Radiation Dose is Significantly Reduced by Use of Contact Force Sensing Catheter During Circumferential Pulmonary Vein Isolation
Giuseppe Stabile, MD1, Antonio De Simone, MD2, Francesco Solimene, MD3, Assunta Iuliano, MD1, Vincenzo La Rocca, MD2, Vincenzo Schillaci, MD3, Alfonso Panella, MD1, Gergana Shopova, MD2, Felice Nappi, MD3, Francesco Urraro, MD3, Giovanni Russo, MD4, Giovanni Napolitano, MD5, Paola Chiariello, MD6
1Casa di Cura Mediterranea, Napoli.2Clinica San Michele, Maddaloni (CE).3Clinica Montevergine, Mercogliano (AV).4Ospedale San Leonardo, Castellammare di Stabile (NA).5Ospedale di Giugliano (NA).6Santa Maria dell’Olmo, Cava dei Tirreni (SA), Italia.
The creation of a durable radiofrequency (RF) lesion depends on several parameters, including catheter tip electrode size and composition, tip orientation, temperature, RF pulse duration, power, blood flow, and catheter to tissue contact. The development of new contact force (CF) sensor catheters has allowed the measurement of the tip to tissue CF during the RF ablation procedure. Here, we describe the clinical experience obtained using CF catheters for atrial fibrillation ablation, with a specific focus on the impact of CF technology on acute procedural data (procedure and fluoroscopy time).
Corresponding Address : Giuseppe Stabile, MDVia SS Martiri Salernitani 24, 84123 Salerno, Italia.
Catheter ablation (CA) has become a well established treatment option for recurrent, symptomatic, drug-resistant atrial fibrillation (AF). Isolating or encircling all accessible pulmonary veins (PVs) is recognized as the cornerstone of any ablation approach.1 One of the major limitation of CA of AF is the high rate of recurrences, during the short- and long-term follow-up, mainly due to electrical reconnection of the PVs. Therefore, more durable and transmural lesions produced by radiofrequency energy (RF) are desirable to improve the procedural outcome.2,3 Crucial in the determining of the efficacy of RF lesion is the electrode-tissue contact. The optimization of electrode–tissue contact may have a two potential benefits.1 First, it allow a more effective RF delivery to tissue with less energy dissipated into the circulating blood pool and creation of more predictable and reliable lesions. This may impact on both the procedure parameters and long-term clinical outcome. Second, monitoring the electrode–tissue contact may help reduce the excessive contact and the complications possibly related to catheter manipulation inside the heart. Here, we describe the clinical experience obtained using CF catheters for AF ablation, with a specific focus on the impact of CF sensing technology on acute procedural data (procedure and fluoroscopy time).
Contact Force Sensing In Catheter Ablation
The efficacy of RF ablation is to a large extent determined by the ability to create durable, transmural lesions. Lesion formation, including durability, is dependent on several interacting factors including catheter tip size, irrigation, stability and orientation to the myocardium, power delivery, ablation duration, and catheter-tissue CF. Yokoyama et al4 showed a direct correlation between CF and the resulting lesion volume in a canine thigh muscle preparation. Using this catheter at constant RF power (saline irrigation) in the canine thigh muscle preparation, tissue temperature and lesion size increased significantly with increasing CF. The incidence of steam pop and thrombus also increased with increasing CF. The incorporation of real-time CF measurement in an irrigated ablation catheter helped to optimize the selection of RF power and RF application time to maximize RF lesion formation and reduce the risk of steam pop and thrombus in clinical application. Until recently, 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.5 The accuracy of these surrogate measures has not been extensively validated.
In this setting steerable sheaths have been introduced to improve CF during AF ablation.6 Ullah et al7 recently demonstrated that steerable-sheaths increased ablation CF, however, there were region-specific heterogeneities in the extent of increment, with some segments where they failed to increase CF.
olved the technology of catheter ablation. Two irrigated CF sensing
catheters are now available: the TactiCath™ (St. Jude Medical, USA)
(TC) (Figure 1) and the ThermoCool® SmartTouch™ (Biosense
Webster, USA) (ST) (Figure 2). The TC catheter measures the CF
by micro-deformations of optical fibers, whereas the ST catheter
measures micro-deformations of a precision spring connecting the
catheter shaft and tip. In bench testing, both systems have a CF
resolution of less than 1 gram.
