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\begin{document}

\title{Underrecognized consequence of three-dimensional mapping tool selection
for atrial fibrillation ablation: when the operators' decision
determines the amount of silent micro-embolic burden}



\author[1]{Thomas Rostock}%
\author[2]{Torsten Konrad}%
\author[3]{Raphael Spittler}%
\affil[1]{Univ Hospital Mainz, II. Medical Department}%
\affil[2]{University Hospital Mainz}%
\affil[3]{University Medical Center Mainz}%


\vspace{-1em}



  
  \date{June 17, 2024}


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\textbf{Underrecognized consequence of three-dimensional mapping tool
selection for atrial fibrillation ablation: when the operators' decision
determines the amount of silent micro-embolic burden}

Thomas Rostock MD, Torsten Konrad MD, Raphael Spittler MD

From the University Hospital Mainz, Center for Cardiology,

Cardiology II / Electrophysiology, Mainz, Germany

Word count: 1460

Funding: (None)

Disclosures: (None)

\textbf{Correspondence to:}

Thomas Rostock, MD

University Hospital Mainz

Center for Cardiology

Cardiology II / Electrophysiology

Langenbeckstr. 1

55131 Mainz, Germany

Email: throstock@gmail.com

Endovascular cardiac interventions carry an inherent risk for
thromboembolic events by different means. While retrograde aortic access
to the heart contains an additional risk for the dislodgement of
calcified vascular and valvular particles, sources of cerebral lesions
during atrial transseptal procedures mainly comprise air and/or thrombus
embolization. Catheter ablation of left atrial (and ventricular)
arrhythmias with radiofrequency (RF) energy furthermore harbors the risk
for the development of a distinct type of embolic material, that is
coagulum-char formation at the heated ablation catheter tip. The
incidence of clinically relevant symptomatic thromboembolic
complications due to left atrial (LA) ablation is lower than 1\% (1).
However, it has been first demonstrated by Lickfett and co-workers
already 15 years ago that LA catheter ablation can be associated with
clinically silent embolic cerebral lesions (2). Since then, the major
focus of research investigating potential mechanisms causing these
silent cerebral lesions was directed at different RF energy application
techniques and energy sources, quality of intra- and peri-procedural
anticoagulation, and sheath-flushing protocols, respectively. However,
the thromboembolic potential of different three-dimensional
electro-anatomical mapping (3D-EAM) systems with its respective mapping
catheter designs has not been adequately addressed in clinical or
experimental studies.

In the current issue of the Journal, Nakamura and co-workers (3) present
a study that investigated the impact of two different mapping (and
ablation) techniques on the occurrence of clinically silent cerebral
events (SCEs) after RF ablation of atrial fibrillation (AF). The study
population comprise a total of 211 consecutive patients undergoing AF
ablation. Of these, 105 patients underwent the procedure with the use of
the CARTO system (Biosense Webster, group C). In this group, two
circular pulmonary vein mapping catheters were used and the ablation was
performed with the `Ablation-Index' technique (under contact-force
guidance). The other 106 patients were treated with the Rhythmia system
(R-group). In the R-group, 3D-EAM was obtained using a mini-basket
catheter (Orion, Boston Scientific) and PV mapping was performed with a
circular mapping catheter. Thus, a triple transseptal approach was used
in both groups. Ablation in the R-group was performed under
local-impedance guidance (IntellaNav catheter, Boston Scientific). One
the day after ablation, all patients underwent brain magnetic resonance
imaging (MRI) and all patients with SCEs underwent follow-up MRI at 3-4
weeks after ablation. In this cohort, a total of 78 (37\%) patients
demonstrated SCE at day-1, with 18\% of patients in the CARTO group and
56\% in the Rhythmia group. Out of this study cohort, 60 patients in
each group were matched on the basis of a propensity score analysis. In
this more specific patient cohort, the overall incidence of SCEs was
31\%. More than half of the Rhythmia patient group demonstrated incident
SCEs after ablation while this incidence was one-of-ten in the CARTO
group patients (52 vs. 10\%). Moreover, the number of lesions per
patient detected in the early post-ablation MRI was 8 in 6 patients in
the CARTO group and 98 in 31 patients. The follow-up MRI, available in
more than 90\% of patients with initially detected lesions, revealed
that 89\% of lesions disappeared and 11\% developed into chronic
cerebral infarcts; all lesions in the CARTO group and 88\% of lesions in
the Rhythmia group dissolved within 3-4 weeks after ablation.

Summarizing these data, the use of structurally complex mapping tools,
such as the mini-basket Orion catheter, appears to harbor an increased
risk for SCEs during an AF ablation procedure. Moreover, not only the
incidence of SCEs was significantly higher, but also the cerebral
embolic burden for the individual patient was markedly increased with
the use of these structurally complex mapping catheters.

