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\begin{document}

\title{Spatial Thermodynamics of very High Power-Short Duration Catheter
Ablation for Pulmonary Vein Isolation in an in-vivo model}



\author[1]{Atsushi Suzuki}%
\author[2]{H. Immo Lehmann}%
\author[2]{Songyun Wang}%
\author[2]{Kay Parker}%
\author[2]{Kristi Monahan}%
\author[2]{Maryam Rettmann}%
\author[2]{Douglas Packer}%
\affil[1]{Mayo Clinic/St. Marys Hospital}%
\affil[2]{Mayo Clinic/St. Marys Campus}%


\vspace{-1em}



  
  \date{May 07, 2024}


\begingroup
\let\center\flushleft
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\selectlanguage{english}
\begin{abstract}
Introduction: The spatial thermodynamics of very high power-short
duration (vHPSD) radiofrequency (RF) application during pulmonary vein
isolation (PVI) in in-vivo model has not been well characterized. This
study was conducted to investigate the distance-temperature relationship
during vHPSD-RF ablation. Methods: PVI was performed using the vHPSD
catheter with the settings of 90W, RF time of 4 sec and 15mL/min
irrigation in a canine model. Catheter contact force (CF) of 10-20g was
defined as `normal' and CF \textgreater{}20g as `firm' CF. Tissue
temperature was monitored using thermocouples implanted at the surface
of the left atrial-pulmonary vein junction, left phrenic nerve, and the
luminal esophagus. PVI using a standard contact-force sensing catheter
(SCF) (settings of 35W, 30sec and 30mL/min irrigation) was performed for
comparison. Results: A total of 334 TC profiles in 4 animals was
investigated. Time to maximum tissue temperature (MTT) (6.0sec
{[}vHPSD/normal CF{]} vs. 30.5 sec {[}SCF/normal CF{]},
p\textless{}0.001; 8.0sec {[}vHPSD/firm CF{]} vs. 24.0sec {[}SCF/firm
CF{]}, p=0.022) was shorter with vHPSD than in SCF groups. MTT within
10mm from catheter-tip was lower in vHPSD ablation with normal CF than
using SCF ablation (median 41.9\selectlanguage{ngerman}°C {[}interquartile-range; 40.2-46.1{]}
vs. 49.5°C {[}45.9-56.2{]}, p=0.013). The distance margin to keep the
MTT below 39ºC, 42ºC, and 50ºC were 4.9mm, 4.2mm, and 3.4mm,
respectively in the vHPDS group. This margin was larger (8.0mm, 6.6mm,
and 4.6mm) in the SCF group. Conclusion: Our study underscores that
vHPSD creates greater resistive heating than conventional catheter
ablation.%
\end{abstract}\selectlanguage{ngerman}%



\sloppy


\textbf{Spatial Thermodynamics of very High Power-Short Duration
Catheter Ablation for Pulmonary Vein Isolation in an \emph{in-vivo}
model}

Running title: Thermodynamics of high power-short duration ablation

Atsushi Suzuki, MD, PhD\textsuperscript{1,2}; H. Immo Lehmann,
MD\textsuperscript{1,3,4}; Songyun Wang, MBBS\textsuperscript{1,5};
\begin{CJK}{UTF8}{gbsn}　　\end{CJK}\selectlanguage{english}Kay D. Parker, CVT\textsuperscript{1}; Kristi H. Monahan,
RN\textsuperscript{1}; Maryam E. Rettmann, PhD\textsuperscript{1};
\begin{CJK}{UTF8}{gbsn}　　　　\end{CJK}\selectlanguage{english}and Douglas L. Packer, MD\textsuperscript{1}

\textsuperscript{1} Translational Interventional Electrophysiology
Laboratory, Mayo Clinic/St. Marys Campus, Rochester, Minnesota,
USA.\textsuperscript{2} Department of Cardiology, Osaka Saiseikai
Nakatsu Hospital, Osaka, Japan. \textsuperscript{3} Department of
Cardiology, Corrigan Minehan Heart Center, Massachusetts General
Hospital, Boston, MA, USA. \textsuperscript{4} Harvard Medical School,
Boston, MA, USA. \begin{CJK}{UTF8}{gbsn}　　　　\end{CJK}\selectlanguage{english}\textsuperscript{5} Department of Cardiology,
Renmin Hospital of Wuhan University, Wuhan, China.

