Download Importance of Atrial Flutter Isthmus in Postoperative Intra

Importance of Atrial Flutter Isthmus in Postoperative
Intra-Atrial Reentrant Tachycardia
David P. Chan, MD; George F. Van Hare, MD; Judith A. Mackall, MD
Mark D. Carlson, MD; Albert L. Waldo, MD
Background—In survivors of congenital heart surgery, intra-atrial reentrant tachycardia (IART) often develops. Previous
reports have emphasized the atriotomy scar as the central barrier around which a reentrant circuit may rotate but have
not systematically evaluated the atrial flutter isthmus in such patients. We sought to determine the role of the atrial flutter
isthmus in supporting IART in a group of postoperative patients with congenital heart disease.
Methods and Results—Nineteen postoperative patients with IART underwent electrophysiological studies with entrainment mapping of the atrial flutter isthmus for determining postpacing intervals. Radiofrequency ablation was performed
at the identified isthmus in an effort to create a complete line of block. Twenty-one IARTs were identified in 19 patients,
with a mean tachycardia cycle length of 293⫾73 ms. The atrial flutter isthmus was part of the circuit in 15 of 21
(71.4%). In the remaining 6 of 21, the ablation target zone was at sites near atrial incisions or suture lines. Ablation was
successful in 19 of 21 (90.4%) IARTs and in 14 of 15 (93.3%) cases at the atrial flutter isthmus.
Conclusions—In most of our postoperative patients, the atrial flutter isthmus was part of the reentrant circuit. The fact that
the atrial flutter isthmus is vulnerable to ablation suggests that whenever IART occurs late after repair of a congenital
heart defect, the atrial flutter isthmus should be evaluated. These data support the theory that some form of conduction
block between the vena cava is essential for the establishment of a stable substrate for the atrial flutter reentrant circuit.
(Circulation. 2000;102:1283-1289.)
Key Words: catheter ablation 䡲 atrial flutter 䡲 heart defects, congenital 䡲 reentry
I
n survivors of congenital heart surgery, intra-atrial reentrant tachycardia (IART) often develops. 1–3 This
tachyarrhythmia, which has also been called atrial flutter, can
be difficult to manage and represents a significant cause for
morbidity and mortality in postoperative patients with congenital heart disease.1 There has been much interest in using
radiofrequency ablation (RFA) to cure IART because it is
often difficult to control with antiarrhythmic drug therapy4
and may be poorly tolerated hemodynamically. Previous
reports have emphasized the atriotomy scar as the central
barrier around which a reentrant circuit could rotate.5–7
The reentrant circuit in typical and reverse typical atrial
flutter is now well understood.8 –14 The critical isthmus that
supports the reentrant circuit in typical and reverse typical
atrial flutter is between the tricuspid annulus, the coronary
sinus os, and the Eustachian ridge adjacent to the inferior
vena cava. In typical atrial flutter, reentry proceeds in a
counterclockwise fashion when the tricuspid annulus is
viewed in the left anterior oblique view, whereas in reverse
typical atrial flutter, it proceeds in a clockwise fashion.15 This
isthmus has been referred to as the atrial flutter isthmus, and
targeting this isthmus with radiofrequency energy has been
associated with a high success rate in ablating typical and
reverse typical atrial flutter.10,11,14,16 –18
Previous reports have indicated that successful RFA can be
achieved in postoperative patients with congenital heart
disease who have IART.5–7,19 Ablation therapy has focused
on extending a line of block from the surgical incision to an
appropriate boundary, such as the atrioventricular (AV)
groove, the inferior vena cava, or the superior vena cava. For
example, Kalman et al7 placed ablative lesions between an
atriotomy scar or suture lines and another boundary, usually
the AV groove, in all but 1 patient. However, we hypothesized, on the basis of a series of studies of atrial flutter in
animal models, that the right atriotomy in such patients could
serve as the needed posterior boundary of the IART reentrant
circuit such that the resulting IART could use the typical and
reverse typical atrial flutter isthmus as part of the reentrant
circuit.20 If this is correct, the atrial flutter isthmus could be
targeted for ablation of the clinical tachyarrhythmia, just as it
is in typical and reverse typical atrial flutter. Previous reports
have not systematically evaluated the atrial flutter isthmus in
such patients. We therefore sought first to determine the role
of the atrial flutter isthmus in supporting IART in a group of
Received January 21, 2000; revision received March 30, 2000; accepted April 10, 2000.
