Despite powerful evidence that the blood-thinning drug warfarin can prevent strokes in people with atrial fibrillation -- a type of irregular heartbeat -- the drug continues to be seriously underprescribed, according to a study by two physicians from the Massachusetts General Hospital (MGH). The report by Randall Stafford, MD, and Daniel Singer, MD, appears in the April 7 issue of Circulation.

Atrial fibrillation is an abnormal rhythm in the contraction of the upper chambers of the heart and is the strongest common risk factor for stroke. By leading to the formation of blood clots that may travel to the brain, the condition accounts for about 80,000 strokes annually. Achieving more widespread use of warfarin, the researchers estimate, could prevent at least 10,000 strokes a year.

The researchers examined how frequently patients with atrial fibrillation received prescriptions for warfarin, based on data from the National Ambulatory Medical Care Survey from 1989 to 1996. Although warfarin use increased from 13 percent of patient visits in 1989 to 40 percent of 1993 visits -- a level the authors believe is still too low -- there was no significant change in usage from 1993 to 1996. They also found that use of aspirin, which also thins the blood but not as effectively as warfarin, increased from 6 percent to 20 percent of patients.

"While not every patient with atrial fibrillation should receive warfarin," says Stafford, "we believe there are many other reasons why doctors may not be prescribing this important drug. The use of blood thinners requires frequent blood tests to reduce the small possibility of abnormal bleeding, and both patients and physicians might be overly concerned about the risks involved with this very important therapy."

The researchers note that the fact that warfarin usage has leveled off at a less-than-optimal level suggests that new strategies, such as specialized anticoagulation clinics, may be needed. In 1996, Staff
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Contact: Susan McGreevey
smcgreevey@partners.org
617-724-2764
Massachusetts General Hospital
8-Apr-1998