DOI: 10.1161/CIRCEP.113.001094
Relationship between Catheter Contact Force and Radiofrequency Lesion Size
and Incidence of Steam Pop in the Beating Canine Heart: Electrode Amplitude,
Impedance and Electrode Temperature are Poor Predictors of
Electrode-Tissue Contact Force and Lesion Size
Running title: Ikeda et al.; Contact Force vs. RF Lesion Size
Downloaded from http://circep.ahajournals.org/ by guest on June 15, 2017
Atsushi Ikeda, MD, PhD1; Hiroshi Nakagawa, MD, PhD1; Hendrik
dri
rikk La
Lamb
Lambert,
mber
mb
ert,
er
t P
t,
PhD
hD2;
shar S
Sharma,
harm
ha
rmaa M
rm
MD,
D M
MPH1;
Dipen C. Shah, MD3; Edouard Fonck, PhD2; Aude Yulzari, MS2; Tushar
JJan
Ja
n V. Pit
Pitha,
tha
ha,, MD
M
MD,, Ph
PhD
hD4; Ralph
Ralp
Ra
lphh Lazzara,
lp
Lazz
La
zzar
zz
a a,, M
MD
D1; Warren
W rren
Wa
rrren
nM
M.. Ja
JJackman,
ck
kma
man,
n, M
MD
D1
Heart Rhythm
h hm
hythm
m IInstitute,
nsti
ns
titu
ti
tu
utee, 4De
Department
epa
part
r me
rt
ment
n ooff Pa
Pathology,
ath
holog
oggy, V
Veterans
e er
et
e an
ns Ad
Admi
Administration
mini
mi
n st
ni
s ra
rati
tion
ti
on Medical
Med
edic
iccall Ce
Center,
e
University of Ok
Okla
Oklahoma
l ho
h maa H
Health
ealt
lhS
Sciences
cie
i nces C
Center,
ente
t r, O
Oklahoma
klah
kl
homa Ci
City
City,
ty, OK;
ty
O ; 2En
OK
Endosense
E
d sense SA
do
SA;; 3Ho
Hospital
o
Cantonal
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Ca
n on
nt
o al
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de Geneve,
Gene
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neevee, Geneva,
Gene
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neva
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Swit
Switzerland
itze
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z rllan
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1
Correspondence:
Hiroshi Nakagawa, MD, PhD
Heart Rhythm Institute
University of Oklahoma Health Sciences Center
1200 Everett Drive (TUH-6E-103)
Oklahoma City, OK 73104
Tel: 405-271-9696
Fax: 405-271-7455
E-mail: [email protected]
Journal Subject Codes: [22] Ablation/ICD/surgery, [5] Arrhythmias, clinical electrophysiology,
drugs
1
DOI: 10.1161/CIRCEP.113.001094
Abstract:
Background - Electrode-tissue CF is believed to be a major factor in RF lesion size.
The purpose of this study was to determine, in the beating canine heart, the relationship between
contact force (CF) and radiofrequency (RF) lesion size and the accuracy of predicting CF and
lesion size by measuring electrogram amplitude, impedance and electrode temperature.
Methods and Results - Eight dogs were studied closed chest. Using a 7F catheter with a 3.5mm
irrigated electrode and CF sensor (TactiCath, ENDOSENSE SA), RF applications were delivered
to 3 separate sites in the right ventricle (RV, 30W, 60 sec, 17 ml/min irrigation) and 3 sites in the
left ventricle (LV, 40W, 60 sec, 30 ml/min irrigation) at either: 1) low CF (median
8g);
(
g); 2))
Downloaded from http://circep.ahajournals.org/ by guest on June 15, 2017
moderate CF (median 21g); and 3) high CF (median 60g). Dogs were sa
sacrificed
sacr
crif
cr
ific
if
iced
ic
ed aand
nd llesion
esio
esio
ionn size
was measured. At constant RF and time, lesion size increased significantly
with
ntly w
ithh in
it
iincreasing
crea
cr
easi
ea
sing
si
n ccontact
ng
force (p<0.01).
incidence
increased
01)
1). Th
1)
Thee in
nci
c de
dence of a steam pop increas
ased
as
ed with both increasing
i crea
in
easing CF and higher ppower.
ea
Peak electrode
temperature
correlated
with
lesion
The
rodee tempera
ro
atu
turre co
corr
rrel
rr
elat
el
ated
at
ed ppoorly
oorl
ryw
ith les
esionn ssize.
ize
zee. T
he ddecrease
he
e reas
ec
a e in
as
i iimpedance
m ed
mp
dan
nce during
the RF application
lesions
in
lication
li
ica
cati
tion correlated
ti
corrre
r latted w
well
ell w
with
i h le
it
lesion
esiionn si
size
ize fo
for
or les
lesions
sionss iin
n tthe
he LV,
V, but
u lesss w
ut
well
elll forr le
les
es
the RV. There
wass a ppoor
relationship
CF
and
amplitude
h wa
here
w
oor re
rela
lationsh
la
shhip
p between
nC
F an
nd the am
ampl
p itud
udde of the
hee bipolar
bip
ip
pol
o ar or unipolar
unipp
ventricular electrog
electrogram,
current,
gram,
m, uunipolar
niipo
p la
l r iinjury
nju
jury
y current
t, andd im
iimpedance.
