Antiplatelet or anticoagulant therapy after coronary artery bypass surgery. A meta-analysis of clinical trials

PURPOSE: To determine the efficacy of antiplatelet or anti-coagulant therapy in preventing graft occlusions after coronary artery bypass surgery. DATA IDENTIFICATION: Studies published from 1966 to 1988 were identified through a computerized search using MEDLINE, by searching the bibliographies of all identified articles, and by consulting with the cardiologists and cardiothoracic surgeons in the Veterans Administration Cooperative Study Group on Antiplatelet Therapy After Coronary Artery Bypass Surgery. STUDY SELECTION: All studies selected were randomized, controlled clinical trials comparing at least one active drug with a placebo or nonplacebo control group. DATA EXTRACTION: Key data were extracted from each article, including the percentage of patients in each treatment group with one or more grafts occluded, the percentage of patients with completed postoperative catheterizations, timing of postoperative catheterization, and timing of start of treatment. These data were easily obtained from each article and did not require multiple observers. RESULTS OF DATA ANALYSIS: All studies had positive treatment-effect sizes in favor of active treatment, although some studies did not achieve statistical significance. A meta-analysis combining all treatment effects clearly shows that active treatment is beneficial (overall effect size = 0.30; CI, 0.21 to 0.38). Efficacy improves with early initiation of treatment. CONCLUSIONS: Early initiation of antiplatelet or anticoagulant drugs reduces the incidence of graft occlusions after coronary artery bypass surgery.