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\begin{document}

\title{The importance of electrical mapping of VT in the approaching era of
clinical imaging}



\author[1]{Paolo Della Bella}%
\author[1]{Antonio Frontera}%
\affil[1]{San Raffaele Hospital}%


\vspace{-1em}



  
  \date{May 24, 2024}


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\selectlanguage{english}
\begin{abstract}
We are facing a new challenge: will imaging be the resolutive tool or
will new mapping catheters and mapping system together with mathematical
simulation solve this rebus? Clinical imaging will always remain
attractive, particularly for elective cases and may add decisive
information to best plan an ablation strategy: it represents a great
tool in the hands of the electrophysiologist; however, as
electrophysiologists, the imaging we should pursue is electrical -- the
depiction of the entire reentry circuit remains the sole proof of the
target to ablate.%
\end{abstract}%



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\emph{}

\emph{Editorial by} \emph{\textbf{Antonio Frontera} and \textbf{Paolo
Della Bella}}

\emph{Arrhythmology Department, IRCCS San Raffale, Milan, Italy}

\par\null

Looking back over the years, the approach to ventricular tachycardia
ablation has changed significantly. Initial efforts began in the 1980's
consisted of intra-operative mapping performed during cardiac surgery
with 20-electrode arrays placed by hand on the endo-epicardial
surface(1): this was the first electrical imaging and was subsequently
used to guide subendocardial resection. Approaches then transitioned to
catheter-based techniques in the 1990s when direct current shock energy
and radiofrequency energy were used to modify abnormal areas responsible
for the genesis of ventricular arrhythmias(2)(3). Later, a significant
transformative step forward was the advent of 3D mapping systems which
allowed for detailed activation mapping and the targeting of
pathological substrate.

However, the cornerstone of electrophysiological mapping has been the
development of multi-spline, multi electrode mapping tools which has
elevated the concept of high density mapping to prominence. Today, 3D
maps created during sinus rhythm provide excellent substrate
characterization(4)(*): LAVA and LPs became our main targets as
expressions of channels and slow conduction areas(5)(6). Furthermore,
due to multi electrode mapping catheters, even mapping of
hemodynamically non tolerated VT has become feasible: the enhanced
recording density and sweeping characteristics that cover a large area
in a short amount of time allow for the electroanatomic imaging of the
diastolic pathway of the VT reentrant circuit (7).

In the last decade, technological advances in pre-procedural imaging(8)
has allowed for the merging of cardiac MRI to 3D mapping systems adding
crucial information such as ventricular thickness(9), scar dimensions,
and coronary artery localization. The role of cardiac imaging has
shifted from a diagnostic to an adjunctive tool to guide our
interventional approaches for the treatment of VT, particularly in the
setting of post-myocardial infarction VT.

In this issue of Journal of Cardiovascular Electrophysiology, Nazarian
et al (\emph{reference} ) published first evidence of specific features
of electroanatomic maps with LGE voltage mapping and have highlighted
the importance of cardiac magnetic resonance as an adjunct for
characterizing the VT substrate in the setting of non ischemic
cardiomyopathy (NICM). The authors have added another piece to the NICM
puzzle: clinical imaging may help the electrophysiologist look
transmurally. In fact, the authors state that late gadolinium enhanced
(LGE) distribution predicts the epicardial distribution of scar in
electroanatomic maps. EGMs are expressions of signal propagation, and
any delay or obstacle found along the trajectory results in longer
duration or fractionation. However, current mapping only takes into
account the planar propagation of the impulse and not the transmurality
of the scar. Nazarian et colleagues elegantly demonstrate what we
suspected: local activity signal abnormalities (LAVA) and delayed
activity (LPs) were more prevalent in non transmural (mid-myocardial and
subepicardial) LGE locations: this confirms that current mapping
technology can still detect, in non-transmural scar, signal
abnormalities. Indeed, sites with transmural LGE were associated with
longer duration EGMs and fractionated potentials: this increased
duration is an expression of delayed propagation in this deep substrate.
However, it is clear we are missing electrical information: clinical
imaging may fill this void.

The battlefield is in the depth of the myocardium where signal
propagates in three dimensions where we are unable to map. This research
opens new scenarios in the setting of VT ablation in NICM patients: the
first step of clinical imaging in the 3D characterization of deep
substrate.

Based on our experience(10)(11), as well as reflected in the
literature(12), NICM poses a difficult substrate in which the outcome,
freedom from ventricular arrhythmias, remains lower as compared to
ischemic cardiomyopathy.

Recently, Tung et colleagues(13) demonstrated via simultaneous
endocardial and epicardial mapping that VT circuits often involve the
3-dimensions; in this research, the authors documented that in NICM
patients, 28\% of cases had the reentry circuit exhibiting planar
propagation and complete reentry confined to the endocardium. 3D
circuitry occurred in 49\% of cases. Recently, our group demonstrated
that during VT, the complete electroanatomic imaging of diastolic
pathway not only allows for targeted ablation of all areas that are
operational during VT, but results in favorable success rates, with up
to 88\% freedom from VT out to 18 months (14). Findings such as these
only emphasize the importance of accurate and thorough mapping of VT
circuitry in order to effectively eliminate VT.