p dance.
pe
Conclusions
strikingly
with
increasing
ns - RF lesion
leesiion size
lesi
siz
i e and
an
nd the
t e incidence
th
iinncide
ciide
d nc
ncee off ssteam
tteeam ppop
opp increase
inc
ncre
reas
asee st
triki
riiki
king
ngly
l w
ly
ithh in
it
incr
increa
crea
ea
CF. Electrogram parameters and initial impedance are poor predictors of CF for RF ablation.
Key words: catheter ablation, radiofrequency, ventricular arrhythmia, atrial fibrillation, conatct
force
2
DOI: 10.1161/CIRCEP.113.001094
Introduction
Several experimental studies have shown that electrode-tissue contact force (CF) is a major
determinant of lesion size during radiofrequency (RF) ablation.1-7 Until recently, contact force
(CF) could not be measured directly by ablation catheters. As a result, surrogate measures of CF
have been proposed, including electrogram amplitude, pre-ablation impedance and changes during
ablation in electrode temperature and impedance.1,3,4
The accuracy of these surrogate measures
has not been extensively validated.
Downloaded from http://circep.ahajournals.org/ by guest on June 15, 2017
Recently, two designs of ablation catheters have been developed
ed to measure rea
real-time
al-ti
tim
m
catheter-tissue CF during catheter mapping and RF ablation. One type of catheter
cath
ca
thet
th
etter uuses
ses three
se
thrree
th
re
optical fibers
CF
deformable
e to
ers
to measure
meas
me
a uree C
as
F as the microdeformation
microdeformatiion
o of a deform
mablee bbody
ody in the catheter tip
-12
2
(TactiCath,, ENDOSENSE
SA).
EN
NDOSENS
SE SA
A). 88-12
Thee other
othe
her catheter
catthetter inc
incorporates
ncor
orpo
or
poraatees a sm
small
mall spri
spring
ingg cconnecting
onnecctii the
elect
c ro
ct
rode
d to th
de
the cath
theter
th
h
sshaft
ha an
ha
haft
nd us
uses a magn
gnettic tra
ans
n miitt
tter and
nd location
locati
tion sensors
ti
senss to
ablation tipp electrode
catheter
and
magnetic
transmitter
measure CF
F as th
the
he mi
microdeflection
icrod
oddeffle
l ctio
i n off the spr
spring
p ingg (THERMOCOOL
(T
THE
HERM
RMOC
RM
OCOO
OC
OO
OL SMARTTOUCH,
SMAR
SM
ARTT
AR
TT
TOU
O CH
CH, Biosense
B osee
Bi
13,14
,14
14
88-14
Webster, Inc).
nc)) 13
IInn bbench
ch
h ttesting,
testing
ti
bboth
oth
th systems
s st
stems
t
have
hhaa e a CF resol
resolution
oll ttion
io off less
l than
th 1gram
1gram.
1
Although clinical practice is suggesting that increasing CF improves RF lesion
formation,11,12 there are no studies correlating RF lesion size to CF in the beating heart. The
purpose of this study was to determine, in the canine beating heart: 1) the relationship between CF
and RF lesion size, as well as the incidence of steam pop; and 2) the accuracy of predicting CF and
RF lesion size by the surrogate measures of CF, i.e., intracardiac electrogram amplitude and
downstroke slope, pre-ablation impedance, and the change in electrode temperature and
impedance during RF delivery.
3
DOI: 10.1161/CIRCEP.113.001094
Methods
Contact Force Sensing Ablation Catheter
The 7 F quadripolar ablation catheter with a CF sensor (TactiCath, ENDOSENSE SA, Geneva,
Switzerland) has a 3.5 mm tip electrode with 6 small irrigation holes (0.4 mm diameter) around the
circumference, located 1.2 mm from the tip for saline irrigation during RF delivery (Fig 1). The
ablation electrode contains a thermocouple to measure the electrode temperature.
