Anatomic and Functional Determinants of Atrial Functional Mitral Regurgitation

Background: It is not well understood why some patients with atrial fibrillation (AF) develop significant atrial functional mitral regurgitation (AFMR). We sought to investigate the mechanistic determinants ofAFMR by comparing anatomic and functional characteristics of patients with AFwho develop significant AFMR (≥2+ MR) to those without AFMR. Methods: We screened AF patients referred for cardiac computed tomography (CCT) before pulmonary vein isolation or appendage occlusion between 2017 and 2019. Patients with primary leaflet pathology, prior mitral surgery, left ventricular dysfunction or dilation, and without echocardiography within six months were excluded. We identified 50 patients with ≥2+ MR, and 50 controls were selected based on age and gender propensity matching. Mitral anatomy was compared by CCT, while diastology and strains were compared by echocardiography. Results: Patients with significant AFMR had larger annular and atrial dimensions (all p < 0.001), insufficient compensatory leaflet growth (p <0.001), shallower posterior leaflet angle (p < 0.001), but similar tenting height and area (p = NS). On strain analysis, they had lower LA strain (p = 0.001) and LV longitudinal strain (p = 0.001), with shorter deceleration time (DT, p = 0.001) and isovolumetric relaxation time (IVRT, p <0.001). Their estimated right ventricular systolic pressure (RVSP) was higher (p = 0.004) with more concomitant significant (≥2+) tricuspid regurgitation (TR, p = 0.006). Conclusions: Patients with significant AFMR have larger atria and annuli with insufficient compensatory leaflet growth but similar tenting height and area with a shallower posterior angle. They also have impaired atrial and ventricular strains and shorter DT and IVRT, with associated higher RVSP and more concomitant TR.