Occlusion by Low-Dose Aspirin and Dipyridamole

surgery, and assigned treatment was started 7 hours after surgery. Vein graft angiography was performed in 927 patients (83%) within 28 days of surgery (mean, 10 days). Aspirin plus dipyridamole significantly (p=0.017) reduced the occlusion rate of distal anastomoses from 18% (placebo) to 12.9%. Occlusion rate in the aspirin group was 14%, which approached statistical significance (p=0.058). Furthermore, only aspirin plus dipyridamole reduced (p=0.01) the number of patients with occluded grafts (placebo, 33%; aspirin, 27.1%; aspirin plus dipyridamole, 24.3%). Mediastinal drainage was slightly higher (p=0.04) in the aspirin plus dipyridamole group (713±456 ml) than in the other two groups (placebo, 670±437 ml; aspirin, 629±337 ml), but hospital mortality (average, 4.6%) and early reoperation (average, 3.9o) rates were similar among the three groups. Thus, low-dose aspirin plus dipyridamole safely improves early saphenous vein aortocoronary graft patency; this effect is an added benefit to a preoperative regimen of dipyridamole. (Circulation 1990;82:765-773)