The CF sensor consists of a deformable body (elastic polymer) and 3 optical fibers (0.125
Downloaded from http://circep.ahajournals.org/ by guest on June 15, 2017
mm diameter, Fig 1) attached circumferentially around the deformablee body.
bodyy. Force on the
the
88,9,11,12
9 11,1
9,
11 12
11
deformable body changes the reflected wavelength of light in the 3 optical
ticall fibers.
fib
iber
ers.
s 8,
By
By
g the
he rreflected
efle
ef
leect
cted
e w
avelength, the system is ab
ble to calculat
a e th
at
he amplitude and displ
l the
monitoring
wavelength,
able
calculate
the
display
vector of the
he C
he
CF
F at 100 ms in
intervals.
nteerval
alss.
al
Experimental
n lM
ntal
Model
od
odel
d
The experimental
m
mental
l pprotocol
rotoco
co
ol was approved
ap
ppr
p oved
d bby
y th
the
he Un
U
University
iversity
ty off Ok
O
Oklahoma
laaho
h ma
m C
Committee
ommitt
tteee on
on thee Use
and Care off Animals
A
Animals.
niimall E
Eight
ight
ht mongrel
ell dogs
do weighing
eighing
eiighi
hin 31 to
t 39 kg
kg were
ere anestheti
anesthetized
theti
ti ed
d with
iith
th sod
sodium
odd
pentobarbital (30 mg/kg) and ventilated mechanically with room air. The right carotid artery was
cannulated for monitoring arterial pressure. A 7 F, 20-electrode catheter was inserted into the right
jugular vein and advanced into the coronary sinus under fluoroscopic guidance. A 10 F ultrasound
catheter (AcuNav, Acuson) was inserted into the left femoral vein and advanced into the right
atrium to be used for intracardiac echocardiography (ICE). Heparin (5,000 IU) was administered
intravenously, with additional doses, as necessary to maintain the ACT >250 seconds. Transeptal
puncture was performed under ICE and fluoroscopic guidance. The CF ablation catheter was
inserted into the left atrium through the transeptal sheath. The CF catheter was initially positioned
centrally within the left atrium, without endocardial contact (confirmed by ICE), to calibrate the
4
DOI: 10.1161/CIRCEP.113.001094
CF sensor to 0 g (baseline non-contact value). The CF ablation catheter was advanced into the left
ventricle (LV) for ablation. After LV ablation was complete, the transeptal sheath was withdrawn
into the right atrium and the CF ablation catheter was positioned into the right ventricle (RV).
Ablation was then performed in the RV as described below.
Ablation Protocol
RF applications were performed at 3 separate sites in the LV (septum, lateral free-wall and apical
region) and 3 separate sites in the RV (basal free-wall, medial wall of the outflow tract and apical
Downloaded from http://circep.ahajournals.org/ by guest on June 15, 2017
region). These 6 locations were sufficiently far apart to accurately identify
ntifyy during
g lesion
n
assessment. The 3 RF applications in the LV and the 3 RF applications in the
were
delivered
at
h RV w
he
eree de
er
deli
livv
li
3 different leve
levels
moderate
vels
ve
l ooff CF
ls
C (one
(oone each, randomized): 1) low
low
o CF (range 22-10
-100 gg,, median 8 g); 2) mo
o
CF (range 220-30
high
CF
(range
median
Fig
CF
0-30 g, mediann 21 g); aand
nd 33)) hi
igh C
F (ran
ange 550-100
0--1000 gg,, med
ediaan 60 gg,, Fi
F
g 2). C
F was
stabilized and
seconds
before
onset
the
a averaged
av
vera
erraged
d over th
the
h 5 se
eco
conds be
befo
fore tthe
for
h ons
he
set of
of th
he RF application.
appliica
cati
tion. Data
ti
D ta ffor
Da
or RF
applications
during
ns were not included
incl
in
cludded
cl
d if
if the
th
he catheter
cath
hetter pposition
ositiion and/or
and/
d//or movement
movvemen
nt had
h d changed
ha
ch
hange
geed du
ged
durin
ablation or if the
the C
CF
F measured
meas red
ed
d immediately
immediatel
i
edi
diattell postt ablation
abl
blati
ti had
had
d changed
ha ed
d (>5-10
((>5
>5 110
0 g).
g)) In
In order
rdd to
selectively examine the effect of CF on lesion size, RF applications were delivered at constant RF
power and application time. In the LV, RF applications were delivered at 40 Watts for 60 sec,
using a saline irrigation flow rate of 30 ml/min. RF applications in the RV were delivered at 30
Watts for 60 sec, using an irrigation flow rate of 17 ml/min. In the event of a steam pop (abrupt
small increase of impedance, audible or not, confirmed by histology with small cavitation or crater
formation) or impedance rise (>10 Ohms), the RF application was continued for the full 60 sec in
order to allow the comparison of lesion size. Lidocaine (100mg) was administered intravenously
just prior to ablation to prevent RF-induced ventricular fibrillation. Additional doses of lidocaine
were administered as needed.
5
DOI: 10.1161/CIRCEP.113.001094
A custom RF generator (Radionics, model RFG-3DJ) was used to allow the recording of
power, impedance and electrode temperature at 20 ms intervals. Intracardiac electrograms (bipolar
and unipolar signals), CF, RF power, impedance, and electrode temperature were monitored
continuously and recorded (LabSystem Duo, CR Bard, Inc).
