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\begin{document}

\title{Impact of Tip Design and Thermocouple Location on the Efficacy and
Safety of Radiofrequency Application}



\author[1]{Junji Yamaguchi}%
\author[1]{Masateru Takigawa}%
\author[2]{Masahiko Goya}%
\author[3]{Claire Martin}%
\author[1]{Miki Amemiya}%
\author[1]{Tasuku Yamamoto}%
\author[1]{Takuro Nishimura}%
\author[1]{Rena Nakamura}%
\author[1]{Yasuhiro Shirai}%
\author[1]{Susumu Tao}%
\author[1]{Shinsuke Miyazaki}%
\author[1]{Yoshihide Takahashi}%
\author[1]{Tetsuo Sasano}%
\affil[1]{Tokyo Medical and Dental University}%
\affil[2]{Tokyo Medical and Dental University Hospital}%
\affil[3]{University of Cambridge}%


\vspace{-1em}



  
  \date{June 18, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
Background \& Objectives The FlexAbilityTM SE catheter has a laser-cut
8Fr 4-mm flexible tip irrigated through laser-cut kerfs with a
thermocouple 0.3mm from the distal end. The TactiCathTM SE catheter has
an 8Fr 3.5-mm tip and 6-irrigation port with a thermocouple 2.67mm
proximal to the tip. We investigated the impact of these differences on
the efficacy and safety of RF-applications. Methods RF applications at a
range of powers (20W, 30W, and 40W), contact forces (5g, 15g, and 25g),
and durations (10-60s) using perpendicular/parallel catheter
orientation, were performed in excised porcine hearts. Lesion
characteristics and incidence of steam pops were compared. Results 540
lesions were examined. The FlexAbilityTM SE catheter produced smaller
lesion depths (4.0mm vs. 4.4mm, p=0.014 at 20W; 4.6mm vs. 5.6mm, p=0.015
at 30W), surface areas (22.7mm2 vs. 29.2mm2 at 20W, p=0.005; 23.2mm2 vs.
28.7mm2, p=0.009 at 30W) and volumes (126.1mm3 vs. 175.1mm3, p=0.018 at
20W; 183.2mm3 vs. 304.3mm3, p=0.002 at 30W) with perpendicular catheter
placement. However, no differences were observed with parallel catheter
placement. Steam-pops were significantly less frequently observed with
the FlexAbilityTM SE catheter (4\% vs. 22\%, p\textless{}0.001)
irrespective of catheter direction to the tissue. Multivariate analysis
showed that use of the TactiCathTM SE catheter, power [?]40W, contact
force [?]25g, RF duration \textgreater{}30s, parallel angle and impedance
drop [?]20\selectlanguage{greek}Ω \selectlanguage{english}were significantly associated with occurrence of steam-pops.
Conclusions The FlexAbilityTM SE catheter reduced the risk of
steam-pops, but produced smaller lesions with perpendicular catheter
placement compared to the TactiCathTM SE catheter.%
\end{abstract}%



\sloppy


\textbf{Impact of Tip Design and Thermocouple Location on the Efficacy
and Safety of Radiofrequency Application}

Short title: Comparison of Flexibility\textsuperscript{TM} and
TactiCath\textsuperscript{TM} ablation catheters

Junji Yamaguchi, MD,\textsuperscript{1*} Masateru Takigawa,
MD,\textsuperscript{1*} Masahiko Goya, MD,\textsuperscript{1}

Claire Martin, MD\textsuperscript{2}, Miki Amemiya,
MD,\textsuperscript{1} Tasuku Yamamoto, MD,\textsuperscript{1} Takuro
Nichimura, MD,\textsuperscript{1} Rena Nakamura,
MD,\textsuperscript{1}Yasuhiro Shirai, MD,\textsuperscript{1} Susumu
Tao, MD,\textsuperscript{1}

Shinsuke Miyazaki, MD,\textsuperscript{1}Yoshihide Takahashi,
MD,\textsuperscript{1}

Tetsuo Sasano, MD\textsuperscript{1}

\textsuperscript{1}Department of Cardiovascular Medicine, Tokyo Medical
and Dental University Hospital, Tokyo, Japan.

\textsuperscript{2}Royal Papworth Hospital, Cambridge, UK

\textsuperscript{*}These authors contributed equally to this work.

\textbf{Conflicts of interest}

Drs. Takigawa and Takahashi received endowments from Medtronic Japan,
Boston Scientific, Japan Lifeline, and WIN international. No other
authors have conflict of interest to declare.

\textbf{Funding}

This work was partially supported by JSPS KAKENHI Grant Number
JP20K17074.

\textbf{Corresponding Author:} Masateru Takigawa, MD, PhD.

Department of Cardiovascular Medicine, Tokyo Medical and Dental
University Hospital, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan.

TEL: +(81)3-3813-6111 FAX: +(81)3-5803-0110 E-mail:
teru.takigawa@gmail.com



\textbf{Abstract}

\textbf{Background \& Objectives}

The FlexAbility\textsuperscript{TM} SE catheter has a laser-cut 8Fr 4-mm
flexible tip irrigated through laser-cut kerfs with a thermocouple 0.3mm
from the distal end. The TactiCath\textsuperscript{TM} SE catheter has
an 8Fr 3.5-mm tip and 6-irrigation port with a thermocouple 2.67mm
proximal to the tip. We investigated the impact of these differences on
the efficacy and safety of RF-applications.

\textbf{Methods}

RF applications at a range of powers (20W, 30W, and 40W), contact forces
(5g, 15g, and 25g), and durations (10-60s) using perpendicular/parallel
catheter orientation, were performed in excised porcine hearts. Lesion
characteristics and incidence of steam pops were compared.

