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Optimal antithrombotic therapy following aortocoronary bypass: a meta-analysis
S E Fremes1, C Levinton, C D Naylor
1Division of Cardiovascular Surgery, Sunnybrook Health Science Center, Toronto, Ontario, Canada.
Insights
Aspirin and anticoagulants improve saphenous vein graft patency after bypass surgery. Dipyridamole offers no additional benefit, and combined therapy warrants further study for clinical event detection.
Area of Science:
- Cardiovascular Surgery
- Pharmacology
- Clinical Trials
Background:
- Saphenous vein graft occlusion is a significant complication after aortocoronary bypass surgery.
- Antithrombotic therapies are commonly used to improve graft patency.
Purpose of the Study:
- To evaluate the efficacy of aspirin, dipyridamole, and anticoagulants in preserving saphenous vein graft patency.
- To compare the effectiveness of different antithrombotic agents and dosages.
Main Methods:
- Meta-analysis of 17 randomized clinical trials.
- Data aggregated using Mantel and Haenszel methods.
- Graft occlusion determined by angiography.
Main Results:
- Aspirin significantly reduced graft occlusion (OR 0.60).
- Anticoagulants also reduced graft occlusion (OR 0.56), with similar efficacy to aspirin.
- Combination therapy of aspirin and anticoagulants showed superiority over anticoagulants alone (OR 0.55).
- Low to medium aspirin doses were more effective than high doses.
- Early postoperative treatment (< or = 6h) was beneficial.
Conclusions:
- Aspirin and anticoagulants are effective in enhancing saphenous vein graft patency.
- Dipyridamole does not provide additional benefit when combined with aspirin.
- Combined aspirin and anticoagulant therapy warrants further investigation for clinical outcomes.
Abstract:
To evaluate the role of antithrombotic therapy, on preserving graft patency, we performed a meta-analysis of randomized clinical trials involving aspirin (ASA), dipyridamole (D), anticoagulants (AC) and placebo or nontreatment controls (P). Manual literature searches were performed supplemented by computerized MEDLINE listings complete to July 1991. Saphenous vein graft occlusion was determined by angiography (patients with > or = 1 distal anastomotic occlusion). The trial data were aggregated with the methods of Mantel and Haenszel. The results are reported as odds ratios (OR) +/- 95% confidence intervals (CI). Seventeen trials were evaluated. Aspirin strongly influenced graft 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 occlusion [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% CI 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 (975 mg). Early postoperative treatment (< or = 6 h) strongly influenced graft occlusion while preoperative administration provided no additional benefit. No mortality advantage was identified for any antithrombotic therapy. Aspirin or anticoagulants enhance saphenous vein graft patency following aortocoronary bypass surgery, and a combination thereof deserves further investigation in a trial large enough to detect the effects of these treatments with respect to clinical events.