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:
  1. 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.
  2. 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).
  3. 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).
  4. 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).
  5. 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.
  6. 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).