The dogs were sacrificed 30 minutes after the final RF application. The hearts were excised
and stained with triphenyl terazolium chloride, which stains intracellular dehydrogenase a deep
red color, distinguishing viable (red) and necrotic (pale) tissue. The hearts were fixed in 10%
Downloaded from http://circep.ahajournals.org/ by guest on June 15, 2017
formalin and sectioned to measure RF lesion size (maximum depth, maximum
at
aximum diameter,
diameterr, ddepth
e
the maximum diameter and surface diameter).
Measurement
m nt of
men
o Electrogram
Ele
l ct
c ro
ogram Parameters
Bipolar electrograms
recorded
between
the
ectrrograms were
ec
re reco
corded
ed
d bet
twe
w en
en th
he tip eelectrode
lect
ctro
ct
rooddee and
nd 2ndd eelectrode
lecctrrodee and
and filt
filtered
terred
d at
Uniipo
pola
laa electrograms
lar
electtrog
ograms were
werre recorded
we
reco
ord
rded
ed
d bbetween
etween
t en tthe
h ttip
he
ip electrode
e ecttrode an
el
andd a ne
ed
dle
l ski
ki
30-500 Hz.. Unipolar
needle
skin
electrode, filtered
f
d at 11-500
-500
-5
00 H
Hz.
z. T
The
he ffollowing
olllowiingg el
electrogram
lectroggram measur
measurements
rem
e en
nts were obtained
obt
btai
aine
n d at each
ne
ablation site
ttee prior
rii to
t the
th onsett off the
the R
RF
F application:
pli
licati
tion 1) bipolar
bipoll ventricular
entric
triic llar potential
ott tiall amplitude
amplit
litt
li
(peak to peak); 2) bipolar ventricular potential mean negative dV/dt (amplitude / duration,
downstroke slope); 3) unipolar ventricular potential amplitude (peak to peak); 4) unipolar
ventricular potential mean negative dV/dt (amplitude / duration, downstroke slope); and 5)
unipolar injury current amplitude (Fig 2).
Statistical Analysis
Statistical analyses were performed using SAS software (version 9.2). The relationships between
average CF, peak electrode temperature and decrease in impedance (the impedance at the onset of
RF application minus the minimum impedance during the RF application) versus lesion depth and
lesion diameter were assessed by a mixed effects model using Proc Genmod, providing beta
6
DOI: 10.1161/CIRCEP.113.001094
coefficients for x variables and their corresponding 95% confidence intervals (CIs). Chi square test
and Fisher’s exact test was used to test the overall association between CF category and the
incidence of steam pop and impedance rise. The relationships between average CF, electrogram
amplitude, mean negative dV/dt (downstroke slope), injury current amplitude, impedance at the
onset of RF application and impedance decrease were assessed by a mixed effects model using
Proc Genmod. The relationship between the degree of impedance decrease and the occurrence of
steam pop was assessed by Mann-Whitney U test. A probability value of <0.05 was considered to
Downloaded from http://circep.ahajournals.org/ by guest on June 15, 2017
be statistically significant.
Results
Relationship
Contact
Force
Lesion
Size
Steam
Pop
hip between Co
hi
C
nttac
actt Fo
Forc
r e an
and
d Le
Lesi
s on S
ize aand
nd In
IIncidence
cciide
d ncee off S
teeam
mP
op
p
A total of 48
4 lesions
leesi
sion
onss were
on
were
r created
cre
reat
ated
at
ed in
ed
n tthe
hee 8 ddogs:
ogss: 244 lesions
og
lesio
ions
n in
ns
in the
th
he RV (30
(30 Watts,
Wat
a ts
ts,, 60
6 seconds)
seccon
onds
ds) at low
ds
CF (n=8), mod
moderate
Watts,
m
derrat
atee CF (n=8)
(n=
n=8)
8 aand
8)
nd hi
high
g CF (n=8);
gh
(n=
n=8)
8 ; an
8)
aand
d 24 llesions
e io
es
i nss in
i the
the LV (40
(400 W
a ts
at
ts,, 600 seconds)
se
at low CF (n
(n=8).
measurements
in
((n=8),
=8
8), mod
moderate
odder
e atte CF ((n=8)
n 8)
n=
8 aand
ndd hi
high
gh CF ((n
gh
n=8
8)).. Lesion
Leesi
L
sion
o mea
easu
sureemeents
ntts were
we e not
ot uutilized
tl
ti
the 4 transmural lesions observed in the RV (1 at moderate CF and 3 at high CF), since these values
would be artificially low. Lesion size was independent of the 3 locations in the RV and the 3
locations in the LV.
At constant RF power and application time, lesion depth and diameter increased
significantly with increasing contact force (Figs 3 and 4). Lesions at lower power (30 Watts) and
moderate CF were significantly deeper (6.7 ± 0.8mm vs. 5.9 ± 1.2 mm) and wider (9.6 ± 1.1 mm vs.
