Appropriate Use of Anticoagulants among Nonvalvular Atrial Fibrillation Patients at a University Hospital in Thailand

Abstract

OBJECTIVE: Warfarin is primarily used for stroke prevention in atrial fibrillation (AF) patients in Thailand. Novel oral anticoagulants (NOACs) are used less commonly due to their high cost. This study aimed to evaluate the appropriate use of anticoagulants and clinical outcomes among nonvalvular AF (NVAF) patients. METHODS: This retrospective study collected data from the electronic medical records of patients who were diagnosed with NVAF between January 2014 and December 2019 at the Faculty of Medicine, Vajira Hospital. Baseline characteristics, prescribed indication, types and doses of anticoagulant, and ischemic and hemorrhagic outcomes were recorded and analyzed. RESULTS: We analyzed 783 patients with NVAF in this study. Of these, 539 (68.90%) were treated with oral anticoagulants (OAC), including 344 patients (43.90%) with warfarin therapy and 195 (24.90%) with NOACs. Meanwhile, 492 (73.10%) patients with CHA2DS2VASC score ≥ 2 received OAC therapy that was suitable for their indication. Of the 344 patients who received warfarin, 112 patients (32.60%) had an optimal time in therapeutic range (TTR) level of ≥ 65%. Of the 195 NOAC patients, only 98 (50.30%) received appropriate doses of NOACs. There was no statistically significant difference in the overall incidence rates of ischemic stroke/systemic embolism, bleeding, cardiovascular death, and all-cause death between the warfarin and NOACS groups. Appropriate TTR levels in the warfarin group was associated with significantly lower incidence rates of cardiovascular death (hazard ratio: 0.14; 95% CI: 0.02–0.79; p = 0.02) and all-cause death (hazard ratio: 0.36; 95% CI: 0.12–0.87; p = 0.01), than inappropriate TTR levels. CONCLUSION: Most NVAF patients received oral anticoagulants with the appropriate indication. Warfarin is the most prescribed oral anticoagulant for patients with NVAF. About half of the patients received inappropriate doses of oral anticoagulants that potentially adversely affected the study outcomes of cardiovascular and all-cause deaths.