To test the thrombosis resistance of a vascular prosthesis coated with antithrombogenic agents, we evaluated a small vessel prosthesis of expanded polytetrafluoroethylene (ePTFE) implanted in the rat aorta and removed 1 week following surgery. Control grafts consisted of 1 mm internal diameter ePTFE. Experimental grafts consisted of 1 mm internal diameter ePTFE noncovalently bonded to tissue plasminogen activator (tPA) and iloprost using the surfactant tridodecylmethylammonium chloride. After 1 week the grafts were harvested, patency was determined, and histologic specimens were prepared for electron microscopy. Six of 10 control grafts were thrombosed, whereas 9 of 10 tPA-iloprost-bonded grafts were patent (p < 0.03). Of concern, there was an unexpectedly high mortality rate in the tPA-iloprost group compared to the control group among animals that died before completion of the study. Evaluation of the safety of these drugs must, therefore, be an early component of future experiments. Nevertheless, these studies indicate that a small vessel prosthesis bonded to tPA and iloprost may ameliorate some of the complications associated with early graft failure.
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