One-year outcomes of inappropriate DOAC dosing in patients with atrial fibrillation

Background Atrial fibrillation (AF) is a major risk factor for thromboembolism, regardless of whether it is paroxysmal, persistent, or permanent. Oral anticoagulation is recommended for patients with clinical AF who are at increased thromboembolic risk, in order to prevent ischaemic stroke and systemic embolism. Despite well-established evidence supporting its efficacy, inappropriate dosing of direct oral anticoagulants (DOACs) remains common in clinical practice and may adversely affect patient outcomes. Purpose To evaluate the impact of DOAC dose appropriateness on one-year clinical outcomes in patients with AF. Methods This single-center retrospective study reviewed 685 patients who underwent an electrocardiogram in the emergency department between March 24 and March 30, 2024. Among these, 141 (20.6%) patients were identified as having either known or newly diagnosed AF. Patients were excluded if they were on warfarin, died during hospitalisation, experienced major bleeding, had incomplete data. Those with an estimated glomerular filtration rate <15 mL/min/1.73 m² or total dependency were also excluded. Dosing appropriateness was assessed according to the European Society of Cardiology guidelines 2024 for AF. Patients were classified as correctly dosed, underdosed, or overdosed. Comparisons between groups were performed using chi-square or Fisher’s exact tests, as appropriate. Results A total of 109 patients were included (mean age 80.8 ± 11.8 years, 64% female). Inappropriate DOAC dosing was identified in 30 patients (28%), of whom 19 (63%) were underdosed and 11 (37%) overdosed. At one-year follow-up, no statistically significant differences were observed in adverse outcomes between dosing groups (all p > 0.05). Nonetheless, overdosed patients exhibited numerically higher rates of all-cause mortality (18.2% vs 17.7%), heart failure hospitalisation (36.4% vs 22.8%), and major bleeding (18.2% vs 8.9%) compared with those appropriately dosed. Unexpectedly, underdosed patients did not show increased event rates, while stroke (6.3%) and myocardial infarction (1.3%) were observed exclusively among appropriately dosed patients. Conclusion In this real-world cohort, inappropriate DOAC dosing at hospital discharge was frequent. Although no statistically significant differences in one-year outcomes were observed, overdosing was associated with numerically higher rates of mortality, bleeding, and hospitalisation. These findings highlight the need for systematic dose reassessment at discharge to optimise anticoagulation safety and efficacy.