Treatment with Warfarin, an anticoagulant drug, may reduce the risk of stroke by more than two-thirds in patients with atrial fibrillation.

An estimated 2,260,000 individuals in the U.S. have atrial fibrillation, an irregular heartbeat in which the atria beat inconsistently and rapidly.

The Atrial Fibrillation Follow-up Investigation of Rhythm Management ( AFFIRM ) study, a large multi-center comparison study of the two strategies for treatment of atrial fibrillation, rate control or sinus rhythm control therapy, found no difference in the risk of death for patients treated with either of the two therapies.
Treatment with the anticoagulant, Warfarin, was included in both therapies, although patients in the sinus rhythm control group could stop Warfarin after at least four weeks of maintained sinus rhythm while receiving an anti-arrhythmic drug.

David G. Sherman, of the University of Texas Health Science Center, San Antonio, and colleagues assessed the occurrence and characteristics of strokes in patients in both treatment groups in the follow-up to the AFFIRM study, ranging from two to six years.

The researchers analyzed the relationship of a number of variables for risk of ischemic stroke, a stroke caused by decreased blood flow to an area of the brain, most commonly due to narrowing of blood vessels or an embolism leading to blockage of the blood supply.
Variables in the analysis included age, sex, and history of stroke, diabetes, coronary artery disease, high blood pressure and smoking.

Eighty-four percent of the rate control patients and 52 percent of the sinus rhythm control patients received Warfarin throughout the study.

The type of treatment was not associated with risk of stroke in the 4,060 patients participating in the study.
Two hundred eleven patients ( 8.2 percent ) had a stroke event.
Ischemic stroke ( 6.3 percent ) was the most common type.

The researchers found seven variables were significantly associated with risk of stroke, including increasing age, female gender, the episode of atrial fibrillation which qualified the patient for the study lasting two or more days, a history of stroke or TIA ( transitory ischemic attack ), and a history of diabetes.
The presence of atrial fibrillation was associated with a 60 percent increase in risk of having an ischemic stroke and the use of Warfarin was associated with a 69 percent decrease in stroke risk.

" These data suggest that the beneficial effect of Warfarin therapy exists not only for patients experiencing atrial fibrillation but also for patients who have a history of AF but who are presumably in sinus rhythm," the authors conclude. " Anticoagulation therapy should be maintained in patients who have a history of atrial fribrillation and risk factors for stroke, even when the recurrent atrial fibrillation has not been documented. "

Source: Archives of Internal Medicine, 2005


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