Longevity of expanded polytetrafluoroethylene grafts for superior vena cava

We previously reported that the expanded polytetrafluoroethylene (ePTFE) graft for superior vena cava (SVC) substitution presents the problems of flexion and kinking when the graft is long. We therefore replaced the SVC of dogs with two types of prosthetic substitutes, ePTFE (Gore-Tex) and spiral-supported ePTFE (Im/praflex), and evaluated the long-term patency of the prosthetic substitutes. Total replacement of the SVC was performed in 9 adult mongrel dogs. The substitutes were ePTFE and spiral-supported ePTFE in 5 and 4 dogs, respectively. The animals were killed about 3 years after replacement of the SVC, and the harvested specimens were histologically examined by light microscopy and scanning electron microscopy. Evaluation of ePTFE revealed late occlusion in 1 of 5 dogs. The spiral-supported ePTFE showed patency in all dogs. In the group with ePTFE grafts, light microscopic examination revealed abnormalities of endothelial cells, granulation, and necrosis. There was no hyperplasia of the subendothelial connective tissue near the center. In the animals with spiral-supported ePTFE grafts, the subendothelial connective tissue showed favorable growth even in the center of the reconstructed site. There was no granulation in the spiral-supported ePTFE group. Scanning electron microscopic examination in the ePTFE group showed that endothelial cells were spindle-shaped and had an irregular surface. The spiral-supported ePTFE group showed an almost regular form of endothelial cells and no abnormalities except for the slightly spindled shape in the center. Therefore, we recommend that spiral-supported ePTFE should be used as an SVC substitute in clinical situations.