\textbf{Total word count:} 4610words (20 pages, including title page,
abstract, manuscript, references, tables and figures)

\textbf{Sources of Funding:} This study was funded by Biosense Webster
Inc. Dr. Packer's work is funded in part by a Clinician Investigator
Award from the Mayo Foundation.

\textbf{Disclosures:} Dr. Packer in the past 12 months has provided
consulting services for Abbott, AtriFix, Biosense Webster Inc., Boston
Scientific, CardioFocus, Johnson \& Johnson, MediaSphere Medical, LLC,
MedLumics, Medtronic, St. Jude Medical, Siemens, SigNum Preemptive
Healthcare, Inc., and Thermedical. Dr Packer received no personal
compensation for these consulting activities. Dr. Packer receives
research funding from the Abbott, Biosense Webster, Boston
Scientific/EPT, CardioInsight, CardioFocus, Endosense, German Heart
Foundation, Hansen Medical, Medtronic, NIH, Robertson Foundation, St.
Jude Medical, Siemens and Thermedical. Dr. Packer and Mayo Clinic
jointly have equity in a privately held company, External Beam Ablation
Medical Devices. Dr. Packer also receives royalties from Wiley \& Sons,
Oxford, and St. Jude Medical, outside the submitted work. The other
authors report no potential conflicts of interest.

\textbf{Correspondence:}

Douglas L. Packer, MD

Heart Rhythm Services

Mayo Clinic, St. Marys Hospital

1216 2nd St SW, AL 2-416

Rochester, MN 55902

Tel: 507-255-6263

Fax: 507-255-3292

E-mail: \emph{packer@mayo.edu}

\emph{May 7\textsuperscript{th}, 2021}

\textbf{Abstract}

\textbf{Introduction:}The spatial thermodynamics of very high
power-short duration (vHPSD) radiofrequency (RF) application during
pulmonary vein isolation (PVI) in \emph{in-vivo} model has not been well
characterized. This study was conducted to investigate the
distance-temperature relationship during vHPSD-RF ablation.

\textbf{Methods:} PVI was performed using the vHPSD catheter with the
settings of 90W, RF time of 4 sec and 15mL/min irrigation in a canine
model. Catheter contact force (CF) of 10-20g was defined as `normal' and
CF \textgreater{}20g as `firm' CF. Tissue temperature was monitored
using thermocouples implanted at the surface of the left
atrial-pulmonary vein junction, left phrenic nerve, and the luminal
esophagus. PVI using a standard contact-force sensing catheter (SCF)
(settings of 35W, 30sec and 30mL/min irrigation) was performed for
comparison.

\textbf{Results:}A total of 334 TC profiles in 4 animals was
investigated. Time to maximum tissue temperature (MTT) (6.0sec
{[}vHPSD/normal CF{]} vs. 30.5 sec {[}SCF/normal CF{]},
p\textless{}0.001; 8.0sec {[}vHPSD/firm CF{]} vs. 24.0sec {[}SCF/firm
CF{]}, p=0.022) was shorter with vHPSD than in SCF groups. MTT within
10mm from catheter-tip was lower in vHPSD ablation with normal CF than
using SCF ablation (median 41.9\selectlanguage{ngerman}°C {[}interquartile-range; 40.2-46.1{]}
vs. 49.5°C {[}45.9-56.2{]}, p=0.013). The distance margin to keep the
MTT below 39ºC, 42ºC, and 50ºC were 4.9mm, 4.2mm, and 3.4mm,
respectively in the vHPDS group. This margin was larger (8.0mm, 6.6mm,
and 4.6mm) in the SCF group.

