CLINICAL RESEARCH
Europace (2009) 11, 48–53
doi:10.1093/europace/eun316
Ablation: Imaging
Ablation of atrial tachycardias after correction
of complex congenital heart diseases: utility
of intracardiac echocardiography
Petr Peichl 1*, Josef Kautzner 1, and Roman Gebauer2
1
Department of Cardiology, Institute for Clinical and Experimental Medicine, Vı́deňská 1958/9, 140 21 Prague 4, Czech Republic; and 2Pediatric Heart Center Motol, Prague,
Czech Republic
Received 21 August 2008; accepted after revision 27 October 2008; online publish-ahead-of-print 23 November 2008
Aims
Our goal was to analyse the utility of intracardiac echocardiography (ICE) for navigation and ablation of atrial tachycardias (ATs) after surgical correction of congenital heart disease (CHD).
.....................................................................................................................................................................................
Methods
Catheter ablation of ATs was performed in seven patients (one woman, mean age 21 + 6 years) after correction of
and results
complex CHD: d-transposition of the great arteries (Mustard procedure in two patients, Senning procedure in two
patients) and univentricular circulation (total cavopulmonary connection in two patients, atriopulmonary connection
in one patient). The ablation was guided by a combination of electroanatomical mapping (CARTO, BiosenseWebster) and ICE (Acuson, Siemens). Intracardiac echocardiography was used during mapping to identify relevant
anatomical structures and monitor tissue contact and for guidance of atrial baffle puncture. Biatrial mapping was
necessary in six of seven patients and atrial baffle puncture in three. The clinical AT was abolished in all patients.
No complications were noted. During follow-up of 23 + 13 months, two patients (28%) had arrhythmia recurrence.
One patient developed atrial fibrillation, and recurrent AT in the other patient was controlled by re-ablation.
.....................................................................................................................................................................................
Conclusion
Despite complicated cardiac anatomy, catheter ablation of AT after complex CHD can be performed safely and with
a high success rate. Intracardiac echocardiography facilitates mapping, identification of relevant cardiac structures, and
could be used for safe guidance of transbaffle puncture.
----------------------------------------------------------------------------------------------------------------------------------------------------------Keywords
Catheter ablation † Intracardiac ultrasound † Congenital heart diseases
Introduction
Methods
Atrial tachycardias (ATs) often occur late after surgical correction of
congenital heart diseases (CHDs).1 – 3 Electroanatomic mapping has
been successfully used to delineate the complex 3D anatomy of
cardiac chambers and evaluate arrhythmia mechanism. However,
access to ablation targets for radiofrequency ablation in patients
after correction of complex CHD may be limited by variant
anatomy and by surgically created obstacles such as baffles or prostheses.4 This makes mapping and catheter ablation a very challenging
procedure. The aim of our report is to analyse the utility of intracardiac echocardiography (ICE) in guiding of these procedures.
Patient population
The study group included seven patients (one female, mean age 21 + 6
years) with regular ATs after correction of complex CHD who underwent catheter ablation in our institution between 2004 and 2007
(Table 1). Index surgical procedure included atrial switch for dtransposition of the great arteries in four patients (Mustard procedure
in two and Senning procedure in another two), total cavopulmonary
connection (TCPC) in two patients, and atriopulmonary connection
in one patient. All patients had documented ATs on ECG prior to
the ablation procedure.
* Corresponding author. Tel: þ420 261365021. E-mail address: [email protected]
Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2008. For permissions please email: [email protected].
49
AT, atrial tachycardia; F, female; IART, intra-atrial re-entrant tachycardia; ICD, implantable cardioverter defibrillator; M, male; PM, pacemaker; TCPC, total cavopulmonary connection.
