Quality of Wafarin Control Affects the Incidence of Stroke in Elderly Patients with Atrial Fibrillation

概要

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Objective Adjusted-dose warfarin therapy can prevent stroke in patients with atrial fibrillation. However, the quality of the warfarin control may be considered to be important for elderly patients. Methods We followed 188 patients (age ≥70 years) with atrial fibrillation (warfarin, 120 patients; non-warfarin, 68 patients) for 2 years. Their warfarin control was assessed by time in therapeutic range (TTR) for an international normalized ratio of prothrombin time of 1.6-2.6, based on the Japanese guidelines of anticoagulation for elderly patients with atrial fibrillation. Results Stroke occurred in 23 patients (12.2%). In warfarin-treated patients, receiver-operator characteristic (ROC) curves suggested that patients with TTR >68% had anticoagulation benefit. In the ROC curves for prediction of stroke, the area under the curve of TTR was 0.709 (95% confidence interval, 0.585 to 0.834; p=0.02). The sensitivity and specificity of TTR ≤68% were 91.7% and 54.0%, respectively. Kaplan-Meier curves showed that the event-free ratio of stroke was significantly higher in patients who achieved this cut-off of TTR. Conclusion The results suggest that the quality of warfarin control is directly associated with the incidence of stroke in elderly patients.