We are facing a new challenge: will imaging be the resolutive tool or
will new mapping catheters and mapping system together with mathematical
simulation solve this rebus?

Clinical imaging will always remain attractive, particularly for
elective cases and may add decisive information to best plan an ablation
strategy: it represents a great tool in the hands of the
electrophysiologist; however, as electrophysiologists, the imaging we
should pursue is electrical -- the depiction of the entire reentry
circuit remains the sole proof of the target to ablate.

In conclusion, let cardiac imaging play an integral role in determining
the underlying etiology and prognostic~significance of VT, but let
electrophysiologists perform the electrical imaging they were deemed to.

\textbf{REFERENCES}

1. Kienzle MG, Miller J, Falcone RA, Harken A, Josephson ME.
Intraoperative endocardial mapping during sinus rhythm: relationship to
site of origin of ventricular tachycardia. Circulation. 1984
Dec;70(6):957--65.

2. Klein LS, Shih HT, Hackett FK, Zipes DP, Miles WM. Radiofrequency
catheter ablation of ventricular tachycardia in patients without
structural heart disease. Circulation. 1992 May;85(5):1666--74.

3. Gonska BD, Cao K, Schaumann A, Dorszewski A, von zur M\selectlanguage{ngerman}ühlen F,
Kreuzer H. Catheter ablation of ventricular tachycardia in 136 patients
with coronary artery disease: results and long-term follow-up. J Am Coll
Cardiol. 1994 Nov 15;24(6):1506--14.

4. Martin R, Maury P, Bisceglia C, Wong T, Estner H, Meyer C, et al.
Characteristics of Scar-Related Ventricular Tachycardia Circuits Using
Ultra-High-Density Mapping: A Multi-Center Study. Circ Arrhythm
Electrophysiol. 2018;11(10):e006569.

5. Vergara P, Trevisi N, Ricco A, Petracca F, Baratto F, Cireddu M, et
al. Late potentials abolition as an additional technique for reduction
of arrhythmia recurrence in scar related ventricular tachycardia
ablation. J Cardiovasc Electrophysiol. 2012 Jun;23(6):621--7.

6. Frontera, Melillo F, Baldetti L, High-Density Characterization of the
Ventricular Electrical Substrate During Sinus Rhythm in Post--Myocardial
Infarction Patients. J Am Coll Cardiol Electrophysiology. 2020 June 13
(in press)

7. Okubo K, Frontera A, Bisceglia C, Paglino G, Radinovic A, Foppoli L,
et al. Grid Mapping Catheter for Ventricular Tachycardia Ablation. Circ
Arrhythm Electrophysiol. 2019;12(9):e007500.

8. Hooks DA, Berte B, Yamashita S, Mahida S, Sellal J-M, Aljefairi N, et
al. New strategies for ventricular tachycardia and ventricular
fibrillation ablation. Expert Rev Cardiovasc Ther. 2015
Mar;13(3):263--76.

9. Takigawa M, Duchateau J, Sacher F, Martin R, Vlachos K, Kitamura T,
et al. Are wall thickness channels defined by computed tomography
predictive of isthmuses of postinfarction ventricular tachycardia? Heart
Rhythm. 2019;16(11):1661--8.

10. Okubo K, Gigli L, Della Bella P. Catheter ablation of ventricular
tachycardia in nonischemic cardiomyopathy. J Arrhythmia. 2018
Aug;34(4):347--55.

11. Oloriz T, Silberbauer J, Maccabelli G, Mizuno H, Baratto F,
Kirubakaran S, et al. Catheter ablation of ventricular arrhythmia in
nonischemic cardiomyopathy: anteroseptal versus inferolateral scar
sub-types. Circ Arrhythm Electrophysiol. 2014 Jun;7(3):414--23.

12. Hennig A, Salel M, Sacher F, Camaioni C, Sridi S, Denis A, et al.
High-resolution three-dimensional late gadolinium-enhanced cardiac
magnetic resonance imaging to identify the underlying substrate of
ventricular arrhythmia. Eur Eur Pacing Arrhythm Card Electrophysiol J
Work Groups Card Pacing Arrhythm Card Cell Electrophysiol Eur Soc
Cardiol. 2018 01;20(FI2):f179--91.

13. Tung R, Raiman M, Liao H, Zhan X, Chung FP, Nagel R, et al.
Simultaneous Endocardial and Epicardial~Delineation of 3D Reentrant
Ventricular Tachycardia. J Am Coll Cardiol. 2020 Mar 3;75(8):884--97.

14. Hadjis A, Frontera A, Limite L, Complete electroanatomic imaging of
the diastolic pathway is associated with improved freedom from
ventricular tachycardia recurrence. Circ EP July 2020 (in press).

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