Saphenous vein graft patency 1 year after coronary artery bypass surgery and effects of antiplatelet therapy. Results of a Veterans Administration Cooperative Study

To determine whether antiplatelet therapies improve saphenous vein graft patency after coronary bypass grafting, we compared 1) aspirin (325 mg once daily), 2) aspirin (325 mg three times daily), 3) aspirin and dipyridamole (325 mg and 75 mg, respectively, three times daily), 4) sulfinpyrazone (267 mg three times daily), and 5) placebo (three times daily). Therapy with dipyridamole and sulfinpyrazone was started 48 hours before bypass graft surgery, and aspirin treatment was begun 12 hours before surgery as a single 325-mg dose. Postoperative treatment was started 6 hours after surgery and continued for 1 year. Graft patency data were obtained early (median, 9 days) and late (median, 367 days) after surgery. The early graft occlusion rate was decreased with all aspirin treatment regimens compared with that of the placebo regimen. At 1 year, in 406 patients with 1,315 grafts, the graft occlusion rate in all of the aspirin groups combined was 15.8% compared with 22.6% for the placebo group (p = 0.029). The patients taking aspirin once daily had a lower occlusion rate (13.2%) compared with the patients receiving placebo (p = 0.050). At 1 year, in the vein grafts placed to vessels less than or equal to 2.0 mm in diameter (804 distal sites), the graft occlusion rate in all of the aspirin groups was 20.1% compared with 32.3% for the placebo group (p = 0.008). In the vein grafts placed to vessels greater than 2.0 mm in diameter (511 distal sites), there was no difference in the occlusion rates between aspirin and the placebo group at 1 year (8.7% vs. 9.0%, p = 0.918). For all grafts shown to be patent in the early study (353 patients with 1,043 grafts), there was no difference in occlusion rates at 1 year when aspirin groups were compared with the placebo group (8.7% vs. 9.4%, p = 0.763). Thus, graft patency is improved at 1 year after bypass graft surgery by aspirin, and the major benefit occurred in vein grafts placed to smaller vessels. Our data indicate that if a vein graft is patent early after coronary artery bypass graft surgery, aspirin might not improve the chance that the vein graft will remain open at 1 year.