BACKGROUND The predictors of ischemic stroke in "low-risk" patients with atrial fibrillation (AF) (CHA₂DS₂-VASc score 0 in men or 1 in women) are debated.

OBJECTIVE This study aimed to investigate the factors associated with ischemic stroke in low-risk patients with AF. Imaging characteristics of their ischemic strokes were also evaluated.

METHODS This was a matched case-control study conducted at a single tertiary institution. We identified 44 patients with de novo ischemic stroke and incidentally found AF with a low-risk CHA₂DS₂-VASc score. A 1:5 age- and sex-matched control group was selected for patients with AF and a low-risk CHA₂DS₂-VASc score but without ischemic stroke and oral anticoagulant therapy. Conditional multivariate logistic regression analysis was performed to identify the predictors.

RESULTS There were no significant differences in age, sex, body mass index, comorbidities, left atrial size, and left ventricular ejection fraction. Smokers were more prevalent in the stroke group than in the nonstroke group (24 of 44 [54.5%] vs 22 of 220 [10.0%]; P < .001). Additionally, the mean white blood cell count was significantly higher in the stroke group (P = .019). In conditional univariate logistic regression analysis, smoking and white blood cell count were significant predictors of stroke. In multivariate analysis, smoking was the only significantly associated factor (matched odds ratio 9.10; 95% confidence interval 2.48-33.42). In the stroke group, 14 of 44 patients (31.8%) had multiple vascular territory infarcts.

CONCLUSION Smoking was the predictor associated with ischemic stroke in patients with AF and a low-risk CHA₂DS₂-VASc score.