No recurrences
317
421
Focal ATs
TCPC
M
7
19
367
277
401
IART within tunnel
TCPC
M
6
12
335
No recurrences
Repeated re-ablations needed to prevent recurrences of IARTs
No recurrences
306
302
218
Four different IARTs
Isthmus-dependent flutter
M
Fontan
M
27
5
4
13
Mustard
Atrial fibrillation, implantation of PM
No recurrences
ICD implant, no recurrences
294
283
313
Isthmus-dependent flutter
Isthmus-dependent flutter
Isthmus-dependent flutter
M
M
20
28
Senning
Mustard
F
21
2
3
1
Sex
Senning
Mapping and ablation
Age (years)
Patient
Table 1 Patient characteristics
Surgical procedure
Arrhythmia
Cycle length (ms)
Follow-up
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Ablation of atrial tachycardias
The patients underwent an electrophysiological study after discontinuation of antiarrhythmic drugs. The procedure was performed under
local anaesthesia in all but one patient. A 7F quadripolar electrode
catheter positioned in the left appendage or an 8F bipolar active fixation lead (Tendril 100 cm, St. Jude Medical, St Paul, MN, USA)
screwed into the right atrium were used as time reference for electroanatomical mapping (CARTO XP, Biosense Webster, Diamond
Bar, CA, USA). An 8F, saline-irrigated tip ablation catheter (Navistar
Thermocool, Biosense Webster) was used for mapping and
subsequent ablation. Simultaneous recordings of atrial electrograms
(filtered at 50 – 500 Hz) and 12-lead surface ECG were digitally
stored (Prucka Cardiolab, GE Medical Systems, Milwaukee, WI, USA).
A 10F, phased-array ultrasound tipped catheter that consists of a
64-element multiple frequency transducer (5 – 10 MHz) (AcuNav,
Acuson—Siemens, Mountain View, CA, USA) was inserted into the
right atrium or systemic atrium via the left femoral vein in six patients
and via the right subclavian vein in one patient with a closure of the
inferior vena cava. The ICE catheter was connected to the ultrasound
system (Sequoia) of the same manufacturer. Intracardiac echocardiography was used to delineate the complex atrial anatomy and to
assist transbaffle puncture whenever needed. A conventional Brockenbrough needle and a supporting sheath (SR 0) (Daig, Minnetonka, MN,
USA) were used for this purpose. When the atrium of pulmonary veins
was cannulated, heparin was administered in order to maintain the
ACT level of 300 s.
In patients with sinus rhythm, an electroanatomical map of the atria
was first created in order to delineate anatomy. Intracardiac echocardiography was used during the mapping to visualize and annotate all
relevant structures (e.g. annuli, appendage, suture lines). All mapping
points with a local activation signal distinguishable from noise were
taken into account, rather than using a distinct voltage cut-off value to
define a scar. Moreover, when low-voltage signals from the mapping
catheter were recorded, ICE was used to ascertain good tissue
contact and then, pacing capture at 10 mA was used to distinguish
dense scar from viable tissue. Following the map creation, programmed
electrical stimulation was performed to induce clinical arrhythmia.
During arrhythmia, an activation map was constructed in order to
characterize the activation sequence. Entrainment mapping was performed only after completing the high-density activation map in order
to prevent termination and/or change in the morphology of the
mapped tachycardia. Radiofrequency energy was applied to transect
the critical isthmus of the circuit and/or to destroy arrhythmia focus.
Radiofrequency current was delivered for maximum of 90 s, with a
maximum power set at 40 W and the maximum temperature at 438C
using an EP-Shuttle generator (Stockert, Biosense Webster). Saline
flow rate was set at 15 – 20 mL/min. When linear ablation lesions were
designed (i.e. cavotricuspid isthmus line), ICE was used to rule out the
presence of ridges and excavations within the target area and, if
present, to verify a good catheter– tissue contact and stability. In case
of re-entrant circuits, re-mapping during atrial pacing was employed to
verify block across the deployed ablation line after termination of AT.
The patients were discharged from the hospital after the procedure
without antiarrhythmic drugs treatment. Antiaggregation or anticoagulation therapy was initiated according to the level of the expected risk
of thrombo-embolism.
Results
Clinical AT in all four patients after atrial correction of dtransposition of the great arteries was isthmus-dependent atrial
50
flutter. In order to gain access to the portion of isthmus located
within the pulmonary venous atrium, a transbaffle puncture was
used in three patients and a pre-existing communication was
employed in the remaining one patient. Intracardiac echocardiography proved to be very useful in guiding this part of the procedure
and allowed safe transbaffle crossing even in one patient with
closure of the inferior vena cava in whom the puncture had to
be performed through the right jugular vein (Figure 1). In all four
patients, conduction block across both portions of the cavotricuspid isthmus was achieved and confirmed by electroanatomical
mapping (Figure 2).