\textbf{Conclusion:} Our study underscores that vHPSD creates greater
resistive heating than conventional catheter ablation.

\textbf{Key words:} Atrial fibrillation; Catheter ablation; Pulmonary
vein isolation; Very high-power and short-duration ablation; Spatial
thermodynamics.

\textbf{Abbreviations:} AF=atrial fibrillation, CF=contact force,
ICE=intracardiac echocardiography, LA=left atrium, LIPV=left inferior
pulmonary vein, LSPV=left superior pulmonary vein, PV=pulmonary vein,
PVI=pulmonary vein isolation, RF=radiofrequency, RIPV=right inferior
pulmonary vein, RSPV=right superior pulmonary vein, SCF=standard
open-irrigation contact-force sensing catheter, vHPSD=very high
power-short duration

\textbf{Background}

Catheter ablation with isolation of the pulmonary veins (PVI) has proven
to be a successful treatment of atrial fibrillation (AF). However to
date, it is marked by potential complications, as well as unsatisfactory
success rates.\textsuperscript{1}Ablation with higher power could
facilitate shortening of ablation time, while reducing procedural
time.\textsuperscript{2-4}A novel, very high power-short duration
(vHPSD) ablation catheter system has been developed for creation of
continuous circumferential lesions for PVI. Several studies have
reported lesion characteristics, efficacy and safety of vHPSD ablation
in several\emph{in-vivo}models.\textsuperscript{5-7} Recently, PVI using
this vHPSD RF catheter and its efficacy in a clinical case series has
been reported.\textsuperscript{8}However, spatial thermodynamics
(relationship between tissue temperature and distance from the catheter)
of vHPSD RF application in an \emph{in-vivo} model have not been well
described. Understanding of the thermodynamics of vHPSD catheter
ablation is critical to achieve high PVI success rates without projected
increments in procedural complications. This study aimed to investigate
spatial thermodynamics during PV isolation using the vHPSD catheter in
an \emph{in-vivo} model. Secondly, it aimed to assess biophysics of
lesion creation and collateral damage of very high-power ablation.

\textbf{Methods}

\textbf{Animal Preparation:} The experimental protocol was approved by
Mayo Clinic's institutional animal care and use committee and performed
in full compliance with the 'Guide for the Care and Use of Laboratory
Animals'. Four adult mongrel dogs (30-40kg, three vHPSD ablation, one
open-irrigated contact force `SCF' ablation) were studied following
methods previously reported.\textsuperscript{9-11} The data, analytic
methods, and study materials are available from the corresponding author
to other researchers for the purposes of reproducing the results or
replicating the procedure upon reasonable request.

\textbf{The System of Very High Power-Short Duration Catheter:} The
vHPSD catheter (Qdot Micro, Thermocool Smart Touch SF-5D Catheter;
Biosense Webster Inc.) has been described
previously.\textsuperscript{5-8} Briefly, it has 6 thermocouples
embedded in its tip (3 proximal and 3 distal) with a distance of 75\selectlanguage{greek}µ\selectlanguage{english}m
from the outer catheter tip surface. The RF generator (nGen RF
generator, Biosense Webster Inc.) used in this study was modified to
produce high-power RF energy and perform accurate and reliable
temperature, impedance, and power measurements. It also entails a
real-time 33msec feedback cycle with a 90W power ramp-up time of less
than 0.5 sec.

