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]