Assessment of left atrial and left atrial appendage flow and stasis in atrial fibrillation

Background Atrial fibrillation (AF) is associated with increased risk of stroke due to development of left atrial (LA) thrombus [1]. Thromboembolic risk is assessed by clinical risk scores (CHA2DS2-VASc). However, these scores have limited predictive value. Echocardiography studies have shown that physiologic factors such as decreased atrial blood flow and increased stasis (LA velocities <0.2m/s) are associated with thrombus formation in the left atrial appendage (LAA) and may thus be better predictors for stroke [2]. Currently available diagnostic tools such as transesophageal echocardiography (TEE), however, are limited as they do not completely assess the complex 3D LA blood flow and are invasive. We have recently shown that atrial 4D flow MRI can overcome these limitations and detect physiologic changes in LA flow in patients with AF, i.e. potentially different predisposition to atrial thrombogenesis. However, previous studies were limited by the lack of a systematic evaluation of differences in LA vs. LAA (site of thrombus formation) and intuitive visualization and quantification of LA and LAA stasis [3].