From the Division of Pediatric Cardiology, Department of Pediatrics (D.P.C., G.F.V.H.), and the Division of Cardiology, Department of Medicine
(J.A.M., M.D.C., A.L.W.), Case Western Reserve University, Cleveland, Ohio.
Correspondence to George F. Van Hare, MD, Pediatric Cardiology, Stanford University, 750 Welch Rd, #305, Palo Alto, CA 94304. E-mail
[email protected]
© 2000 American Heart Association, Inc.
Circulation is available at http://www.circulationaha.org
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September 12, 2000
postoperative patients with congenital heart disease in whom
entrainment mapping techniques were used during electrophysiological study. Second, we sought to determine whether
the atrial flutter isthmus could be a potential target site for
successful RFA to cure the IART when it has been determined to be part of the reentrant circuit in this patient
population.
Methods
Patient Selection
From 1994 to 1998, there were 35 postoperative patients with
congenital heart disease who were examined at University Hospitals
of Cleveland with findings of IART. Of these, 19 underwent
electrophysiological studies that included careful entrainment mapping of the atrial flutter isthmus as part of evaluation for RFA
therapy. This latter group of patients comprises our cohort for the
present retrospective study. The procedures followed were in accordance with institutional guidelines, and patients or their parents or
guardians gave informed consent for the procedures.
Electrophysiological Study
Each patient underwent standard electrophysiological testing in a
laboratory with either biplane fluoroscopy or single-plane fluoroscopy that allowed rapid movement of the fluoroscopy arm from right
anterior to left anterior oblique projections. Electrode catheters were
placed to record from the coronary sinus, the bundle of His, and the
right ventricle. In addition, when possible, a 20-pole halo electrode
catheter was placed in the right atrium such that it encircled the
tricuspid valve, with the distal pair of electrodes near the os of the
coronary sinus. All intracardiac electrograms were recorded (bandpass 50 to 300 Hz) simultaneously with surface ECG leads V1, 1, II,
III, and aVF (bandpass 0.05 to 300 Hz) on a commercially available
computer amplifier system (Quinton Electrophysiology) in a digital
format. After measurements of intervals and assessment of AV node
function, IART was initiated with standard programmed stimulation
techniques. Entrainment mapping was performed, as previously
described,6,7 during IART for assessment of postpacing intervals
(PPI). This was performed by both pacing and recording from the
distal electrode pair of a mapping catheter that was initially placed at
the atrial flutter isthmus. Pacing was performed at cycle lengths 20
to 30 ms shorter than the tachycardia cycle length. The PPI and the
tachycardia cycle length (TCL) were compared. The pacing site was
considered to be part of the reentrant circuit if the PPI minus the TCL
was ⬍10 ms. If the atrial flutter isthmus was not found to be part of
the reentrant circuit, alternative atrial sites were mapped by entrainment, particularly near the atriotomy incision. Particular attention
was paid to sites where double potentials were recorded because
these were considered to represent sites where conduction block
existed along the line of an atriotomy or suture line.21,22
After determination of the location of the critical isthmus of the
IART, multiple radiofrequency lesions were made in an effort to
create a complete line of block in this isthmus. The targeted
temperature was 60°C for 30 to 60 seconds for each lesion. Each
lesion was placed individually, after which the catheter was moved
by 2 to 3 mm and another lesion was placed. Success was defined as
termination of IART with subsequent lack of inducibility of the
original tachycardia. Later in the series, bidirectional conduction
block through the atrial flutter isthmus was also used as a criterion
for success.17 This was judged both in the clockwise direction,
observing a change in the order or atrial activation of the lateral atrial
wall during proximal coronary sinus pacing, as well as the counterclockwise direction, observing a change in the order of atrial
activation at the coronary sinus versus the site where the His bundle
was recorded. A change in P-wave morphology with low lateral right
atrial pacing from inverted to upright in lead aVF was also used as
a criterion of counterclockwise isthmus block.18
Results
Patients
The mean age of our cohort of 19 patients at the time of the
electrophysiological study was 22.8⫾12.9 years (Table 1).
