OPTIMAL ANTITHROMBOTIC THERAPY FOLLOWING AORTOCORONARY BYPASS - A METAANALYSIS

To evaluate the role of antithrombotic therapy, on preserving graft pa tency, we performed a meta-analysis of randomized clinical trials invo lving aspirin (ASA), dipyridamole (D), anticoagulants (AC) and placebo or nontreatment controls (P). Manual literature searches were perform ed supplemented by computerized MEDLINE listings complete to July 1991 . Saphenous vein graft occlusion was determined by angiography (patien ts with greater-than-or-equal-to 1 distal anastomotic occlusion). The trial data were aggregated with the methods of Mantel and Haenszel. Th e results are reported as odds ratios (OR) +/- 95% confidence interval s (CI). Seventeen trials were evaluated. Aspirin strongly influenced g raft occlusion [ASA +/- D vs P: OR 0.60, 95% CI 0.51, 0.71, P < 0.0001 ], but dipyridamole provided no additional benefit [ASA + D vs ASA: OR 0.94, 95% CI 0.72, 1.24, P = 0.71]. Anticoagulants reduced graft occl usion [AC vs P: OR 0.56, 95% CI 0.33, 0.93, P = 0.025] and the results were similar to that achieved with aspirin [ASA vs AC: OR 0.95, 95% C I 0.62, 1.44, P = 0.87]. The combination of aspirin and anticoagulants was superior to anticoagulants alone in two limited trials [ASA + AC vs AC: OR 0.55, 95% CI 0.33, 0.88, P = 0.01]. A low (100 mg) to medium (325 mg) daily aspirin dosage was more effective than a high dose (97 5 mg). Early postoperative treatment (less-than-or-equal-to 6 h) stron gly influenced graft occlusion while preoperative administration provi ded no additional benefit. No mortality advantage was identified for a ny antithrombotic therapy. Aspirin or anticoagulants enhance saphenous vein graft patency following aortocoronary bypass surgery, and a comb ination thereof deserves further investigation in a trial large enough to detect the effects of these treatments with respect to clinical ev ents.