PREVENTION OF ONE-YEAR VEIN-GRAFT OCCLUSION AFTER AORTOCORONARY-BYPASS SURGERY - A COMPARISON OF LOW-DOSE ASPIRIN, LOW-DOSE ASPIRIN PLUS DIPYRIDAMOLE, AND ORAL ANTICOAGULANTS

Aspirin, alone or in combination with dipyridamole, is known to preven t occlusion of aortocoronary vein grafts. The benefit of dipyridamole in addition to aspirin remains controversial, and the efficacy and saf ety of oral anticoagulants for prevention of vein-graft occlusion have not been established. We assessed one-year angiographic vein-graft pa tency after aortocoronary-bypass surgery in 948 patients assigned to r eceive aspirin, aspirin plus dipyridamole, or oral anticoagulants in a prospective, randomised trial. The design was double-blind and placeb o-controlled for the aspirin groups, but open for oral anticoagulant t reatment. Dipyridamole (5 mg/kg per 24 h intravenously for 28 h, follo wed by 200 mg twice daily) and oral anticoagulants (desired prothrombi n time range 2.8-4.8 international normalised ratio) were started befo re surgery, and aspirin (50 mg per day) was started after surgery. Cli nical outcome was assessed by the incidence of myocardial infarction, thrombosis, major bleeding, or death. Occlusion rate of distal anastom oses was 11% in the aspirin plus dipyridamole group versus 15% in the aspirin group (relative risk 0.76, 95% CI 0.54-1.05) and 13% in the or al anticoagulants group. Clinical events occurred in 20.3% of patients receiving aspirin plus dipyridamole compared with 13.9% of the aspiri n group (relative risk 1.46, 95% CI 1.02-2.08) and 16.9% of the oral a nticoagulants group. Our data provide no convincing evidence that addi tion of dipyridamole to 50 mg aspirin per day improves aortocoronary v ein-graft patency. Moreover, there is evidence that the combination in creases the overall clinical-event rate. Compared with aspirin, oral a nticoagulants provided no benefit.