Dual-Loop Intra-Atrial Reentry in Humans
Dipen Shah, MD; Pierre Jaı̈s, MD; Atsushi Takahashi, MD; Meleze Hocini, MD; Jing Tian Peng, MD;
Jacques Clementy, MD; Michel Haı̈ssaguerre, MD
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Background—Dual-loop atrial reentrant tachycardias have not been clinically described.
Methods and Results—Five patients (3 men, 2 women; mean age, 48⫾16 years) were studied 24⫾15 years after surgical
closure of an ostium secundum atrial septal defect for drug-resistant atrial tachycardia. Complete tachycardia mapping
was performed in the right atrium with multipolar catheters and a 3-dimensional electroanatomic mapping system
(Biosense), followed by linear radiofrequency ablation of the narrowest part of each complete loop. Six tachycardias
with a typical flutter morphology, a cycle length of 262⫾40 ms, and a superior f-wave axis (⫺77⫾11°) were mapped,
4 with a Biosense map including 106⫾32 points. Five figure-8 tachycardias had a counterclockwise loop around the
tricuspid valve sharing a common anterior channel with a clockwise loop around the lateral atriotomy scar. One
tachycardia was thought to have 2 counterclockwise loops around the same obstacles. Radiofrequency delivery in the
cavotricuspid isthmus in each case transformed the tachycardia without any pause in a different morphology tachycardia
with an inferior P-wave axis (50⫾42°) and nearly the same cycle length (272⫾39 ms) but with the periatriotomy loop
alone. This arrhythmia required ablation of a second isthmus: between the lower end of the atriotomy and the inferior
vena cava in 4 and the superior tricuspid annulus in 1. After a follow-up of 19⫾6 months, there were no recurrences.
Conclusions—Figure-8 double-loop tachycardias mimicking the ECG pattern of a common atrial flutter occur in some
patients after a surgical atriotomy. Ablation of 1 loop produces a sudden transformation to a new reentrant tachycardia
formed of the remaining loop that requires ablation at a second isthmus. (Circulation. 2000;101:631-639.)
Key Words: atrial flutter 䡲 catheter ablation 䡲 heart defects, congenital 䡲 heart septal defects 䡲 surgery
T
Electrophysiological Study and Ablation
ypical right atrial (RA) flutter in humans exemplifies the
paradigm of single-loop reentry,1 and knowledge of its
circuit has allowed its elimination by interruption of conduction in a vulnerable “isthmus.”2– 4 Although ventricular arrhythmias with a figure-8 activation pattern have been demonstrated,5–7 such an atrial arrhythmia has not been described
clinically. In this report, we describe the complete circuit of
intra-atrial figure-8 reentry in humans and its treatment by
radiofrequency (RF) ablation at 2 isthmuses.
Mapping and catheter ablation were performed with informed
consent after 4 to 6 hours of fasting and after all antiarrhythmic drugs
had been stopped for 48 hours. Femoral venous access was obtained
to introduce a 6F quadripolar diagnostic catheter, a 7F quadripolar
thermocouple equipped ablation catheter, and a duodecapolar Halo
catheter (Cordis-Webster) into the RA. Bipolar electrograms were
filtered between a band pass of 30 to 500 Hz and recorded at high
gains of 0.1 mV/cm at a paper speed of 100 mm/s. A programmable
stimulator (Cardiostimulateur Ela Medical) with a 2-ms output pulse
width and an amplitude 4 times the threshold was used.
Methods
Mapping Techniques
Between February 1996 and December 1997, 5 patients with a
double-loop atrial arrhythmia were investigated in our laboratory.