Figure 1. A 3D reconstruction of left atrium by means of the TactiCath™ (St. Jude Medical, USA) catheter. Local contact force values are displayed

Figure 2. A 3D reconstruction of left atrium by means of the ThermoCool® SmartTouch™ (Biosense Webster, USA) catheter. Local contact force value is displayed

The theoretically possible benefits of CF sensing technology are
numerous.
Safety may be improved by reducing the risk of perforation
during catheter manipulation and ablation. Although several initial
experiences8-12 comparing the CF catheters with standard openirrigated
tip catheter in AF ablation failed to demonstrate a reduction
in complication rate with the use of CF sensing catheters, recently
Acka et al13 evaluated if CF catheters reduce cardiac perforations
and other major complications and offer equal safety compared to
the non CF catheters and magnetic navigation system, in 1.517
ablation procedures. Complications occurred in 11.3% (n=172) of
the procedures. In 2.8% (n=43) a major complication occurred, 0.9%
(n=13) had a perforation, 8.5% (n=129) had a minor complication
and 2 patients died (0.1%). No cardiac perforation occurred in the
CF group, which was significantly different from non CF procedures
(0.0% vs. 1.6%; relative risk 0.76, 95% CI 0.74-0.79, P=0.031) and
equal to magnetic navigation system (0.0%). This was also observed
in the AF subgroup (557 patients) (0.0% vs. 3.3%; RR 0.67, 95% CI
0.63-0.72, P=0.021), and the occurrence of major complications was
lower for CF versus non CF procedures (2.1% vs. 7.8%, P=0.010).
They concluded that CF-guided CA is superior to non CF catheter
with regard to procedural safety and avoidance of cardiac perforation.
This difference was due to a reduction of cardiac perforation and
major complications in the AF subgroup.
Although clinical practice is suggesting that increasing CF
improves RF lesion formation, there are no studies correlating RF
lesion size to CF in the beating heart. However CF sensing catheters
allowed a lower incidence of acute reconnection, and less need of
complementary segmentary RF applications.14-16
Impact Of CF On Fluoroscopy Time
Reddy et al17 were the first to study the relationship between
contact force and clinical outcome during RF catheter ablation of
atrial fibrillation in the TOCCATA study. Thirty-two patients with
paroxysmal AF underwent PV isolation by using a radiofrequency
ablation catheter with a CF sensor integrated at its tip (TC). They
failed to demonstrate any impact of CF values on procedural and
fluoroscopy times, although they observed a trend towards a reduced
fluoroscopy time (from 55±32 min vs 32±24 ms, p=0.25) in patients in
which the mean CF was > 20 gr as compared with patients in which
the mean CF was ≤ 10 gr. Similar results were reported by Wutzler
et al18 They analyzed 143 patients who underwent PV isolation.
In 31 patients, PV isolation was performed by monitoring the
catheter-tissue contact with a sensing catheter (TC). One hundred
and twelve patients in whom conventional PVI was performed
without CF information, using an open irrigated ablation catheter
(CoolPath, IBI/St. Jude Medical, St. Paul, MN, USA) served as the
control group. Circumferential PV isolation was performed with a
3D-Mapping-System (Ensite NavX, St. Jude Medical). A significant
reduction in procedure duration was seen in the CF mapping group
(128.4 ±29 min vs. 157.7 ±30.8 min, p = 0.001). There were no
significant differences observed in ablation time, total ablation energy
or fluoroscopy time, although all were reduced in the CF group.
On contrary using the ST catheters several study demonstrated a
relevant the impact of CF technology on fluoroscopy and procedure
time during AF ablation (Table 1).
