Abstract.
Background. Pulmonary veins (PV) reconnection is the most
common reason for atrial fibrillation (AF) recurrence. The
ablation-index is a marker of ablation lesion quality which use achieves
high percentages of first pass isolation and improved results of AF
ablation. Most operators use a double trans-septal approach with
confirmation of PV isolation with a circular mapping catheter. In the
present study we aimed to show that an ablation-index guided procedureusing a single trans-septal approach and ablation catheter only
would achieve adequate PV isolation while demonstrating the critical
role of the carina in PV isolation.
Methods. 76 consecutive patients with paroxysmal AF: 34
patients underwent WACA, 32 patients underwent WACA+ (including empiric
carina isolation) and 10 patients underwent a staged procedure of WACA
followed by WACA+ in case of lack of first pass isolation. All
procedures were performed via single trans-septal.
Results. Compared to WACA-only, WACA+ increased the odds of PV
isolation from 65% to 91%, p=0.012. In WACA-only, ablation of the
carina was needed to achieve PV isolation. The role of the carina was
confirmed in 10 patients with sequential ablation. PV isolation was
confirmed by inserting a circular mapping catheter through the single
trans-septal sheath. At 18 months of follow-up [IQR 15.2-20.8
months], freedom from AF was 84% for the entire cohort.
Conclusion. Our study confirms the high success rate of PV
isolation using ablation index and shows that this can be achieved via
single trans-septal crossing. Our study confirms the role of the carina
in PV isolation.
Introduction :
Radiofrequency (RF) catheter ablation is an accepted therapy for
patients with symptomatic, drug-refractory, paroxysmal atrial
fibrillation (AF). A fundamental step during this ablation procedure,
involves performing electrical isolation of the pulmonary veins (PVs) by
creation of a set of circular lesions around the pulmonary veins antrum
(WACA).1-10 However, permanent and complete isolation
of all pulmonary veins is challenging. In fact, electrical reconnection
of the pulmonary veins is the most frequent finding when a second
ablation procedure is performed following recurrence of atrial
fibrillation.11-16 Therefore, technological
innovations that will improve the thoroughness of ablation during WACA
are continuously developed.
The Visitag module with ablation-index was recently integrated in the
Carto 3V4 mapping system (Biosense Webster, Inc, Diamond Bar, CA,USA) as
an indicator of ablation lesion quality. The ablation-index formula
incorporates contact force (CF), power and ablation-delivery time into a
single value that also takes into account catheter stability at the time
of RF delivery. In a prospective study, Das et. al showed that lack of
achievement of minimum values of ablation-index, at any given pulmonary
vein segments, was predictive of pulmonary vein reconnection at a
repeated electrophysiology study performed two months
later.17 More recently, Hussein et al. reported a 97%
isolation of the pulmonary veins following a first pass of WACA when an
ablation index of 500 and 400 were used at the roof-ridge and the
posterior-inferior quadrants, respectively.18 In the
remaining 3% of WACA with lack of first pass isolation, additional RF
delivery was needed and this was invariably at the carina
level.18 In these studies, a double trans-septal
technique was performed to allow for the introduction of a circular
mapping catheter along the ablation catheter in the left atrium, to
monitor and confirm PV isolation during WACA. Continuous recording of
the PV electrograms during WACA may represent a potential bias since the
operator could instinctively ablate longer of more diffusely in area of
WACA associated with changes in activation on the circular mapping
catheter or leading to PV isolation.