8.0 ± 1.9 mm) than lesions at higher power (40 Watts) at low CF (Fig 3C). Lesions at lower power
(30 Watts) and high CF were similar in depth and diameter to lesions at higher power (40 Watts) at
moderate CF (Fig 3C). Lesion depth and diameter correlated well with average CF for both RV
and LV. (Fig 4). Peak electrode temperature during the RF application correlated poorly with
7
DOI: 10.1161/CIRCEP.113.001094
lesion depth and diameter (Fig 5). The decrease in impedance during the RF application relatively
correlated well with lesion depth and diameter for lesions in the LV: 95% CI = (0.13, 0.28) and
95% CI = (0.20, 0.33), respectively, and in the RV: 95% CI = (0.03, 0.14) and 95% CI = (0.06,
0.19), respectively, Figs 6A and 6B.
The incidence of a steam pop increased significantly with increasing CF at 40 Watts
(p=0.03) and with higher power (40 Watts vs. 30 Watts, p=0.02, Fig 7). At 30 Watts in the RV, a
steam pop occurred during 0/8 RF applications at low CF, 1/8 RF applications at moderate CF and
Downloaded from http://circep.ahajournals.org/ by guest on June 15, 2017
1/8 RF applications at high CF. At 40 Watts in the LV, a steam pop occurred during
RF
g 0/8
/8 R
applications at low CF, 4/8 RF applications at moderate CF and 5/8 RF
applications
high
F appl
pllicattio
plic
i ns aatt hi
hig
gh CF.
gh
$QLPSHGDQFHULVH•2KPVLQFUHDVH
occurred
LPS
PSHG
PS
HGDQ
HG
DQQFH
F ULVVH •2KPVLQFUHDVH from
m the
thhe minimum
m value
vallue
u during RF) occurre
e only
in 3/8 RF applications
CF
Watts).
at
ap
ppllications at hhigh
hiigh
hC
F and
an hi
hhigh
gh ppower
ow
werr (40
40 W
Watts
atts
at
ts)). An
ts
n impedance
imppeda
danc
nce rise
s did
se
id not
noot occur
oc
lower CF or
Watts.
o at 330
0W
atts.
Relationship
Parameters
Contact
Force
Lesion
h p between
hip
bettween Surrogate
Surroga
g te P
arameters
t
and
dC
onta
t ctt F
orrce and
nd
dL
esio
i n Size
S ze
Si
The peak-to-peak
amplitude
downstroke
o peak
ak
k amplit
plit
lit de
d and
d ddo
o nstroke
stt ke slope
lo off the
th bi
bipolar
la and
d unipolar
nipolar
ipoll ventricular
entric
triic llar
potentials correlated poorly with CF (Fig 8A-8D). The amplitude of unipolar injury current
correlated better with CF, but still had a wide overlap in values (Fig 8E). The ratio of injury
current/unipolar ventricular potential amplitude correlated less well with CF than injury current
amplitude, Y=0.34 + 0.01*X, 95% CI = (0.002, 0.02), p=0.022 and Y=4.19 + 0.14*X, 95% CI =
(0.06, 0.22), p=0.006, respectively. Impedance at the onset of RF application (initial impedance)
also correlated very poorly with CF (Fig 8F). The degree of decrease in impedance during the RF
application correlated only slightly better with CF (Fig 8G). At higher RF power (40 Watts), the
occurrence of a steam pop correlated with the degree of impedance decrease (Fig 8H), but there
was no significant relationship between the time of steam pop and the degree of impedance
8
DOI: 10.1161/CIRCEP.113.001094
decrease (Fig 8I).
Discussion
To our knowledge, this is a first study to examine the relationship between RF lesion size and CF
in the beating heart. We found a very wide range of lesion size (depth and diameter) for RF
applications with varying CF, but same power and application time. Under these conditions
(constant RF power and time), lesion size correlated well with CF (Figs 3 and 4). Increasing from
low CF to high CF increased lesion depth by 70% at 30 Watts and by 90% at 40 Watts ((Fig
g 3C).
Downloaded from http://circep.ahajournals.org/ by guest on June 15, 2017
Lesions produced at 30 Watts and moderate CF were larger than lesions
produced
Watts and
ns pro
roodu
duce
cedd at 440
ce
0 Wa
low CF, and
moderate CF
nd lesi
lesions
sion
si
onss at 300 Wa
on
W
Watts
tts and high CF were si
similar
imi
m lar to lesions aatt 40 Watts and moder
(Fig 3). These
indicate
comparable
increasing
esee data indi
ica
catte th
tthat
at iincreasing
ncre
nc
r assin
re
ng CF
F is
i com
mpara
r bl
ra
blee to in
ncrrea
eassingg RF
RF power.
poower.
r
r.