Ten of the patients were male. In most cases, the clinical
tachycardia had developed at a remote time from the congenital heart surgical repair (mean time from surgery to ablation,
16.9 years; range, 2 to 37 years).
In our cohort of 19 patients, 21 distinct IARTs were
identified (Table 2). The mean tachycardia cycle length was
293⫾73 ms. At the electrophysiological study, 10 of the 21
tachycardias were either incessant or developed spontaneously at the time of catheter manipulation. Using entrainment
mapping techniques, a target isthmus was identified in each
tachycardia. The atrial flutter isthmus was found to be part of
the circuit by entrainment criteria in 15 (71.4%) of the
tachycardias and therefore was targeted for ablation. In the
remaining 6 tachycardias, the target zone for ablation of the
reentrant circuit was localized to sites near atrial incisions
and/or suture lines rather than the atrial flutter isthmus. Only
2 of the tachycardias with the classic atrial flutter circuit
circulated in a clockwise direction (as in reverse typical atrial
flutter) by visualization of the tricuspid valve as a clock face
in the left anterior oblique (Figures 1 and 2). In 1 of these
patients, both clockwise and counterclockwise rotation were
observed at different times. The PPI-TCL interval was
2.6⫾3.9 ms when pacing was performed at the chosen target
isthmus. Initial success of ablation was achieved in 19 of the
21 (90.4%) IARTs. When the atrial flutter isthmus was
identified as the target isthmus, successful ablation was
achieved in 14 of 15 (93.3%) of cases. The success rate of
RFA at other sites was 5 of 6 (83.3%) IARTs. At last
follow-up, 7 of the 19 successfully ablated tachycardias had
recurred. It is notable that only 4 of 14 (28.7%) ablated
tachycardias involving the atrial flutter isthmus recurred,
whereas 3 of the 5 ablated tachycardias not involving the
atrial flutter isthmus recurred (60%). It is also notable that of
the 6 typical or reverse typical atrial flutters for which
bidirectional isthmus block could be demonstrated, only 1
recurred, whereas of the 2 flutters for which bidirectional
block could not be demonstrated, both recurred (Table 2).
Five patients had attempted repeat ablation that was successful in 4 and unsuccessful in 1. No complications were noted
in association with either the electrophysiological study or the
ablation procedures.
Discussion
IART in long-term survivors of surgical repair of congenital
heart disease is an important clinical problem. Ablation
therapy has proven to be effective in managing this particularly difficult problem in patients who have had relatively
simple atrial surgery7 as well as those with Mustard and
Senning procedures for transposition6 but has had a lower
long-term success rate with patients who have undergone the
Fontan procedure.5,23 Previous reports have concentrated on
the use of ablative techniques to create block in the isthmus
between the atriotomy incision and the AV groove in an
attempt to eliminate the IART reentrant circuit.5–7,19,23 The
Chan et al
TABLE 1.
Flutter Isthmus in Postoperative Atrial Reentry
Patient Characteristics
Age at First
Ablation, y
Congenital Cardiac Lesion
Surgical Procedure(s)
Years Since Surgery
at Time of Ablation
1
10.7
Single RV, asplenia
Fontan atriopulmonary connection
8
2
26.4
Secundum ASD, unroofed
coronary sinus
Closure
21
3
14.7
Taussig-Bing anomaly
Mustard
12
4
14.4
D-TGA
Mustard
13
5
17.1
Primum and secundum ASD
Closure
16
6
17.1
D-TGA
Mustard
15
7
14.4
Tetralogy of Fallot
Complete repair via atriotomy
10
8
3.5
Secundum ASD
Closure
2
9
3.3
TAPVC
Complete repair via atriotomy
3
10
48.9
TOF and ASD
ASD closure
32
11
14.3
D-TGA
Senning
13
12
20.5
Aortic and mitral stenosis,
small LV
Mitral valve replacement
18
13
29.9
Aortic valvar stenosis
Open valvuloplasty
37
14
27.7
Tetralogy of Fallot
Complete repair
20
15
31.5
AV canal
Complete repair
24
16
44.3
WPW
Surgical ablation via right atriotomy
12
17
33.7
Tetralogy of Fallot
Complete repair via atriotomy and ventriculotomy
27
18
43.4
ASD
Closure
25
19
17.2
ASD and VSD
Closure of both defects
13
Patient
1285
RV indicates right ventricle; ASD, atrial septal defect; D-TGA, D-transposition of the great arteries; TAPVC, total anomalous
pulmonary venous connection; TOF, tetralogy of Fallot; LV, left ventricle; WPW, Wolff-Parkinson-White syndrome; and VSD, ventricular
septal defect.