\textbf{Results}

540 lesions were examined. The FlexAbility\textsuperscript{TM} SE
catheter produced smaller lesion depths (4.0mm vs. 4.4mm, p=0.014 at
20W; 4.6mm vs. 5.6mm, p=0.015 at 30W), surface areas
(22.7mm\textsuperscript{2} vs. 29.2mm\textsuperscript{2} at 20W,
p=0.005; 23.2mm\textsuperscript{2} vs. 28.7mm\textsuperscript{2},
p=0.009 at 30W) and volumes (126.1mm\textsuperscript{3} vs.
175.1mm\textsuperscript{3}, p=0.018 at 20W;
183.2mm\textsuperscript{3}vs. 304.3mm\textsuperscript{3}, p=0.002 at
30W) with perpendicular catheter placement. However, no differences were
observed with parallel catheter placement. Steam-pops were significantly
less frequently observed with the FlexAbility\textsuperscript{TM} SE
catheter (4\% vs. 22\%, p\textless{}0.001) irrespective of catheter
direction to the tissue. Multivariate analysis showed that use of the
TactiCath\textsuperscript{TM} SE catheter, power [?]40W, contact force
[?]25g, RF duration \textgreater{}30s, parallel angle and impedance drop
[?]20\selectlanguage{greek}Ω \selectlanguage{english}were significantly associated with occurrence of steam-pops.

\textbf{Conclusions}

The FlexAbility\textsuperscript{TM} SE catheter reduced the risk of
steam-pops, but produced smaller lesions with perpendicular catheter
placement compared to the TactiCath\textsuperscript{TM} SE catheter.

\textbf{Keywords}

Catheter ablation; FlexAbility\textsuperscript{TM} SE;
TactiCath\textsuperscript{TM} SE; Lesion size

\textbf{Introduction}

Radiofrequency (RF) catheter ablation is an established treatment for
cardiac arrhythmias. Optimal lesion formation and avoidance of excessive
heating are necessary for effective ablation (1). Multiple factors
including power, duration, catheter-tissue contact force (CF), electrode
diameter, ablation circuit impedance, irrigation flow, tissue thickness,
and myocardial blood flow have been reported to be associated with
lesion characteristics (2,3).

Recently, a variety of new catheters have been developed and used in a
clinical setting. Since each catheter has unique features, ablation
lesion characteristics and complication rates may differ among
catheters. Operators must understand the features of each catheter to
optimize efficacy and safety. The open-irrigated ablation catheters,
FlexAbility\textsuperscript{TM} SE and TactiCath\textsuperscript{TM} SE
\selectlanguage{english}(Abbott, St. Paul, MN), have different irrigation flows, electrode
sizes and locations of the thermocouple, but little is known about the
effect of these differences. The aim of this study was to investigate
the lesion characteristics and adverse events of these catheters in ex
vivo conditions.

\textbf{Methods}

Irrigated Ablation Catheters

Two open-irrigated ablation catheters were compared. Images of the
catheter tips are shown in Figure 1A. The
FlexAbility\textsuperscript{TM} SE ablation catheter has a laser-cut
4-mm flexible 8Fr tip, which is irrigated from the proximal to distal
end through laser-cut kerfs, and from four holes on the distal end of
the tip. The TactiCath\textsuperscript{TM} SE ablation catheter has a
3.5-mm 8Fr tip and has 6-hole irrigation holes on the side of the tip.
Both catheters have a single thermocouple embedded within the tip for
temperature monitoring, and the distance from the tip is 0.3mm in the
FlexAbility\textsuperscript{TM} SE catheter and 2.64mm in the
TactiCath\textsuperscript{TM} SE catheter.

Experimental Model

A circulating saline bath (400 mL/min, NaCl 3.5 g/L) isotonic to blood,
a submersible load cell (KW-201, Tanita, Tokyo, Japan), and a
deflectable sheath were assembled. The load cell was installed on the
bottom of the bath with 5.0 L saline at 37\selectlanguage{ngerman}°C, and a section of the left
ventricular myocardium was placed on the ground plate on a load cell
apparatus. CF applied to the overlying myocardial tissue through the
ablation catheter was measured by the load cell in order to provide the
same conditions between the TactiCath\textsuperscript{TM} SE (which has
direct CF-sensing capability) and FlexAbility\textsuperscript{TM} SE
catheters. The accuracy of CF in this model was verified by a CF-sensing
catheter with EnSite Precision (Abbott) mapping system as shown in
Supplementary Figure 1. Briefly, the correlation coefficient between the
CF measured by the load cell and CF in the
TactiCath\textsuperscript{TM}SE catheter was R = 0.97 for perpendicular
catheter placement and R = 0.77 for parallel catheter placement.
Temperature, power and impedance values were continuously monitored
during RF delivery using the EnSite Precision cardiac mapping system.

RF applications

A calibrated roller pump (CoolPoint, Abbott) connected to the catheter
delivered saline solution at 20 ml/min for the
FlexAbility\textsuperscript{TM} SE\textsuperscript{M} catheter and 17-30
ml/min for the TactiCath\textsuperscript{TM} SE catheter (17 ml/min at
20W and 30W, 30 ml/min at 40W) during RF delivery as recommended by the
manufacturer for clinical use of each catheter. An Ampere RF generator
(Abbott) was connected to deliver 550 kHz unmodulated sine-wave RF
energy pulses in a temperature-controlled mode (maximum temperature
40\selectlanguage{english}). Different power settings, contact intensities, RF duration, and
catheter orientation were used during the experiment, as discussed in
the following sections.

