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\begin{document}

\title{A Case Series of Very Slow Atrioventricular Nodal Reentrant Tachycardia
Resembling Junctional Tachycardia}



\author[1]{Koji Higuchi}%
\author[2]{Satoshi Higuchi}%
\author[1]{Bryan Baranowski}%
\author[1]{Oussama Wazni}%
\author[2]{Melvin M. Scheinman}%
\author[1]{Patrick Tchou}%
\affil[1]{Cleveland Clinic Miller Family Heart and Vascular Institute}%
\affil[2]{University of California San Francisco Division of Cardiology}%


\vspace{-1em}



  
  \date{May 29, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
\textbf{Introduction:} The surface EKG of typical atrioventricular nodal
reentrant tachycardia (AVNRT) shows simultaneous ventricular-atrial (RP)
activation with pseudo R' in V1 and typical heart rates ranging from
150-220/min. Slower rates are suspicious for junctional tachycardia
(JT). However, occasionally we encounter typical AVNRT with slow
ventricular rates. We describe a series of typical AVNRT cases with
heart rates under 110/min. \textbf{Methods:} A total of 1972 patients
with AVNRT who underwent slow pathway ablation were analyzed. Typical
AVNRT was diagnosed when; 1) evidence of dual atrioventricular nodal
conduction, 2) tachycardia initiation by atrial drive train with A-H-A
response, 3) septal ventriculoatrial (VA) time \textless{} 70 ms, and 4)
ventricular-atrial-ventricular (V-A-V) response to ventricular overdrive
(VOD) pacing with post pacing interval-tachycardia cycle length
(PPI-TCL) \textgreater{} 115ms. JT was excluded by either termination or
advancement of tachycardia by atrial extrastimuli (AES) or atrial
overdrive (AOD) pacing. \textbf{Results:} We found 11 patients (Age
20-78 years old, 6 female) who met the above-mentioned criteria. The TCL
ranged from 560ms to 782ms. Except for one patient showing tachycardia
termination, all patients demonstrated a V-A-V response and PPI-TCL over
115ms with VOD. AES or AOD pacing successfully excluded JT by either
advancing the tachycardia in 10 patients or by tachycardia termination
in one patient. Slow pathway was successfully ablated, and tachycardia
was not inducible in all patients. \textbf{Conclusions:} This case
series describes patients with typical AVNRT with slow ventricular rate
(less than 110/min) who may mimic JT. We emphasize the importance of
using pacing maneuvers to exclude JT.%
\end{abstract}%



\sloppy


\textbf{A Case Series of Very Slow Atrioventricular Nodal Reentrant
Tachycardia Resembling Junctional Tachycardia}

Short title: Very Slow Typical Atrioventricular Nodal Reentrant
Tachycardia

Koji Higuchi, MD*, Satoshi Higuchi, MD**, Bryan Baranowski, MD*, Oussama
Wazni, MD, FHRS*, Melvin M. Scheinman, MD, FHRS**, Patrick Tchou, MD,
FHRS*

* Section of Cardiac Electrophysiology and Pacing, Robert and Suzanne
Tomsich Department of Cardiovascular Medicine, Sydell and Arnold Miller
Family Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio,
USA

**Division of Cardiology, Section of Cardiac Electrophysiology,
University of California, San Francisco, San Francisco, California, USA

Corresponding Author: Patrick Tchou, MD

Desk J2-2, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, Ohio 44195

Email: TCHOUP@ccf.org

\textbf{Conflict of interest:} None for all authors

This research did not receive any specific grant from funding agencies
in the public, commercial, or not-for-profit sectors.

Word count: 2099



\textbf{Abstract}

\textbf{Introduction:} The surface EKG of typical atrioventricular nodal
reentrant tachycardia (AVNRT) shows simultaneous ventricular-atrial (RP)
activation with pseudo R' in V1 and typical heart rates ranging from
150-220/min. Slower rates are suspicious for junctional tachycardia
(JT). However, occasionally we encounter typical AVNRT with slow
ventricular rates. We describe a series of typical AVNRT cases with
heart rates under 110/min.

\textbf{Methods:} A total of 1972 patients with AVNRT who underwent slow
pathway ablation were analyzed. Typical AVNRT was diagnosed when; 1)
evidence of dual atrioventricular nodal conduction, 2) tachycardia
initiation by atrial drive train with A-H-A response, 3) septal
ventriculoatrial (VA) time \textless{} 70 ms, and 4)
ventricular-atrial-ventricular (V-A-V) response to ventricular overdrive
(VOD) pacing with post pacing interval-tachycardia cycle length
(PPI-TCL) \textgreater{} 115ms. JT was excluded by either termination or
advancement of tachycardia by atrial extrastimuli (AES) or atrial
overdrive (AOD) pacing.

