Experimental replacement of the inferior vena cava: factors affecting patency.

To evaluate factors influencing graft patency in the venous system, we replaced the inferior vena cava (IVC) in 50 dogs. Expanded polytetrafluoroethylene ( ePTFE ) grafts with external support were implanted into 32 animals while autogenous, spiral jugular vein grafts were used to replace the IVC in 18 dogs. 111In-labeled autologous platelets and 125I-labeled canine fibrinogen were utilized to evaluate early thrombus formation. A distal arteriovenous (AV) fistula significantly (P less than 0.05) decreased both platelet and fibrin deposition on ePTFE grafts 3 hours following implantation. Patency rate of 12 ePTFE grafts with a temporary AV fistula was higher (75%) than that of grafts without fistula (25%) at 3 months (P less than 0.05). Spiral vein grafts with fistula showed 91% patency at 3 months; without fistula patency was only 67%. Venograms confirmed patency in five grafts followed up to 6 months. Antiplatelet therapy resulted in 100% patency in ePTFE and vein grafts during its administration, and vein grafts maintained patency after discontinuation of antiplatelet treatment. Spiral vein grafts showed no decrease in cross-sectional area at 3 months, while the cross-sectional area of ePTFE grafts decreased significantly (59%). Distal AV fistula decreases platelet and fibrin deposition leading to early occlusion in ePTFE grafts and produces excellent patency in spiral vein grafts. Antiplatelet therapy appears to further improve patency.