In one patient with TCPC, two intra-atrial re-entrant tachycardias were inducible, which circulated around the central scar
within the intra-atrial tunnel. The common atrium was reached
using a retrograde approach and critical isthmuses were transsected by catheter ablation and connected to the nearest anatomical barriers. The other TCPC patient presented with two ATs that
were focal and originated from different foci within the common
atrium. In this case, the access into the atrium was achieved
through pre-existing fenestration and navigated by ICE (Figure 3A
and B).
The patient after atriopulmonary connection (Fontan procedure) presented with four different inducible intra-atrial
re-entrant tachycardias originating mostly from the right atrial
free wall, and repeated procedures were needed to abolish all
arrhythmias. Besides the lateral wall, catheter ablation across the
ridge between the superior vena cava and pulmonary anastomosis
was necessary to prevent arrhythmia recurrences (Figure 3C).
In total, biatrial mapping was necessary in six of seven patients
(86%) and atrial baffle puncture in three of six patients (50%).
Intracardiac echocardiography proved useful in delineation of
cardiac anatomy in all cases and in guidance of transbaffle access
whenever performed. Inducible ATs were abolished in all patients.
Mean procedural and fluoroscopic times were 278 + 78 and 20 +
15 min, respectively. No complications were observed. An implantable cardioverter-defibrillator was inserted after the ablation procedure in one patient with a previous history of cardiac arrest and
low ejection fraction of the systemic right ventricle.
During follow-up of 23 + 13 months, two patients (28%) had
arrhythmia recurrence. One patient after atrial correction of transposition of great arteries had repeated episodes of atrial fibrillation,
which were successfully suppressed by a combination of amiodarone and dual chamber pacemaker implant. In patient after atriopulmonary correction, two re-ablations were required to control
IART recurrences.
Discussion
This study presents initial experience with a combination of electroanatomical mapping and ICE to navigate catheter ablation of
ATs after surgical correction of complex CHD. It describes the
ICE guidance for transbaffle puncture to obtain biatrial access.
Value of 3D mapping
Electroanatomic mapping (CARTO)5,6 or non-contact mapping
system (EnSite)7,8 has been recently reported to describe arrhythmia mechanism and to facilitate catheter ablation of ATs after
P. Peichl et al.
Figure 1 Patient after atrial correction of d-transposition of
the great arteries according to Senning. (A) Fluoroscopic image
in the anteroposterior view showing the location of the needle
at the site of the transbaffle puncture in a patient with closure
of the inferior vena cava. Quadripolar catheter is inserted in
the left atrial appendage and ICE probe is positioned along the
baffle. (B) Tenting of thick intra-atrial baffle before the puncture.
CHD. However, the complexity of mapping and ablation varies
according to the type of CHD and its surgical correction. Compared
with patients after simple atriotomy (e.g. in patients after surgical
repair of atrial septal defect) in whom the re-entry circuit is
located mostly in the right atrium,9 the spectrum of ATs in patients
after correction of complex CHD is much broader. Re-entrant circuits may be confined in both atria and/or ATs could be focal in
Ablation of atrial tachycardias
Figure 2 Patient after Mustard correction of d-transposition of
the great arteries. (A and B) Position of the ablation catheter on
the cavotricuspid isthmus from both sides of the intra-atrial baffle
(A, in systemic venous atrium; B, in pulmonary venous atrium). (C)
Electroanatomical map of both atria in the left anterior oblique
view after creation of ablation lines during pacing in the low systemic venous atrium. Activation times are colour-coded (red as
the earliest, violet as the latest). Note the late activation (violet
colour) in the low lateral right atrium that documents the presence of block across the isthmus. IVC, inferior vena cava; MA,
mitral annulus; SVC, superior vena cava; TA, tricuspid annulus.
