A Controlled Clinical Trial of Antithrombotic Therapy in Patients Undergoing Aortocoronary Artery Bypass Grafting

Over 25,000 coronary artery bypass graft (CABG) procedures, involving more than 50,000 saphenous vein grafts, are performed yearly in the United States. The recognized one-year graft failure rate of 20-30% would imply thrombosis of at least 5,000 vein grafts per year. To improve graft patency rates, we have investigated the benefits of aspirin (ASA), warfarin (Coumadin®), or placebo in a randomized prospective study involving 216 patients undergoing CABG operations. A total of 412 vein grafts were performed. Clinical and angiographic follow-up at 1 to 2 years after operation is not yet completed, but preliminary results show 71% of grafts patent in ASA-treated patients, 64% in warfarin-treated patients, and 52% in the placebo group. 89% of warfarin-treated patients have at least one graft patent compared with 73% of placebo- and 75% of ASA-treated patients. The incidence of late myocardial infarctions has been lower in warfarin-treated (1.4%) and ASA-treated (4%) patients than in the placebo group (8%). Relief from angina is also markedly improved in treated groups, with 44% of ASA-treated and 56% of warfarin-treated patients angina free, compared to 27% of patients in the placebo group. There have been only 4 cardiac-related deaths, (3 in the placebo group and 1 in the ASA group). Eight patients were dropped from the study because of drugrelated problems. Four patients bled on warfarin therapy, one ASA patient bled, while two had ASA-allergic reactions and one developed gastritis. Follow-up is continuing.

Preliminary results suggest that antithrombotic therapy is feasible in CABG patients and appears to promote graft patency, relieve angina pectoris and increase longevity.