More early bleeds associated with high baseline direct oral anticoagulant levels in atrial fibrillation: the MAS study

Abstract

AbstractTreatment with direct oral anticoagulants (DOAC) in patients with atrial fibrillation (AF) is effective and safe. However, bleeding complications still occur. Whether the measurement of DOAC levels may further improve treatment efficacy and safety is still an open issue. In the "Measure and See" Study venous blood was collected 15 to 30 days after DOAC initiation in patients with AF who were then followed-up for 1 year to record the occurrence of major and clinically relevant nonmajor bleeding. DOAC plasma levels were measured in 1 laboratory, and results were kept blind to patients and treating doctors. Trough DOAC levels were assessed in 1657 patients (957 [57.7%] and 700 patients treated with standard and low dose, respectively). Fifty bleeding events were recorded during 1606 years of follow-up (3.11% pt/yrs). Fifteen bleeding events (4.97% pt/yrs) occurred in patients with C-trough standardized values in the highest activity class (>0.50); whereas 35 events (2.69% pt/yrs) occurred in those with values in the 2 lower classes (≤0.50, P = .0401). Increasing DOAC levels and low-dose DOAC use were associated with increased bleeding risk in the first 3 months of treatment. Overall, 19% of patients receiving low doses had standardized activity values in the highest class. More bleeding occurred in patients treated with low (4.3% pt/yrs) vs standard (2.2% pt/yrs; P = .0160) dose DOAC. Early measurement of DOAC levels in patients with AF identified many individuals with high activity levels despite the low doses use and had more bleeding risk during the first 3 months of treatment. This trial was registered at www.ClinicalTrials.gov as #NCT03803579.