Ablation protocol

To obtain a range of lesion sizes, myocardial lesions were created at
separate sites with contact force set at 5, 15 and 25g, and power
settings set at 20, 30 and 40 W. For each contact force and power
setting, RF delivery was delivered for 10, 20, 30, 45 and 60 seconds.
The catheter was placed perpendicularly and parallelly to the tissue
(Figure 1B). Three lesions for each combination of settings were created
(270 lesions for each catheter). After creating every lesion, the
ablation electrode and the electrode--tissue interface were examined for
char formation. The incidence of an audible pop was noted.

Lesion assessment

After RF delivery, lesion surface was measured as shown in Figure 1C.
The myocardium was cross-sectioned along the surface length at the level
of each lesion. The cross-sectioned area was also measured as shown in
Figure 1C. Each lesion was measured with a dial caliper with a
resolution of 0.1 mm by one observer; the observer was not blinded to
the lesion protocol. Surface area and lesion volume were calculated from
the following formulae:

Lesion volume = (1/6) x \selectlanguage{greek}π \selectlanguage{ngerman}× (e\textsuperscript{2} × d + c×
a\textsuperscript{2}/2)

Lesion surface area = \selectlanguage{greek}π \selectlanguage{ngerman}× a/2 × b/2 (4)

Lesions with steam-pops were excluded from the lesion size analysis.

Statistical analysis

The data are presented as median (interquartile range). Continuous
variables were compared by Wilcoxon rank-sum test. Categorical variables
were compared by an \selectlanguage{greek}χ\selectlanguage{english}\textsuperscript{2} test or Fisher's exact test.
Significant differences were further evaluated by using Bonferroni's
method for pairwise multiple comparisons. A P-value \textless{} 0.05 was
considered statistically significant. All statistical analyses were
performed with R software (The R Foundation for Statistical Computing,
Vienna, Austria).

\textbf{Results}

RF delivery

A summary of the total lesion count (N=270 lesions for each catheter)
including steam-pops and char formation and parameters of RF-delivery is
shown in Table 1. Average power was significantly higher with the
TactiCath\textsuperscript{TM} SE catheter compared to
FlexAbility\textsuperscript{TM} SE (19W vs. 20W, p=0.004 at 20W setting;
27W vs. 29W, p\textless{}0.001 at 30W setting; 34.5W vs. 38W,
p\textless{}0.001 at 40W setting), reflecting the lower temperature
control rate (0\% vs. 0\% at 20W; 1.1\% vs. 20\%, p\textless{}0.001 at
30W; 3.3\% vs. 46.7\% at 40W). Steam-pops were observed more frequently
with the TactiCath\textsuperscript{TM} SE catheter at 30W (1.1\% in
FlexAbility\textsuperscript{TM} SE vs. 8.9\% in
TactiCath\textsuperscript{TM} SE, p=0.034) and 40W (13.3\% in
FlexAbility\textsuperscript{TM} SE vs. 57.8\% in
TactiCath\textsuperscript{TM} SE, p\textless{}0.001).

Lesion characteristics

Lesion characteristics are summarized in Table 2. Lesions with
steam-pops were excluded from the lesion metrics. At 20W, the
TactiCath\textsuperscript{TM} SE catheter provided larger lesions than
the FlexAbility\textsuperscript{TM} SE catheter (depth: 4.0mm vs. 3.8mm,
p=0.021, surface area: 26.4mm\textsuperscript{2} vs.
30.0mm\textsuperscript{2}, p=0.068; lesion volume:
175.1mm\textsuperscript{3} vs. 149.0mm\textsuperscript{3}, p=0.067).
When the catheter was placed perpendicularly to the tissue, lesion depth
(4.4mm vs. 4.0mm, p=0.014), surface area (29.2mm\textsuperscript{2} vs.
22.7mm\textsuperscript{2}, p=0.005) and lesion volume
(175.1mm\textsuperscript{3} vs. 126.1mm\textsuperscript{3}, p=0.018)
were significantly larger with the TactiCath\textsuperscript{TM} SE
catheter. However, when the catheter was placed parallelly, no
difference in lesion characteristics was observed between these two
catheters. The same findings were also observed at 30W and 40W settings.
However, comparison of lesion sizes in 40W was less reliable due to
exclusion of multiple points due to more frequent steam-pops with the
TactiCath\textsuperscript{TM} SE catheter (52/90 {[}57.8\%{]} vs. 11/90
{[}12.2\%{]}, p\textless{}0.001).

A positive relationship between lesion volume and RF duration was
observed for both catheters as shown in Figure 2. With perpendicular
catheter placement, lesions were generally larger with the
TactiCath\textsuperscript{TM} SE than FlexAbility\textsuperscript{TM} SE
catheters (Figure 2A,C), while no significant difference in lesion size
was observed with parallel catheter placement (Figure 2B,D).

Temperature control

As shown in Table 1, RF-regulation due to the temperature-control
setting was more frequently observed with the
FlexAbility\textsuperscript{TM} SE catheter at 30W (20\% vs. 0\%,
p\textless{}0.001) and 40W (46.7\% vs. 3.3\%, p\textless{}0.001)
settings. Further, as shown in Table 3, this finding was more marked
with perpendicular catheter placement than with a parallel angle at 30W
(31.1\% vs. 8.9\%, p=0.016) and 40W (66.7\% vs. 26.7\%) settings, which
resulted in lower average power delivery with perpendicular catheter
placement. In contrast, RF-delivery was not frequently regulated by the
temperature-control setting regardless of the catheter orientation in
any power settings with the TactiCath\textsuperscript{TM} SE catheter
(Table 3).

