Ten RCTs involving 1,750 patients were included. The secondary outcomes were based on fewer than 10 studies.
In terms of study quality, no results on the independence of the outcome assessment were presented.
There was no evidence of publication bias.
The overall risk of graft occlusion was lower in the treated group than in the control or placebo group; the OR was 0.46 (95% CI: 0.32, 0.66). This was also the case when studies reporting 12- and 24-month follow-up were pooled separately; the ORs were 0.50 (95% CI: 0.29, 0.87) and 0.58 (95% CI: 0.39, 0.88), respectively.
The beneficial effect of treatment was stronger in the studies that compared antiplatelet drugs with placebo (OR 0.43, 95% CI: 0.27, 0.67) than in those that compared anticoagulant treatment with placebo (OR 0.54, 95% CI: 0.28, 1.04). In the analyses of antiplatelet drugs versus placebo, the significant heterogeneity was removed with the exclusion of one study, and the beneficial effect remained (OR 0.38, 95% CI: 0.24, 0.59).
The beneficial effect of antithrombotic treatment compared with control or placebo was stronger in those studies in which prosthetic grafts were used (OR 0.25, 95% CI: 0.11, 0.57) than in those studies in which saphenous vein grafts were used (OR 0.55, 95% CI: 0.41, 0.73). There was no significant beneficial effect of antithrombotic treatment in the studies in which both prosthetic and saphenous vein material was used (OR 0.64, 95% CI: 0.23, 1.81).
The beneficial effect of antithrombotic treatment compared with control or placebo was present in studies of patients with above the knee and below the knee grafts; the ORs were 0.29 (95% CI: 0.16, 0.53) and 0.46 (95% CI: 0.32, 0.66), respectively.
All-cause mortality was lower in patients who received antithrombotic treatment than in the control or placebo group (OR 0.70, 95% CI: 0.51, 0.95). In terms of adverse events, there was no statistically significant difference between the treated and control groups for cerebrovascular accident, myocardial infarction, lower extremity amputation or bleeding, though there was a trend towards an increased risk of bleeding.