\documentclass[10pt]{article}

\usepackage{fullpage}
\usepackage{setspace}
\usepackage{parskip}
\usepackage{titlesec}
\usepackage[section]{placeins}
\usepackage{xcolor}
\usepackage{breakcites}
\usepackage{lineno}
\usepackage{hyphenat}





\PassOptionsToPackage{hyphens}{url}
\usepackage[colorlinks = true,
            linkcolor = blue,
            urlcolor  = blue,
            citecolor = blue,
            anchorcolor = blue]{hyperref}
\usepackage{etoolbox}
\makeatletter
\patchcmd\@combinedblfloats{\box\@outputbox}{\unvbox\@outputbox}{}{%
  \errmessage{\noexpand\@combinedblfloats could not be patched}%
}%
\makeatother


\usepackage{natbib}




\renewenvironment{abstract}
  {{\bfseries\noindent{\abstractname}\par\nobreak}\footnotesize}
  {\bigskip}

\titlespacing{\section}{0pt}{*3}{*1}
\titlespacing{\subsection}{0pt}{*2}{*0.5}
\titlespacing{\subsubsection}{0pt}{*1.5}{0pt}


\usepackage{authblk}


\usepackage{graphicx}
\usepackage[space]{grffile}
\usepackage{latexsym}
\usepackage{textcomp}
\usepackage{longtable}
\usepackage{tabulary}
\usepackage{booktabs,array,multirow}
\usepackage{amsfonts,amsmath,amssymb}
\providecommand\citet{\cite}
\providecommand\citep{\cite}
\providecommand\citealt{\cite}
% You can conditionalize code for latexml or normal latex using this.
\newif\iflatexml\latexmlfalse
\providecommand{\tightlist}{\setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}%

\AtBeginDocument{\DeclareGraphicsExtensions{.pdf,.PDF,.eps,.EPS,.png,.PNG,.tif,.TIF,.jpg,.JPG,.jpeg,.JPEG}}

\usepackage[utf8]{inputenc}
\usepackage[ngerman,english]{babel}



\usepackage{float}








\begin{document}

\title{Atrioventricular block with coronary sinus potential dissociation after
lateral mitral isthmus block: What is the mechanism?}



\author[1]{Yosuke Nakatani}%
\author[2]{Philipp Krisai}%
\author[3]{Takashi Nakashima }%
\author[4]{Romain Tixier}%
\author[5]{Nicolas Welte}%
\author[4]{Josselin Duchateau}%
\author[6]{Thomas Pambrun}%
\affil[1]{University of Toyama}%
\affil[2]{University of Bordeaux}%
\affil[3]{1.	Electrophysiology and Ablation Unit and L’Institut de rythmologie et modélisation cardiaque (LIRYC)}%
\affil[4]{Centre Hospitalier Universitaire de Bordeaux}%
\affil[5]{Centre Hospitalier Universitaire de Bordeaux Hôpital Haut-Lévêque}%
\affil[6]{Hopital du Haut Leveque/LIRYC, Bordeaux}%


\vspace{-1em}



  
  \date{May 20, 2024}


\begingroup
\let\center\flushleft
\let\endcenter\endflushleft
\maketitle
\endgroup








\sloppy


\textbf{EP Rounds}

\textbf{Atrioventricular block with coronary sinus potential
dissociation after lateral mitral isthmus block: What is the mechanism?}

Yosuke Nakatani, MD, PhD; Philipp Krisai, MD; Takashi Nakashima, MD,
PhD; Romain Tixier, MD; Nicolas Welte, MD; Josselin Duchateau, MD;
Thomas Pambrun, MD

Department of Cardiac Pacing and Electrophysiology, IHU Liryc,
Electrophysiology and Heart Modeling Institute, Univ. Bordeaux, Bordeaux
University Hospital (CHU), 33600 Pessac- Bordeaux, France

\emph{Short running title:} AV block with coronary sinus potential
dissociation

Funding: YN is supported by the JHRS-EHRA Fellowship. PK is supported by
the University of Basel, the Mach-Gaensslen foundation, and the
Bangerter-Rhyner foundation.