Adverse event rates

As shown in Table 1, no char formation was observed but 72/540 (13.3\%)
(n=12 with FlexAbility\textsuperscript{TM} SE and n=60 with
TactiCath\textsuperscript{TM} SE, P\textless{}0.001) steam-pops were
observed. At both 30W (1.1\% vs. 8.9\%, p=0.034) and 40W (12.2\% vs.
57.8\%, p\textless{}0.001) settings, use of the
FlexAbility\textsuperscript{TM} SE catheter significantly reduced the
incidence of steam-pops.

As shown in Table 4, power [?]40W (Odds ratio (OR) 53.0,
p\textless{}0.001), contact force[?]25g (OR 2.1, p=0.047), RF duration
\textgreater{}30s (OR 8.0, p\textless{}0.001), parallel angle (OR 2.1,
p=0.045), and impedance drop [?]20\selectlanguage{greek}Ω \selectlanguage{english}(OR 3.0, p=0.005) remained as positive
predictors of steam-pop but use of the FlexAbility\textsuperscript{TM}SE
catheter (OR 0.07, p\textless{}0.001) was negatively associated with
steam-pops by multivariate analysis.

\textbf{Discussion}

To the best of our knowledge, this is the first study comparing the
lesion metrics and safety profiles of two open irrigated ablation
catheters from Abbott Medical (FlexAbility\textsuperscript{TM} SE and
TactiCath\textsuperscript{TM}SE), demonstrating that:

Compared to the TactiCath\textsuperscript{TM} SE catheter, use of the
FlexAbility\textsuperscript{TM} SE catheter leads to a significantly
lower incidence of steam-pops, but produces smaller lesions with
perpendicular catheter placement.

Regulation of RF-delivery due to the temperature-control setting was
more frequently observed with the FlexAbility\textsuperscript{TM} SE
catheter.

Difference in lesion characteristics between catheters

In our study, the FlexAbility\textsuperscript{TM} SE catheter produced
smaller lesions than the TactiCath\textsuperscript{TM} SE catheter,
especially for perpendicular catheter placement (Figure 3A). A higher
rate of temperature control in the FlexAbility\textsuperscript{TM} SE
catheter, resulting in a lower average power, can partially explain this
finding. However, lesion size was smaller with the
FlexAbility\textsuperscript{TM} SE catheter with perpendicular catheter
placement even at a 20W setting, in which temperature control was not
observed. Another possible explanation is that the
FlexAbility\textsuperscript{TM} SE catheter has a larger tip size of 8Fr
4mm, compared to 8Fr 3.5mm for the TactiCath\textsuperscript{TM} SE
catheter. In general, the current density of a larger tip catheter is
lower for the same power setting, and therefore the current density of
the FlexAbility\textsuperscript{TM} SE catheter should be lower,
resulting in smaller lesion creation under the same power settings (5).
Additionally, Flexability\textsuperscript{TM} SE has more efficient
cooling effect than TactiCath\textsuperscript{TM} SE due to differences
in irrigation profile.

Frequency of steam-pops

Our analysis suggests that high power, high contact force, long RF
duration and large impedance decrease were independent predictors of
steam-pop, which is consistent with previous studies (6-9).
Additionally, our study demonstrated that parallel catheter placement
was positively associated and use of the
FlexAbility\textsuperscript{TM}SE catheter was negatively associated
with steam-pops. The safety of the TactiCath\textsuperscript{TM} SE
catheter has been shown in a randomized controlled clinical study for
paroxysmal atrial fibrillation patients (10). However, the superiority
of the FlexAbility\textsuperscript{TM} SE catheter in avoiding
steam-pops was demonstrated in the present study (20W:0\% 30W:1.1\% 40W:
12.2\% in FlexAbility\textsuperscript{TM}SE, and 20W:0\% 30W:8.9\%
40W:57.8\% in TactiCath\textsuperscript{TM} SE), whilst the incidence of
steam-pops with the TactiCath\textsuperscript{TM} SE catheter was
similar to the previous reports of TactiCath\textsuperscript{TM} Quartz
catheter (Abbott, St. Paul, MN) and IntellaNav MiFi OI catheter (Boston
Scientific, Marlborough, MA) (11,12).

Since temperature control plays an essential role in preventing
steam-pops and char formation, the FlexAbility\textsuperscript{TM} SE
catheter benefits from a high temperature control rate. Although
parallel catheter placement was an independent predictor of steam-pop in
our study, this finding has not yet been confirmed by other studies. One
study reported that greater tissue heating with a perpendicular compared
to parallel catheter placement is accompanied by increased incidence of
steam pops (13). In contrast, larger lesion volume and larger impedance
decrease, known as predictors of steam pop, have been observed more
frequently with a parallel than perpendicular catheter placement in
several studies (14,15).

Although the ultimate reason for the higher incidence of steam-pops with
a parallel catheter placement in our study is unknown, we propose the
following possibilities. With the TactiCath\textsuperscript{TM} SE
catheter, the current density is known to be higher at the proximal
region of the tip than the distal region. When the catheter is placed
parallel to the tissue, the area of high current density connects with
the tissue. In the TactiCath\textsuperscript{TM} SE catheter, a lower
incidence of RF regulation based on the temperature-control setting may
result in a higher average power with parallel catheter placement,
leading to increased incidence of steam pops. However, the incidence of
steam-pops with the FlexAbility\textsuperscript{TM} SE catheter was
generally low, and further studies including tissue temperature
monitoring are required to better understand the impact of catheter
contact angle.

