Atrial fibrillation and the risk of ischemic stroke: does it still matter in patients with a CHA2DS2-VASc score of 0 or 1?

BACKGROUND AND PURPOSE Atrial fibrillation (AF) is an independent risk factor for stroke. Recent studies have demonstrated that the CHA(2)DS(2)-VASc scheme is useful for selecting patients who are truly at low risk. The goal of the present study was to compare the risk of ischemic stroke among AF patients with a CHA(2)DS(2)-VASc score of 0 (male) or 1 (female) with those without AF. METHODS The study enrolled 509 males (CHA(2)DS(2)-VASc score=0) and 320 females (CHA(2)DS(2)-VASc score=1) with AF who did not receive any antithrombotic therapy. Patients were selected from the National Health Insurance Research Database in Taiwan. For each study patient, 10 age-matched and sex-matched subjects without AF and without any comorbidity from the CHA(2)DS(2)-VASc scheme were selected as controls. The clinical end point was the occurrence of ischemic stroke. RESULTS During a follow-up of 57.4 ± 35.7 months, 128 patients (1.4%) experienced ischemic stroke. The event rate did not differ between groups with and without AF for male patients (1.6% vs 1.6%; P=0.920). In contrast, AF was a significant risk factor for ischemic stroke among females (hazard ratio, 7.77), with event rates of 4.4% and 0.7% for female patients with and without AF (P<0.001). CONCLUSIONS AF males with a CHA(2)DS(2)-VASc score of 0 were at true low risk for stroke, which was similar to that of non-AF patients. However, AF females with a score of 1 were still at higher risk for ischemic events than non-AF patients.