Approximately 2.3 million adults in the United States have atrial fibrillation. This number is expected to increase significantly over the next few years as the population ages. Persons with atrial fibrillation have an increased risk of stroke, morbidity, and mortality compared with those without this rhythm disturbance. One strategy for treating persons with atrial fibrillation is to control heart rate with anti-arrhythmic drugs combined with the use of antithrombotic medications. Multiple studies and systematic reviews have evaluated the use of warfarin (Coumadin) and aspirin in the prevention of stroke in nonrheumatic atrial fibrillation; however, there has been no meta-analysis that compares aspirin with warfarin treatment. Cooper and associates used a network meta-analysis to compare these two treatment options in patients with nonrheumatic atrial fibrillation.

The authors used the CENTRAL database of the Cochrane Collaboration and a MEDLINE search to identify randomized controlled trials of warfarin and aspirin therapy in nonrheumatic atrial fibrillation. Trials were included if they had at least 12 months of follow-up data. To compare different treatment regimens, the authors used mixed-treatment comparison analysis. Main outcome measures included rate of stroke per 1,000 person-years and number of bleeding episodes.

Nineteen studies were included in the analysis, with 17,833 patients randomized to nine treatment strategies. Treatments, including adjusted standard-dose warfarin, adjusted low-dose warfarin, ximelagatran (withdrawn from market), and aspirin, significantlyloweredtheriskofstroke compared with placebo. Bleeding episodes, including major and fatal bleeds, were elevated in all groups, but this was not statistically significant. For example, if the incidence of ischemic stroke events was 51 per 1,000 person-years in this population, warfarin would prevent 28 strokes but would cause 11 major or fatal bleeds. Using aspirin would reduce strokes by 16 but cause six major or fatal bleeds.

The authors conclude that oral anticoagulants reduce the risk of ischemic stroke in persons with nonrheumatic atrial fibrillation, but at a higher risk of bleeding compared with aspirin. Oral anticoagulants and aspirin were found to significantly reduce the risk of ischemic stroke compared with placebo. When providing stroke prevention treatment in patients with nonrheumatic atrial fibrillation, both benefits and harms warrant consideration.