Regulation of RF-delivery under the temperature-control setting

As described above, regulation of RF-delivery under the
temperature-control setting may impact both lesion characteristics and
steam-pop events. We demonstrate in this study that this regulation was
more frequently observed with the FlexAbility\textsuperscript{TM} SE
catheter than the TactiCath\textsuperscript{TM} SE catheter (60
{[}22\%{]} vs. 4 {[}4\%{]}, p\textless{}0.001). Firstly, this may be due
to the location of the thermocouple in determining the sensitivity to
thermal change in the tissue during RF delivery. The location of the
thermocouple is only 0.3 mm proximal to the tip in the
FlexAbility\textsuperscript{TM} SE catheter, compared to 2.64mm in the
TactiCath\textsuperscript{TM} SE catheter. Our results compliment a
previous study showing that the tip temperature of the
FlexAbility\textsuperscript{TM} SE catheter provides better safety
feedback compared to the Thermocool\textsuperscript{TM} and ThermoCool
SF\textsuperscript{TM} catheters, where the thermocouple is located
2.0mm and 6.6 mm from the distal end of the tip (16).

Termination of RF-delivery in the FlexAbility\textsuperscript{TM} SE
catheter was more frequently observed with perpendicular catheter
placement. This may be due to the localized temperature measurement
capability of the catheter due to the distal placement and proximity to
tissue of the thermocouple. When the catheter is placed parallel to the
tissue, the kerfs direct irrigation flow towards the tissue surface thus
enabling effective cooling of the tissue (16). However, when the
catheter is placed perpendicularly, the irrigation flow spreads from
proximal to distal, which may lead to relatively insufficient cooling
(Figure 4, see supplemental VIDEO).

Clinical implications

The present study suggests that RF application should be performed in
accordance with the characteristics of each catheter (Figure 3B). The
FlexAblility\textsuperscript{TM} SE catheter has a thermocouple at the
distal end of the tip, which enables it to monitor tissue temperature
more accurately, therefore safer RF application can be performed.
Although lesion volume from the FlexAbility\textsuperscript{TM} SE
catheter is similar to that of the TactiCath\textsuperscript{TM} SE
catheter with parallel catheter placement, it becomes smaller when the
catheter is placed perpendicularly. The TactiCath\textsuperscript{TM} SE
catheter has an advantage in creating larger lesions even with a
perpendicular placement, but in order to ensure safety, risk factors for
steam-pops such as impedance decrease and contact force should be
carefully monitored, because of the lower sensitivity in measuring
tissue temperature due to the proximal location of the thermocouple.

Limitations

The primary limitation is that this study was performed on an in vitro
model and the results cannot be translated directly into clinical
practice. However, these limitations similarly affect both catheters, so
that differences between the two catheters may be preserved.

Secondly, CF was measured using a submersible load cell and not using a
catheter incorporating a CF sensor in both catheters because of the
absence of contact force sensing technology in the
FlexAbility\textsuperscript{TM} SE catheter. However, this technique did
provide a reliable correlation to CF for the
TactiCath\textsuperscript{TM} SE catheter (for perpendicular angle R =
0.97 and for parallel angle R = 0.77).

Finally, to avoid frequent temperature-control in ex-vivo setting, the
flow rate (=20ml/min) was used for FlexAbility\textsuperscript{TM} SE in
this study, which may result in smaller lesions.

\textbf{Conclusions}

Although the TactiCath\textsuperscript{TM} SE catheter produces larger
lesions, the FlexAbility\textsuperscript{TM} SE catheter may reduce
adverse events during RF-delivery. Catheter angle to the tissue should
be taken into consideration with the FlexAbility\textsuperscript{TM} SE
catheter in order to maintain a lesion volume similar to the
TactiCath\textsuperscript{TM} SE catheter.

\textbf{Acknowlegement}

We appreciate a technical support for this experiment from Mr. Kazuyoshi
Moriya, Mr. Masashi Uemoto, Mr. Ryoto Shiga, Miss. Miso Suzuki, and
Miss. Lisa Sakurai from Abbott Medical Japan LIS.

\textbf{References}

1. El Haddad M, Taghji P, Phlips T, et al. Determinants of acute and
late pulmonary vein reconnection in contact force-guided pulmonary vein
isolation: identifying the weakest link in the ablation chain. Circ
Arrhythm Electrophysiol. 2017;10:e004867.

2. Ariyarathna N, Kumar S, Thomas SP, Stevenson WG, Michaud GF. Role of
Contact Force Sensing in Catheter Ablation of Cardiac Arrhythmias:
Evolution or History Repeating Itself? JACC Clin Electrophysiol 2018; 4:
707-723.

3. Petersen HH, Chen X, Pietersen A, Svendsen JH, Hauns\selectlanguage{ngerman}ø S. Tissue
temperatures and lesion size during irrigated tip catheter
radiofrequency ablation: an in vitro comparison of
temperature-controlled irrigated tip ablation, power-controlled
irrigated tip ablation, and standard temperature-controlled ablation.
Pacing Clin Electrophysiol 2000; 23: 8-17.

4. Nakagawa H, Yamanashi WS, Pitha JV, Arruda M, Wang X, Ohtomo K,
Beckman KJ, McClelland JH, Lazzara R, Jackman WM. Comparison of in vivo
tissue temperature profile and lesion geometry for radiofrequency
ablation with a saline-irrigated electrode versus temperature control in
a canine thigh muscle preparation. Circulation. 1995; 91:2264--2273.

5. Barkagan M, Leshem E, Rottmann M, Sroubek J, Shapira-Daniels A, Anter
E. Expandable Lattice Electrode Ablation Catheter: A Novel
Radiofrequency Platform Allowing High Current at Low Density for Rapid,
Titratable, and Durable Lesions. Circ Arrhythm Electrophysiol 2019; 12:
e007090.

6. Ikeda A, Nakagawa H, Lambert H, Shah DC, Fonck E, Yulzari A, Sharma
T, Pitha JV, Lazzara R, Jackman WM. Relationship between catheter
contact force and radiofrequency lesion size and incidence of steam pop
in the beating canine heart: electrogram amplitude, impedance, and
electrode temperature are poor predictors of electrode-tissue contact
force and lesion size. Circ Arrhythm Electrophysiol 2014; 7: 1174-80.

