Rationale and design of the Anticoagulant Therapy after Left Atrial Appendage Closure (ATLAAC) Trial

Introduction: Left atrial appendage closure (LAAC) has become a recommended addition to oral anticoagulation for patients with atrial fibrillation, who undergo cardiac surgery. The procedure significantly reduces the risk of stroke and systemic arterial embolism, potentially making oral anticoagulation (OAC) unnecessary or even harmful, when considering the associated increased risk of bleeding. This publication describes the rationale and design of a randomized trial, testing the hypothesis that stopping OAC is noninferior to continuing OAC after surgical LAAC in terms of the primary endpoint. Methods: The ATLAAC trial is a multicenter, randomized, controlled trial, aiming to enroll 1,220 patients with atrial fibrillation, who have undergone surgical LAAC and remain on OAC. A cardiac CT scan is performed to confirm success of the LAAC. Patients with successful closure are randomized to stop or continue OAC. The primary endpoint is the first occurrence of ischemic stroke, systemic arterial embolism, or major bleeding over an expected mean follow-up of 4 years. Secondary endpoints include all-cause mortality, cardiovascular mortality, any bleeding leading to hospitalization, blood transfusion, venous thromboembolism, myocardial infarction, and quality of life measures. Trial status: Enrollment for the ATLAAC trial began in March 2024. As of January 18th, 2025, 554 patients have been enrolled in the study and 319 patients have been randomized. Recruitment is expected to continue for approximately 12 months. Follow-up will be stopped once 128 primary endpoints have occurred. Conclusions: The ATLAAC trial will evaluate the safety of stopping OAC after surgical LAAC. Trial registration number: EU-CT: 2022-502986-92-00, clinicaltrials.gov ID: NCT06401616.