\textbf{Results:} We found 11 patients (Age 20-78 years old, 6 female)
who met the above-mentioned criteria. The TCL ranged from 560ms to
782ms. Except for one patient showing tachycardia termination, all
patients demonstrated a V-A-V response and PPI-TCL over 115ms with VOD.
AES or AOD pacing successfully excluded JT by either advancing the
tachycardia in 10 patients or by tachycardia termination in one patient.
Slow pathway was successfully ablated, and tachycardia was not inducible
in all patients.

\textbf{Conclusions:} This case series describes patients with typical
AVNRT with slow ventricular rate (less than 110/min) who may mimic JT.
We emphasize the importance of using pacing maneuvers to exclude JT.

\textbf{Keywords} : Typical AVNRT, Junctional tachycardia, Slow
ventricular rate

\textbf{Abbreviations}

AV: atrioventricular

AVNRT: atrioventricular nodal reentrant tachycardia

JT: junctional tachycardia

EPS: electrophysiological study

TCL: tachycardia cycle length

AH: atrial-His

HV: His-ventricular

VOD: ventricular overdrive pacing

AOD: atrial overdrive pacing

AES: atrial extrastimululs

PPI: post pacing interval

TCL: tachycardia cycle length



\textbf{Introduction}

Dual atrioventricular (AV) nodal physiology is a common finding during
an electrophysiologic study. This finding provides a substrate for the
common form of atrioventricular nodal reentrant tachycardia
(AVNRT)\textsuperscript{1}. The typical form of AVNRT (slow-fast type)
shows a short R-P or a simultaneous R-P during tachycardia with heart
rates usually ranging from 150/min to 220/min\textsuperscript{2}. Pseudo
R' in V1 is a common feature. However, if the heart rate during
tachycardia is relatively slow, junctional tachycardia (JT) emerges as
part of the differential diagnosis. Notably, while catheter ablation of
AVNRT has been reported with a very high success rate and low incidence
of heart block\textsuperscript{2}, catheter ablation of JT has a lower
success rate and higher rates of complete heart block. Therefore, during
the electrophysiological study, using maneuvers such as atrial overdrive
pacing (AOD) and atrial extrastimulus (AES)\textsuperscript{3,4} to
differentiate AVNRT and JT is important.

In this study, we reported a series of patients with slow, symptomatic
typical AVNRT below 110 bpm resembling JT, which were successfully
diagnosed and ablated.

\textbf{Methods}

\textbf{Study population}

We retrospectively analyzed 1972 patients (1569 patients from Cleveland
Clinic, 403 patients from the University of California, San Francisco)
who underwent catheter ablation of AVNRT ablation between Jan 2013 to
Sep 2021.

\textbf{Electrophysiologic Study}

After giving informed written consent, patients underwent
electrophysiologic studies (EPS). Atrial overdrive and extrastimulus
were delivered to induce supraventricular tachycardia. Isoproterenol
infusion was used to facilitate sustained tachycardia if needed. In
order to demonstrate that the mechanism of this tachycardia is the
typical slow-fast AVNRT, not automaticity (i.e., JT) or ventricular
dependent reentry, AOD, AES, or ventricular overdrive (VOD) pacing were
delivered during tachycardia. AVNRT was diagnosed using criteria as
follows; 1) evidence of dual AV nodal physiology at the initiation of
tachycardia, 2) tachycardia initiation by atrial drive train with A-H-A
response, 3) septal ventriculoatrial (VA) time \textless{} 70 ms, and 4)
ventricular-atrial-ventricular (V-A-V) response to ventricular overdrive
(VOD) pacing with post pacing interval minus tachycardia cycle length
(PPI-TCL) \textgreater{} 115ms. 5) Demonstration that both the slow
pathway (SP) and fast pathway (FP) are capable of conducting faster than
the TCL during entrainment. 6) During atrial entrainment via the SP,
atrial septal PPI-TCL is less than 50 ms. 7) Advancement or termination
of the tachycardia was demonstrated by AOD or AES\textsuperscript{3,4}.
These maneuvers also serve to exclude concealed nodoventricular or
nodofascivular pathways.

From the EPS, the following data were also investigated; tachycardia
cycle length (TCL), atrial-His (AH) interval during tachycardia,
His-ventricular (HV) interval during tachycardia, AH interval during
sinus.