By measuring
CF
prior
RF
meaasu
suri
riing C
F pr
prio
i r to the
io
hee oonset
nsset ooff an
nR
F application,
appl
ap
p ic
icat
atio
at
io
on, an
an appropriate
ap
ppr
prop
o ri
op
riat
atee RF
at
R power
pow
wer an
aand
n time
can be selected
achieve
(lesion
depth)
minimize
steam
Low
ectedd to
t ach
chie
ch
ieve
ie
vee eefficacy
ffic
ff
icac
ic
acyy (l
ac
lesio
es on de
es
dept
ptth)
h aand
nd m
i im
in
imiz
izee the
iz
the ri
risk
skk of
of st
stea
eam
ea
m po
pop.
p Lo
p.
L
w CF
may be compensated
mpensated
mpe
penssat
ated
ed
d bby
y dde
delivering
eli
l ve
veri
ringg hig
higher
igher
he RF power.
he
pow
ower
e . Th
Thee in
inci
incidence
ciide
d ncce off ssteam
team
te
a ppop
op may
ay bbee
decreased while maintaining similar RF lesion size by using lower RF power and maintaining
good CF.
Peak electrode temperature during RF applications was not predictive of lesion depth or
diameter (Fig 5). The decrease in impedance during the RF application (initial impedance minus
minimum impedance) correlated relatively well with lesion size (especially in the LV at 40 Watts,
Fig 6). The degree of impedance decrease correlated with the occurrence of a steam pop at higher
RF power (40 Watts), but did not correlate with the time of occurrence of the steam pop (Figs 8H
and 8I). One limitation of the impedance decrease is that this measure is not available before the
onset of the RF application.
This study also demonstrates that the surrogate parameters of CF have limited or no value.
9
DOI: 10.1161/CIRCEP.113.001094
Electrogram amplitude (unipolar and bipolar) and downstroke slope correlated very poorly with
CF. Even the amplitude of the injury current is a weak predictor of CF, although the presence of an
injury current indicates some contact. Impedance is also not predictive of the magnitude of CF.
These findings indicate the surrogate measures are very poor predictors of CF and confirm the
importance of directly measuring CF.
Study Limitation
A principal limitation of the study was that all RF applications were delivered for a relatively long
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interval (60 sec). The impact of CF on lesion size may be even greaterr during
g shorter RF
application times. The role of CF may also be greater or lesser at higher
her orr lower
l we
lo
werr RF power
pow
owee than
the 30 Watts
Watts
Further
t and
tts
andd 440
0 Wa
W
ttts used in this study. Furthe
her studies are re
he
rrequired
quuir
i ed to compare the
importancee off CF to diff
different
application
fer
erentt RF
RF power
powerr and
nd app
plicaati
tion ttime.
im
mee..
Clinical Implications
m ica
mpli
atio
tiions
Incorporating
real-time
measurement
RF
ablation
catheter
o poratiing real
orp
all-ti
tiime CF measureme
ntt in an iirrigated
rrig
igatted
ig
dR
F ab
blaattiion cathe
h te
t r sh
sshould
ouldd help
optimize the
maximize
hhee selection
ell ti off RF power
po er and
nd
d application
li ti ttime
im tto
o ma
iimi
mii e RF lesion
l io fformation
o ati
tio aand
reduce the risk of steam pop in clinical application.
Funding Sources: This study was supported in part by a grant from Endosense SA.
Conflict of Interest Disclosures: H Nakagawa, DC Shah and WM Jackman are consultants for
Endosense SA. H Lambert, E Fonck and A Yulzari are employees of Endosense SA. The other
authors report no conflicts.
References:
1. Avitall B, Mughal K, Hare J, Helms R, Krum D. The effects of electrode-tissue contact on
radiofrequency lesion generation. PACE. 1997;20:2899-2910.
2. Haines DE. Determinants of lesion size during radiofrequency catheter ablation: the role of
10
DOI: 10.1161/CIRCEP.113.001094
electrode-tissue contact force and duration of energy delivery. J Cardiovasc Electrophysiol.
1991;2:509-515.
3. Strickberger SA, Vorperian VR, Man KC, Williamson BD, Kalbfleisch SJ, Hasse C, Morady F,
Langberg JJ.. Relation between impedance and endocardial contact during radiofrequency catheter
ablation. Am Heart J. 1994;128:226-229.
4. Zheng X, Walcott GP, Hall JA, Rollins DL, Smith WM, Kay GN, Ideker RE. Electrode
impedance: an indicator of electrode-tissue contact and lesion dimensions during linear ablation. J
Interv Card Electrophysiol. 2000;4:645-654.
5. Eick OJ, Wittkampf FH, Bronneberg T, Schumacher B. The LEFTR-Principle: a novel method
to assess electrode-tissue contact in radiofrequency ablation. J Cardiovasc Electrophysiol.
1998;9:1180-1185.
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6. Wittkampf FHM, Nakagawa H. RF catheter ablation: lessons and lesions.
