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\begin{document}

\title{An iatrogenic single-loop macroreentrant biatrial tachycardia developing
after persistent atrial fibrillation ablation}



\author[1]{Jian Zhou}%
\author[1]{Jinbo Yu}%
\author[1]{Xiaorong LI}%
\author[1]{Bing YANG}%
\affil[1]{Shanghai East Hospital}%


\vspace{-1em}



  
  \date{June 17, 2024}


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\selectlanguage{english}
\begin{abstract}
Biatrial macro-reentrant tachycardia (Bi-MAT) is a relatively uncommon
arrhythmia. Sometimes, it can be produced by the left atrial (LA)
anterior or septal-anterior linear ablation. However, data concerning
the proarrhythmic role of this ablation lesions are lacking. Here, we
reported a case of a single-loop Bi-MAT developing after the LA anterior
ablation line performed in one patient with persistent atrial
fibrillation.%
\end{abstract}%



\sloppy


\textbf{Introduction}

Extensive left atrial ablation beyond pulmonary vein isolation (PVI) in
the treatment of persistent AF is associated with a high incidence of
iatrogenic atrial tachycardia (AT). The most possible mechanisms of
these tachycardias are macro- or micro-reentries, and the reentry
circuits mostly confined to the left atrium. Bi-MAT is a relatively-rare
reentrant type which reported previously. But notice, a recent study
found that Bi-MATs developed in 31\% of persistent AF cases when the
left atrial anterior linear ablation is performed.\textsuperscript{1} To
date, there are only sporadic reports of Bi-MAT during or post AF
ablation. Herein, we present a case of a single-loop Bi-MAT, which
developed in persistent AF catheter ablation.

\textbf{Case report}

A 70-year-old male was referred for catheter ablation of persistent
drug-resistant AF. He had a 5-year history of symptomatic AF, which had
been persistent for the last 6 months. The initial AF ablation procedure
consisted of PVI, linear ablation of the cavotricuspid isthmus (CTI),
then complex fractionated electrogram-based ablation at the anterior and
posterior LA and a linear ablation at the LA roof were completed, but AF
was not terminated and external electrical cardioversion (using one 150J
biphasic shock) was required to restore sinus rhythm. Unfortunately, he
had a recurrence after a one-year follow-up, the electrocardiogram (ECG)
during clinical symptoms revealed a regularity AT (atrial cycle length
270ms) with 2:1 atrioventricular conduction. The P waves in the inferior
and precordial leads V\textsubscript{1}-V\textsubscript{3} were
positive, suggesting LA originated; Leads I, aVL, and
V\textsubscript{4}-V\textsubscript{6} showed either a flat or
low-amplitude upright component; and there was an isoelectric segment
between P waves (\emph{Figure 1A} ).

In the redo procedure, a quadripolar catheter was placed into the
coronary sinus (CS) and it demonstrated a consistent proximal-to-distal
activation pattern during the tachycardia. Counterclockwise peri-mitral
atrial flutter (PMAFL) was confirmed by classical entrainment criteria.
Then 3-dimensional detailed LA endocardial electroanatomic mapping was
performed during the PMAFL, extensive low-voltage zones (LVZs) with
fractionated electrograms, caused by spontaneous scarring and prior
ablation, were observed on the anterior and posterior wall. The
reinforced defragmentation ablation was performed in the initial
posterior and anterior ablation area, and a linear ablation at the LA
anterior wall (connecting right PV roof to the anterior mitral annulus)
were completed, which prolonged the AT cycle length to 305ms
(\emph{Figure 1B} ). Next, entrainment pacing and activation mapping
were performed again to identify the reentry circuit, and it turned out
that the changed AT with a biatrial macro-reentrant circuit using most
of the mitral annulus in the LA circuit (including the anterolateral and
posterior wall but not the LA anterior septum), and the right atrium
(RA) septum in the RA circuit (\emph{Figure 2A} and\emph{2B} ). Finally,
irrigated radiofrequency targeted at the endocardial breakthrough site
of RA septum with a temperature setting of 43\selectlanguage{ngerman}°C, a maximum power output
of 30W, and an infusion rate of 17mL/min was successfully led to
termination and non-inducibility of tachycardia (\emph{Figure 3} ). Then
the LA anterior linear ablation, prior PVI, LA roof, and CTI ablation
lines were checked to bidirectional block.