Limiting the number of trans-septal crossings during an ablation
procedure is important, particularly for safety reasons but also for an
economic perspective. We therefore performed the present study to show
that: 1) An ablation-index guided procedure using a single
trans-septal approach would succeed in achieving complete acute PV
isolation while obviating the need for a double transeptal. 2) RF
ablation of the carina area is crucial for achieving complete PV
isolation. Accordingly, we tested the following new strategy: 1) WACA
based on the new ablatio-index was performed with a single trans-septal
puncture. 2) The completeness of pulmonary vein isolation was confirmed
with the ablation catheter. As part of the study protocol, at the end of
the procedure the ablation catheter was replaced by a standard circular
mapping catheter to confirm that the assessment of PV isolation made
with the ablation catheter is indeed correct. 3) We tested the
contribution of carina ablation to achieve acute complete PV isolation
by comparing the acute success rate (defined as first pass complete PV
isolation) among patients undergoing a standard WACA vs. patients
undergoing WACA plus carina isolation (WACA+).
Methods .
Study patients. The study included consecutive patients with
symptomatic, drug-refractory paroxysmal AF, referred for a first
ablation. All the procedures were performed by a single operator (R.R.)
experienced with atrial fibrillation ablation procedure, including the
use of contact-force sensing ablation-catheters and the use of Visitag
and ablation-index. The AF ablations were performed between December
2017 and April 2019. Outcome data were extracted from an institutional
review board-approved registry.
Atrial fibrillation ablation technique. The procedure was
performed under uninterrupted warfarin therapy (aiming for an INR of 2
on the day of the procedure) or after skipping a single dose of new oral
anticoagulants (NOAC). All antiarrhythmic agents, except amiodarone,
were discontinued before the procedure. A computerized tomography
angiogram (CTA) of the left atrium was performed before the ablation to
assess the left atrial size, PV anatomy and to exclude the presence of
left atrial appendage thrombi. Patients in whom the CTA could not
definitively exclude the presence of left atrial appendage thrombi
underwent a trans-esophageal echocardiogram (TEE) before or during the
procedure. The ablation procedure was conducted under general
anesthesia.
One decapolar and 1 quadripolar catheter were positioned in the coronary
sinus and the His bundle position through the right femoral vein. One
8.5F long sheath (SL1, St. Jude Medical, Minneapolis, USA) was
introduced into the left atrium with a single trans-septal puncture.
Intravenous bolus of heparin was injected intravenously just prior to
the trans-septal puncture and repeated as needed to maintain an
activated clotting time (ACT) of >350 seconds throughout
the procedure. All PVs were visualized by selective angiography. The PV
antrum was defined with angiography and the segmented left atrial CTA
imported in the Carto 3 mapping system (Biosense Webster). A Lasso
circular mapping catheter (Biosense Webster) was introduced through the
SL1 sheath into the left atrium for electrical mapping of the PVs and
then retrieved. At this point, an irrigated ablation catheter3.5-mm D-F
curve ablation catheter with smart-touch technology (Navistar
Thermocool, Biosense Webster) was introduced through the original SL1
sheath into the left atrium for ablation. In case of difficulties in
positioning the ablation catheter in the left atrium, the SL-1 sheath
was replaced with a steerable sheath (Agilis 8.5F, t. Jude Medical,
Minneapolis, USA). The ablation catheter was used to create a
fast-anatomic map (FAM) of the left atrium, to set landmarks (PV
drop-off points into the left atrium) necessary to merge the CTA scan of
the left atrium to the FAM (Carto Merge, Biosense Webster, Inc).
Ablation was performed with a “point by point” technique. Settings
were: catheter irrigation-flow rate of 18 mL/min, target temperature 45°
and maximal energy of 25 W for the posterior atrial wall and 30 W for
the ridge and carina areas. During the ablation we aimed to achieve a
contact force of 10 to 50 grams at all times. RF energy was applied at
each ablation site using the automated lesion tagging ablation-index to
mark the location and efficacy of each lesion. The ablation-index
settings were: catheter stability position minimum-time of 5 seconds,
and maximum range 3-4 mm, minimum force 3 g, (the blue and yellow marks
give two different contact force values) and lesion tag of 2 mm. The
maximal RF time at each ablation site was 60 seconds. We aimed for a
minimum ablation-index value of 415 for the back wall and posterior half
of the carinas, 515 for the anterior ridge, roof, inferior quadrants and
anterior half of the carinas. We aimed for ablation dots that overlap
each other along the WACA. The exclusion of gaps in between the dots was
also evaluated with the use of the grid function on the mapping system.