7. Seiler J, Roberts-Thomson KC, Raymond JM, Vest J, Delacretaz E,
Stevenson WG. Steam pops during irrigated radiofrequency ablation:
feasibility of impedance monitoring for prevention. Heart Rhythm 2008;
5: 1411-6.

8. Theis C, Rostock T, Mollnau H, Sonnenschein S, Himmrich E, Kämpfner
D, Ocete BQ, Bock K, Münzel T, Konrad T. The Incidence of Audible Steam
Pops Is Increased and Unpredictable With the ThermoCool® Surround Flow
Catheter During Left Atrial Catheter Ablation: A Prospective
Observational Study. J Cardiovasc Electrophysiol 2015; 26: 956-962.

9. Bourier F, Popa M, Kottmaier M, Maurer S, Bahlke F, Telishevska M,
Lengauer S, Koch-Büttner K, Kornmayer M, Risse E, Brkic A, Reents T,
Hessling G, Deisenhofer I. RF electrode-tissue coverage significantly
influences steam pop incidence and lesion size. J Cardiovasc
Electrophysiol 2021; 32:1594-1599.

10. Reddy VY, Dukkipati SR, Neuzil P, Natale A, Albenque JP, Kautzner J,
Shah D, Michaud G, Wharton M, Harari D, Mahapatra S, Lambert H, Mansour
M. Randomized, Controlled Trial of the Safety and Effectiveness of a
Contact Force-Sensing Irrigated Catheter for Ablation of Paroxysmal
Atrial Fibrillation: Results of the TactiCath Contact Force Ablation
Catheter Study for Atrial Fibrillation (TOCCASTAR) Study. Circulation
2015; 132: 907-15.

11. Calzolari V, De Mattia L, Indiani S, Crosato M, Furlanetto A,
Licciardello C, Squasi PAM, Olivari Z. In Vitro Validation of the Lesion
Size Index to Predict Lesion Width and Depth After Irrigated
Radiofrequency Ablation in a Porcine Model. JACC Clin Electrophysiol
2017; 3: 1126-1135.

12. Tsutsui K, Kawano D, Mori H, Kato R, Ikeda Y, Sumitomo N, Fukaya H,
Iwanaga S, Nakano S, Muramatsu T, Matsumoto K. Characteristics and
optimal ablation settings of a novel, contact-force sensing and local
impedance-enabled catheter in an ex vivo perfused swine ventricle model.
J Cardiovasc Electrophysiol 2021. doi: 10.1111/jce.15253. Epub ahead of
print. PMID: 34559441.

13. Ching KC, Elayi CS, Oussama MW, Khan MN, Conor B, Karen P, Callahan
T, Zakaib J, Fahmy TS, Schweikert RA, Saliba W, Dresing T, Burkhardt JD,
Cummings JE, Arruda M, Natale A: Steam pops in real life: Confessions of
open irrigated catheters. Heart Rhythm 2007;4:S11(abstract).

14. Knecht S, Reichlin T, Pavlovic N, Schaer B, Osswald S, Sticherling
C, Kühne M. Contact force and impedance decrease during ablation depends
on catheter location and orientation: insights from pulmonary vein
isolation using a contact force-sensing catheter. J Interv Card
Electrophysiol 2015;43:297-306.

15. González-Suárez A, Berjano E, Guerra JM, Gerardo-Giorda L.
Computational Modeling of Open-Irrigated Electrodes for Radiofrequency
Cardiac Ablation Including Blood Motion-Saline Flow Interaction. PLoS
One 2016; 11:e0150356.

16. Winterfield JR, Jensen J, Gilbert T, Marchlinski F, Natale A, Packer
D, Reddy V, Mahapatra S, Wilber DJ. Lesion Size and Safety Comparison
Between the Novel Flex Tip on the FlexAbility Ablation Catheter and the
Solid Tips on the ThermoCool and ThermoCool SF Ablation Catheters. J
Cardiovasc Electrophysiol 2016; 27: 102-9.

\textbf{Tables}

Table 1. Summary\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
& Number of lesions & Number of lesions &\tabularnewline
\midrule
\endhead
& FlexAbility\textsuperscript{TM} SE & TactiCath\textsuperscript{TM} SE
& P-value\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}20W & 90 & 90 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}30W & 90 & 90 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}40W & 90 & 90 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Total & 270 & 270 &\tabularnewline
& Average power (W) & Average power (W) &\tabularnewline
& FlexAbility\textsuperscript{TM} SE & TactiCath\textsuperscript{TM} SE
& P-value\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}20W & 19 {[}19-20{]} & 20 {[}19-20{]} & 0.004\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}30W & 27 {[}25-28{]} & 29 {[}29-30{]} &
\textless{}0.001\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}40W & 34.5 {[}31-37{]} & 38 {[}38-39{]} &
\textless{}0.001\tabularnewline
& Temperature control & Temperature control &\tabularnewline
& FlexAbility\textsuperscript{TM} SE & TactiCath\textsuperscript{TM} SE
& P-value\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}20W & 0 & 0 & 1\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}30W & 18 (20.0\%) & 0 & \textless{}0.001\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}40W & 42 (46.7\%) & 3 (3.3\%) & \textless{}0.001\tabularnewline
& Steam-pop & Steam-pop &\tabularnewline
& FlexAbility\textsuperscript{TM} SE & TactiCath\textsuperscript{TM} SE
& P-value\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}20W & 0 & 0 & 1\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}30W & 1 (1.1\%) & 8 (8.9\%) & 0.034\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}40W & 11 (12.2\%) & 52 (57.8\%) & \textless{}0.001\tabularnewline
Char formation & 0 & 0 & 1\tabularnewline
\bottomrule
\end{longtable}

