Effect of Dipyridamole and Aspirin on Late Vein-Graft Patency after Coronary Bypass Operations

To study the prevention of occlusion of aortocoronary-artery bypass grafts, we conducted a prospective, randomized, double-blind trial comparing long-term administration of dipyridamole (begun two days before operation) plus aspirin (begun seven hours after operation) with placebo in 407 patients. Results at one month 1 showed a reduction in the rate of graft occlusion in patients receiving dipyridamole and aspirin. At vein-graft angiography performed in 343 patients (84 per cent) 11 to 18 months (median, 12 months) after operation, 11 per cent of 478 vein-graft distal anastomoses were occluded in the treated group, and 25 per cent of 486 were occluded in the placebo group. The proportion of patients with one or more distal anastomoses occluded was 22 per cent of 171 patients in the treated group and 47 per cent of 172 in the placebo group. All grafts were patent within a month of operation in 94 patients in the placebo group and 116 patients in the treated group; late development of occlusions was reduced from 27 per cent in the placebo group to 16 per cent in the treated group. The results show that dipyridamole and aspirin continue to be effective in preventing vein-graft occlusion late after operation, and we believe that such treatment should be continued for at least one year. (N Engl J Med 1984; 310:209–14.) THE occlusion of aortocoronary vein grafts increases progressively, involves over 50 per cent of grafts 11 years after operation, and is directly related to changes in left ventricular function, symptoms, and survival. 2 3 4 5 6 7 8 Thus, the maintenance of vein-graft patency is critical to the welfare of the patient. We previously reported that dipyridamole and aspirin therapy that was started before and continued immediately after aortocoronary bypass operation suppressed the pathophysiologic mechanisms leading to vein-graft occlusion in dogs 9 10 11 and markedly reduced such occlusion in patients early after operation. 1 It is not known whether dipyridamole and aspirin therapy started before operation and continued throughout . . .