The grid function identifies all areas where radiofrequency energy was
delivered including those were Visitag did not tag the ablation due to
poor catheter stability. This feature allows for better identification
of potential gaps hiding in between the Visitag dots.
Ablation groups. The first 34 patients underwent two WACA
ablation lesions, each one encircling the antrum of two ipsilateral
pulmonary veins (WACA group). A second group of 32 patients underwent,
in addition to the WACA ablation, also ablation along the carinas (WACA+
group) (fig.1). After realizing that the WACA+ plus had better results
in terms of PV isolation, we added a small third group of 10 patients
who underwent a staged procedure. For these 10 patients, we first
performed a standard WACA step. Upon completion of the WACA, the
presence of PV isolation was evaluated by placing the ablation catheter
at the carina, proximal to the WACA line. Isolation was assumed to be
present if pulmonary vein potentials were not recorded distal to the
WACA and exit block was demonstrated. In case of residual electrograms
recorded with the ablation catheter distal to the WACA, the location of
earliest activation was tagged on the mapping system. As for the
original 2 groups (WACA and WACA+ groups), the isolation was then
confirmed with the circular mapping catheter.
Ablation endpoint. Upon completion of the
ablation set, the ablation catheter was withdrawn from the left atrium
and replaced by a lasso circular mapping catheter. The acute end-point
of the procedure was first pass electrical isolation of the PVs
demonstrated by disappearance of local PV electrograms and confirmed by
standard pacing maneuvers, to confirm entrance and exit block, with a
lasso circular mapping catheter. In case of lack of isolation, the
conduction gaps were tagged on the mapping system and additional RF
ablation with the same ablation index targets was delivered in the
identified gap areas. At this point the ablation catheter was once again
exchanged for the circular mapping catheter and PV isolation was checked
again. In case of lack of isolation, the same maneuver was repeated
until the vein was isolated. After a waiting period of 20 minutes from
the last ablation, each pulmonary vein was assessed for entrance and
exit block. Each vein was also assessed for the presence of dormant
pulmonary vein-left atrium connection with intravenous adenosine 18 mg
injection. Patients with evidence of dormant connections revealed by
adenosine challenge, received additional ablations according to the
mapping catheter until the connections were completely abolished.
Post-procedure Care. After the ablation procedure, patients on
warfarin received low molecular weight heparin until an INR of 2.0–3.0
was achieved. Warfarin was administered for at least 3 months in
patients with CHA2DS2VASc 0–1 score or indefinitely in patients with
CHA2DS2VASc of 2 or more. Patients previously treated with NOACs,
underwent the ablation after skipping one dose. The NOAC therapy was
restarted between 3-5 hours post procedure and continued for at least 3
months in patients with CHA2DS2VASc 0–1 score or indefinitely in
patients with CHA2DS2VASc of 2 or more. Antiarrhythmic therapy was
restarted immediately after the procedure and continued for 1 month.
Follow-Up. Clinical and electrocardiographic follow-up was
performed at 3, 6, 9, and 12 months, respectively, and every 6 months
thereafter. Holter monitoring was performed at 2- and 3-months post
procedure and then twice every 6 months. Holter recordings and
trans-telephonic monitoring were also performed when symptoms suggested
recurrence. Episodes of atrial tachycardia on Holter (number of
episodes, number of beats and heart rate) lasting less then 30 seconds
were analyzed for the prediction of atrial fibrillation recurrence. AF
recurrence was defined by the presence of symptoms suggestive of AF
and/or electrocardiographic documentation of> 30 seconds of
AF/atrial flutter/atrial tachycardia beyond the first 3 months after the
procedure off antiarrhythmic drugs AADs.