Table 2. Lesion size\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
& FlexAbility\textsuperscript{TM} SE & TactiCath\textsuperscript{TM} SE
& P-value\tabularnewline
\midrule
\endhead
20W & & &\tabularnewline
Total & N=90 & N=90 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion depth & 3.8 {[}2.8-4.4{]} & 4.0 {[}3.1-5.0{]} &
0.021\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Surface area & 26.4 {[}20.3-34.7{]} & 30.0 {[}23.9-34.5{]} &
0.068\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion volume & 149.0 {[}90.3-212.1{]} & 175.1 {[}99.7-279.5{]} &
0.067\tabularnewline
Perpendicular & N=45 & N=45 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion depth & 4.0 {[}2.7-4.5{]} & 4.4 {[}3.3-5.4{]} &
0.014\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Surface area & 22.7 {[}18.8-32.5{]} & 29.2 {[}23.5-37.4{]} &
0.005\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion volume & 126.1 {[}75.7-213.7{]} & 175.1 {[}97.8-281.0{]} &
0.018\tabularnewline
Parallel & N=45 & N=45 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion depth & 3.8 {[}2.9-4.2{]} & 3.9 {[}3.1-4.7{]} &
0.28\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Surface area & 28.7 {[}24.2-39.3{]} & 30.1 {[}26.7-33.8{]} &
0.78\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion volume & 165.3 {[}101.2-229.9{]} & 175.0 {[}106.7-274.8{]} &
0.63\tabularnewline
30W & & &\tabularnewline
Total & N=89 & N=82 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion depth & 4.7 {[}3.3-5.2{]} & 5.0 {[}3.8-6.1{]} &
0.019\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Surface area & 26.9 {[}22.1-37.3{]} & 30.9 {[}26.7-35.7{]} &
0.23\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion volume & 204.8 {[}131.0-332.5{]} & 281.4 {[}145.0-422.3{]} &
0.011\tabularnewline
Perpendicular & N=44 & N=41 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion depth & 4.6 {[}3.5-5.1{]} & 5.4 {[}4.1-6.3{]} &
0.015\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Surface area & 23.2 {[}20.0-26.3{]} & 28.7 {[}22.3-32.9{]} &
0.009\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion volume & 183.2 {[}107.7-227.9{]} & 304.3 {[}156.2-437.8{]} &
0.002\tabularnewline
Parallel & N=45 & N=41 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion depth & 4.9 {[}3.2-5.3{]} & 4.6 {[}3.5-5.9{]} &
0.39\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Surface area & 34.6 {[}27.1-46.2{]} & 32.7 {[}28.6-37.8{]} &
0.25\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion volume & 241.8 {[}143.0-353.9{]} & 252.5 {[}143.4-382.6{]} &
0.66\tabularnewline
40W & & &\tabularnewline
Total & N=79 & N=38 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion depth & 5.0 {[}4.0-6.0{]} & 5.0 {[}4.3-6.0{]} &
0.437\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Surface area & 34.0 {[}28.3-44.6{]} & 42.1 {[}33.7-51.7{]} &
\textless{}0.001\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion volume & 268.8 {[}163.8-392.0{]} & 270.2 {[}175.2-423.0{]} &
0.346\tabularnewline
Perpendicular & N=41 & N=24 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion depth & 4.8 {[}4.0-5.9{]} & 5.1 {[}4.5-6.1{]} &
0.06\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Surface area & 28.7 {[}21.2-33.0{]} & 45.1 {[}39.1-54.2{]} &
\textless{}0.001\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion volume & 216.5 {[}127.7-288.8{]} & 310.0 {[}177.2-430.5{]} &
0.009\tabularnewline
Parallel & N=38 & N=14 &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion depth & 5.2 {[}4.1-6.2{]} & 5.0 {[}4.0-6.0{]} &
0.426\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Surface area & 40.6 {[}35.0-51.7{]} & 38.5 {[}31.3-46.3{]} &
0.217\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}Lesion volume & 337.8 {[}202.9-461.9{]} & 236.7 {[}180.6-418.8{]} &
0.201\tabularnewline
\bottomrule
\end{longtable}

Table 3. Temperature control and average power by catheter placement\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
& Perpendicular & Parallel & P-value\tabularnewline
\midrule
\endhead
FlexAbility\textsuperscript{TM} SE & & &\tabularnewline
Temperature control & & &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}20W & 0 & 0 & 1\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}30W & 14 (31.1\%) & 4 (8.9\%) & 0.016\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}40W & 30 (66.7\%) & 12 (26.7\%) & \textless{}0.001\tabularnewline
Average power (W) & & &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}20W & 20 {[}19-20{]} & 19 {[}19-20{]} & 0.26\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}30W & 25 {[}23-28{]} & 28 {[}26-29{]} &
\textless{}0.001\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}40W & 31 {[}27-35{]} & 36 {[}33-38{]} &
\textless{}0.001\tabularnewline
TactiCath\textsuperscript{TM} SE & & &\tabularnewline
Temperature control & & &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}20W & 0 & 0 & 1\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}30W & 0 & 0 & 1\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}40W & 3 (6.7\%) & 0 & 0.24\tabularnewline
Average power (W) & & &\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}20W & 20 {[}19-20{]} & 20 {[}19-20{]} & 0.83\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}30W & 29 {[}29-30{]} & 29 {[}29-30{]} & 1\tabularnewline
\begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}40W & 38 {[}38-39{]} & 39 {[}38-39{]} & 0.003\tabularnewline
\bottomrule
\end{longtable}

