Left Atrial Geometry and Hemodynamics Quantified from 4D Flow MRI in Primary Mitral Regurgitation

4D flow MRI is increasingly used for research exploration of patients with mitral regurgitation (MR), as it provides extensive time and space-resolved coverage of left atrial (LA) blood flow. Since LA is a major end-stage target chamber in MR, we aimed at designing 4D flow processing pipeline to quantify LA inner hemodynamics. Such pipeline comprised a segmentation step based on feature tracking (FT) and computation of flow indices such as high velocity weighed area and vorticity magnitude. FT contours were also used to calculate mitral annulus angulation. Results on 21 MR patients revealed that LA flow characteristics were associated to echocardiographic or 2D MRI regurgitant volume, while geometry-related mitral annulus angulation was associated to peak oxygen consumption, which is the standard measure of exercise capacity linked to prognosis in MR patients. Interestingly, none of the conventional strain indices were significantly correlated to regurgitant volume or to exercise capacity.