Late Thrombogenicity of Grafts in the Venous System

Abstract

Although some previous experiments have demonstrated encouraging early results with venous vascular prosthesis, the long-term results have not been sufficiently investigated. The late thrombogenicity of 12 autogenous vein grafts and eight polytetrafluoroethylene (PTFE) grafts, three of which had been subjected to endothelial seeding, was evaluated 6 months after implantation in the canine venous system by determination of the survival time of the indium-labelled autogenous platelets and of the light and electron microscopic appearance of the graft-to-blood interface. Twelve dogs receiving autogenous vein grafts had a platelet half-life of 64 ± 13 (mean ± s.d.) hours and a completely thrombus-free internal graft surface covered by a smooth endothelium. The platelet half-life in five dogs with non-seeded PTFE grafts was significantly ( P < 0.01) shorter (44 ± 11h). The PTFE-to-blood interface consisted of a 100- to 170-μm-thick pseudointima with a thrombus-free surface area of 25-90% and substantial endothelial coverage in only two animals. Three dogs receiving endothelial-seeded PTFE grafts had a platelet half-life of 38, 46 and 53h, respectively, a 10- to 80-μm-thick pseudointima covered with typical endothelium, and a thrombus-free surface area of 90-100%. Our results demonstrate that PTFE grafts are still thrombogenic at 6 months following implantation in the canine venous system. Therefore, additional measures are required to maintain graft patency. Our limited experience with endothelial seeding does not allow any definite conclusions, but our findings indicate that this procedure might be beneficial.