SOUNDSTAR reconstruction of pulmonary valve and contiguous
structures
The Soundstar™ catheter is advanced in the right atrium and positioned
in “home view” through a femoral vein [22]. After choosing a
stable reference (i.e. surface ECG), with the ICE catheter in contact
with the cardiac tissue, respiration gating (RG) is acquired. Thus,
contour acquisition can start. In order to increase the accuracy of the
reconstruction and procedural safety, it is highly recommended that
contours be acquired in the same cardiac (i.e. end of QRS) and
respiratory phase. The steps for an optimal anatomical reconstruction
workflow are listed below:
- With the ICE beam in “home view” position, the contours of the right
ventricle inflow and outflow tracts (with tags on tricuspid annulus),
right coronary cusp (RCC), non-coronary cusp (NCC), and AORTA can be
acquired (Fig. 2, Panel A). ICE images are displayed in two
dimensions. Thus, in order to fill all the volume of the cardiac
chambers and main vessels, multiple scans must be acquired, possibly
on several planes. The more scans are acquired, the more the volume is
filled in. By performing counterclockwise and clockwise rotations of
the handpiece, it is possible to acquire more lateral (Fig. 2, Panel
B) and septal (Fig. 2, Panel C) portions of RV and tricuspid valve,
respectively. In each scan it is also recommended to acquire tags of
the tricuspid annulus in order to anatomically open the tricuspid
orifice. Overcoming the more septal projection of the tricuspid valve,
a further clockwise rotation of the handpiece allows visualization of
the most septal portion of the right ventricle outflow tract (RVOT)
together with the AORTA [RCC, NCC, and left ventricle (LV)] (Fig.
2, Panel D). At this level one can appreciate the semilunar aspect of
the aortic valve. Often it is possible to discern between the valvular
annulus, the sinus of Valsalva and the sinus-tubular junction.
- By taking advantage of the markers related to the tricuspid valve,
which have been acquired on various projections, it is possible to
highlight the valve on the SOUND MAP of the RV and open it as an
“anatomical structure.” This allows the operator to safely advance
the ICE catheter into the right ventricle with an anterior deflection
of the probe. (We suggest setting the CARTO “main window” and the
“additional window” to have a RAO projection and a posterior view to
help navigate the tricuspid ring). Once inside the RV, keeping the ICE
beam pointing downwards, it is possible to acquire the RV apex in
different positions by means of slight clockwise or counterclockwise
rotations (Fig. 3, Panel A). During these acquisitions it is possible
to visualize intracavitary structures, such as the moderator band and
papillary muscles, reconstructing their thickness into the sound map,
if necessary, for ablation purposes (not the subject of this paper).
By advancing the ICE catheter to the base of the RVOT and rotating
clockwise, it is possible to acquire the classic LV projections up to
the mitral valve (Fig. 3, Panel B).
- A further clockwise rotation allows the aortic valve to be visualized
in short-axis view. In this projection it is possible to acquire the
aortic cusps (left, right, and non-coronary). Note: the aortic valve
has a semilunar shape; thus, the three cusps are also well visualized
in the same scan when the left main (LM) of the left coronary arteries
appears (Fig. 4, Panel A). In general, the LM arises 1 cm above the
valvular plane and the contours of the three cusps should not be taken
at this level in order to avoid designing the valvular plane at too
high a level. At this stage, if the clinical practice of the imaging
center allows integration with CT images, it is highly recommended to
acquire FLOATING OS contours on cusp junctions and on the insertion of
the LM. Once the LM has been identified, with a slight clockwise
rotation it should be possible to follow and acquire the bifurcation
in the anterior descending artery and circumflex artery (Fig. 4, Panel
B). At this level, multiple scans can be performed to acquire each
tract of these arteries in short-axis view. Sometimes it is possible
to follow (and reconstruct) the anterior descending artery to the
medial tract (Fig. 5, Panel A and B).
- For both the aortic and pulmonary cusps, slight rotations are
recommended in order to acquire more projections to improve the
definition and correct proportions. Proceeding with clockwise
rotation, passing the short axis of the aortic valve, the ICE beam
cuts the most septal portion of the pulmonary artery in long-axis
view. Here, it is possible to acquire the LCC, RCC, RVOT, LPC, and PA
(Fig. 6, Panel A). With a slight clockwise rotation, the anterior cusp
of the pulmonary valve is also displayed. This will allow
reconstruction of the APC, LPC, PA, and RVOT (Fig. 6, Panel B).
Depending on the anatomy of the patient, it may be necessary to
slightly advance or withdraw the probe. Rotating further clockwise
will give access to viewing the right cusp of the pulmonary valve
(RCP) on the long axis; hence, it will be possible to acquire the
RVOT, AORTA, RPC, and PA (Fig. 6, Panel C). All through the described
acquisitions, it is also crucial to tag valvular points at the level
of the leaflet attachments on the annulus, in order to open the valve
as an “anatomical structure.” During each phase of point 4, the
operator must be careful to fill in as much as possible of the right
ventricle volume under the valve, spanning the diameter from the
septal to lateral wall: this will help to provide a more accurate,
extended navigation of the electro-catheters (Video S1). The valvular
annulus points (acquired in “floating” modality, always at the end
of QRS, with the valve closed) will be kept as reference for the valve
plane in the other projections (see step 6 below).
- Once the ICE beam is directed towards the most lateral aspect of the
RV wall, a gentle withdrawal of the probe to the RV inflow region
(under the HIS location) sometimes allows the aorta to be displayed
from below. Refining the projections with probe rotations makes it
possible to recognize the origin of the right coronary artery 1 cm
above the valve plane, at the bottom of the right sinus of Valsalva
(Fig. 7, Panel A). From this point, further counterclockwise rotations
make it possible to reconstruct the entire medial tract of the artery
while it crosses the atrioventricular groove between the right
ventricle and the right atrial appendage (Fig. 7, Panel B). These
projections allow further RV volume to be filled in.
- The final part of the workflow acquires images of the pulmonary cusps
and vessel in short-axis view. The general maneuvers to perform are as
follows: withdrawing the probe in the “home view,” advancing the ICE
catheter upwards 1-3 cm above into the atrium or towards the superior
vena cava (SVC), making a slight tilt of the handpiece to the right
(for a posterior deflection of the beam), and applying a clockwise
rotation. The beam should cut the pulmonary artery at the valve level.
The already reconstructed SOUND map can guide the operator accurately
during the slight rotation and tilting movements (Video S2). This
projection can display the APC, LPC, RPC, AORTA [the LPC can be
found closer to the RCC; the cusp oriented to the right side (away
from LV) is the RPC, while the one farthest from the aorta is the
APC] (Fig. 8, Panel A). The reconstruction of the valve cusps in
short-axis view may be misleading if the contours are not traced in
the same ECG trace (at the end of the QRS); hence, one must keep in
mind that the valve is semilunar, and, therefore, the commissures
lines may also be seen 1 cm above the ventricular arterial junction.
This is why the previous acquired valvular annulus tags (during
long-axis visualization) must be used as references for the valvular
plane. If the image cannot be set on the exact plane, contours of the
intersections between the cusps (commissures) can be acquired as
“floating” instead of as “map.” It will give an idea where each
cusp lies on the cranial view (Fig. 8, Panel B). At this point, slight
clockwise and counterclockwise rotations can be performed in order to
cross the AP and RVOT in short-axis view, filling the volume of these
structures into the SOUND map (Fig. 8, Panel C).