present report has demonstrated that despite the presence of
an atriotomy scar, the atrial flutter isthmus is a part of the
reentrant circuit IART in many patients with a variety of
types of congenital heart disease anatomy and can be targeted
for ablation with a good rate of success. Alternatively, when
the atrial flutter isthmus was not part of the reentrant circuit
and other areas of the right atrium were targeted for ablation,
the results of ablation were not as good. We suggest that this
improved result relates to the well-defined atrial anatomy and
the relative ease of localizing the band of tissue of interest at
the atrial flutter isthmus. This is in comparison to the
somewhat variable locations of the atriotomy scar and suture
lines among patients. Thus, it may be technically more
difficult to establish a line of block at other atrial sites,
especially sites that include pectinate muscles. Furthermore,
the techniques for documenting successful creation of a
complete line of block are well developed in classic (typical
and reverse typical) atrial flutter and involve the observation
of the pattern of right atrial lateral wall activation during
coronary sinus pacing, P-wave morphology during lateral
wall pacing, and order of coronary sinus os versus low septal
right atrial activation during lateral wall activation.17 The
adoption of these criteria for proof of bidirectional block of
the atrial flutter isthmus has been responsible for a dramatic
improvement in long-term success rate for ablation of classic
atrial flutter, and this point is borne out in our results, in
which the demonstration of bidirectional block was predictive
of long-term success. Such methods and criteria are as yet
undeveloped in IART that does not involve the atrial flutter
isthmus.
Value of Entrainment Mapping
The concept of entrainment24,25 has been adapted to
mapping studies of various tachyarrhythmias, including
IARTs.6,7,26 It is a particularly powerful technique in
identifying components of the reentrant circuit, including a
target isthmus for ablation. It should be noted that patients
with IART often have much slower TCLs than those seen
in patients with typical atrial flutter and usually lack the
classic sawtooth atrial flutter waves on the surface ECG
(Figure 1). Prior studies of postoperative atrial arrhythmias
have never carefully assessed the tricuspid valve–Eustachian ridge isthmus in an organized, careful, and prospective fashion to determine whether it is in or out of the
circuit. Having done this in this study, we have found that
a surprisingly large number of patients who might otherwise have been classified as having incisional reentry in
fact have IART involving the typical atrial flutter isthmus.
Despite the fact that the typical appearance of atrial flutter
was lacking in many of these patients, our series demonstrates that patients who are considered to have IART may
still be approached in the same way for ablation as those
with typical and reverse typical atrial flutter, provided that
the atrial flutter isthmus is demonstrated to be part of the
circuit by entrainment mapping.
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September 12, 2000
TABLE 2.
Tachycardia Characteristics
Evidence for Success
Target Site
Flutter
Isthmus in
Circuit
TCL,
ms
PPI-TCL,
ms
Result
Term
Noninducible
CW
Block
CCW
Block
Recurrence
Y-F
IART
No.