The 3 men and 2 women had a mean age of 48⫾16 years
(mean⫾SD), had undergone surgical closure of an ostium secundum
atrial septal defect 24⫾15 years earlier, and had developed symptomatic tachycardia in the last 5⫾7 years. Two had ⬎1 documented
supraventricular tachycardia: 1 with 2 morphologies of atrial
tachycardia and 1 with paroxysmal atrial fibrillation in addition to a
single morphology of atrial tachycardia. They were selected from 15
consecutive patients studied during the same period for supraventricular tachycardia after surgical closure of an atrial septal defect;
the remaining patients had single-loop circuits.
Sequential mapping of the cavotricuspid isthmus was performed
during supraventricular tachycardia by recording activation at the
ostium of the coronary sinus, at the lateral edge of the cavotricuspid
isthmus (7 o’clock on the tricuspid annulus in the left anterior
oblique view), and in its center (6 o’clock on the annulus) relative to
the surface ECG onset of the flutter wave—in lead II, III, or aVF.
Activation in the cavotricuspid isthmus was categorized as lateral to
medial, medial to lateral, or convergent/colliding.8
A duodecapolar Halo catheter was placed in 2 patients with its
most distal bipole at 7 o’clock on the tricuspid annulus and its most
proximal bipole at 2 o’clock in the left anterior oblique view. Gentle
torquing of the catheter shaft in either direction produced movement
Received April 26, 1999; revision received August 30, 1999; accepted September 15, 1999.
From the Department de Rhythmologie, Hôpital Cardiologique du Haut-Lévêque, Bordeaux-Pessac, France.
Presented in part at the 19th Scientific Session of the Annual Meeting of the North American Society of Pacing and Electrophysiology, San Diego,
Calif, May 6 –9, 1998.
Correspondence to Dr Dipen C. Shah, Department de Rhythmologie, Hôpital Cardiologique du Haut-Lévêque, Ave de Magellan, 33604
Bordeaux-Pessac, France.
© 2000 American Heart Association, Inc.
Circulation is available at http://www.circulationaha.org
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Summary of the Surface ECG and Intracardiac Mapping Features of the Double-Loop Tachycardias and Transformed Tachycardia
Tachycardia Transformed by RF in the
Isthmus
Double-Loop Tachycardias
ECG
Morphology;
f-Wave
Axis
Age,
y
Sex
n
1
63
F
1
⫺ve: II, III,
aVF; ⫺80°
2
51
M
1
3
51
M
4
19
F
Patient
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5
55
F
Mapping
ECG
Morphology
f-Wave
Axis
Mapping
(Loop 2)
I/H/3D
DualIsthmus
Ablation
245
H: no
change
Y
Dom⫹ve:
III, aVF;
⫺30°
255
I:byst/H:LRA
full CL
Y
Y
Dom⫹ve:
II, III, aVF;
⫹45°
350
3D: 89 pts
full CL
Y
(1) CW-scar
Y
Dom⫹ve:
II, III, aVF;
⫹65°
270
3D: 93 pts
full CL
Y
(2) CCW-TV
(2) CCW-scar
Y
Dom⫹ve:
II, III, aVF;
⫹70°
250
3D: 84 pts
full CL
Y
CCW-TV
CW-scar⫹SVC
Y
Dom⫹ve:
II, III, aVF;
⫹90°
260
3D: 83 pts
full CL
Y
CL, ms
Isthmus
Activation
3D Mapped
Points, n
Loop 1
Loop 2
Transformed
250
L3M
141, Full CL
CCW-TV
CW-scar
Y
Dom⫹ve:
II, III, aVF;
⫹65°
⫺ve: II, III,
aVF; ⫺60°
225
L3M
CCW-TV
CW-scar
Y
1
⫺ve: II, III,
aVF; ⫺90°
335
L3M
64, Full CL
CCW-TV
CW-scar
2
(1) ⫺ve: II,
III, aVF;
⫺90°
(1) 270
L3M
111, Full CL
(1) CCW-TV
(2) ⫺ve: II,
III, aVF;
⫺90°
(2) 230
L3M
⫺ve: II, III,
aVF; ⫺75°
260
L3M
1
111, Full CL
CL,
ms
CL indicates cycle length; I, isthmus; H, halo activation; 3D, 3D electroanatomic mapping with Biosense; ⫺ve, negative; ⫹ve, positive; L3 M, lateral-to-medial
cavotricuspid isthmus activation; CCW, counterclockwise; TV, around tricuspid annulus; CW, clockwise; Scar, around atriotomy; Dom, dominant; byst, convergent
activation; LRA, lateral right atrium; pts, points; and ⫹SVC, around SVC.
of the electrode-bearing portion so that the lateral right atrial wall
could be scanned.