With this study, the authors provide an important contribution to the so
far widely neglected issue of the thromboembolic potential of
endovascular mapping catheters; hitherto neglected since the embolic
profile of AF ablation procedures were mainly attributed to embolic
material formations arising from ablation catheters and sheaths. It is
the credit of the authors to bring the attention of interventional
electrophysiologists to the role of mapping catheters with a complex
structural arrangement in the development of SCEs. In a previous study
by the same group, the 3D-EAM systems CARTO and Rhythmia were compared
in the context of LA tachycardia ablation with a nearly identical result
(4). The strengths of the current study are the large number of patients
included, the propensity score matching comparison and the rigorous
post-ablation work-up with brain MRI on the day after the procedure and
again after around four weeks. The follow-up MRI was available in almost
all patients (92\%). And here, the good news is also the bad news: while
almost 90\% of lesions detected immediately after the procedure
disappeared during a 4-week follow-up, more than 10\% of lesions
developed into chronic cerebral infarcts. All chronic infarcts were
observed in patients treated with the Rhythmia system. Unfortunately,
this study did not perform any cognitive or neuropsychological testing
before and after ablation. Although SCEs are considered to remain
clinically asymptomatic, it would be interesting to see whether
sophisticated neurocognitive testing will reveal alterations between
pre- and acute post-ablation performance as well as differences between
patients with and without development of chronic cerebral infarcts at
longer follow-up. Nevertheless, although catheter ablation of AF
obviously is associated with incident cerebral embolic lesions in a
substantial number of patients, a net clinical benefit in terms of
preservation of cognitive function and prevention of dementia (both
Alzheimer disease and vascular dementia) has been well-established for
patients who underwent successful AF catheter ablation (5).

It is with this background that we have to consider this important new
information for our daily routine clinical practice. The presented study
revealed that non-paroxysmal AF (not influenceable) and being treated
with the Rhythmia system were independent positive predictors of SCEs.
Thus, when we decide to use the Rhythmia system for the AF (or AT)
ablation procedure, we should evaluate the patient status for parameters
that were observed in this study to be associated with an increased risk
for SCEs:

\begin{itemize}
\tightlist
\item
  Is the left atrium significantly enlarged?
\item
  Is the left atrial appendage emptying velocity markedly reduced?
\item
  Does the patient have a history of TIA/stroke?
\end{itemize}

If all these questions receive a yes-answer, the use of the Rhythmia
system is probably something best avoided. Thus, an appropriate and
differentiated indication for the use of the Rhythmia system may
decrease the number of SCEs. Likewise, although no data are provided in
the current study, it is conceivable that a shorter catheter dwell time
in the left atrium would reduce the risk for SCEs further.

Thus, even under consideration of all well-defined strategies to
minimized the risk for (mainly small and clinically silent) cerebral
lesions, we now should keep in mind that already only our choice of the
3D-EAM system to guide the ablation procedure may determine the risk
independently.

\textbf{References}

\begin{enumerate}
\tightlist
\item
  Deneke T, Jais P, Scaglione M, Schmitt R, Di Biase L, Christopoulos G,
  Schade A, M\selectlanguage{ngerman}üggge A, Bansmann M, Nentwich K, Müller P, Krug J, Roos M,
  Halbfass P, Natale A, Gaita F, Haines D. Silent cerebral
  events/lesions related to atrial fibrillation ablation: a clinical
  review. J Cardiovasc Electrophysiol.2015;26:455-463.
\item
  Lickfett L, Hackenbroch M, Lewalter T, Selbach S, Schwab JO, Yang A,
  Balta O, Schrickel J, Bitzen A, Lüderitz B, Sommer T. Cerebral
  diffusion-weighted magnetic resonance imaging: a tool to monitor the
  thrombogenicity of left atrial catheter ablation. J Cardiovasc
  Electrophysiol.2006;17:1-7.
\item
  Nakamura k, Sasaki T, Take Y, Minami K, Inoue M, Asahina C, Sasaki W,
  Kishi S, Yoshimura S, Okazaki Y, Motoda H, Niijima K, Miki Y, Goto K,
  Kaseno K, Yamashita E, Koyama K, Funabashi N, Naito S. Incidence and
  characteristics of silent cerebral embolisms after
  radiofrequency-based atrial fibrillation ablation: a propensity
  score-matched analysis between different mapping catheters and indices
  for guiding ablation. J Cardiovasc Electrophysiol.2020; in press.
\item
  Nakamura k, Sasaki T, Take Y, Minami K, Inoue M, Kishi S, Yoshimura S,
  Sasaki W, Okazaki Y, Motoda H, Niijima K, Miki Y, Goto K, Yamashita E,
  Koyama K, Funabashi N, Naito S. Impact of the type of electroanatomic
  mapping system on the incidence of cerebral embolism after
  radiofrequency catheter ablation of left atrial tachycardias. Heart
  Rhythm.2020;17:250-257.
\item
  Kim D, Yang PS, Sung JH, Jang E, Yu HT, Kim TH, Uhm JS, Kim JY, Pak
  HN, Lee MH, Lip GYH, Joung B. Less dementia after catheter ablation
  for atrial fibrillation: a nationwide cohort study. Eur Heart J;2020.
  In press. doi:10.1093/eurheartj/ehaa726.
\end{enumerate}

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