2.3 Three-Dimensional transesophageal echocardiography
Real-time 3D TEE was performed for all patients during TMVI, using an
iE33 ultrasound system equipped with a fully sampled matrix-array TEE
transducer (X7-2t). 3D images of the MV were acquired with live 3D zoom
mode or one beat full volume mode.
All images were digitally stored
for offline analysis.
Using commercially available software (GI3DQ, QLAB, Philips), the 3D
relationship between aortic valve and MV was assessed. First, the
end-systolic frame was defined as the last frame during the aortic valve
opening.
Then,
using the 2 orthogonal MV long-axis planes, the MV short-axis cut plane
was determined to include the planes of the prosthesis sewing ring, the
annuloplasty ring, or the projected native mitral annulus including the
posterior saddle-shaped top and the lateral and medial commissures
(Figure 1, A-C). The aortic valve long-axis cut plane (Figure 1D, green
line; and Figure 1E) was determined to cross both the bottom of the
right-coronary cusp and the aortic valve commissure between left- and
non-coronary cusps. Aortic annular plane was then obtained as the line
that connected mitral anterior leaflet insertion point with the bottom
of the right-coronary cusp. In patients with aortic valve replacement,
the aortic annular plane was carefully determined as the plane
perpendicular to the long-axis of the prosthetic valve. 3D derived AM
angle was measured as the obtuse angle between the aortic annulus and
the MV short-axis (Figure 1F).
Post-procedural AM angle, defined
as the obtuse angle between the aortic annulus and the transcatheter
heart valve short-axis, was also measured following the same steps as
above, in which the short-axis cut plane of the transcatheter heart
valve was determined to include the plane of the stent valve edge in LA.
Notably,
the larger the AM angle, the more parallel the LVOT and MV inflow will
be and the smaller the angle, the more likely that the MV inflow is
directed toward the LVOT and upper septum. We also collected the data of
the AM angle measured by MDCT in 26 patients from the medical record,
with which the accuracy of the AM angle by 3D TEE was evaluated.
Using commercially available software (3DQ, QLAB, Philips), the LVOT
cross sectional area after stent valve implantation was evaluated from
one-beat full volume images including MV and basal LV. The LV long-axis
plane in late-systole was determined by following the same process as
the determination of the AM angle. A short-axis cut plane (red dotted
lines; Figure 2A), perpendicular to the LV long-axis plane, was then
moved manually up and down with rotation to search for
the smallest area at each level:
the level of the valve stent distal edge defined as the most distal
portion of the mitral valve stent that was closest to the LV apex and
the level of the middle portion of the valve stent (Figure 2, B and C).
At both levels, LVOT areas were measured as the area surrounded by the
contour of the basal LV wall and the tangent line of the valve stent or
the mitral anterior leaflet. Further, the aortic annular area was
measured at the level of lowest aortic cusp hinge point (Figure 2D).
LVOT dimensions were also measured at each level using LV long-axis cut
plane (Figure 2A). In a patient with systolic anterior motion of the
anterior mitral leaflet (SAM), LVOT area and dimension at the valve
stent distal edge were altered to those at the level of MV leaflet tip
(Figure 2, E-H).
2.4 Observer variability
To evaluate reliability of measurements, we randomly selected 6
patients. Two independent observers repeated the measurements of the 3D
derived pre- and post-procedure AM angle (total 12 variables) and
post-procedure LVOT area at valve
stent distal edge, middle portion, and aortic annulus (total 18
variables). One observer repeated the measurements at least 1 month
later. The intraobserver and interobserver variability was calculated as
the absolute differences between the corresponding 2 measurements in the
percentage of their mean (±standard deviation) and interclass
correlation.