An anterior or septal-anterior ablation line, connecting right pulmonary
veins to the mitral annulus, has been suggested as an alternative to
mitral isthmus (MI) ablation for PMAFL. But it can produce an obstacle
to the conduction in the LA septum and might increase the risk of
developing biatrial macro-reentries.\textsuperscript{2} If an
electro-anatomic activation map could not identify a complete reentrant
circuit in a single chamber, detailed activation mapping and entrainment
pacing in both atria are required to clarify the critical reentrant
circuit. Besides MI or CTI linear ablation, the Bi-MAT also can be
terminated by the ablation of the breakthrough site of RA or LA septum.
But notice that sequential endocardial ablation, or sometimes, bipolar
ablation configuration from both sides are needed to achieve complete
conduction block.\textsuperscript{3}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

\textbf{Figure 1:} \textbf{(A)} : Surface 12-lead ECG recorded during AT
with an atrial tachycardia cycle length (TCL) of 270ms; and\textbf{(B)}
: electroanatomic mapping of a changed AT (TCL: 305ms) after LA anterior
wall linear ablation, a redo activation map and entrainment could not
identify a complete AT circuit around the mitral annulus, the ''early''
to ''late'' activation time in LA was 227ms, and a long PPI was observed
in the left anterior septum (PPI-TCL: 70ms). LAO, left anterior oblique
view; MV, mitral valve; PPI, post-pacing interval.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

\textbf{Figure 2:} \textbf{A} and \textbf{B} : Detailed electroanatomic
activation and entrainment mapping of the changed AT after LA anterior
linear ablation, a biatrial macro-reentrant circuit using most of the
mitral annulus in the LA circuit (including the anterolateral and
posterior wall but not the LA anterior septum), and the RA septum in the
RA circuit (excluding the RA free-wall). It showed a long post pacing
interval (PPI) in front of the crista terminalis (\textbf{solid red
line} ) (PPI-TCL: 41ms). CT: crista terminalis; PA, posteroanterior
view; RL, right lateral view; RIPV, right inferior pulmonary vein; RSPV,
right superior pulmonary vein; SVC, superior vena cava; TV, tricuspid
valve.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

\textbf{Figure 3:} Electroanatomic mapping and Intracardiac recordings
during Bi-MAT ablation (paper speed 100 mm/s); Note that the ablation
catheter targeted at the endocardial breakthrough site of RA septum,
radiofrequency prolonged TCL to 440ms and then successfully terminated
the tachycardia.

\textbf{Conflict of interest}

The authors report no financial relationships or conflicts of interest
regarding the content herein.

\textbf{References}

\begin{enumerate}
\tightlist
\item
  Mikhaylov EN, Mitrofanova LB, Vander MA, Tatarskiy RB, Kamenev AV,
  Abramov ML, et al. Biatrial tachycardia following linear anterior wall
  ablation for the perimitral reentry: incidence and
  electrophysiological evaluations. \emph{J Cardiovasc Electrophysiol} .
  2015;26:28-35.
\item
  Kitamura T, Martin R, Denis A, Takigawa M, Duparc A, Rollin A, et al.
  Characteristics of Single-Loop Macroreentrant Biatrial Tachycardia
  Diagnosed by Ultrahigh-Resolution Mapping System. \emph{Circ Arrhythm
  Electrophysiol} . 2018;11:e005558.
\item
  Yu J, Chen K, Yang B, Zhang F, Ju W, Chen H, et al. Peri-mitral atrial
  flutter: personalized ablation strategy based on arrhythmogenic
  substrate. \emph{Europace.} 2018;20:835-842.
\end{enumerate}

\selectlanguage{english}
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