Dynamic assessment of the changing geometry of the mitral apparatus in 3D could stratify abnormalities in functional mitral regurgitation and potentially guide therapy

Introduction In functional mitral regurgitation (FMR), effective regurgitant orifice area (EROA) displays a dynamic pattern. The impact of dynamic changes of annulus dysfunction and leaflets tenting on phasic EROA was explored with real-time three-dimensional transesophageal echocardiography (RT3D-TEE). Methods RT3D-TEE was performed in 52 FMR patients and 30 controls. Mitral annulus dimensions and leaflets tenting were measured throughout systole (TomTec, Germany). Phasic EROA was measured by proximal isovelocity surface area (PISA) method. Results Mitral annulus had the minimal area and an oval shape with saddle configuration during early systole in controls, which enlarged and became round and flattened towards mid and late systole (P<0.05). In contrast, annulus in FMR was significantly larger, rounder and flatter (P<0.001), which further dilated and became more flattened at late systole (P<0.05 vs control). Leaflet tenting height in FMR decreased in mid systole and remains unchanged towards late systole. The leaflet tenting volume peaked at early and late systole with a mid-systolic trough in both FMR and controls. But tenting volume of patients with FMR was significantly larger than that of controls (all P<0.001 vs control in whole systole). Further analysis demonstrated that early tenting volume (β value=0.053, P<0.05) was a predictor of early EROA, whereas late tenting volume (β value=0.031, P<0.05) and late annular displacement velocity were predictors of late EROA. Conclusions The early and late peak EROAs of FMR was primarily contributed by tenting volume at early systole and late systole respectively. These findings would be of value to consider in interventions aimed at reducing the severity of FMR.