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esi
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on
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CE
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7. Biase LD,
Arruda M,
D, Natale
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a al
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A Barrerr
Barrerr C, Tan C, Elayi CS, Ching
Ching CK, Wang
Wangg P,
P, Al-Ahmad A, Arru
Burkhard JD
Schweikert
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D, Wisnoskey
Wisnosk
skey
sk
ey BJ,
BJ,, Chowdhury
Choowdhu
wddhu
hury
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y P,
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Marc
Ma
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Arm
rm
rmag
mag
agan
nij
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a L,
an
L, Litwak
Litw
wak K,
K, Schweike
Sc
Schw
chw
hwei
eike RA,
Cummings JE.
JE. Relationship
Relationsship between
betwee
be
een contact
ee
co
ontac
actt forces,
foorcces,, lesion
lesiionn characteristics,
charaacterissticss, “popping,”
“pop
op
pping
ng,
ng,”
,” and
and char
formation: Experience
with
robotic
system.
Cardiovasc
Electrophysiol.
Exp
xperiencce w
itth rob
obotic
icc nnavigation
avig
ig
igat
g tio
on sy
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em. J C
arrddiova
va
asc E
lect
ctro
ct
rophys
ro
y io
ys
ol.
2009;20:436-440.
3 4440.
36-44
8. Yokoyama
H,, Sh
Shah
DC,
Lambert
H,, L
Leo
G,, A
Aeby
N,, IIkeda
A,, Pi
Pitha
Sharma T,
ma K,
K, Nakagawa
Nakaga
gaw
wa H
ah
hD
C, L
ambe
b rt H
eo G
eb
by N
keeda
d A
Pith
ha JV
JV, Sha
Lazzara R, Jackman
WM.
Novel
sensor
radiofrequency
nW
M. N
M.
o ell contact
ov
con
o ta
tact
ct force
for
o ce
c se
sens
nssor inco
iincorporated
in
nco
corp
rpor
rp
orat
or
a ed
at
d iin
n iirrigated
r ig
rr
igat
atted ra
radi
d ofrequenn
ablation catheter
size
pop. Circ
Electrophysiol.
ath
ttheter
hette predicts
dictt llesion
esii si
i e andd incidence
incid
ide
off steam
te pop
Ci Arrhythm
A h thh El
t h
2008;1:354-362.
9. Shah DC, Lambert H, Nakagawa H, Langenkamp A, Aeby N, Leo G. Area under the real-time
contact force curve (force-time integral) predicts radiofrequency lesion size in an in vitro
contractile model. J Cardiovasc Electrophysiol. 2010;21:1038-1043.
10. Thiagalingam A, d’Avila A, Foley L, Guerrero JL, Lambert H, Leo G, Ruskin JN, Reddy VY.
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11. Kuck KH, Reddy VY, Schmidt B, Natale A, Neuzil P, Saoudi N, Kautzner J, Herrera C,
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Yulzari A, Lambert H, Neuzil P, Natale A, Kuck KH. The relationship between contact force and
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13. Perna P, Heist EK, Danik SB, Barrett CD, Ruskin JN, Mansour M. Assessment of catheter tip
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14. Martinek M, Lemes C, Sigmund E, Derndorfer M, Aichinger J, Winter S, Nesser HJ,
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Figure Legends:
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Figure 1: Schematic representation of the distal end of the 7F contact forcee (CF)
sensing
(CF) se
sens
nsin
ns
ingg ablation
in
ab
catheter. Th
The
sensor
three
optical
fibers
circumferentially
Fiber
T
he CF sens
sor iincludes
nncclude
lu
ude
dess th
hreee op
opti
tica
ti
c l fi
fibe
b rss attached
attac
acche
ache
hedd circ
ci
irc
rcum
umfe
um
ferenttia
fe
iall
llyy with
ll
wit
ithh Fi
ibe
b r Bragg
Gratings (FBG)
body.
the
deformable
FBG) to a de
FB
ddeformable
foorm
mab
ble bod
ody.
od
y CF
y.
C oon
n th
he de
efo
form
mable body
bod
oddy changes
ch
hange
g s thee FBG
ge
F G refractive
FB
reefrracc
index pattern
change in
rn wh
which
hicch ch
chan
changes
ange
an
g s th
ge
thee re
refl
reflected
flec
fl
ecte
ec
t d wa
wave
wavelength
vele
ve
lenggth ooff li
ligh
light
ghtt in tthe
gh
he 3 ooptical
ptic
pt
iccal ffibers.
ical
iber
ib
ers.
er
s. Th
Thee cha
reflected wavelength
w
h is
is pproportional
ropo
ro
port
po
rtio
rt
iona
io
ona
nall to CF
CF (magnitude
(mag
(m
agni
ag
nitu
ni
tude
tu
de and
andd angle),
ang
ngle
le)), measured
le
meas
me
asur
as
u ed aatt iintervals
ur
nter
nt
e vals of 1100ms.
