Abstract 10765: Dilated and Tilted Mitral Annulus by Left Atrial Dilation May Cause Mitral Regurgitation in Nonvalvular Atrial Fibrillation

Abstract

Background: Although mitral annular dilation has been considered to be the primary mechanism of mitral regurgitation (MR) in patients with nonvalvular atrial fibrillation (AF), whether a stretched mitral annulus is sufficient to cause significant MR remains controversial. The aim of this study was to clarify it. Methods: The presence of MR and left atrial dimension (LAD) were evaluated by echocardiography. Cardiac magnetic resonance imaging was performed in patients with AF and MR (AF-MR; n=23) or without MR (AF-noMR; n=56) and in controls with normal sinus rhythm (n=130). Using 4-chamber view, we quantified the end-systolic septolateral mitral annular diameter (MAD), angle (Angle) between the mitral annulus and the perpendicular line of the long axis of the left ventricle passing through the base of the anterior leaflet (Line), and the distance (Distance) between the mitral leaflets coaptation point and the Line (Figure). Results: LAD was significantly increased in AF-MR compared to AF-noMR and controls (50±9 mm, 41±7 mm, 36±5 mm, respectively, AF-MR vs. AF-noMR, P<0.001, AF-MR vs. controls, P<0.001). MAD, Angle and Distance were significantly increased in AF-MR compared to AF-noMR and controls (Figure). CONCLUSIONS: In concert with mitral annular dilation, tilted mitral annulus by left atrial dilatation may cause incomplete coaptation of the mitral leaflets resulting in the development of MR in nonvalvular AF.