Table 4. Predictors of steam-pop\selectlanguage{english}
\begin{longtable}[]{@{}llllll@{}}
\toprule
\begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
Steam-Pop (-) N=468\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
Steam-Pop (+) N=72\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
Univariate\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
Multivariate\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
OR (95\% CI)\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Catheters\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
TactiCath\textsuperscript{TM}: 210 (44.9\%)
FlexAbility\textsuperscript{TM} SE: 258 (55.1\%)\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
TactiCath\textsuperscript{TM}: 60 (83.3\%)
Flexablity\textsuperscript{TM}: 12 (16.7\%)\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
\textless{}0.001\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
\textless{}0.001\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
0.07 (0.03-0.16) for FlexAbility\textsuperscript{TM} SE\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Power\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
20W: 180 (38.5\%) 30W: 171 (36.5\%) 40W: 117 (25.0\%)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
20W: 0 (0\%) 30W: 9 (12.5\%) 40W: 63 (87.5\%)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Power\emph{\textgreater{}}40W \textless{}0.001\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Power\emph{\textgreater{}}40W \textless{}0.001\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
53.0 (20.8-135.0)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Contact force\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
5g: 164 (35.0\%) 15g: 154 (32.9\%) 25g: 150 (32.1\%)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
5g: 16 (22.2\%) 15g: 26 (36.1\%) 25g: 30 (41.7\%)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Weight\emph{\textgreater{}}25g 0.11\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Weight\emph{\textgreater{}}25g 0.047\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
2.1 (1.0-4.2)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
RF duration\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
10s: 106 (22.6\%) 20s: 102 (21.8\%) 30s: 90 (19.2\%) 45s: 86 (18.4\%)
60s: 84 (17.9\%)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
10s: 2 (2.8\%) 20s: 6 (8.3\%) 30s: 18 (25.0\%) 45s: 22 (30.6\%) 60s: 24
(33.3\%)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Duration\textgreater{}30s \textless{}0.001\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Duration\textgreater{}30s \textless{}0.001\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
8.0 (3.6-17.4)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Parallel\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
128 (48.8\%)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
42 (57.5\%)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.16\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.045\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
2.1 (1.0-4.1)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Impedance drop\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
17.5 {[}13.8-23.0{]}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
26.0 {[}20.0-29.3{]}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Imp drop\emph{\textgreater{}}20\selectlanguage{greek}Ω \selectlanguage{english}\textless{}0.001\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Imp drop\emph{\textgreater{}}20\selectlanguage{greek}Ω \selectlanguage{english}0.005\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
3.0 (1.4-6.4)\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

\textbf{Figure legends}

\textbf{Figure 1.}

(A) Catheter tips of both catheters. The
Flexibility\textsuperscript{TM}SE ablation catheter has a laser-cut 4-mm
flexible 8Fr tip, which is irrigated from the proximal to distal end
through the laser-cut kerfs. The TactiCath\textsuperscript{TM} SE
ablation catheter has a 3.5-mm 8Fr tip and has 6-hole irrigation holes
on the side of the tip. Both catheters have a single thermocouple
embedded within the tip for temperature monitoring, and the distance
from the tip is 0.3mm in the FlexAbility\textsuperscript{TM} SE catheter
and 2.64mm in the TactiCath\textsuperscript{TM} SE catheter.

(B) Scheme of catheter orientation. The catheter was placed
perpendicularly or parallelly to the tissue.

(C) Scheme of the surface and cross-sectioned lesion. Surface area and
lesion volume were calculated from the following formulae:

surface area = \selectlanguage{greek}π \selectlanguage{ngerman}× a/2 × b/2.

lesion volume = (1/6) × \selectlanguage{greek}π \selectlanguage{ngerman}× (e\textsuperscript{2} × d + c×
a\textsuperscript{2}/2).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}



\textbf{Figure 2.}

Lesion volume for each power and catheter contact angle. In
perpendicular lesions, lesion volume tended to be larger for the
TactiCath\textsuperscript{TM} SE catheter than for the
FlexAbility\textsuperscript{TM} SE catheter. However for the parallel
lesions, no significant differences were seen at any RF duration and
power settings between catheters.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}



\textbf{Figure 3.}

(A) Sample image of cross-sectioned lesions. All lesions were created
under the same settings of 30W, 10g and 30s duration. The left two
lesions were created by perpendicular catheter placement, whereas the
right two lesions were created by parallel catheter placement.

(B) Summary of the features of FlexAbility\textsuperscript{TM} SE and
TactiCath\textsuperscript{TM} SE catheter lesions.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}



\textbf{Figure 4.}

The images of irrigation flow of FlexAbility\textsuperscript{TM} SE
using green dye.

(A) When the catheter is placed parallel to the tissue, irrigation flow
spreads both from the proximal to distal end through laser-cut kerfs and
from four holes on the distal end of the tip.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image4/image4}

\end{center}
\end{figure}

(B) When the catheter is placed perpendicular to the tissue, the distal
holes were obstructed the by the tissue contact, resulted in irrigation
flow spreading only from the proximal laser-cut kerfs, which may provide
insufficient cooling.



\textbf{Supplementary Figure 1.}

Relationship between contact force measured from the
TactiCath\textsuperscript{TM} SE catheter and weight on a scale. In the
perpendicular angle lesions, weight on the scale had a very strong
positive linear relationship to the CF on
TactiCath\textsuperscript{TM}SE (R = 0.97), whereas in the parallel
angle lesions, weight on the scale had a weaker yet still strong
positive linear relationship (R = 0.77).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image5/image5}

\end{center}
\end{figure}

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

