Changes in the manufacture of expanded microporous polytetrafluoroethylene: effects on patency and histological behavior when used to replace the superior vena cava

Polytetrafluoroethylene (PTFE) has been used clinically and experimentally as a vein substitute. Since its introduction, changes have been made in the manufacture of the material. This study was designed to evaluate the effects of pore size (fibril length), PTFE cover, and spiral tube support on long-term patency and histological behavior when this material is used as a replacement for the precava in the dog. A graft of 30-mu pore size has adequate fibroblastic ingrowth, a neointima of 200 mu or less, and the best long-term patency. The PTFE cover results in less fibroblastic involvement of the prosthetic graft and prevents late occlusion caused by transmural fibrosis in the 90-mu graft. The spiral support does not affect patency and may be indicated when external pressure on the tube must be avoided.