Beneficial effect of aspirin in maintaining the patency of small-caliber prosthetic grafts after thrombolysis with urokinase or tissue-type plasminogen activator

Despite successful thrombolysis of occluded prosthetic grafts, rethrombosis remains a problem. We investigated the efficacy of aspirin in maintaining patency of polytetrafluoroethylene grafts (3 mm x 3.5 cm) in canine femoral arteries after thrombolytic therapy. After induction of thrombosis, either tissue-type plasminogen activator (t-PA) or urokinase (UK) was infused just proximal to the thrombus (4000 U/min) until complete thrombolysis was achieved. Five of the 10 UK-treated dogs and five of the 10 t-PA-treated dogs received aspirin immediately after recanalization and aspirin was continued (325 mg/day) for 4 weeks or until occlusion occurred. A systemic aspirin effect was confirmed by marked depression of serum thromboxane B₂ and absent platelet aggregation. Only two of the 10 grafts in the aspirin-free group remained patent for 4 weeks. The remaining eight grafts had all reoccluded by 2 weeks. None of the 10 grafts in the aspirin-treated group reoccluded during the 4 weeks. This significantly improved patency (p < .001) in the aspirin-treated group was observed equally in grafts treated with t-PA or UK. Thus aspirin is a potent agent in preventing rethrombosis after thrombolytic recanalization of prosthetic grafts.