Clinical events preceding switching and discontinuation of oral anticoagulant treatment in patients with atrial fibrillation

AIMS: Switching between oral anticoagulants and treatment discontinuation are common events related to therapy with non-vitamin K antagonist oral anticoagulants (NOACs). However, knowledge on the reasons leading to these treatment changes is scarce. The aim of this study was to identify clinical events preceding anticoagulant switching and NOAC discontinuation during oral anticoagulant therapy in patients with atrial fibrillation. METHODS AND RESULTS: We performed a nationwide register-based study including Danish atrial fibrillation patients initiating a NOAC between August 2011 and February 2016 (n = 50 623). We explored potential reasons leading to changes in anticoagulant treatment by identifying clinical events preceding switches from vitamin K antagonists (VKA) to NOAC, switches from NOAC to VKA, and discontinuations of NOACs. Among 23 531 anticoagulant users changing treatment, we identified 13 295 switches from VKA to NOAC, 5206 switches from NOAC to VKA, and 8995 discontinuations of NOACs. Approximately half of all treatment changes were preceded by a hospitalization. A relevant specific clinical event or procedure was identified prior to 18.3% of switches from VKA to NOAC, prior to 23.0% of switches from NOAC to VKA, and prior to 26.6% of discontinuations. Switches from VKA to NOAC were most often preceded by thromboembolic events (7.0%), whereas cardioversion was the most common specific event prior to a switch from NOAC to VKA (11.4%). Discontinuations were most often preceded by bleeding events (7.6%). CONCLUSION: For about one in five patients, treatment changes during anticoagulant therapy were preceded by a major clinical event. However, the majority of patients changed treatment for reasons not recorded in health registries.