Comparison of monthly bleeding rates after direct oral anticoagulant initiation for venous thromboembolism and atrial fibrillation.

BACKGROUND: Direct oral anticoagulants (DOACs) are commonly used for the treatment of atrial fibrillation (AF) and venous thromboembolism (VTE) but increase the risk of bleeding. OBJECTIVES: We aimed to evaluate the distribution of bleeding events after anticoagulant initiation. METHODS: Adult patients in the Michigan Anticoagulation Quality Improvement Initiative registry on DOAC for AF or VTE were followed from anticoagulant start to identify any bleeding event within 12 months. The primary outcome was any bleeding; secondary outcomes were bleeding subtypes. Monthly event rates were compared by Poisson and proportion tests. RESULTS: A total of 2663 patients (mean age 66.9 years, 49% male sex [as recorded in the electronic health record], 72.1% AF) who were starting DOACs were followed. Bleeding event rates were highest after anticoagulant initiation. For VTE, patients experienced 110, 55, and 36 bleeding events per 100 patient-years the first 3 months of anticoagulation, respectively. For AF, patients experienced 66, 43, and 33 bleeding events per 100 patient-years the first 3 months of anticoagulation, respectively. After adjustment for covariates, bleeding was higher for patients with VTE compared with AF, with 51 vs 34 bleeds per 100 patient-years (rate ratio, 0.68; 95% CI, 0.58-0.80; P < .001), largely driven by differences in the first month of anticoagulation (141 vs 75 bleeds per 100 patient-years; rate ratio, 0.53; 95% CI, 0.38-0.74; P < .001). CONCLUSION: Bleeding rates were highest during the first 3 months of oral anticoagulation; bleeding was higher for patients with VTE compared with AF. These findings emphasize the need for careful management and monitoring after DOAC initiation.