorethylene (ePTFE) in the contralateral carotid in 8 dogs. Two dogs were sacrificed for graft evaluation at 7, 28, 90, and 180 days after surgery. Only one SIS graft was occluded at 28 days and the other 7 were patent. Six of 8 ePTFE grafts were occluded with thrombi. One was patent at 7 and one at 90 days. At 7 days postimplant, the luminal surface of the SIS graft was covered by a thick (30 μm), compact fibrin meshwork. By 28 days endothelial cells were seen completely covering the fibrin meshwork which stained for FVIII-related antigen. Smooth muscle cells were observed in the neointima. Most ePTFE grafts had fibrin on the luminal surface which formed fibrin thrombi with platelets and numerous red blood cells. Complete endothelial coverage of the ePTFE grafts was not observed by 180 days. There was not a pronounced neointima seen on the luminal surface of the graft. The vasa vasorum was present in the fibrous capsule surrounding the ePTFE graft, but it did not penetrate into the graft as seen in the SIS graft. At 90 days the SIS vascular graft had the histological appearance similar to a normal artery. The SIS graft patency and healing characteristics were superior to the synthetic ePTFE graft and warrant further investigation.
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