Table 1. Impact of CF sensing technology on on procedural and fluoroscopy time
Study | Important features | CF sensing
technology | Aims and methods | Fluoroscopy time | Procedure time | Key findings |
---|
Reddy et
al 17
2012 | 32 PAF | Optical fibers | an OIC with CF
mapping capabilities | Higher CF was not associated to changes
in fluoroscopy time (32±24 vs 55±32
min, p=0.25) | Higher CF was not associated
to changes in procedure time
(211±88 vs 188±51 min, p=0.61) | CF did not affect procedural
parameters |
Wutzler et
al 18
2014 | 143 with PAF and
PerAF | Optical fibers | an OIC
or an OIC with CF
mapping capabilities | There were no significant differences
observed in fluoroscopy time, although
reduced
in the contact force group | Procedure duration was
significantly shorter in the
contact force group (128.4 ±29
min vs. 157.7 ±30.8
min, p = 0.001). | the use of CF information
resulted in a shorter procedure
time |
Martinek et
al 8 2012 | 50 PAF | Precision
spring | a standard 3.5-mm
OIC or a catheter with
CF measurement
capabilities | 28.6 ±17.4 vs 23.6±13.1 min, p= 0.312 | 185±46 vs 154±39 min
p= 0.022 | The use of CF sensing technology
was able to significantly reduce
ablation and
procedure times in PVI. |
Marion et al
9 2014 | 60 PAF | Precision
spring | a new OIC CF catheter
or a non-CF OIC | CF use was associated with significant
reductions in fluoroscopy exposure (20.1
± 4 vs 26.7
± 5 minutes, p < 0.01) | CF technology was associated with
a significant
reduction in
overall procedure time | the use of CF information
resulted in a shorter procedure and
fluoroscopy times |
Stabile et al
19 2014 | 95 PAF | Precision
Spring | a new OIC with CF
sensing | Patients in whom the mean CF during
ablation was > 20 g required shorter
procedural time (92±23 vs.160±67 min,
p = 0.01) as compared with patients in
whom this value was < 10 g. | value below the median of 543
gs required longer procedural
(158.0±74.0 vs. 117.0±52.0 min,
p = 0.004)
times as compared with those in
whom FTI was above this value | CF affected procedural
parameters, in particular
procedural and fluoroscopy
times, without increasing
complications |
Sciarra et al
10 2014 | 63 PAF | Precision
spring | impact of a standard
OIC, SF OIC and CF
catheter | ST and CF catheter obtained a reduction
of fluoroscopy time (OIC 34 ± 18 min, CF
20 ± 10 min, p < 0.001; SF 21 ± 13 min,
p = 0.02 vs OIC) | STc resulted in a reduction of
procedural time (TCc 181 ± 53 min,
STc 140 ± 53 min, p < 0.001; SFc
170 ± 51 min, p = NS vs TCc). | Both the CF and the SF OIC
catheters significantly reduced
radiofrequency and fluoroscopy
times, as well as pulmonary veins
reconnection rate at 30 min.
