JACC in a Flash | The risk of ischemic stroke among patients with atrial fibrillation (AFib) and a CHA₂DS₂-VASc score of 1 appears to be lower than previous studies have indicated, according to a study based on data from Swedish nationwide health registries.

The study, led by Leif Friberg, MD, PhD, of the Karolinska Institute, Department of Clinical Sciences at Danderyd Hospital and Department of Cardiology at Danderyd Hospital, Stockholm, Sweden, looked at 140,420 patients with nonvalvular AFib, who were not receiving anticoagulant therapy between 2005 and 2010. All patients had a CHA₂DS₂-VASc score of 1.

Unlike previous studies, this one used a broad definition of "stroke" to include ischemic stroke, unspecified stroke, transient ischemic attack, and pulmonary embolism. As a result of this broad definition, results indicated a 44% higher annual risk for this patient group than for traditional definitions of stroke. For patients with a CHA₂DS₂-VASc score of 1, annual stroke rate varied between 0.5-0.9%, depending on the definition of "stroke." For women with a CHA₂DS₂-VASc score of 1, annual "stroke" rates varied between 0.1% and 0.2%, whereas men with a CHA₂DS₂-VASc score of 1 had an annual "stroke" rate of 0.5% and 0.7%. Among the entire national cohort of AFib patients, 46.2% of men and 22.5% of women with a CHA₂DS₂-VASc score of 1 had warfarin use at baseline.

According to Friberg et al., earlier findings prior to this study "may have led to unnecessary, and potentially harmful" use of oral anticoagulants in low-risk patients.

In an ACC Journal Scan, Geoffrey D. Barnes, MD, notes that "of particular interest are the various definitions of 'stroke' assessed in this study, including use of transient ischemic attack and pulmonary embolism." "Even when the looser definition of stroke was assessed, risk in this cohort remained <1% per year," he says. "While no formal bleeding risk was assessed in this same study, there are legitimate concerns about the balance between stroke and bleeding risk when anticoagulating AF patients with a CHA₂DS₂-VASc score of 1. Clinicians should recall that the European guidelines favor anticoagulation for men (but not for women) with a CHA₂DS₂-VASc score of 1, which is justified based on these study results."

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References

1. Friberg L, Skeppholm M, Terent A. J Am Coll Cardiol. 2015;65:225-32.

Keywords: CardioSource WorldNews, ACC Publications

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