Disclosures: None for any authors

Address for correspondence: Dr. Yosuke Nakatani, Department of Cardiac
Pacing and Electrophysiology, H\selectlanguage{ngerman}ôpital Cardiologique du Haut-Lévêque
Avenue de Magellan, 33604, Bordeaux-Pessac, France. Telephone:
+33-5-57656542; Fax: +33-5-57656509; E-mail:
\emph{yosuke3gbst@gmail.com}

\textbf{KEYWORDS}

Atrial tachycardia; Catheter ablation; Atrioventricular block; Vein of
Marshall; Alcohol ablation; Coronary sinus

\textbf{CASE PRESENTATION}

A 61-year-old man was referred to our institution for ablation of an
atrial tachycardia (AT) occurring after previous ablation of atrial
fibrillation (AF). The earlier procedure consisted of pulmonary vein
isolation and cavotricuspid isthmus (CTI) ablation along with
elimination of complex fractionated atrial electrograms (CFAEs) located
at the roof and lateral wall of the left atrium, within the coronary
sinus (CS), and at both sides of the interatrial septum. Baseline
surface electrocardiogram showed sinus rhythm and first-degree
atrioventricular (AV) block with a PR interval of 360 ms (Figure 1A). A
decapolar catheter was positioned in the CS, and a quadripolar catheter
in the left atrial appendage (LAA). Intracardiac recording revealed
that: (1) LAA potentials preceded CS potentials, which exhibited a
distal-to-proximal activation sequence (Figure 1B); (2) all pulmonary
veins were still isolated; (3) CTI was still blocked, and (3) a line of
block was observed at the left atrial roof. The clinical AT (Figures 1C
and 1D) with the cycle length of 300 ms was induced by programmed atrial
stimulation. High density mapping and post-pacing intervals were
consistent with a localized reentry utilizing the vein of Marshall (VOM)
epicardially and the mitral isthmus endocardially (Figure 1E). Ethanol
was infused to the VOM as previously described\textsuperscript{1} and
resulted in immediate AT termination. Bidirectional lateral mitral
isthmus block was then confirmed by differential pacing maneuver.
However, a transitory and complete AV block with a junctional escape
rhythm spontaneously occurred (Figure 2A). For the duration of the
complete AV block, LAA potentials consistently corresponded to P waves,
and ventricular potentials constantly preceded CS potentials, which had
no correlation with P waves (Figure 2B). These findings suggested that
the LAA and the CS were activated by the sinus rhythm and the junctional
rhythm, respectively. After the recovery of the AV conduction, the CS
exhibited a proximal-to-distal activation sequence (Figure 2C). What is
the mechanism of AV block with CS potential dissociation after the
creation of a block line at the lateral mitral isthmus?

\textbf{DISCUSSION}

To investigate the underlying mechanism, bi-atrial activation was mapped
in sinus rhythm (Figures 3A and 3B). Both sides of the interatrial
septum were transected by an incomplete line of block between the fossa
ovalis and the CS. While one end of this line joined a posterior scar
contiguous to the inferior vena cava (at the right side of the septum)
and the right pulmonary vein isolation line (at the left side of the
septum), a narrow isthmus of residual slow conduction was located at the
annular end of the line. Initial PR prolongation was, therefore, due to
a conduction slowing through the interatrial septum. As the CTI and roof
lines were blocked, the sinus node activation propagated to the left
atrium via the Bachman bundle, then in a clockwise direction around the
mitral annulus through the lateral mitral isthmus, then to the AV node
through the CS which exhibited a distal-to-proximal sequence, and
finally collided with the delayed activation of the interatrial septum
(Figure 3C).

After VOM ethanol infusion blocked the lateral mitral isthmus, the
narrow isthmus at the interatrial septum remained as the only path for
electrical propagation from the sinus node to the AV node (Figure 3D).
We hypothesized that electrical conduction of this narrow isthmus was
fragile enough to be temporarily blocked. Thus, the supra-nodal complete
AV block observed in the current procedure was most likely due to a
complete isolation of the lower parts of both atria. This isolation
resulted in a complete dissociation of the sinus rhythm and the
junctional rhythm, which separately activated the LAA and the CS,
respectively (Figure 2B).

