MVN analysis
The Mitral Valve Navigation (MVN) analysis was performed as previously described.[11] Imaging data sets were analyzed by the core laboratory echocardiographer using Philips Mitral Valve Navigation software (Qlab version 13; Philips Medical Systems). Images with the highest volume rate (≥ 10 Hz) and best image quality were selected for analysis. The MVN software provides semiautomated 3D modeling and quantification of the mitral annulus and apparatus (Figure 1). Measurements were performed by two core laboratory echocardiographers, which were blinded to the result of 3D VCA. The mean of three measurements of each parameter was calculated and reported as final value.
The end-systolic frame was identified as the last systolic frame just before aortic valve closure and selected to perform MVN analysis. For the definition of annulus geometry, we assessed anterior–posterior (AP) diameters, lateral/medial (ALPM) diameters, annulus height, annulus area and circumference, and the MV annular ellipticity (defined as ALPM/AP diameter).The ratio of annular height to commissural width (AHCWR) was computed as a surrogate of annular saddle-shaped flattening.[7] Severity of prolapse or leaflet tethering was quantified using prolapse height/volume or tenting height /volume, respectively. Two-dimensional and 3D echocardiographic parameters were index to body surface area (BSA) as appropriate, such as AP diameter index (APi).
Secondary leaflet tethering (MVPt+ group) was defined as tenting volume index (TVi)> 0.7 ml/m2, based on the scatterplot of TVi of our MVP patients and normal value for healthy subjects (Figure 2A). Note that there are no references regarding the threshold of normal values of tenting volume index (TVi) in the literature.[12, 13]