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].