Direction
of Reentry
1
1
N/A
SVC-RA junction medial
No
330
5
S
Yes
Yes
N/A
N/A
2
1
N/A
SVC-RA junction anterior
No
280
0
S
Yes
Yes
N/T
N/T
N
2
CCW
Septal isthmus
Yes
305
0
S
Yes
Yes
N/T
N/T
Y-S
3
1
CCW
Inferior SVA at coronary
sinus os
Yes
230
0
S
Yes
Yes
N/T
N/T
N
4
1
CCW
Inferior SVA at coronary
sinus os
Yes
230
0
S
Yes
Yes
N/T
N/T
N
5
1
CCW
Posterior isthmus
Yes
213
0
S
Yes
Yes
N/T
N/T
N
6
1
N/A
Low posterior SVA
No
280
0
S
Yes
Yes
N/T
N/T
Y
7
1
CCW
Posterior isthmus
Yes
180
6
S
Yes
Yes
N/T
N/T
N
8
1
CCW and
CW
Posterior isthmus
Yes
256
0
S
Yes
Yes
Yes
Yes
N
Patient
9
1
CW
Posterior isthmus
Yes
195
0
S
Yes
Yes
Yes
No
Y-S
10
1
N/A
Low lateral RA
No
405
10
S
Yes
Yes
N/A
N/A
N
11
1
CCW
Retrogradeposteromedial PVA
Yes
275
0
S
Yes
Yes
Yes
N/T
N
12
1
CCW
Posterior isthmus
Yes
370
3
S
Yes
Yes
Yes
Yes
N
2
N/A
Mid septum, right
atrium
No
425
10
F
Yes
No
N/A
N/A
N/A
13
1
CCW
Posterior isthmus
Yes
185
0
S
N/T
Yes
No
Yes
Y-S
14
1
CCW
Posterior isthmus
Yes
430
0
F
No
No
No
No
N/A
15
1
N/A
SVC-RA junction lateral
No
240
8
S
N/T
Yes
N/A
N/A
Y
16
1
CCW
Posterior isthmus
Yes
340
0
S
N/T
Yes
Yes
Yes
N
17
1
CCW
Septal isthmus
Yes
405
8
S
N/T
Yes
Yes
Yes
Y-S
18
1
CCW
Posterior isthmus
Yes
260
5
S
Yes
Yes
Yes
Yes
N
19
1
CCW
Posterior isthmus
Yes
320
0
S
Yes
Yes
Yes
Yes
N
Term indicates termination of tachycardia during RFA; CW, clockwise; CCW, counterclockwise; N/A, not applicable because atrial flutter isthmus not involved; SVC,
superior vena cava; RA, right atrium; PVA, pulmonary venous atrium in Mustard or Senning; S, success; F, failure; N/T, not tested; N, no recurrence; Y-F, recurrence
with failed reablation; Y-S, recurrence with successful reablation and Y, recurrence without repeat ablation.
Why Does Late Postoperative Atrial
Flutter Develop?
There is a relatively high incidence of IART among patients
who are survivors of congenital heart surgery.1 Atrial flutter
as a primary arrhythmia is rare in children without structural
heart disease but is seen relatively more frequently in adults
without structural heart disease. It is now understood that for
atrial flutter to occur, a stable line of block between the vena
cavae must be present or must develop.20 Olgin et al16 have
proposed that in patients with typical or reverse typical atrial
flutter, a line of block along the crista terminalis forms the
posterior barrier for the atrial flutter circuit, and both Nakagawa et al10 and Kalman et al11 have demonstrated that the
tricuspid annulus forms the anterior barrier. Clearly, not all
adults are prone to atrial flutter, and this suggests that block
in the region of the crista terminalis is likely related to tissue
abnormalities associated with atrial dilation, aging, or other
factors. We suggest that the presence of 1 or more atriotomy
scars or suture lines in young patients who have undergone
surgical repair of a congenital heart lesion may serve to
provide the posterior barrier needed to support a stable
reentrant circuit. Indeed, as summarized recently,20 this is
consistent with the findings in several canine models of atrial
flutter, including those of Frame et al.27 In these models, a
line of block between the superior vena cava and inferior vena
cava has been demonstrated to be necessary to support
sustained atrial flutter. Further mapping studies are needed in
patients with tachycardia involving the atrial flutter isthmus
to better delineate the remainder of the tachycardia circuit.
Implications for Nomenclature
These findings have implications for the nomenclature in use
for describing atrial macroreentrant tachycardias in patients
who have had atriotomies. The term “incisional reentry” was
coined by Kalman et al7 and was used to describe a reentrant
atrial tachycardia in patients in whom the reentrant circuit
traveled around an atriotomy and in which an isthmus existed
between the atriotomy and the AV groove (ie, between 2
anatomic barriers). Our data suggest that there are 2 groups of
patients that may be described: those whose tachycardia
involves the atrial flutter isthmus and those whose
tachycardia circuit is distant from this isthmus. In the second
group, the evidence for involvement of an atrial incision is
fairly good, whereas in the first group, involvement of the
Chan et al
Flutter Isthmus in Postoperative Atrial Reentry
1287
Figure 1. Rhythm strip with 4 leads in patient 9, who had repair of total anomalous pulmonary venous connection. Tracing shows IART
with 2:1 AV conduction. Note that P waves are upright in all 4 leads and there are discrete P waves rather than more typical sawtooth
flutter waves seen in patients with typical atrial flutter. Tracing is recorded at 100 mm/s.
atrial incision is currently speculative. We favor continued
use of the term “incisional reentry” to apply only to those
tachycardias in which the atrial flutter isthmus has been
shown by entrainment mapping to not be a part of the circuit.
