ePTFE Vascular Grafts Research Articles

The effects of pore size and endothelial cell seeding upon the performance of small-diameter e-PTFE vascular grafts under controlled flow conditions.

The purpose of this study was to determine the effects of endothelial cell seeding and graft internodal distance upon the performance of 4-mm-ID e-PTFE grafts during acute reduced blood flow conditions. PTFE grafts especially manufactured with three different mean internodal distances (28, 40, and 52 microns) were evaluated. Fifteen dogs (n = 5 for each design of PTFE graft) underwent bilateral carotid artery replacements with 6 cm lengths of 4-mm-ID PTFE grafts. In each dog one graft was seeded with enzymatically derived endothelial cells; the contralateral graft was nonseeded. All grafts were evaluated 5 weeks postoperatively. Dogs with bilaterally patent grafts were subsequently subjected to flow conditions through the graft that were maintained at 30% of the initial flow rates for 4 hr. Following controlled low flows the grafts were excised and assessed for patency, thrombus-free surface area, inner capsule thickness and prostacyclin production. Endothelial cell seeding of these small-diameter e-PTFE vascular grafts improved patency and thrombus-free surface areas in grafts of all pore sizes, with these parameters being greatest in the 40-microns grafts. Inner-capsule healing in these grafts was controlled and related to the pore size. PGI2 production was improved in endothelial cell seeded grafts of all pore sizes. However, neither endothelial cell seeding nor graft pore size affected the performance of these e-PTFE grafts under conditions of reduced blood flows.

The Influence of Supporting Rings on the Healing of the Ringed Expanded Polytetrafluoroethylene Vascular Graft

The influence of supporting rings on the healing of the ringed expanded polytetrafluoroethylene (ePTFE) vascular graft (ringed graft) was studied. In 12 dogs (32-42 kgm), a 4cm segment of each common iliac artery was excised and replaced with an equal length of 6mm ePTFE vascular graft. Ringed graft was used on one side and plain on the other. Dogs were sacrificed at intervals of 1, 2, 4, 6, 8 and 12 weeks. All grafts remained patent. The degree of pannus extension and pannus thickness showed no differences between both grafts at each interval. It was covered by a monolayer of endothelial-like cells as seen by scanning electron microscopy. The growth rates of endothelialization measured from the proximal anastomosis were 1.3 and 1.4 mm/week in the plain and ringed grafts, respec tively. Anastomotic intimal hyperplasia (> 50 microns) was noted in 25% and 33% at the proximal and distal anastomoses, respectively, in both grafts. The outer surface was covered by adherent connective tissue particularly encapsu lating the rings without affecting the non-ringed portion in the ringed grafts. We conclude that the supporting rings of the ePTFE graft have no significant influence on the healing and neointimal development.