Comparison of Monthly Bleeding Rates After DOAC 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. We evaluated the distribution of bleeding events following anticoagulant initiation. Methods Adult patients in the Michigan Anticoagulation Quality Improvement Initiative (MAQI 2 ) 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 test. Results A total of 2663 patients (mean age 66.9 years, 49% male sex, 72.1% AF) starting DOACs were followed. Bleeding event rates were highest following anticoagulant initiation. For VTE, patients experienced 110, 55, and 36 bleeding events per 100 patient-years the first three months of anticoagulation respectively. For AF, patients experienced 66, 43, and 33 bleeding events per 100 patient-years the first three months of anticoagulation respectively. After adjustment for covariates, bleeding was higher for patients with VTE compared to AF with 51 versus 34 bleeds per 100-patient years (rate ratio [95% confidence interval] 0.68 [0.58-0.80], p<0.001), largely driven by differences in the first month of anticoagulation (141 versus 75 bleeds per 100-patient years, rate ratio [95% confidence interval] 0.53 [0.38-0.74], p<0.001). Conclusion Bleeding rates were highest during the first three months of oral anticoagulation; bleeding was higher for patients with VTE compared to AF. These findings emphasize the need for careful management and monitoring after DOAC initiation.