Characteristics of patients with Atrial Fibrillation treated with direct oral anticoagulants and New Insights into inappropriate dosing: Results from the French National PAF Registry.

BACKGROUND AND AIMS: Since the introduction of direct oral anticoagulant (DOAC) for atrial fibrillation (AF) therapy, inappropriate and/or underdosing of these drugs has been a major clinical challenge. We evaluated the characteristics of AF patients treated with inappropriate and low dose DOACs.

METHODS: AF patients treated with inappropriate and low dose DOACs from October 2021 to December 2021 were evaluated from the Prospective French National Registry (PAF).

RESULTS: We evaluated 1890 AF patients receiving DOACs (Apixaban 55%, Dabigatran 7% and Rivaroxaban 38%). Inappropriate dosing was noted in 18% of the population. Patients with appropriate dosing had less comorbidities: younger age (75±10 vs. 82±8 year-old, p<0.0001), reduced chronic renal failure (26% vs. 61%, p<0.0001) and lower CHA2DS2VASc and HASBLED scores (3±2 vs. 4±3, p<0.0001; 2±1 vs. 2±2, p<0.0001), respectively. In multivariate analysis older age (p<0.0001) and a higher CHA2DS2VASc score (p=0.0056) were independently associated with inappropriate DOAC dosing. Among 472 patients (27%) treated with low dose rivaroxaban or apixaban, 46% were inappropriately underdosed. Patients inappropriately underdosed were younger (82.3±8.4 vs. 85.9±5.9 yrs, p<0.0001) with less chronic renal disease (47% vs. 98%, p<0.0001). However, these patients had higher rates of prior haemorrhagic events (18% vs. 10%, p=0.01), clopidogrel use (11% vs. 3%, p=0.0002) and apixaban prescription (74% vs. 50%, p<0.0001).

CONCLUSION: Within this large registry, DOACs were associated with inappropriate dosing in 18% of cases. Independent predictors of inappropriate dosing were high CHA2DS2VASc scores and older age. Moreover, 46% of patients treated with low dose DOACs were inappropriately underdosed and more frequently occurred with apixaban.