Warfarin is safe and effective as a preventive against stroke in patients with atrial fibrillation

Warfarin is safe and effective as a preventive against stroke in patients with atrial fibrillation, according to an article in the November 26th issue of The Journal of the American Medical Association.

According to background information in the article, multiple randomized clinical trials have demonstrated warfarin to be highly effective in reducing the risk of ischemic stroke in patients with atrial fibrillation with relatively low rates of bleeding. However, concerns persist about the effectiveness and safety of warfarin use in typical clinical settings because the randomized trials enrolled highly selected patients, included few very elderly people, and closely monitored patients' level of anticoagulation.

In the current study, Alan S.Go, M.D., and his American colleagues evaluated the effect of warfarin on risk of thromboembolism, hemorrhage, and death in patients with atrial fibrillation within a usual care setting. The study was conducted between July 1, 1996, and December 31, 1997, with follow-up through August 31, 1999, in one large integrated-health care system. A total of 11,526 adults were included in the study (women, 43 percent; average age, 71 years). None of the participants had atrial fibrillation associated with a valvular condition.

Among 11,526 patients, 397 thromboembolic events occurred (372 ischemic strokes). Warfarin therapy was associated with a 51 percent lower risk of thromboembolism and stroke compared with no warfarin therapy (either no antithrombotic therapy or aspirin) after adjustment for potential confounders and likelihood of receiving warfarin.

"Warfarin was effective in reducing thromboembolic risk in the presence or absence of risk factors for stroke," the authors wrote. An "analysis estimated a 64 percent reduction in odds of thromboembolism with warfarin compared with no antithrombotic therapy. Warfarin was also associated with a reduced risk of all-cause mortality [death, 31 percent lower risk]. Intracranial hemorrhage was uncommon, but the rate was moderately higher among those taking warfarin versus those not taking warfarin. However, warfarin therapy was not associated with an increased adjusted risk of nonintracranial major hemorrhage."

"Our results materially extend ... prior findings by providing contemporary and precise estimates of thromboembolism and hemorrhage rates in a broad population of individuals with atrial fibrillation, along with more complete adjustment for potential confounders and attempts to control for the likelihood of receiving warfarin over time," they added.

"Overall, our results demonstrate that findings of the randomized trials of anticoagulation for atrial fibrillation translate well into clinical practice. Our study adds further support for the routine use of anticoagulation for eligible patients with atrial fibrillation who are at moderate to high risk for stroke, particularly when well-organized management of anticoagulation can be provided," the researchers concluded.

 



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