Background: Atrial fibrillation (AF) is the most common cardiac arrhythmia, with increasing prevalence in Japan. Although prothrombin time-international normalized ratio (PT-INR) targets for monitoring warfarin therapy in patients with nonvalvular AF (NVAF) are well defined, real-world patient characteristics and PT-INR levels remain unknown among Japanese patients with NVAF who initiate and continue warfarin (warfarin maintainers) versus those who switch from warfarin to direct oral anticoagulants (DOACs; warfarin switchers).
Methods: Patients with NVAF receiving oral anticoagulants between February 2013 and June 2015 were identified using a nationwide electronic medical record (EMR) database from 69 hospitals in Japan. Demographics and characteristics of patients, PT-INR, time in therapeutic range (TTR), and frequency in range (FIR) of PT-INR between warfarin maintainers and warfarin switchers were assessed.
Results: A total of 1705 patients met inclusion criteria and were examined (1501 warfarin maintainers versus 204 warfarin switchers). CHADS2, CHA2DS2-VASc, and HAS-BLED scores were comparable between groups. However, these scores were significantly higher among warfarin switchers at the time of switching than at the time of warfarin initiation. Furthermore, TTR and FIR of PT-INR were lower in warfarin switchers than in maintainers. Nevertheless, TTR and FIR were below 50% (PT-INR, 1.6-2.6) in both patient groups.
Conclusions: In this EMR-based clinical study, patients who switched to DOACs had both poor or inadequate PT-INR control and higher risk factors of stroke. Many patients receiving warfarin did not achieve sufficient PT-INR therapeutic range. DOACs could be recommended in Japanese patients with NVAF with inadequate PT-INR control and increased risk of stroke.
Keywords: DOAC; Prothrombin time–international normalized ratio; atrial fibrillation; oral anticoagulant; time in therapeutic range; warfarin.
Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.