The influence of node-fibril morphology on healing of high-porosity expanded polytetrafluoroethylene grafts

PURPOSE: To manufacture high-porosity expanded polytetrafluoroethylene (ePTFE) vascular grafts with the same internodal distance but different node-fibril morphology, and to evaluate their biologic behaviors in a canine carotid artery implantation model. MATERIALS AND METHODS: Several types of high-porosity ePTFE vascular grafts with the same inside diameter (4 mm) and wall thickness (650 microm) were manufactured under different heating, stretching conditions. The luminal surface and cross section of the grafts were photographed by scanning electron microscopy and the node-fibril structure was examined. Two typical types of high-porosity ePTFE vascular grafts were then selected and proceeded to an animal study. The test grafts were explanted after an interval of 12 weeks and subjected to histomorphometric analyses. RESULTS: The following two types of high-porosity ePTFE vascular grafts were selected; one had a through-pore structure extending from the outer to the inner surface and the other had a random-node architecture with tortuous path channels extending from the outer to the inner surface. The histomorphometric analyses of thrombus-free surface, thickness of pseudointima, cellular ingrowth, capillary ingrowth, and cellular proliferation revealed no significant differences between the grafts. CONCLUSION: In high-porosity ePTFE vascular grafts, graft healing enhanced by transmural tissue ingrowth may be not largely dependent on node-fibril morphology. This knowledge will be helpful to design a new type of high-porosity ePTFE vascular grafts available for clinical use.