Final considerations: a tentative re-classification of ventricular arrhythmias originating from the right ventricle outflow tract.
Once the described workflow has been completed, an accurate reconstruction of the PV plane, the PA, and the RV underneath the valve is obtained, and this allows to easily navigate the catheters in the map using multiplanar orientations [22]. Usually, we display two contemporary zoomed projections of the pulmonary valve: one on the sagittal plane (from right or left view) or on the coronal plane (from anterior or posterior view); and one on the transverse plane, from the superior (cranial) or inferior (caudal) view. In this way, using the sagittal or coronal projections, we identify if the catheter is above or below the valve. Conversely, using transverse projections, we can know with certainty which wall the catheter is in perfect contact with (the lateral, septal, anterior, medial, or posterior wall). Navigating the regions underneath or above the valve, we can be assisted by a cranial or caudal view respectively. Moving the region of interest from a lateral to a septal aspect, we can change between a right or left view.
Since we use ICE systematically, we realized the former classification of the anatomical location of RVOT-type VAs [3] can be overcome. In fact, the old historical division into three sites (site 1, site 2, and site 3) identifying the posterior, medial, and anterior aspects of the septum of the lateral wall was simply based on radioscopic views (RAO and LAO). In our opinion, a new classification, similar to that used for aortic cusp VAs, should be used. Independently if the origin of the VAs is above or below the pulmonary valve, the regions to be described should be the RPC area, the LPC area, and the APC area. According to this new concept, with rare exceptions, the RPC should comprise the old sites 1-2 of the lateral free wall, the APC should encompass the old site 3 of both the free and septal walls, and the LPC should correspond to the old sites 1-2 of the septal wall. If more accuracy is desired, one could specify if the point of interest is in a junction area (LPC-APC junction, RPC-LPC junction, or RPC-APC junction). This classification is not only more anatomically appropriate, it also brings the advantage of improving etiological knowledge of these forms of arrhythmias. Indeed, proving that pulmonary cusps may be the real site of origin of all RVOT-type VAs is a fascinating and elegant hypothesis to be demonstrated through high definition. For this reason, the work by Zhang et al is pioneering, but it is limited by the use of pulmonary angiography as the method for visualizing the pulmonary cusps [13]. In our experience, ICE with CARTOSOUND map reconstruction allows a 3D reconstruction in great detail, avoiding fluoroscopy and iodine contrast use with a pigtail catheter [23]. Beside this, CARTOSOUND module allows “in vivo” reconstruction of the course of coronary arteries, easily of the left one, whit more complexity for the right one. As mentioned above, this is relevant in term of safety of ablation, because of close proximity of left main, its bifurcation and the proximal part of left anterior descending with the left pulmonary sinus of Valsalva. Finally, SOUND maps could be merged with TAC or MRI 3D shell reconstruction of the heart (CARTOMERGE and CARTOSEG module) thus providing a definitely “image-guided” procedural workflow with maximized ratio between efficacy and safety [24].