Varied silent ischemic stroke (SS) prevalence occurs in patients with atrial fibrillation (AF). Stroke history is worth 2 points in the CHADS2 scoring system. An unknown proportion of patients with AF with a CHADS2 score of 0 or 1 have been undertreated for stroke prevention. We investigated SS risk factors using magnetic resonance imaging and estimated SS impact on clinical outcomes in patients with AF. We analyzed a total of 1,200 patients (400 with AF and 800 with sinus rhythm) who had brain magnetic resonance imaging performed for routine health checkups. Clinical outcomes including symptomatic stroke, dementia, and cognitive disorder were also evaluated in patients with AF (follow-up duration: 66.7 ± 35.9 months; range 10 to 162). SS was observed in 113 patients with AF (28.3%), which was significantly higher than that in 53 subjects (6.6%) with sinus rhythm (p <0.001, odds ratio [OR] 5.549). Independent risk factors for SS in patients with AF were age (OR 1.049), hypertension (OR 2.086), dyslipidemia (OR 2.073), and valvular AF (OR 3.157). Symptomatic stroke incidence during the follow-up was significantly greater in patients with AF with SS than without SS (5.6% vs 2.7% per year, respectively; p = 0.022, hazard ratio 1.787, 95% confidence interval 1.089 to 2.933). Using current scoring systems without correcting for subclinical stroke, clinicians have likely underestimated the stroke risk in low-risk patients with AF; thus many patients with AF might not receive optimal anticoagulation treatment. In conclusion, a screening tool for detecting SS could be considered for stroke risk evaluation in patients with AF, especially those with valvular AF, elderly patients, and patients with dyslipidemia or hypertension.
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