Mitral Regurgitation Associated with Mitral Annulus Remodeling and Left Atrial Dilatation

Background: Atrial functional mitral regurgitation (MR) involves functional MR with left atrial (LA) dilatation and mitral annulus (MA) remodeling. The relationship between LA dilatation and MA remodeling, and the mechanism of MR associated with MA remodeling, are unclear and were investigated in this study. Methods: This single-center, cross-sectional retrospective study prospectively enrolled 97 consecutive patients with atrial fibrillation (AF) referred for three-dimensional transesophageal echocardiography. Mitral valve echocardiographic data of 18 AF patients with moderate or severe MR (MR group) and 79 with mild or less severe MR (non-MR group) were analyzed. Results: The LA volume index was larger and tenting height was lower in the MR group than in the non-MR group (63.9±17.9 mL/m2 vs. 43.6±13.9 mL/m2; p<0.001; 3.9 mm vs. 4.9 mm; p = 0.041). Anteroposterior (AP) diameter, annulus area, and sphericity index (AP diameter/anterolateral-posteromedial diameter) of MA were larger in the MR group than in the non-MR group (30.1 mm vs. 26.4 mm; p<0.001; 8.8 cm2 vs. 7.4 cm2; p = 0.002; 80.1% vs. 74.5%; p<0.001, respectively). Linear regression analysis indicated that AP diameter was moderately correlated with LA volume index (R = 0.535, p<0.001). The area under the receiver operating characteristics curve of the AP diameter for the association with significant MR was significantly larger than that for the annulus area (0.8003 vs. 0.7180; p = 0.003). Multivariable analysis revealed that AP diameter (p = 0.006) and sphericity index (p = 0.041) were independently associated with significant MR, but annulus area was not (p = 0.083). Conclusions: LA dilatation correlated with MA remodeling, primarily via enlargement of AP diameter. Circular change with AP diameter enlargement in MA may be a key mechanism of MR associated with MA remodeling.