Evaluation of Collagen-Coated Woven Velour Polyester and Expanded Polytetrafluoroethylene Grafts During Early Lytic Therapy in an Animal Model

Abstract

This study was conducted to determine the relative safety of early urokinase lytic therapy in expanded polytetrafluoroethylene (ePTFE) and collagen-impregnated woven velour polyester (CIWVP) grafts. Twelve mixed-breed dogs were selected and implanted with thin-wall ePTFE and CIWVP grafts in the external iliac artery position. At 3, 4, 6, and 12 weeks, three dogs were selected for lytic therapy. After exposure of the previously implanted grafts, lytic therapy was initiated with a bolus of 100,000 units of urokinase, followed by 4000 units/minute for two hours, then reduced to 2000 units/minute for a subsequent two hours. Hypertension was induced by methoxamine hydrochloride at the conclusion of lytic therapy. Direct observation and angiography were used to assess for bleeding and contrast extravasation hourly until completion. The animals were then sacrificed and the grafts excised and microscopically examined for incorporation, pseudointimal deposition, and accelerated collagen layer degradation. None of the implanted grafts showed evidence of transluminal or suture line bleeding or extravasation of contrast material. Hypertension did not change these results. Analysis demonstrated a thicker pseudointimal, giant cell infiltration, extensive incorporation, and occasional fragmentation of the CIWVP graft when compared with the ePTFE grafts. The systemic fibrinolytic state did not cause collagen layer degradation. No evidence existed of suture line or transluminal bleeding from CIWVP or ePTFE grafts during urokinase lytic therapy conducted at 3, 4, 6, or 12 weeks in a canine model. Microscopic examination demonstrated a difference in pseudointima, graft incorporation, and inflammatory response when the two conduits were compared. Urokinase did not appear to accelerate collagen layer breakdown.