Heparinization of polytetrafluoroethylene (ePTFE) grafts. The effect on pseudointimal hyperplasia

A study was undertaken to evaluate the effect of a covalent heparinization on thrombogenicity of ePTFE grafts in sheep. With scanning electron microscopy heparinization occurred as a thin smooth layer covering the network of ePTFE. Most of it had disappeared already after 2 hours. In long-term experiments a high and low flow part of the ePTFE graft was created in the carotid artery system. The heparinization had no effect on patency and there was no difference between the high and low flow parts of the graft. The graft surface was covered with fibrous tissue, which was significantly thicker than the pannus in the host vessel. In the graft interstices (internodal distance of 30 micron) capillaries were seen without difference between occluded and patent grafts. The capillary density was significantly higher proximally than distally.