We suggest the use of the term “postoperative atrial flutter”
for those tachycardias that involve the atrial flutter isthmus in
postoperative patients. Finally, the term “intra-atrial reentrant
tachycardia” probably should be used to refer to both types,
particularly those not yet differentiated by diagnostic electrophysiology study.
repair of congenital heart disease have a reentrant circuit that
uses the atrial flutter isthmus.
Our patients were not randomized to 2 distinct approaches
of either mapping the atrial flutter isthmus first or evaluating
the atriotomy sites initially. This prevents a head-to-head
comparison of the two approaches. However, as with the
prior series, our study included consecutive patients with
stable tachyarrhythmias undergoing attempted RFA. This
should have limited possible bias in the selection of patients
for ablation.
Study Limitations
Conclusions
The present study was retrospective in its data collection.
However, the objective of the study was to determine the role
of the atrial flutter isthmus in supporting the reentrant circuit
in congenital heart surgery survivors. In this respect, these
patients were approached prospectively, as evaluation of the
atrial flutter was part of the plan at the time of the diagnostic
electrophysiologic study. Other sites were evaluated only
when the atrial flutter isthmus had been excluded as the
critical isthmus by entrainment mapping. Thus, although we
know the role of the atrial flutter isthmus in each of these
patients, we do not know the role of other portions of the
atrium (eg, the superior vena cava–right atrial junction),
except in those patients who had the atrial flutter isthmus
excluded by entrainment mapping. Therefore, this study does
not rule out the potential for successful ablation directed at
alternative sites even in patients whose circuits involve the
atrial flutter isthmus. However, the important point remains
that a large percentage of patients with IART after surgical
We have shown that in the majority of postoperative patients
in our study, the atrial flutter isthmus was part of the reentrant
circuit. The fact that the atrial flutter isthmus is a vulnerable
target for successful ablation suggests that whenever IART
occurs late after repair of a congenital heart defect, one
should evaluate the involvement of the atrial flutter isthmus
in the reentrant circuit. This does not mean that true incisional
reentry does not occur, nor that more than 1 potential
reentrant circuit cannot be present, nor that other approaches
to cure IART may not be useful or appropriate. However,
with recent advances in both our understanding of the nature
of the atrial flutter isthmus and in the assessment of successful isthmus ablation, a reasonably high likelihood of longterm successful ablation in such patients should be expected.
Furthermore, recognition of the importance of the atrial
flutter isthmus for maintenance of IART in these patients
invites consideration of intra-operative methods to prevent
postoperative occurrence of IART. The most obvious consid-
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Circulation
September 12, 2000
Figure 2. Intracardiac electrograms in patient 9 showing entrainment pacing during IART from proximal coronary sinus electrodes positioned at mouth of coronary sinus. Halo catheter demonstrates clockwise rotation. Note that at termination of pacing, atrial electrogram
recorded by the proximal electrode pair of the mapping catheter demonstrates PPI equivalent to TCL. Tracing is recorded at 200 mm/s.
CS indicates coronary sinus; Dis, distal electrode pair; prx, proximal electrode pair; Halo, 20-electrode Halo catheter in right atrium (1 is
distal, 6 is proximal); HBE1, His bundle electrogram.
eration would be to place a lesion in the atrial flutter isthmus
prophylactically at the time of surgery. Other potential
considerations relate to placement of the atriotomy incision in
such a way that it cannot act as a stable line of block between
the vena cavae. Finally, these data lend still more support to
the theoretical concept that some form of conduction block
between the vena cavae is essential for the establishment of a
stable substrate for the classic atrial flutter reentrant circuit.
Acknowledgment
This study was supported in part by grant HL-38408 from the
National Institutes of Health, National Heart, Lung, and Blood
Institute, Bethesda, Md.
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