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CHA2DS2-VASc score of 1 linked to lower stroke risk than previously reported

Key clinical point: Stroke risk was low in patients with atrial fibrillation and a CHA2DS2-VASc score of 1.

Major finding: Risk of stroke was 0.1% to 0.2% in women and 0.5% to 0.7% in men.

Data source: Retrospective study of 140,420 patients with nonvalvular AF.

Disclosures: Several Swedish foundations supported the study. Dr. Friberg reported no relevant financial conflicts of interest.

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CHA2DS2-VASc score has drawbacks

Given the current state of knowledge, patients with atrial fibrillation who are younger than 65 years but have a CHA2DS2-VASc score of 1 are unlikely to benefit from anticoagulation therapy.

Dr. Friberg and his colleagues make two important observations regarding risk score thresholds for oral anticoagulant therapy. First, they highlight the wide cohort-to-cohort variation in reported CHA2DS2-VASc–stratified rates of stroke for atrial fibrillation patients who are not anticoagulated. Second, they reveal how sensitive estimates of stroke rates are to variations in interrogating administrative databases, which are used repeatedly as sources of “real world” rates of stroke. They 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.

Going forward, 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. If variation in reported rates cannot be reconciled, then recommendations should reflect this uncertainty.

Dr. Daniel E. Singer is at Harvard Medical School in Boston, and Dr. Michael D. Ezekowitz is at Sidney Kimmel Medical College at Thomas Jefferson University in Philadelphia. Dr. Singer has been a consultant to, advised, and or received research funding from Boehringer Ingelheim, Bristol-Myers Squibb, Johnson & Johnson, Merck, and St. Jude Medical, and Medtronic. Dr. Ezekowitz reported having been a consultant and advisory board member for all those companies and several others. These remarks were taken from their editorial accompanying Dr. Friberg’s report (J. Am. Coll. Cardiol. 2015 Jan. 19 [doi:10.1016/j.jacc.2014.11.013]).


 

FROM THE JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY

References

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 online January 19 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 Dr. Leif Friberg at 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.

Dr. Leif Friberg

Dr. Leif Friberg

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 atrial fibrillation (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 OAC, 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.

Their study, 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 (TIA), 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.”

Several Swedish foundations supported the study. Dr. Friberg reported no relevant financial conflicts of interest.

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