\textbf{Thermocouple Implantation and Distance Monitoring:} Thermocouple
(TC) implantation and distance monitoring: (Physitemp Instrument Inc.,
Clifton, NJ, USA) were implanted epicardially via a left-sided
thoracotomy. Detailed tissue TC implantation and methods for measurement
of distance from the ablation catheter electrode to thermocouples have
been described in previous our reports.\textsuperscript{9-11}

\textbf{Vascular Access and Catheterization:} Introducer sheaths were
placed in the right or left external jugular vein and right femoral
artery and vein. A 6-Fr decapolar catheter was advanced into the
coronary sinus. Intracardiac echocardiography (ICE; Siemens Acuson,
Mountain View, CA) with a 10Fr catheter (5.5-10 MHz) was used to measure
LA size (superior-inferior, medial-lateral axis, perimeter, and area of
LA), each PV antral diameter, and to guide the transseptal puncture.
After transseptal puncture, the sheath was exchanged over a guidewire
for an 8.5Fr steerable sheath (Agilis, St. Jude Medical, St. Paul, MN,
USA).

\textbf{Ablation Procedure ofIsolation of the Pulmonary Veins:} In three
animals, PVI was performed using the vHPSD catheter with application of
90W for 4 sec, and a temperature limit at 65\selectlanguage{ngerman}ºC. Irrigation flow was set
to 15mL/min with an average contact force (CF) of 10-20g (vHPSD with
normal CF group) or \textgreater{}20g (vHPSD with firm CF
group).\textsuperscript{12} Full thickness temperature at the ablation
site was monitored using epicardial thermocouples implanted at each
site. Tissue temperature data of PVI using a conventional standard
open-irrigated-tip CF catheter (`SCF', Thermocool Smart Touch) was
obtained for comparison in one animal. Settings of `SCF' ablation were
35W/30sec, irrigation flow rate of 30mL/min and CF of 10-20g (SCF with
normal CF group) or \textgreater{}20g (SCF with firm CF group). Tissue
temperature during ablation was monitored in the same manner as in vHPSD
ablation cases. Spatial thermodynamics were compared between vHPSD with
`normal' CF and SCF with `normal' CF, vHPSD with `firm' CF and SCF with
`firm' CF.

\textbf{Gross and Microscopic Pathology:} At the end of each procedure,
30mL of 1.0\% triphenyltetrazoliumchloride was injected and animals and
ventricular fibrillation was induced. Methods of gross and microscopic
pathology have been described in our previous
reports.\textsuperscript{11} Each segment was stained with
Hematoxylin--Eosin as well as Masson Trichrome stains and examined with
light microscopy. PV lesions were measured using a digital caliper.
Lesion circumferentiality (continuous transmural PV lesion length) of
lesions was assessed.

\textbf{Statistical Analysis:} Continuous variables are expressed as
mean±standard deviation or median with the quartiles (median
{[}quartiles{]}), and compared by 2-sample student \emph{t} tests,
Welch's \emph{t} tests or Mann--Whitney U tests, depending on
distribution of variables. Categorical variables were compared using the
chi-squared test or Fisher's exact test. Associations between continuous
variables were assessed using Pearson's or Spearman's rank correlation
tests. Receiver operating characteristic (ROC) curve and Youden index
were used to determine the optimal distance margin from the catheter-tip
to establish a tissue temperature of \textless{}39°C, \textless{}42°C
and \textless{}50°C. Statistical analyses were performed using the SPSS
statistical software (version 21.0, SPSS, Inc., Chicago, IL, USA). A
two-sided p-value \textless{}0.05 was considered to indicate statistical
significance.

\textbf{Results}

\textbf{Baseline LA/PV dimensions:} Four animals (33.1±1.2 kg) underwent
assessment of LA/PV dimensions. LA diameter was 29.1±1.5 mm
(mid-lateral), 31.2±1.8 mm (superior--inferior), and diameter of PV
ostium was LSPV of 14.6±1.5 mm, RSPV of 14.8±1.8 mm, LIPV of 11.8±0.5
mm, and RIPV of 12.1±1.2 mm.

