The effect of carbon coating and porosity on early patency of expanded polytetrafluoroethylene grafts: an experimental study.

PURPOSE: Synthetic vascular grafts have never achieved long-term patency comparable to autologous saphenous vein. Changes in graft wall porosity and carbon coating of the luminal surface have both been suggested to improve patency. METHODS: Forty-two mongrel dogs, weighing 20 to 30 kg, underwent bilateral aortoiliac grafting with one of three randomly selected grafts: group I, 60 microns carbon-coated, thin-walled expanded polytetrafluoroethylene (ePTFE); group II, 60 microns thin-walled uncoated ePTFE; or group III, regular ePTFE. All grafts were 10 cm long and had an internal diameter of 5 mm. Twenty-one dogs were killed at 60 days and 21 dogs were killed at 120 days. Thus in each group there were 14 60 microns, thin-walled, carbon-coated ePTFE grafts; 14 60 microns, thin-walled, uncoated ePTFE grafts; and 14 regular ePTFE grafts. RESULTS: At 60 days, 12 (85.7%) of 14 group I, 13 (92.3%) of 14 group II, and 9 (64%) of 14 group III grafts were patent. At 120 days, 12 (85.7%) of 14 group I, 11 (78.6%) of 14 group II, and 6 (42.9%) of 14 group III grafts were patent. The patency of the 60 microns carbon-coated, thin-walled ePTFE at 120 days was significantly improved compared with that of the regular ePTFE (p < or = 0.05). The patency of the 60 microns thin-walled uncoated ePTFE was improved relative to conventional ePTFE at 120 days, although this difference was not statistically significant. There was no significant difference in patency between 60 microns carbon-coated, thin-walled ePTFE and 60 microns thin-walled uncoated ePTFE. When the results were analyzed simply on the basis of graft porosity, the 60 microns porosity grafts had a significantly improved patency compared to the regular ePTFE at 120 days (p < 0.05). Histologically, the 60 microns porosity grafts had significantly better tissue ingrowth along their entire length, regardless of the presence or absence of carbon coating. This ingrowth was present at both 60 days and 120 days. CONCLUSIONS: Our data suggest that increasing ePTFE graft porosity to 60 microns improves overall patency. However, the addition of carbon lining did not appear to further augment patency.