Moreover, the CF catheter reduced
overall duration of the procedure |
Jarman et
al 11 2014 | 600 with PAF and
PerAF | Precision
spring | CF and non CF
catheters | the use of CF catheters was associated
with reduced fluoroscopy time in
multivariate analysis (reduction by 7.7
(5.0-10.5) minutes; p<0.001) | | Fluoroscopy time was lower when
CF technology was employed in all
types of AF ablation procedures |
Sigmund et
al 12 2015 | 198 with PAF and
PerAF | Precision
spring | 3.5-mm OIC with CF
measurement
capabilities and a
standard OIC | total fluoroscopy time could be
significantly reduced from 28.5 ± 11.0 to
19.9 ± 9.3 minutes (P = 0.0001) | Procedural data showed a
significant decline in overall
procedure time of 34 minutes (p =
0.0001; 225.8 ± 53.1 vs 191.9 ±
53.3 minutes). | The use of CF technology was able
to significantly reduce ablation,
procedure, and fluoroscopy times
as well as dose in RFCA of AF |
PAF= paroxysmal atrial fibrillation; OIC= open-irrigated-tip catheter; CF= contact force; PVI= pulmonary vein isolation; FTI= force-time integral; SF= surround flow; PerAF= persistent atrial fibrillation
Martinek et a18 assessed the impact of direct catheter force
measurement on acute procedural parameters during RF CA in
50 consecutive patients with paroxysmal AF. Fifty consecutive
patients with paroxysmal AF who underwent their first procedure
of circumferential PV isolation were assigned to either RF CA using
(1) a standard 3.5-mm open-irrigated-tip catheter (Thermocool®,
NavistarTM; Biosense Webster) or
(2) a catheter (ST) with contact force measurement capabilities. All
RFA were performed using a 3-D electroanatomic mapping system
with CT integration (Carto3®; Biosense Webster). Procedural data
showed a remarkable decline in ablation time (RF time needed for
PV isolation) from 50.5 ± 15.9 to 39.0 ± 11.0 minutes (P = 0.007)
with a reduction in overall procedure duration from 185 ± 46 to 154
± 39 minutes (P = 0.022). In parallel, the total energy delivered could be significantly reduced from 70,926 ± 19,470 to 58,511 ± 14,655
Ws (P = 0.019). The number of acute PV reconnections declined
from 36% to 12% (P = 0.095).
Marion et al (9) studied 60 patients with paroxysmal AF comparing
circular antral CA (guided by Carto 3® System, BiosenseWebster)
using either a new open-irrigated CF catheter (ST) or a non-CF
open-irrigated catheter (EZ Steer Thermocool, Biosense Webster).
Overall, 30 patients were enrolled in each group. Though complete
PV isolation was achieved in all cases in both groups, CF use was
associated with significant reductions in fluoroscopy exposure
(20.1±4 vs 26.7±5 minutes, p < 0.01) and RF time (45.2±18 vs
65.4±22 minutes, p= 0.01).
Stabile et al,19 in a multicentre prospective study, assessed the effect
of direct CF measurement on acute procedural parameters during RF
CA of AF. All the patients underwent the first ablation procedure
for paroxysmal AF with antral PV isolation, aiming at entry and exit
conduction block in all PVs, by means of a open-irrigated tip catheter
with CF sensing (ST), guided by Carto 3® System (BiosenseWebster).
Ninety-five patients were enrolled in nine centres and successfully
underwent ablation. Overall procedure time, fluoroscopy time, and
ablation time were 138.0+67.0, 14.3+11.2, and 33.8+19.4 min,
respectively. The mean CF value during ablation was 12.2+3.9 g. Force
time integral (FTI) analysis showed that patients achieving a value
below the median of 543.0 gs required longer procedural (158.0+74.0 vs. 117.0+52.0 min, p= 0.004) and fluoroscopy (17.5+13.0 vs. 11.0+7.7
min, p = 0.007) times as compared with those in whom FTI was
above this value. Patients in whom the mean CF during ablation was
> 20 g required shorter procedural time (92.0+23.0 vs.160.0+67.0
min, p = 0.01) as compared with patients in whom this value was <
10 g.
Sciarra et al10 analyzed the impact of the ST catheter and the
Surround Flow (BiosenseWebster) catheter (SF) and ThermoCool
(BiosenseWebster) catheter, in terms of feasibility and acute efficacy,
in 63 patients with paroxysmal AF who underwent PV antral isolation,
guided by Carto 3® System (BiosenseWebster). They found that the
use of both ST and SF catheters obtained a reduction of fluoroscopy
time (ThermoCool 34±18 min, ST 20±10 min, p<0.001; SF 21±13
min, p=0.02 vs ThermoCool) and RF time (ThermoCool 41±13 min,
ST 30±14 min, p=0.013; SF 30±9 min, p<0.01 vs ThermoCoolC).
