Anticoagulant drug lowers stroke risk.

People with atrial fibrillation -- an irregular beating pattern of the heart's upper chambers that often develops with age -- experience five times the risk of stroke as individuals with normally beating hearts. A new study now confirms that the anticoagulant warfarin can dramatically lower this risk.

The study -- conducted by more than 100 physicians at 16 Department of Veterans Affairs medical centers across the United States -- is the fifth to demonstrate warfarin's antistroke benefits. Some of the previous studies also suggested that a daily dose of aspirin can reduce stroke risk among patients with atrial fibrillation (SN: 3/24/90, p.180).

In the new study, reported in the Nov. 12 NEW ENGLAND JOURNAL OF MEDICINE, physicians administered either warfarin or a placebo to 571 men between the ages of 60 and 74. Forty-six of the men had already suffered a stroke.

Overall, the researchers found that warfarin treatment reduced the men's stroke risk by 79 percent. Moreover, they found that the drug was just as effective among men over age 70 as among the younger men. Warfarin also appeared to benefit patients who had experienced a previous stroke, although the researchers caution that the number of prior stroke sufferers was too small to support a definitive conclusion.

The researchers suggest that warfarin works by preventing the formation of blood clots within the heart's atrial chambers. Atrial fibrillation fosters such clotting by allowing blood to pool in the heart.

"For the present, all patients with chronic atrial fibrillation should be considered candidates for long-term low-intensity warfarin therapy," cardiologist Daniel E. Singer of the Massachusetts General Hospital in Boston concludes in an editorial accompanying the new report.