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\title{Idiopathic Right Ventricular Arrhythmias With Changes in the QRS
Morphology After Ablation}



\author[1]{Mohamad El Moheb}%
\author[2]{Marwan Refaat}%
\affil[1]{Massachusetts General Hospital}%
\affil[2]{American University of Beirut Medical Center}%


\vspace{-1em}



  
  \date{June 02, 2024}


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Idiopathic ventricular arrhythmias~(VA) is defined as premature
ventricular complexes (PVCs) or ventricular tachycardias (VT) that occur
in the absence of structural heart disease. Endocardial radiofrequency
(RF) ablation is often curative for idiopathic VA. The success of the
procedure depends on the ability to localize the abnormal foci
accurately. These arrhythmias typical originate from the right
ventricular outflow tract (RVOT), specifically from the superior septal
aspect, but can also originate from the left ventricular outflow tract
(LVOT) and the coronary cusps.\textsuperscript{1} The QRS
electrocardiogram (ECG) characteristics have been helpful in patients
with VAs, patient with accessory pathways and patients who have
pacemakers.\textsuperscript{2} VAs originating from the RVOT have
typical ECG findings with a left bundle branch block (LBBB) morphology
and an inferior axis.\textsuperscript{3}

In the current issue of the Journal of Cardiovascular Electrophysiology,
Hisazaki et al. describe five patients with idiopathic VA suggestive of
RVOT origin and who required ablation in the left-sided outflow tract
(OT) in addition to the initial ablation in the RVOT for cure to be
achieved. Patients exhibited monomorphic, LBBB QRS pattern with an
inferior axis on ECG, consistent with the morphology of VAs originating
from the RVOT. Interestingly, all patients had a common distinct ECG
pattern: qs or rs (r [?] 5 mm) pattern in lead I, Q wave
ratio{[}aVL/aVR{]}\textgreater{}1, and dominant S-waves in leads V1 and
V2. Mapping of the right ventricle demonstrated early local activation
time during the VA in the posterior portion of the RVOT, matching the
QRS morphology obtained during pacemapping. Despite RF energy delivery
to the RV, the VAs recurred shortly after ablation in four patients and
had no effect at all in one patient. A change in the QRS morphology was
noted on the ECG that had never been observed before the procedure. The
new patterns were suggestive of left-sided OT origin: the second VAs
exhibited an increase in the Q wave ratio {[}aVL/aVR{]} and R wave
amplitude in lead V1, decrease in the S wave amplitude in lead V1, and a
counterclockwise rotation of the precordial R-wave transition. Early
activation of the second VA could not be found in the RVOT, and the
earliest activation time after mapping the LV was found to be relatively
late. Real-time intracardiac echocardiography and 3D mapping systems
were used to determine the location immediately contralateral to the
initial ablation site in the RVOT. Energy was then delivered to that
site which successfully eliminated the second VA. The authors postulated
that the second VAs shared the same origins as the first VAs, and the
change in QRS morphology is likely attributed to a change in the exit
point or in the pathway from the origin to the exit point. The authors
further explained that the VAs originated from an intramural area of the
superior basal LV surrounded by the RVOT, LVOT and the transitional zone
from the great cardiac vein to the anterior interventricular vein
(GCV-AIV).

A limitation of this study is that GCV-AIV ablation was not attempted;
however, the authors' approach is safer and was successful in
eliminating VA. Another limitation is that left-sided OT mapping was not
initially performed. Nevertheless, given the ECG characteristics, local
activation time, and mapping, it was appropriate to attempt a RVOT site
ablation.

Overall, the authors should be commended for their effort to describe in
detail patients with idiopathic VAs that required ablation in the
left-sided OT following ablation in the RVOT. Although change in QRS
morphology after ablation has been previously described, the authors
were the first to describe the ECG patterns of these
patients.\textsuperscript{4--7} The results of this study have important
clinical implications. First, the authors have demonstrated the
importance of anatomical approach from the left-sided OT for cure to be
achieved. Second, insight into the location of the origin of the VA may
be helpful to physicians managing patients with VAs from the RVOT.
Finally, continuous monitoring of the ECG during ablation for a change
in QRS morphology should be considered to identify patients who will
require further ablation. We have summarized in Table 1 important ECG
characteristics indicative VA of specific origins, based on the findings
of this study and previous studies in the
literature.\textsuperscript{3,8--15}

\textbf{REFERENCES}

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2. Refaat M, Mansour M, Singh JP, Ruskin JN, Heist EK.
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13. Good E, Desjardins B, Jongnarangsin K, et al. Ventricular
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