Abstract 16638: 4D Flow MRI Analysis of the Left Atrial Hemodynamics After Atrial Fibrillation Surgery

Introduction: Postoperative anticoagulation therapy after atrial fibrillation (AF) surgery remains a controversial topic because left atrial (LA) blood flow velocity and pattern remain unclear. This study utilizes four-dimensional (4D) flow magnetic resonance imaging (MRI) to analyze postoperative LA hemodynamics following various atrial fibrillation surgeries.

Methods: This retrospective study included nine patients (mean age, 73 ± 8 years; range, 56-83 years) who underwent AF surgeries from August 2021 to June 2022. Maze surgery was performed in 3, pulmonary vein isolation (PVI) and left atrial appendage closure (LAAC) in 3, and the LAAC alone in 3 patients. Postoperative 4D flow MRI scans of the left atrium were performed, and image analysis was conducted. Blood flow velocity in the left atrium was measured, with velocities below 10 cm/s considered flow stasis. The percentage of flow stasis within one systolic-diastolic cycle was evaluated as % stasis. Furthermore, the presence or absence of a physiological vortex flow was assessed from the flow images.

Results: Sinus rhythm was postoperatively maintained in 6 patients, and 3 patients were analyzed in AF. The left atrial % stasis was significantly low in the sinus rhythm group (46.0 ± 22.7 in the sinus rhythm group vs. 100 in the AF group, p=0.027). The absence of vortex flow was observed during sinus rhythm in one patient after Maze surgery. Conversely, vortex flow was identified during AF in the patient after LAAC, being accompanied by moderate mitral regurgitation.

Conclusions: Any type of AF surgery does not always provide physiological LA blood flow. Further, 4D flow MRI analysis contributes to our understanding of the discrepancy between ideals and reality which may or may not require anticoagulant therapy regardless of postoperative rhythm.