Prevention of thromboembolism in atrial fibrillation : A meta-analysis of trials of anticoagulants and antiplatelet drugs

• Published in: Journal of general internal medicine : JGIM Vol. 15; no. 1; pp. 56 - 67
• Main Authors: SEGAL, J. B, MCNAMARA, R. L, MILLER, M. R, NINA KIM, GOODMAN, S. N, POWE, N. R, ROBINSON, K. A, BASS, E. B
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 2000; Springer Nature B.V; Blackwell Science Inc
• Subjects: Anticoagulants; Anticoagulants - therapeutic use; Aspirin; Aspirin - therapeutic use; Atrial Fibrillation - complications; Biological and medical sciences; Blood. Blood coagulation. Reticuloendothelial system; Cardiac arrhythmia; Cardiology; Clinical Review; Clinical trials; Collaboration; Drugs; Hemorrhage; Humans; Internal medicine; Medical sciences; Medicine; Meta-analysis; Odds Ratio; Patients; Pharmacology. Drug treatments; Platelet Aggregation Inhibitors - therapeutic use; Prevention; Randomized Controlled Trials as Topic; Stroke; Thromboembolism; Thromboembolism - etiology; Thromboembolism - prevention & control; Treatment Outcome; Warfarin - therapeutic use; United States > US; Baltimore Maryland; Human; Nervous system diseases; Stroke; Chemoprophylaxis; Warfarin; Arrhythmia; Coumarine derivatives; Atrial fibrillation; Cardiovascular disease; Anticoagulant; Acetylsalicylic acid; Excitability disorder; Antiplatelet agent; Cerebral disorder; Metaanalysis; Vascular disease; Heart disease; Central nervous system disease; Clinical trial; Thromboembolism; Cerebrovascular disease
• ISSN: 0884-8734; 1525-1497
• DOI: 10.1046/j.1525-1497.2000.04329.x

Appropriate use of drugs to prevent thromboembolism in patients with atrial fibrillation (AF) involves comparing the patient's risk of stroke and risk of hemorrhage. This review summarizes the evidence regarding the efficacy of these medications.
We conducted a meta-analysis of randomized controlled trials of drugs used to prevent thromboembolism in adults with nonpostoperative AF. Articles were identified through the Cochrane Collaboration's CENTRAL database and MEDLINE until May 1998.
Eleven articles met criteria for inclusion in this review. Warfarin was more efficacious than placebo for primary stroke prevention (aggregate odds ratio [OR] of stroke = 0.30, 95% confidence interval [CI] 0.19, 0.48), with moderate evidence of more major bleeding (OR 1.90; 95% CI 0.89, 4.04). Aspirin was inconclusively more efficacious than placebo for stroke prevention (OR 0.56, 95% CI 0.19, 1.65), with inconclusive evidence regarding more major bleeds (OR 0.81, 95% CI 0.37, 1.77). For primary prevention, assuming a baseline risk of 45 strokes per 1,000 patient-years, warfarin could prevent 30 strokes at the expense of only 6 additional major bleeds. Aspirin could prevent 17 strokes, without increasing major hemorrhage. In direct comparison, there was evidence suggesting fewer strokes among patients on warfarin than among patients on aspirin (aggregate OR 0.64, 95% CI 0.43, 0.96), with only suggestive evidence for more major hemorrhage (OR 1.60, 95% CI 0.77,3.35). However, in younger patients, with a mean age of 65 years, the absolute reduction in stroke rate with warfarin compared with aspirin was low (5.5 per 1,000 person-years) compared with an older group (15 per 1,000 person-years).
In general, the evidence strongly supports warfarin for patients with AF at average or greater risk of stroke. Aspirin may prove to be useful in subgroups with a low risk of stroke, although this is not definitively supported by the evidence.