\textbf{Catheter Ablation}

Catheter ablation was performed with a 4 mm tip non-irrigated
radiofrequency ablation catheter or a 3.5 mm saline cooled catheter. For
temperature-controlled delivery, power was titrated from 30-50 W with a
temperature limit of 50\selectlanguage{ngerman}° to 60° for a duration of 60-90 seconds to
achieve accelerated junctional beats with intact AV and VA conduction.
For the saline cooled catheter, power was initiated at 20-25 W and
titrated up to 35 W while monitoring accelerated junctional beats.
Ablation endpoints were lack of inducibility of AVNRT and no more than
single slow-fast AV nodal echo beats with programmed stimulation in
either the basal state or during isoproterenol infusion.

\textbf{Results}

We identified 5 patients from Cleveland Clinic and 9 patients from the
University of California, San Francisco, who had very slow (110 bpm or
less) typical AVNRT. Three additional patients were excluded because
they did not undergo AOD or AES pacing maneuvers as noted in the Methods
section, although tachycardia was no longer inducible after their slow
pathway ablation. Therefore, a total of 11 patients were included in
this analysis. Patient characteristics and electrophysiologic study data
are shown in \textbf{Table 1.} Ages ranged from 20 to 78 years. There
were six females and five males. One patient was undergoing a 4th
ablation (Case 4), and two patients had their 2nd ablations (Case 7 and
9). All other patients were undergoing their initial ablation. The
tachycardia cycle length ranged from 560ms to 782ms. Septal VA times
were all within 70ms. All patients except for one demonstrated V-A-V
response by VOD, which showed PPI-TCL over 115ms. VOD reproducibly
terminated tachycardia in one patient (Case 8), and thus VOD could not
be obtained.

We delivered AOD or AES to distinguish this tachycardia from JT.
Advancement of the tachycardia was recognized by overdrive pacing from
at least one location of the atrium (usually from the coronary sinus
ostium) in 5 patients. Termination of tachycardia was recognized in one
patient by overdrive atrial pacing (Case 4). With regards to the
response to AES, 6 patients showed an A-H-A response, while one patient
(Case 1) showed A-H-H-A response with the advancement of the
tachycardia, likely due to a double ventricular response.

All patients underwent successful slow pathway ablation rendering their
tachycardia not inducible after ablation.

\textbf{Patient Example (Case 4)}

\textbf{Figure 1} shows ECGs during sinus (A) and reentrant arrhythmia
(B) of a patient example (Case 4) who underwent 3 slow pathway ablations
prior to the current study. This patient had been in this incessant
arrhythmia shown in panel B after the 3rd ablation. The surface ECG
showed a very slow junctional type arrhythmia (HR 75/min), and the
patient was significantly symptomatic when in this arrhythmia. The
patient was treated as having a junctional arrhythmia, and beta-blocker
therapy was prescribed, which did not improve her symptom. Due to the
inefficacy of this treatment, the patient was referred for further
possible ablation. Intracardiac studies showed simultaneous VA
activation with septal VA timing of 59ms. VOD showed V-A-V response with
PPI-TCL 177ms \textbf{(Figure 2).} AES delivered during the slow pathway
refractory period (on time with retrograde fast pathway depolarization)
terminated the tachycardia, which proved that slow pathway conduction
was part of the tachycardia mechanism \textbf{(Figure 3)} . AOD
delivered from CS 1-2 successfully entrained the tachycardia. The septal
PPI-TCL confirmed a reentrant mechanism \textbf{(Figure 4)} . After the
successful slow pathway ablation, this tachycardia could never be
inducible, and the patient became asymptomatic.

\textbf{Discussion}

The typical form of AVNRT uses the slow pathway as the anterograde limb
and the fast pathway as the retrograde limb with perinodal atrial tissue
bridging the fast to the slow pathways. The ECG of typical AVNRT shows a
short R-P or simultaneous R-P during tachycardia with pseudo R' in V1.
However, this finding needs to be differentiated from JT as the ECG of
JT may resemble typical AVNRT, especially when the tachycardia is
relatively slow. In these tachycardias, a patient may be significantly
symptomatic even when in slow heart rate given the simultaneous atrial
and ventricular activation, which generates atrial contraction during
mitral and tricuspid valves closure resulting in palpitation, heart
pounding, fatigue, or poor exercise tolerance.