Although the interatrial septum is a frequent target of CFAE ablation,
this will rarely result in an AV block\textsuperscript{2,3} unless
coexisting linear lesions disrupt the alternative conduction paths from
the sinus node to the AV node. Given the high incidence of CTI-, roof-,
and mitral-dependent flutters during a follow up after AF ablation,
linear lesions are frequently created in the recurrent procedure.
However, cautious analysis of interatrial conduction is needed before
creating linear lesions in the CTI, roof, and mitral isthmus, when
extensive CFAE ablation was previously performed at the interatrial
septum. Furthermore, extensive ablation of the interatrial septum should
probably be avoided to respect physiological atrial activation and to
spare associated contractile function.

In the present case, a dual-chamber pacemaker was implanted before
patient discharge.

\textbf{REFERENCES}

\begin{enumerate}
\tightlist
\item
  Pambrun T, Denis A, Duchateau J, Sacher F, Hocini M, Jaïs P,
  Haïssaguerre M, Derval N. MARSHALL bundles elimination, Pulmonary
  veins isolation and Lines completion for ANatomical ablation of
  persistent atrial fibrillation: MARSHALL-PLAN case series. J
  Cardiovasc Electrophysiol 2019;30:7-15.
\item
  Verma A, Sanders P, Champagne J, Macle L, Nair GM, Calkins H, Wilber
  DJ. Selective complex fractionated atrial electrograms targeting for
  atrial fibrillation study (SELECT AF): a multicenter, randomized
  trial. Circ Arrhythm Electrophysiol 2014;7:55-62.
\item
  Hayward RM, Upadhyay GA, Mela T, Ellinor PT, Barrett CD, Heist EK,
  Verma A, Choudhry NK, Singh JP. Pulmonary vein isolation with complex
  fractionated atrial electrogram ablation for paroxysmal and
  nonparoxysmal atrial fibrillation: A meta-analysis. Heart Rhythm
  2011;8:994-1000.
\end{enumerate}

\textbf{FIGURES}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

\textbf{Figure 1 A:} Surface electrocardiogram \textbf{(} ECG) at
baseline. \textbf{B:} Intracardiac ECG at baseline. \textbf{C:} Surface
ECG during AT. \textbf{D:} Intracardiac ECG during atrial tachycardia
(AT). \textbf{E:} The activation map during AT. Yellow arrows indicate
the suspected tachycardia circuit. CS, coronary sinus; LAA, left atrial
appendage; LPV, left pulmonary vein; MA, mitral annulus; PPI, post
pacing interval; TCL, tachycardia cycle length.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

\textbf{Figure 2} \textbf{A:}Surface electrocardiogram (ECG) after the
ethanol infusion to the vein of Marshall (VOM). \textbf{B:} Intracardiac
ECG after the ethanol infusion to VOM. Arrows indicate P waves. Note
that P waves preceded atrial potentials in the LAA, and ventricular
potentials preceded atrial potentials in the CS. \textbf{C:}
Intracardiac ECG after the restoration of atrioventricular conduction.
CS, coronary sinus; LAA, left atrial appendage.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

\textbf{Figure 3} The activation maps of the left atrium (\textbf{A} )
and right atrium (\textbf{B} ). Electrical propagation is indicated by
yellow arrows. An incomplete block line (white line) was observed at
both sides of the interatrial septum, and a narrow isthmus was located
at its annular end. The schema of the electrical activation in the atria
before (\textbf{C} ) and after (\textbf{D} ) the ethanol infusion to the
vein of Marshall (VOM). A gray area indicates a slow conduction area.
AVN, atrioventricular node; BB, Bachman bundle; CS, coronary sinus; CTI,
cavotricuspid isthmus; FO, fossa ovalis; IVC, inferior vena cava; LAA,
left atrial appendage. LIPV, left inferior pulmonary vein; LSPV, left
superior pulmonary vein; MA, mitral annulus; MI, mitral isthmus; RAA,
right atrial appendage; RIPV, right inferior pulmonary vein; RSPV, right
superior pulmonary vein; SN, sinus node; SVC, superior vena cava; TA,
tricuspid annulus.

\selectlanguage{english}
\FloatBarrier
\end{document}

