According to this study:
* Certain oral anticoagulants are superior to aspirin in the prevention of ischemic stroke.
* Bleeding episodes occur more frequently with those oral anticoagulants than with aspirin.
A recent review of the literature on stroke-prevention treatment regimens for patients with nonrheumatic atrial fibrillation revealed that certain oral anticoagulants are associated with lower rates of stroke than aspirin but also with a greater incidence of bleeding episodes.
The authors analyzed randomized, controlled trials included in a 2001 Cochrane database review as well as others published between January 2000 and March 2005, and identified through Cochrane and MEDLINE. Only those studies involving anticoagulant and antiplatelet therapies for atrial fibrillation and at least one year of follow-up were included, for a total of 19 trials, 17,833 patients, and nine treatment strategies--alternate-day aspirin, daily aspirin, fixed low-dose warfarin, fixed low-dose warfarin and aspirin, indobufen, adjusted low-dose warfarin, adjusted standard-dose warfarin, placebo, and ximelagatran. (Ximelagatran has raised concerns about liver toxicity and hasn't yet been approved for long-term use in the United States or Europe.)
A mixed-treatment comparison method was implemented to compare the various treatment regimens. The primary end points in the review were the incidence of ischemic stroke and of major or fatal bleeding episodes per 1,000 person-years of follow-up; the mean interval of follow-up among all the trials was 1.8 years.
The researchers estimated the baseline risk of ischemic stroke in patients with atrial fibrillation at 51 events per 1,000 person-years. Using that figure for comparison, they found that adjusted standard-dose and low-dose warfarin, ximelagatran, and aspirin prevented ischemic stroke more often than placebo. Estimating the number of strokes prevented and the number of significant bleeding episodes per 1,000 person-years yielded the following results: adjusted standard-dose warfarin, 28 strokes and 11 bleeding episodes; aspirin, 16 strokes and six bleeding episodes; indobufen, 33 strokes and 22 bleeding episodes; and ximelagatran, 29 strokes and 10 bleeding episodes.
The authors note that because the incidence of atrial fibrillation is likely to increase as the U.S. population ages, the results of their review can be used to determine which stroke-prevention regimens can confer the greatest benefit to patients with nonrheumatic atrial fibrillation.
AK