Evaluation of collagen-coated woven velour polyester and expanded polytetrafluoroethylene grafts during early lytic therapy in an animal model

This study was conducted to determine the relative safety of early urokinas e lytic therapy in expanded polytetrafluoroethylene (ePTFE) and collagen-im pregnated woven velour polyester (CIWVP) grafts. Twelve mixed-breed dogs were selected and implanted with thin-wall ePTFE an d CIWVP grafts in the external iliac artery position. At 3, 4, 6, and 12 we eks, three dogs were selected for lyric therapy. After exposure of the prev iously implanted grafts, lytic therapy was initiated with a bolus of 100,00 0 units of urokinase, followed by 4000 units/minute for two hours, then red uced to 2000 units/minute for a subsequent two hours. Hypertension was indu ced 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, pseudoi ntimal 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 chang e 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 e PTFE grafts during urokinase lytic therapy conducted at 3, 4, 6, or 12 week s in a canine model. Microscopic examination demonstrated a difference in p seudointima, graft incorporation, and inflammatory response when the two co nduits were compared. Urokinase did not appear to accelerate collagen layer breakdown.