\textbf{Isolation of the Pulmonary Veins (PVI) using vHPSD or a
conventional standard open-irrigation contact force catheter (SCF):}A
total of 152 RF applications were performed using vHPSD (n=135) or SCF
(n=17). Three right-inferior PVs (RIPVs) were ablated to assess internal
esophageal temperature as monitored through the intraluminal temperature
probe in 3 animals for vHPSD ablation. Six of 135 RF applications
(sufficiently apart from each other, placed in the right-superior
{[}RSPV{]} antrum in one of the 3 animals) were performed in order to
compare individual PV lesions created by vHPSD catheter. Seventeen RF
applications using the SCF were also evaluated in the left-superior
PV{[}LSPV{]} and left-inferior PV {[}LIPV{]} in the remaining 1 animal.
PVI data using vHPSD and SCF is summarized in Table 1. PVI was achieved
in 7 of 8 PVs in the vHPSD, and 2 of 2 PVs in the SCF group (p=0.617).

During ablation, an audible steam pop occurred in 8 of 135 RF
applications (5.9\%) in the vHPSD group, and 2 of 17 (11.7\%) in the SCF
group (p=0.310). No pericardial effusions were observed in either group.
Table 2 shows a comparison of ablation parameters between vHPSD
ablations with and without steam pop occurrence. Maximum and average
output, catheter tip temperature and contact force were not different
between groups. Importantly, initial impedance was higher and impedance
drop larger in ablations with steam pop compared to those without steam
pop (Table 2).

\textbf{Spatial Thermodynamics (Tissue Temperature-Distance
Relationship):} During 99 of 152 RF applications (82 RF applications
using vHPSD catheter and 17 RF applications using SCF), a total of 334
tissue TC profiles: 222 at LA-PV junction, 81 at internal esophagus and
31 at phrenic nerve were analyzed. Figure 1A shows a representative case
of time course changes of power, tissue impedance, catheter tip
electrode temperature and tissue thermocouple temperature during vHPSD
ablation. Spatial thermodynamics (data from all tissue thermocouples)
are summarized in Table 3. Figure 1B shows a representative time course
of temperature change during RF application using vHPSD and SCF. Tissue
temperature time-course at the distance \textless{}10mm from the
catheter tip (180 tissue TC profiles) is also summarized in Table 3.
Maximum tissue temperature was lower in vHPSD ablation with normal CF
than in SCF ablation with normal CF (median 41.9°C
{[}interquartile-range; 40.2-46.1{]} vs. 49.5°C {[}45.9-56.2{]},
p=0.013), in contrast, there was no significant difference between them
with firm CF (44.4°C {[}39.8-52.1{]} vs. 47.5°C {[}41.7-49.0{]},
p=0.696). However, time to maximum tissue temperature (6.0sec {[}vHPSD
with normal CF{]} vs. 30.5sec {[}SCF with normal CF{]},
p\textless{}0.001 and 8.0sec {[}vHPSD with firm CF{]} vs. 24.0sec {[}SCF
with firm CF{]}, p=0.022) were significantly shorter in the vHPSD groups
compared to the SCF groups. Figure 2A shows the relationship between
maximum tissue temperature and distance from catheter tip of each site.
There was robust correlation between maximum tissue temperatures and
minimum distance from the catheter in all groups (r=-0.672;
p\textless{}0.001 in vHPSD with normal CF, r=-0.740; p\textless{}0.001
in SCF with normal CF, r=-0.759; p\textless{}0.001 in vHPSD with firm
CF, r=-0.694; p\textless{}0.001 in SCF with standard CF). Figure 2B
shows the results of a ROC analysis using maximum tissue temperature and
distance data. The optimal distance margin to keep the tissue
temperature below 39ºC, 42ºC, and 50ºC were 4.9mm, 4.2mm, and 3.4mm in
the vHPDS, in comparison with 8.0mm, 6.6mm and 4.6mm in the SCF group.