Comprehensive 3-dimensional (3D) endocardial activation maps
of the RA were generated in 5 patients (4 before and 4 after
cavotricuspid isthmus ablation, including both before and after in 3
patients) with the Cordis-Biosense EP navigation system and Navistar mapping and reference catheters. The technique has been
described in detail elsewhere.9,10 Automatically assigned activation
times were manually verified and corrected when necessary, and a
single activation was contextually assigned for fractionated and
double-spike potentials on the basis of simultaneous tip unipolar
signals and surrounding activation.11
Definitions
Local block was defined by a conduction delay between contiguously located points of ⱖ30 ms produced by an activation detour
around the block. The complete reentrant circuit was considered to
be the spatially shortest route of unidirectional activation encompassing the full range of mapped activation times (⬎90% of the cycle
length of the tachycardia) and returning to the site of earliest
activation. Bystander fronts encompassed a significantly smaller
range of activation timings and failed to return to the site of earliest
activation. Double-loop reentry was considered to exist when 2
loops, each fulfilling the definition of a reentrant circuit, were
simultaneously documented; ie, another front also demonstrated
unidirectional activation spanning the full cycle length with terminal
activation returning to the site of earliest activation. A figure-8
activation pattern was defined as a specific type of double-loop
reentry involving 2 simultaneously coexisting loops rotating in
opposite directions and sharing a common segment of unidirectional
activation. Atriotomy scars were located and defined by contiguous
low-voltage (⬍0.5 mV) double potentials commensurate with the
surgical incision in the anterior right atrial free wall. Their position
was confirmed by conventional or Biosense mapping in
sinus rhythm.
The mean P- or f-wave axis of each tachycardia was calculated on
the basis of the maximum amplitude in the limb leads relative to the
intervening truly isoelectric baseline in case of P-wave tachycardias
or the plateau in case of the typical sawtooth morphology flutters.
Ablation
RF energy was delivered in the cavotricuspid isthmus and from the
inferior margin of the atriotomy scar down to the inferior vena cava
(IVC). In 1 case, RF applications were delivered from the lower end
of the scar as defined above to the nearest segment of the tricuspid
annulus. The ablation sites were chosen on the basis of catheter
stability as demonstrated fluoroscopically and on the electroanatomic and conventional mapping data. Sequential point-by-point
ablation was performed with a catheter equipped with a 4-mm-tip
electrode thermocouple connected to a Stockert-Cordis RF generator
delivering a 550-kHz unmodulated sine wave output between the tip
electrode and a 575-cm2 back plate placed under the patient’s left
shoulder. RF energy was delivered in the temperature-controlled
mode (60°C to 70°C) for 60 to 90 seconds. Sedation with intravenous
Midazolam was used as necessary. Successful ablation was defined
as termination of the tachycardia by RF application and noninducibility of any organized atrial tachycardia. Isthmus block was
verified during pacing in sinus rhythm and defined as a detour of
activation around the cavotricuspid isthmus; similarly, complete
block of the atriotomy incision line was defined by a detour of
activation around the atriotomy and the contiguous great vessel (IVC
or superior vena cava [SVC]) or annulus.
