Low-dose aspirin versus anticoagulants for prevention of coronary graft occlusion. The prevention of graft occlusion by aspirin (100 mg/day) or heparin followed by phenprocoumon was investigated in a randomized trial in 235 patients after aortocoronary bypass operation. Aspirin treatment started 24 hours before, and heparin 6 hours and phenprocoumon 2 days after surgery. The results of the vein graft angiography and the clinical outcome 3 months postoperatively did not differ: 22% of 218 vein graft distal anastomoses in the aspirin group and 20% of 272 in the anticoagulant group were occluded. At least 1 occluded distal anastomosis was present in 38% of 74 patients in the aspirin-treated group and in 39% of 86 in the anticoagulant group. Worst-case analysis of all randomized patients showed graft occlusions, cardiovascular complications or lost to follow-up in 42% of 122 aspirin-treated patients compared with 41% of 113 patients treated with anticoagulants. For grafts with endarterectomy the occlusion rate was lower in the aspirin (12% of 49) than in the anticoagulant (22% of 41) group (p less than or equal to 0.05). Increased perioperative blood loss in the aspirin group (1,211 +/- 814 ml in the first 48 hours vs 874 +/- 818 ml in the anticoagulant group [p less than or equal to 0.001]) without a higher reoperation rate indicates effective platelet inhibition with low-dose aspirin. Because occlusion rates were equal but high in these patients with advanced stage of coronary artery disease, a combination of low-dose aspirin and anticoagulation should be investigated to reduce graft occlusion rates further. 