Aim: We investigated the influence of preadmission anticoagulation on infarct volume in patients with nonvalvular atrial fibrillation (NVAF). Methods: Data were collected on consecutive ischemic stroke patients with NVAF admitted to Osaka University Hospital between 2004 and 2011. Patients were divided into 3 groups: the no-anticoagulation group, the subtherapeutic anticoagulation group [admission prothrombin time international normalized ratio (PT-INR) <1.6], and the therapeutic anticoagulation group (PT-INR ≧1.6). In analyses of neurological outcome, we excluded patients with a modified Rankin Scale (mRS) score of >1 before onset. Results: Of the 68 patients, 45 were classified into the no-anticoagulation group, 9 into the subtherapeutic group, and 14 into the therapeutic group. The median value of infarct volume was 60 (interquartile range 9–176), 142 (64–184), and 8 (3–46) ml in each group, respectively. Infarct volume in the therapeutic group was significantly smaller than in the subtherapeutic group (p = 0.010), and tended to be smaller than in the no-anticoagulation group (p = 0.086). National Institute of Health Stroke Scale score at admission, and mRS score at discharge were significantly reduced in the therapeutic group compared with those in the other groups (p = 0.028 and p = 0.017, respectively). Conclusion: Therapeutic anticoagulation reduces infarct volume and improves neurological outcome after ischemic stroke in patients with NVAF.

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