\textbf{Gross and Microscopic Pathology Outcomes:} In gross pathology
investigation, PV lesion circumferentially (continuous transmural PV
lesion length/circumferential PV length) was 96.7±6.5\% in the vHPSD and
89.7±14.6\% in the SCF group (p=0.533). Comparison of lesion
characteristics and collateral damages in surrounding organs between
vHPSD and SCF ablation is summarized in Table 1. Figure 3A and 3B shows
gross and microscopic pathology of transmural circumferential left
superior PV lesions. Table 4 shows comparison of lesion characteristics
created by vHPSD with normal and firm CF. Endo-/epicardial lesion size
and transmurality were not different between normal and firm CF.

Eight of 135 lesions in vHPSD and 2 of 17 lesions in SCF group appeared
with subendocardial hemorrhage consistent with audible steam pop during
the ablation procedure. In the gross pathology investigation, no
collateral lung and phrenic nerve injury was observed.

As for esophageal collateral damage in vHPSD ablation, 6 extraluminal
esophageal lesions were observed in 11 RF applications, with gross and
microscopic pathology (Figure 3C and 3D) showing that the deepest
collateral lesion nearly reached the longitudinal muscular layer of the
esophagus, and no evidence of an intraluminal esophageal lesion was
found in any case. Average contact force of RF applications with
extraluminal esophageal injury (25.3±2.8 {[}22 to 30g{]}) was not
different from that without the extraluminal esophageal injury
(22.8±7.1g {[}13 to 31g{]}, p=0.437).

\textbf{Discussion}

\textbf{Major findings:} In this validation study using a vHPSD
catheter, spatial thermodynamics and biophysics of ablation were largely
similar to those of an SCF catheter. Heat propagation latency and
distance appeared different between the two ablation catheters, however,
maximum tissue temperature achieved within 10mm from the catheter was
not different between the vHPSD and SCF group.

\textbf{Efficacy of the vHPSD Catheter Ablation and Lesion
Characterization:} The present study showed the vHPSD catheter created
transmural ablative lesions in the canine LA, achieving electrical PV
isolation using one forth the RF application time than with SCF. This
vHPSD catheter provided real time (33ms interval) feedback of
catheter-tip electrode temperature and impedance monitoring even as high
RF energy was applied. The feedback of impedance change was especially
important to avoid steam pop occurrence. Focusing on a single lesion
created by this vHPSD catheter, endocardial lesion diameter was 4 to 5mm
with a transmurality of 74\%. Therefore, this catheter provides durable
PVI with recommended interlesion distance of less than
4-5mm.\textsuperscript{13,14}

\textbf{Spatial Thermodynamics and Safety of the vHPSD catheter:} This
study provided the data regarding \emph{in-vivo} spatial thermodynamics
for this vHPSD RF catheter compared with SCF RF ablation. Tissue
temperature increase was steeper using vHPSD compared to SCF. The
maximum tissue temperature of vHPSD ablation was lower than SCF ablation
when catheter contact force was within a range of 10-20g, in contrast,
no difference was present when contact force was greater than 20g.
Additionally, the heat propagation distance (data from the ROC analysis)
appeared shorted in vHPSD ablation compared with the SCF ablation.
Tissue heating during RF energy delivery consists of ``resistive''
heating within 1-3mm of the tip with ``conductive heating'' beyond that
point.\textsuperscript{15} Our results show that tissue temperature
changes beyond that point.

Incidence of steam pops, was similar between vHPSD and SCF ablation. In
previous reports, applied contact force has been one of the major
factors for steam pop occurrence.\textsuperscript{16,17}However, there
was no significant difference between ablations with, and without, steam
pop occurrence; initial impedance and the impedance drop in the present
study were mildly different, underscoring that impedance monitoring is a
key factor also in using this new technology. Higher initial impedance
may have resulted in more rapid increase of tissue temperature by
resistive heating, leading to a more significant impedance drop compared
to ablation using the standard settings.