51
Figure 3 An example of the Fontan circulation. (A) Doppler
colour-coded flow within the fenestration in the intra-atrial
tunnel in a patient after total cavopulmonary connection. Intracardiac echocardiography was used to navigate the catheter into the
fenestration. (B) The mapping catheter introduced through the
communication from the channel into the common atrium. (C)
Intracardiac echocardiography image of the right atrium in a
patient after atriopulmonary connection. The mapping catheter is
positioned on the ridge between the superior vena cava and pulmonary anastomosis. Ablation across this ridge terminated the clinical re-entrant tachycardia. Note the close relation to the right
coronary artery (arrow). LA, left atrium; PA, pulmonary artery;
RA, right atrium; SVC, superior vena cava; TA, tricuspid annulus.
52
origin. This was confirmed in our series where electroanatomical
mapping described the mechanism of all ATs correctly.
ICE-guided biatrial access
The most common re-entry circuit in patients after atrial correction of d-transposition of the great arteries is re-entry around
the tricuspid annulus or the inferior vena cava.10 In order to
achieve complete conduction block across the isthmus, mapping
and linear ablation in both atria are necessary in most cases.10,11
Although the pulmonary venous atrium can be reached via the retrograde approach (i.e. through the aorta and right ventricle), it is
usually difficult to obtain good catheter stability on the isthmus.
In addition, mechanical prosthesis in tricuspid position may
prevent retrograde access. In our series, we described approach
to the pulmonary venous atria using transbaffle puncture guided
by ICE. In our experience, ICE provides direct monitoring and
selection of a suitable site for the puncture. One of our cases
documents that the transbaffle puncture can be safely performed
even via the superior vena cava. In addition, ICE can be used for
early detection of potential complications, e.g. pericardial effusion.
Similarly, access from the venous tunnel to the atrium may be
required in patients with TCPC. We clearly documented that
ICE could be used for detection and localization of the pre-existing
communication and navigation of the mapping catheter through
the canal. Theoretically, it could also be used for guidance of puncture of a tunnel wall, although this procedure was not necessary in
our series. As an alternative, access to the atrium has been
described in patients with extra-atrial tunnel using direct percutaneous transthoracic approach.12
Delineation of anatomy
Exact delineation of individual anatomy is crucial for the characterization of intra-atrial re-entrant circuits and localization of anatomical obstacles for impulse propagation. Addition of ICE to the
CARTO system facilitated the mapping of the atria and allowed
easy identification of anatomical landmarks (i.e. left atrial appendage, pulmonary veins, etc.) and correlation of local electrograms
to specific anatomical structures (i.e. suture lines, atretic tricuspid
valve, etc.). Moreover, when linear lesions are designed, conduction gaps within the lines are usually associated with variable anatomical structures on the endocardial surface (ridges or
excavations).13 In such case, ICE enabled visualization of these
sites and helped to monitor tissue contact. Complete block
across the line was achieved in all patients.
Besides ICE, integration of images from computer tomography
with electroanatomical maps (CARTO MergeTM ) has been proposed for depiction of the complex anatomy.14,15 However,
merged reconstruction represents only virtual image, and its
quality is highly dependent on the segmentation and registration
accuracy. In our experience, ICE provides an advantage over
image integration as it enables real-time imaging.
Study limitation
The relatively small number of patients limits observations made by
this study. However, only patients with complex CHD were
selected in whom ICE is expected to provide the greatest
P. Peichl et al.
benefit. Secondly, the use of ICE is associated with additional
costs, and no data are available which prove that ICE decreases
the duration of the procedure, fluoroscopic time, and/or affects
the success rate.
Conclusions
Ablation of ATs in patients after surgical correction of complex
CHD could be performed successfully and safely despite complicated anatomy and difficult access to the relevant cardiac
chamber. Addition of ICE to electroanatomical mapping for
such procedures is useful for navigation of catheter position,
monitoring tissue contact, identification of relevant anatomical
structures, guidance of the transbaffle puncture, or localization
of interatrial communication and for early detection of potential
complications.
Conflict of interest: none declared.
Funding
This study was supported by research grant no.: MZO 00023001 of
the Ministry of Health of the Czech Republic (Research in Cardiovascular Diseases, Diabetes Mellitus and Transplantations of LifePreserving Organs).
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