The use of ST catheter resulted in a reduction of procedural time
(ThermoCool 181±53 min, ST 140±53 min, p<0.001; SF 170±51
min, p=NS vs ThermoCool). The percentage of isolated PVs was
comparable between groups (ThermoCool 96 % vs ST 98 % vs SF 96
%; p=NS). The percentage of deconnected PVs at 30 min was lower
in ThermoCool (89 %) than in ST (95 %) and in SF (95 %) group
(p<0.05).
Jarman et al11 studied the impact of CF sensing technology on
the clinical outcome of ablating AF. A total of 600 AF ablation procedures (200 using CF sensing and 400 using non-CF catheters)
performed between 2010 and 2012 (46% paroxysmal, 36% persistent,
18% long-lasting persistent) were analyzed. First time AF ablation
procedures employing CF catheter (ST) from 4 centers were
matched retrospectively to those without CF catheter (ThermoCool,
BiosenseWebster, and SF) in a 1:2 manner by type of AF. Among all
cases, the use of CF sensing catheters was associated with reduced
fluoroscopy time in multivariate analysis (reduction by 7.7 (5.0-10.5)
minutes; p<0.001). Complication rates were similar in both groups.
Sigmund et al12 assessed the impact of direct CF measurement on
acute procedural parameters and outcome of RF CA for paroxysmal
and persistent AF. Ninety-nine consecutive patients with paroxysmal
(63.6%) or persistent AF underwent left atrial RF CA using a 3.5-
mm open-irrigated-tip catheter with CF measurement capabilities
(ST). For comparison a case-matched cohort with standard openirrigated-
tip catheters (ThermoCool, BiosenseWebster) was used
(99 patients). Procedural data showed a significant decline in RF
ablation time from 52 ± 20 to 44 ± 16 minutes (P = 0.003) with a
remarkable mean reduction in overall procedure time of 34 minutes
(P = 0.0001; 225.8 ± 53.1 vs 191.9 ± 53.3 minutes). In parallel, the
total fluoroscopy time could be significantly reduced from 28.5 ±
11.0 to 19.9 ± 9.3 minutes (P = 0.0001) as well as fluoroscopy dose
from 74.1 ± 58.0 to 56.7 ± 38.9 Gy/cm2 (P = 0.016). Periprocedural
complications were similar in both groups.
Many factors justify the reduction in procedural and fluoroscopy
time observed with CF sensing catheters. It may relate to increased
operator’s confidence during navigation, related to the confidence in
the validity of geometry produced by CF sensing feedback,20 or to the
reduction in time required to complete contiguous lesions. Olson et
al21 demonstrated that the decreased lesion size due to intermittent
contact can be overcome by increasing duration of ablation time.
The CF sensing technology giving the feedback on the quality of
catheter-tissue contact helps to reduce the number of RF pulses with
intermittent or poor contact which require longer ablation times and
often fluoroscopy time. Moreover avoiding ablation at sub-optimal
CF may reduce late development of gaps within linear lesions, often
performed during AF ablation. Finally, the reduced incidence of
acute reconnection, and less need of complementary segmentary RF
applications14-16 allow a reduction in the overall procedure time and
therefore also in fluoroscopy time.
Although the great amount of the study showed a positive impact
of CF sensing catheter on acute procedural data and above all
procedural and fluoroscopy time, several issue remain to be clarified.
The overall quality of the studies which evaluated the impact of
the new CF catheters in AF ablation is poor: none of them is a
randomized one, some are retrospectively, only few are multicenter
studies. Second, whereas the studies using the ST catheter showed a
significant reduction in the fluoroscopy time, this was not observed
in the study18 using the TC catheter. However only few patients were
enrolled. Further studies using this technology are warranted to assess
this issue. Third, the ST catheter has usually been compared with the
Thermocool®, NavistarTM (BiosenseWEbster) catheter. Only one
study10 compared the ST with the SF, and in this case no difference
on procedural and fluoroscopy times were founded.
CF sensing technology appears to significantly impact on short term results with shorter procedural and fluoroscopy times, lower
incidence of acute reconnection, and less need of complementary
segmentary radiofrequency applications. Further randomized studies
are warranted to confirm these preliminary data and to compare the
CF with other technologies aiming to improve AF CA.