Starting Aspirin Therapy After Operation Effects on Early Graft Patency

Background. Although aspirin therapy started before operation improves vein graft patency after coronary artery bypass grafting, it also causes bleeding. The objective of this prospective, centrally directed, randomized, double-blind, placebo-controlled trial was to compare the effects of aspirin therapy started before operation with aspirin started 6 hours after operation on early (7-10-day) graft patency. Methods and Results. Patients were randomized to receive either aspirin 325 mg or placebo the night before surgery; after operation, all patients received aspirin 325 mg daily, with the first dose administered through the nasogastric tube 6 hours after operation. Angiography was performed in 72% of the analyzed patients an average of 8 days after operation, and the primary end point was saphenous vein graft patency in 351 patients. Internal mammary artery graft patency was also assessed in 246 patients because many individuals received both internal mammary artery and vein grafts. In the patients given preoperative aspirin, the vein graft occlusion rate was 7.4±1.3% compared with 7.8±1.5% in those who received preoperative placebo (p =0.871). In the subgroup of patients receiving Y grafts, 0.0% of the grafts were occluded in the preoperative aspirin group compared with 7.0±3.6% in the preoperative placebo group (p=0.066). The internal mammary artery occlusion rate was 0.0% (0 of 131) in the aspirin group compared with 2.4±1.4% (three of 125) in the placebo group (p=0.081). Patients in the aspirin group received more transfusions than those in the placebo group (median, 900 versus 725 ml,p=0.006). The reoperation rate for bleeding in the aspirin group was 6.3% compared with 2.4% in the placebo group (p=0.036). Median chest tube drainage within the first 6 hours after operation was 500 ml in the aspirin group compared with 448 ml in the placebo group (p=0.011). Conclisions. Thus, preoperative aspirin is associated with increased bleeding complications and offers no additional benefit in early vein graft patency compared with starting aspirin therapy 6 hours after operation. There was a trend, although not significant, toward improved early patency for Y grafts and internal mammary artery grafts with preoperative aspirin. (Circulation 1991;84:520-526)