Abstract:
Introduction : Radiofrequency ablation (RFA) slow pathway
modification for catheter ablation of AV nodal reentrant tachycardia
(AVNRT) is traditionally performed using a 4mm, non-irrigated (NI) RF
ablation catheter. Slow pathway modification using irrigated,
contact-force sensing (ICFS) RFA catheters has been described in case
reports, but outcomes have not been systematically evaluated.
Methods : Acute procedural outcomes of 200 consecutive patients
undergoing slow pathway modification for AVNRT were analyzed. An ICFS
3.5mm RFA catheter (ThermoCool SmartTouch STSF, Biosense Webster, Inc.)
was utilized in 134 patients, and a 4mm NI RFA catheter (EZ Steer,
Biosense Webster, Inc.) was utilized in 66 patients. Electroanatomic
maps were retrospectively analyzed in a blinded fashion to determine
proximity of ablation lesions to the His region.
Results : Baseline characteristics of patients in both groups
were similar. Total RF time was significantly lower in the ICFS group
compared to the NI group (5.53±4.6 vs. 6.24±4.9 min, p=0.03). Median
procedure time was similar in both groups, ICFS 108.0 (87.5-131.5) vs.
NI 100.0 (85.0-125.0) min, p=0.2). Ablation was required in closer
proximity to the His region in the NI group compared to the ICFS group
(14.4 ± 5.9 mm vs, 16.7 ± 6.4 mm, respectively, p=0.01). AVNRT was
rendered non-inducible in all patients, and there was no arrhythmia
recurrence during follow-up in both groups. Catheter ablation was
complicated by AV block in one patient in the NI group.
Conclusion : Slow pathway modification for catheter ablation of
AVNRT using an irrigated, contact-force sensing RFA catheter is
feasible, safe, and may facilitate shorter duration ablation while
avoiding ablation in close proximity to the His region.
Keywords: radiofrequency ablation, atrioventricular nodal
reentrant tachycardia, irrigated catheter, slow pathway modification
Introduction :
Radiofrequency ablation (RFA) is a safe and effective treatment option
for AV nodal reentrant tachycardia (AVNRT), and is most frequently
performed using a 4mm, non-irrigated (NI) RF ablation catheter in a
temperature-controlled mode, although use of irrigated RF ablation
catheters is increasingly common. The location of RF application for
slow pathway modification is selected to optimize efficacy while
maintaining a safe distance to the presumed location of the compact AV
node to minimize risk of creating AV block.1 Optimal
energy delivery during RFA requires stable contact at the
catheter-tissue interface. Utilization of irrigated, contact-force
sensing (ICFS) catheters has increased over time for a range of
indications.2-4 Availability of contact-force data
during ablation may facilitate effective ablation, while ablation
electrode irrigation may improve efficiency lesion creation,
particularly when power during NI RF ablation is limited by temperature
at the ablation electrode.
Although slow pathway modification using ICFS RFA catheters has been
described in case reports, outcomes have not been systematically
evaluated. The aim of this study is to compare acute outcomes of RF
ablation for slow pathway modification using a 3.5mm ICFS RFA catheter
to those using a NI 4mm RF ablation catheter.
Methods :
Retrospective chart review identified 200 consecutive patients who
underwent slow pathway modification for AVNRT between March 2019 and
June 2021. Patients were excluded from the study if they had prior
ablation, were undergoing an additional ablation at time of AVNRT
ablation or had unavailable mapping data. All available medical records,
including baseline characteristics, ECG, and electrophysiology study
were reviewed and analyzed by investigators. Data collection and
analysis was performed according to protocols approved by the NYU
Langone Health Institutional Review Board. Surface and intracardiac
electrograms (EGMs) were digitally recorded and stored (EP Workmate,
Abbott Medical, Inc.). All procedures were performed under conscious
sedation and AVNRT diagnosis was confirmed using established
criteria.5, 6 An ICFS 3.5mm RFA catheter (ThermoCool
SmartTouch STSF, Biosense Webster, Inc.) was utilized in 134 patients,
and a 4mm NI RFA catheter (EZ Steer, Biosense Webster, Inc.) was
utilized in 66 patients. NI RFA was performed with an initial power
setting of 50W in a temperature control mode and temperature limit 55°C
and RF generator in “fast mode.” ICFS RFA was performed in a power
control mode with an initial power setting of 35W and standard
irrigation settings and RF generator in “STSF mode.” Power settings
were not altered intraoperatively. Non-fluoroscopic 3-dimensional
mapping was performed using the Carto 3 (Biosense-Webster, Inc.,)
mapping system in all patients. Catheter ablation was considered acutely
successful if AVNRT was rendered noninducible, and there was ≤ 1
inducible AV nodal reentrant echo beat with isoproterenol infusion up to
20mcg/min. Electroanatomic maps (EAM) were analyzed in a retrospective
fashion by blinded investigators to determine the shortest distance
between an EAM point with a His electrogram and the nearest ablation
lesion (His distance) as a surrogate marker of ablation-related AV
conduction injury risk (Figure 1). Intraprocedural data including
radiofrequency (RF) time, case length, fluoroscopy time and details of
electrophysiology study were collected and analyzed.
Patients were followed at least three months after the date of their
procedure. Patients received routine outpatient follow-up at 1-month
post-ablation and subsequently at the discretion of their referring
cardiologist. The primary outcomes were survival free of recurrent AVNRT
after slow pathway modification, and occurrence of major complications
including ablation related AV block. Secondary outcomes were procedure
duration, RF time, and shortest distance between the electroanatomic
mapping point with a His electrogram and the nearest ablation lesion.
Categorical data were analyzed across the 2 groups with the chi squared
test and were reported as frequencies and percentages. Continuous data
were analyzed using the Mann-Whitney U test and were reported as mean+ standard deviation. SPSS Statistics software 25.0 (IBM, Armonk,
NY) was used for data analysis.
Results :
The baseline clinical characteristics of the 134 patients who underwent
NI RFA and 66 patients who underwent ICFS RFA were similar (Table 1).
Baseline electrophysiologic features of patients in both groups were
similar apart from obstructive sleep apnea (OSA) (Table 2). A steerable
sheath was used more frequently in patients who underwent ICFS catheter
ablation compared to patients who underwent ablation with a NI catheter
(88% vs. 51%, respectively, P<0.001). Six patients underwent
transseptal puncture in the ICFS group, as compared to two in the NI
groups. Total RF time was significantly lower in the ICFS group compared
to the NI group (5.5±4.6 vs. 6.2±4.9 min, p=0.03). Median procedure time
was similar in both groups, ICFS 108 (88-132) min vs. NI 100 (85 -125)
min, p=0.2). Ablation was required in closer proximity to the His region
in the NI group compared to the ICFS group (14 ± 6 mm vs, 17 ± 6 mm,
respectively, p=0.01). The proportion of cases in which ablation was
required within 1 cm of a location with a His electrogram was
significantly greater in the NI catheter group as compared to the ICFS
group (20% vs. 9%, respectively, p=0.04, Figure 2). AVNRT was
successfully rendered uninducible in all patients.
After ablation, patients had at-least one post-procedure outpatient
evaluation. There were no recurrent arrhythmias noted during the
follow-up period (Table 3). One patient in the NI ablation group
developed persistent AV block with a His distance of 17 mm, while there
were no cases of persistent AV block in the ICFS ablation group. There
were no vascular access complications, including AV fistula or hematoma,
in either cohort.