An irregular heartbeat, or atrial fibrillation, affects some 2.5 million Americans. Clot formation associated with atrial fibrillation is believed to be a contributing factor in about 15 percent of the 740,000 strokes that occur each year in the United States, yet very few of the people who would benefit from a medication to treat atrial fibrillation receive it. According to a study directed by Lawrence M. Brass, M.D., professor of neurology and chief of the neurology service at the VA Connecticut Healthcare System in West Haven, only 38 percent of patients who had atrial fibrillation received warfarin, a blood thinner used to reduce the tendency for blood to form clots. Researchers believe that if more patients took warfarin, tens of thousands of strokes could be prevented, saving thousands of lives each year. “We have a medication that has been shown to be highly effective,” says Dr. Brass, “but we have found that the medical community is not getting this therapy to all of the patients who need it.” The results of the study appeared in the December issue of Stroke and are part of the ongoing efforts to enhance clinical practice in the Center for Outcomes Research and Evaluation at Yale-New Haven Hospital, Dr. Brass says.