While the usual heart rates of typical AVNRT during tachycardia range
from 150/min to 220/min, some patients present with slow AVNRT if the
conduction time of the slow pathway is long and its effective refractory
period is short (compared to fast pathway). This type of slow typical
AVNRT mimics JT and sometimes may be mistakenly treated as JT as
described in Case 4. These slow tachycardias should be distinguished
from JT with appropriate pacing maneuvers so that appropriate ablation
treatment can be performed.

\textbf{Conclusion}

We report a case series of patients with slow typical AVNRT (less than
110/min), which may mimic JT. Comprehensive electrophysiologic studies
are necessary to exclude JT and direct appropriate ablation treatment.



\textbf{References:}

1. Denes P, Wu D, Dhingra RC, Chuquimia R, Rosen KM. Demonstration of
dual A-V nodal pathways in patients with paroxysmal supraventricular
tachycardia. \emph{Circulation.} 1973;48(3):549-555.
DOI:10.1161/01.cir.48.3.549

2. Jackman WM, Beckman KJ, McClelland JH, et al. Treatment of
supraventricular tachycardia due to atrioventricular nodal reentry by
radiofrequency catheter ablation of slow-pathway conduction. \emph{N
Engl J Med.} 1992;327(5):313-318. DOI:10.1056/NEJM199207303270504

3. Fan R, Tardos JG, Almasry I, Barbera S, Rashba EJ, Iwai S. Novel use
of atrial overdrive pacing to rapidly differentiate junctional
tachycardia from atrioventricular nodal reentrant
tachycardia.\emph{Heart Rhythm.} 2011;8(6):840-844.
DOI:10.1016/j.hrthm.2011.01.011

4. Padanilam BJ, Manfredi JA, Steinberg LA, Olson JA, Fogel RI,
Prystowsky EN. Differentiating junctional tachycardia and
atrioventricular node reentry tachycardia based on response to atrial
extrastimulus pacing. \emph{J Am Coll Cardiol.} 2008;52(21):1711-1717.
DOI:10.1016/j.jacc.2008.08.030



\textbf{Figure Legends}

\textbf{Figure 1. Sinus rhythm and tachycardia ECG}

Panel A: Twelve-lead surface ECG of sinus rhythm. Note the prolonged PR
interval of 290ms consistent with poor or lack of anterograde conduction
via the fast pathway. This likely explains the incessant nature of this
patient's frequent tachycardia.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

Panel B: Twelve-lead surface ECG of the slow tachycardia. Pseudo R' can
be recognized in V1. Time lines for both panels are 400 ms per large
division.



\textbf{Figure 2. Response during ventricular overdrive pacing}

Overdrive pacing from right ventricular apex (RVa 1-2) during
tachycardia resulted in a post pacing V-A-V response and a long PPI-TCL
of 177ms. This maneuver excludes a ventricular nodal/Hisian mechanism.
It also demonstrates that the retrograde fast pathway is capable of
conducting faster than the TCL.

Intracardiac electrograms as follows: HRA= high right atrium, CS=
coronary sinus, HIS= His bundle, RVa= right ventricular apex.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}



\textbf{Figure 3. Atrial extrastimulus during tachycardia}

AES delivered at the high right atrium (HRA 1-2) activating the septal
regions during retrograde fast pathway conduction (i.e. collision with
the retrograde fast pathway impulse) caused block in the slow pathway
terminating the tachycardia. This termination demonstrates that the slow
pathway is a part of the reentrant circuit.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

AES= atrial extrastimuli



\textbf{Figure 4.}

AOD from CS 1-2 advanced the tachycardia with an A-H-A response. AOD was
delivered just after the slow pathway refractory so that it
anterogradely captured and advanced the tachycardia via the slow
pathway. Note that the PPI at the proximal CS electrograms (CS 9,10) as
a proxy for septal activation had a PPI-TCL of 30 or 40 ms depending on
how one measures the TCL. This value confirmed that the atrial septum
near the tricuspid annulus was part of the reentrant circuit.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image4/image4}

\end{center}
\end{figure}

AOD: atrial overdrive pacing

\textbf{Hosted file}

\verb`image5.emf`  available at \url{https://authorea.com/users/455630/articles/552928-a-case-series-of-very-slow-atrioventricular-nodal-reentrant-tachycardia-resembling-junctional-tachycardia}

\textbf{Table 1}

TCL=tachycardia cycle length, VOD=ventricular overdrive, PPI-TCL=post
pacing interval minus tachycardia cycle length, SA-VA=ventricular
stimulus to atrial interval minus ventricular atrial interval during
tachycardia, AOD=atrial overdrive, AES=atrial extrastimulus.

\selectlanguage{english}
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\end{document}

