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.
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.