Why the study?
Reduced dose DOACs are prescribed more often than expected in clinical practice, but only reduced dose dabigatran demonstrated similar stroke reduction and lower major bleeding versus warfarin in pivotal studies.
Do reduced dose DOACs reduce stroke and major bleeding compared to high TTR warfarin in patients with nonvalvular atrial fibrillation?
Do reduced dose DOACs reduce stroke and major bleeding compared to high TTR warfarin in patients with nonvalvular atrial fibrillation?
Reduced dose DOACs are associated with lower risks of major bleeding and stroke compared to high-quality warfarin treatment in NVAF patients, supporting their preferred use when dose reduction is indicated.
May support reduced-dose DOACs when indicated in NVAF; leaves open need for randomized confirmation versus high-TTR warfarin.
Direct oral anticoagulants (DOACs) used in nonvalvular atrial fibrillation (NVAF) are dose-reduced in elderly and patients with impaired renal function. Only reduced dose dabigatran is concluded as having similar stroke risk reduction and lower risk of major bleeding than warfarin in the pivotal studies. In clinical practice, reduced dose is prescribed more often than expected making this an important issue. The objective of this study was to compare effectiveness and safety between reduced dose DOACs and high TTR warfarin treatment (TTR ≥ 70%) in NVAF. A Swedish anticoagulation registry was used in identifying eligible patients from July 2011 to December 2017. The study cohort consisted of 40,564 patients with newly initiated DOAC (apixaban, dabigatran, or rivaroxaban) (11,083 patients) or warfarin treatment (29,481 patients) after exclusion of 374,135 patients due to not being warfarin or DOAC naïve, not being prescribed reduced dose, having previous mechanical heart valve (MHV), or being under 18 years old. The median durations of follow up were 365, 419, 432 and 473 days for apixaban, dabigatran, rivaroxaban and warfarin, respectively. Warfarin TTR identified from Auricula was 70.0%. Endpoints (stroke and major bleeding) and baseline characteristics were collected from hospital administrative registers using ICD-10 codes. Cohorts were compared using weighted adjusted Cox regression after full optimal matching based on propensity scores. DOACs are associated with lower risk of major bleeding (HR with 95% CI) 0.85 (0.78-0.93), intracranial bleeding HR 0.64 (0.51-0.80), hemorrhagic stroke HR 0.68 (0.50-0.92), gastrointestinal bleeding HR 0.81 (0.69-0.96) and all-cause stroke HR 0.87 (0.76-0.99), than warfarin. Apixaban and dabigatran are associated with lower risk of major bleeding, HR 0.70 (0.63-0.78) and HR 0.80 (0.69-0.94), and rivaroxaban is associated with lower risk of ischemic stroke, HR 0.73 (0.59-0.96), with higher major bleeding risk, HR 1.31 (1.15-1.48), compared to warfarin. Apixaban is associated with higher all-cause mortality compared to warfarin, HR 1.12 (1.03-1.21). DOACs are associated with lower risk of major bleeding and all-cause stroke, than high quality warfarin treatment, with exception of rivaroxaban that carried higher risk of major bleeding and lower risk of stroke or systemic embolism. In this large observational registry-based NVAF cohort, DOACs are preferred treatment in patients with indication for DOAC dose reduction, even in a high TTR setting.
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Jansson et al. (2023) studied this question.
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