Figure 2: Examples of measurements of electrogram parameters on a bipolar ventricular potential
(top) and unipolar ventricular potential (bottom). Electrogram amplitude was measured from
peak-to-peak. The mean negative dV/dt was measured as the amplitude of the downstroke divided
by its duration. The amplitude of injury current was measured on the unfiltered unipolar
electrogram from the baseline to the peak of ST elevation.
Figure 3: Radiofrequency (RF) ablation lesion size as function of low CF, moderate CF and high
CF. A. Examples of RF lesions (30 Watts, 60 sec) in the right ventricle (RV). Increasing from
low to high CF, increased the lesion depth from 4.8 mm to 8.7 mm and increased lesion diameter
12
DOI: 10.1161/CIRCEP.113.001094
from 5.9 mm to 9.4 mm. B. Examples of RF lesions (40 Watts, 60 sec) in the left ventricle (LV).
Increasing from low to high CF, doubled the lesion depth from 5.0 mm to 10.5 mm and almost
tripled lesion diameter from 5.7 mm to 15.0 mm. The crater in the high CF lesion resulted from a
steam pop. C. Lesion measurements (mean ± SD) at low, moderate and high CF for the RV (top)
and LV (bottom). Measurements include maximum depth, maximum diameter, depth at
maximum diameter and surface lesion diameter. Increasing from low to high CF, increased lesion
depth in the RV from 5.0 ± 0.7 mm to 8.5 ± 1.3 mm and increased lesion depth in the LV from 5.9
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± 1.2 mm to 11.2 ± 0.9 mm. Lesion measurements were not utilized inn the 4 transmural
lesions
transmuraal le
les
observed in the RV (1 at moderate CF and 3 at high CF)
Figure 4: R
Relationship
lesion
size.
Graphs
lesion
depth
function
of
elationship between
betweeen CF
CF and
d RF
F lesio
io
on si
ize. A.
A G
Gr
rap
phs off le
esion
on dep
pth
h as
as a fu
fun
nc
CF in the RV
(right
panel),
highly
B.
R (left
(le
left
ft panel)
ft
panell) and
d LV
LV (ri
igh
ghtt pane
neel)
l), showing
shhowiing a hi
high
ghlly ssignificant
gh
igniifiicant
ig
ntt rrelationship.
elatio
el
i nshi
hip. B
hi
Graphs of lesion diameter
diamete
teer as a ffunction
unctio
i n off C
CF
F iinn the
h R
RV
V (left
(llefft pa
ppanel)
neel)
l and
ndd LV
LV (r
((right
ight
ig
ht ppanel),
anel
an
e ),
) aalso
showing a si
relationship.
interval.
significant
i if
ifiic t relationship
lati
ti shi
hip CI
CI:confidence
nfid
fid
iinter
ntt all
Figure 5: Non-significant relationship between peak electrode temperature during the RF
application and RF lesion depth (A) and diameter (B).
Figure 6: Relationship between the decrease in impedance during the RF application and RF
lesion depth (A) and diameter (B).
Figure 7: Incidence of steam pop for RF applications at low, moderate and high CF in the RV (30
Watts for 60 sec, left panel) and LV (40 Watts for 60 sec, right panel).
13
DOI: 10.1161/CIRCEP.113.001094
Figure 8: Weak relationships between surrogate parameters and CF. Graphs of bipolar
electrogram amplitude vs. CF (A), mean negative dV/dt of the bipolar electrogram vs. CF (B),
unipolar electrogram amplitude vs. CF (C), mean negative dV/dt of the unipolar electrogram vs.
CF (D), amplitude of the unipolar injury current vs. CF (E), initial impedance (impedance at the
onset RF application) vs. CF (F) and impedance decrease vs. CF (G). The deference of the degree
of impedance decease between RF applications with and without steam pop (H), and the
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relationship between the degree of impedance decrease and the time off occurrence of th
the
he ssteam
t
pop (I).
14
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Relationship between Catheter Contact Force and Radiofrequency Lesion Size and Incidence of
Steam Pop in the Beating Canine Heart: Electrode Amplitude, Impedance and Electrode
Temperature are Poor Predictors of Electrode-Tissue Contact Force and Lesion Size
Atsushi Ikeda, Hiroshi Nakagawa, Hendrik Lambert, Dipen C. Shah, Edouard Fonck, Aude Yulzari,
Tushar Sharma, Jan V. Pitha, Ralph Lazzara and Warren M. Jackman
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Circ Arrhythm Electrophysiol. published online November 7, 2014;
Circulation: Arrhythmia and Electrophysiology is published by the American Heart Association, 7272 Greenville Avenue,
Dallas, TX 75231
Copyright © 2014 American Heart Association, Inc. All rights reserved.
Print ISSN: 1941-3149. Online ISSN: 1941-3084
The online version of this article, along with updated information and services, is located on the
World Wide Web at:
http://circep.ahajournals.org/content/early/2014/11/07/CIRCEP.113.001094
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