Considering lesion characteristics and spatial thermodynamics, very high
power-short duration (90W/4sec) RF ablation using vHPSD with a contact
force of 10 to 20g appears reasonably more efficient compared to
conventional RF catheter ablation using a SCF. Temperature latency with
an SCF catheter was substantially longer raising a question regarding
difference in SCF safety. Some of these findings are similar to those of
other additional manuscripts, although with less rigorous review of the
spatial hemodynamics and biophysics created lesions.

\textbf{Limitations:} There are limitations to this study that should be
considered. First, the number of included samples, especially those
created by the SCF was small. Second, this study was done in an \emph{in
vivo} canine model; dogs are an established animal model for catheter
ablation studies, but cardiac anatomy and size are slightly different
than that in humans. Therefore, catheter manipulation, tissue
thermodynamics, lesion size, and efficacy might be different in humans.
Third, TC implantation was performed using thoracotomy. Opening the
chest with subsequent pericardiotomy affects the structural relationship
and possibly impacted the change in temperature. Forth, the catheter tip
contact force direction to the tissue TC was not investigated in this
study. Tissue temperature-distance relationship was simply based on the
spatial distance between the catheter-tip and tissue TC. Maximum tissue
temperature was varied even at the similar catheter-TC distance, this
may have been resulted from difference of the contact force direction.
Lastly, this study included only acutely studied animals, no follow-up
after catheter ablation was conducted, hence chronic durability of
lesions as well as occurrence of chronic complications such as pulmonary
vein stenosis was not evaluable.

\textbf{Conclusion}

This study of vHPSD ablation provided more robust data detailing the
spatial thermodynamics and biophysics utilized to create rapid high
output lesions, not acknowledged in several other studies in an
\emph{in-vivo} model for understanding the biophysics of very high-power
ablation. There was an appreciable difference in heat propagation
latency between the two ablation catheters present, reflecting the
difference between resistive and conductive heating. Overall effects
appeared equivalent to conventional catheter ablation, but the efficacy
was greater driven by the imputed resistive heating.

\textbf{References}

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3. Bhaskaran A, Chik W, Pouliopoulos J, et al. Five seconds of 50-60 W
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\textbf{Figure Legends}

\textbf{Figure 1. Change of tissue temperature. A:} Exemplary case of
time course of output, tissue impedance change, catheter tip electrode
temperature and tissue TC temperature. Output, impedance and catheter
tip electrode temperature from record of CARTO3 and RF
generator.\textbf{B:} Change of tissue temperature during RF application
using very high power-short duration (vHPSD) and standard contact-force
sensing catheter (SCF). Numbers with mm indicate the distance between
catheter and TC. CF=contact force, LA--PV=left atrium--pulmonary vein
junction, RF=radiofrequency, TC=thermocouple.

\textbf{Figure 2. Analysis of Spatial Thermodynamics. A:} Relationship
between maximum tissue temperature and distance catheter of each site.
Each point represents the maximum tissue temperature and the distance
from the catheter. \textbf{B:} Heat propagation distance (the results of
a ROC analysis using maximum tissue temperature and distance data). The
abbreviations as in Figure 1.

\textbf{Figure 3. Gross and microscopic pathology of transmural
circumferential lesion. A:} Gross pathology of transmural
circumferential left superior PV (LSPV) lesion. Black arrow indicates RF
lesion created by very high power-short duration (vHPSD)
catheter.\textbf{B:} Microscopic pathology of transmural LSPV lesion.
Black arrow indicates the area of thermal necrotic tissue which is well
demarcated from normal atrial myocardium (black dotted arrow). Asterisk
(*) indicates pericardial fat tissue. \textbf{C:} Extra-luminal
esophageal lesion (white arrows in left panel) was consisted with the
sites where right inferior PV lesions were observed epicardially (white
dotted arrows in left panel). No evidence of intra-luminal esophageal
lesion was observed (right panel). \textbf{D:} Upper panel shows the
section of esophageal lesion. Upside of the section is luminal of the
esophagus. Microscopic pathology showed that the deepest collateral
lesion nearly reached to the longitudinal muscular layer of esophagus
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