Patients with atrial fibrillation who had CHA2DS2-VASc scores of 1 were at lower risk of ischemic stroke than previously reported, according to a retrospective analysis of hospital registry data. The research appeared in the Journal of American College of Cardiology. Depending on the definition of stroke used, risk was 0.1% to 0.2% in women and 0.5% to 0.7% in men – so low that oral anticoagulants (OACs) would not be expected to benefit patients of either sex, said Leif Friberg, MD, PhD, from the Karolinska Institute in Stockholm and his associates. Past studies had potentially overestimated the risk of stroke in this population, which “may have led to unnecessary, and potentially harmful, OAC treatment of low-risk patients,” they said. European and U.S. guidelines both recommend using the CHA2DS2-VASc (heart failure, hypertension, age >75, diabetes mellitus, prior stroke or transient ischemic attack, vascular disease, age 65-74 years, female) scoring system to assess stroke risk in patients with AF. But past studies have reported a threefold variation (ranging from 0.6% to greater than 2.0%) in stroke risk among AF patients with CHA2DS2-VASc scores of 1 who were not receiving OACs, the researchers noted. Anticoagulation therapy is likely to benefit AF patients whose annual risk of stroke exceeds 1%, but not patients whose risk is only 0.6%, they added. Tabled 1PointsConditionc1Congestive heart failureH1Hypertension: blood pressure consistently above 140/90 mmHg (or treated hypertension on medication)A1Age >75 yearsD1Diabetes mellitusS22Prior stroke or TIA or thromboembolismV1Vascular disease (e.g. peripheral artery disease, myocardial infarction, aortic plaque)A1Age 65–74 yearsSc1Sex category Open table in a new tab Score Concerns“Dr. Friberg and his colleagues conclude that the true stroke rate for patients with a CHA2DS2-VASc score of 1 is less than 0.7% per year, too low for oral anticoagulant therapy to benefit patients with AF.“Guideline writers should be aware of the drawbacks of the CHA2DS2-VASc score. They should focus on the absolute rates of stroke corresponding to risk prediction point scores and be alert to potential biases in studies reporting these rates. Investigators should work to harmonize methods for analyzing large AF databases.”Daniel E. Singer, MD, is at Harvard Medical School in Boston, and Michael D. Ezekowitz, MD, PhD, is at Sidney Kimmel Medical College at Thomas Jefferson University in Philadelphia. These remarks were taken from their editorial accompanying Dr. Friberg's report (J Am Coll Cardiol 2015;65:233-5). “Dr. Friberg and his colleagues conclude that the true stroke rate for patients with a CHA2DS2-VASc score of 1 is less than 0.7% per year, too low for oral anticoagulant therapy to benefit patients with AF. “Guideline writers should be aware of the drawbacks of the CHA2DS2-VASc score. They should focus on the absolute rates of stroke corresponding to risk prediction point scores and be alert to potential biases in studies reporting these rates. Investigators should work to harmonize methods for analyzing large AF databases.” Daniel E. Singer, MD, is at Harvard Medical School in Boston, and Michael D. Ezekowitz, MD, PhD, is at Sidney Kimmel Medical College at Thomas Jefferson University in Philadelphia. These remarks were taken from their editorial accompanying Dr. Friberg's report (J Am Coll Cardiol 2015;65:233-5). Their study (J Am Coll Cardiol 2015;65:225-32), which included 140,420 patients in Sweden with nonvalvular AF, assessed the effect of varying definitions of stroke on estimates of stroke risk. Using a broad definition that included ischemic stroke, transient ischemic attack, and pulmonary embolism led to a 44% greater annual risk of stroke than if only ischemic strokes were considered, the investigators reported. They disagreed with classifying pulmonary embolism events and TIAs as strokes, as some past studies have done. “Primary prevention of pulmonary embolism among patients with AF has, to the best of our knowledge, not been studied and is not an approved indication for OAC treatment,” they said. “We also did not find it relevant to count TIA as an endpoint in studies that describe stroke risk. As a diagnosis, TIA is difficult to validate.”