Results
Electrophysiological Study and Mapping of the
Baseline Tachycardia
All patients were in spontaneous persistent flutter at the
beginning of the study, an apparently typical atrial flutter with
prominent negative deflections in leads II, III, aVF, and V6; a
Shah et al
Figure-8 Intra-Atrial Reentry
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Figure 1. Figure-8 tachycardia with clockwise periatriotomy loop, coexisting counterclockwise peritricuspid loop, and transformation produced by cavotricuspid isthmus ablation. A, 3D electroanatomic map of baseline figure-8 tachycardia in RA (64 points) in 2 perspectives: left,
modified left anterior oblique (LAO); right, modified right anterior oblique (RAO). More than 90% of cycle length of 330 ms is mapped within
RA (note bar showing mapped activation time color range, 7 to 316 ms). Reference electrogram (Ref) is recorded from within coronary sinus.
Selected electrograms at various points in RA are shown. Red and brown roundels represent double potentials. Activation proceeds in complete counterclockwise loop (thick black arrow from red to purple zone) around tricuspid valve viewed en face in LAO perspective and in similarly complete but clockwise loop around oblique line of block represented by double potentials in anterolateral RA wall. Cavotricuspid isthmus is activated from anterolateral to posteromedial (counterclockwise) as in typical counterclockwise atrial flutter. This circuit is
schematically depicted in illustration on left side of B. B, RF energy was delivered in cavotricuspid isthmus, producing transformation of
tachycardia from superior-axis P wave (left side of ECG tracing) to inferior-axis P wave with nearly same cycle length (350 ms) (right) as result
of transformation of circuit shown in illustrations on left and right. Transformation (arrow) is instantaneous and without any intervening pause.
C, 3D electroanatomic map of 89 points of transformed tachycardia in RA. As in A, reference electrogram is recorded from within coronary
sinus; ⬎90% of the cycle length is mapped in RA (⫺2 to 330 ms). Double potentials are marked by red roundels. Color activation sequence
and selected electrograms show that there is still complete clockwise activation loop around atriotomy scar in anterolateral RA wall (thick
black arrow), but now activation around tricuspid valve is no longer unidirectional. Cavotricuspid isthmus is blocked, with collision of opposing wave fronts from 2 directions, both descending, confirming its bystander nature. This activation is schematically depicted on right of B.
This tachycardia was successfully ablated by RF delivery at second isthmus between atriotomy scar and IVC. In A and C, each selected
electrogram is accompanied by its activation time. Common amplitude and time scales for map electrograms are shown accompanying point
with timing of 104 ms in A and 312 ms in C. Bottom scale bar indicates atrial size.
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February 15, 2000
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Figure 1C
superiorly directed mean f-wave axis of –77⫾11°; and a
cycle length of 262⫾40 ms.
Four RA 3D electroanatomic maps of 106⫾32 points were
obtained during different tachycardias in 4 patients (Table).
In all cases, the cavotricuspid isthmus was activated unidirectionally from lateral to medial; the interatrial septum was
activated caudocranially while activation coursed anteriorly
to the SVC in the medial-to-lateral direction (counterclockwise) before descending down the free wall anterior to the
atriotomy scar to return to the cavotricuspid isthmus. This
descending front bifurcated into 2 toward the inferior end of
the atriotomy scar. One continued into the cavotricuspid
isthmus, whereas the other passed posteriorly through the
narrow isthmus formed by the scar and the IVC, ascended
upward along the posterior aspect of the RA free wall and the
posterior RA. This clockwise circuit was completed by
activation rejoining the descending corridor anterior to the
atriotomy scar both around the SVC and between it and the
superior aspect of the atriotomy scar (Figures 1 and 2). In 1
of these cases, a clockwise loop formed around the SVC and
a contiguous atriotomy scar, along with a counterclockwise
loop around the tricuspid annulus.
The 2 loops of activation spanning the full tachycardia
cycle length were recorded in 1 case with conventional
mapping only, with sequential isthmus mapping and with the
Halo in position around the tricuspid annulus. Counterclockwise activation around the tricuspid annulus (including
lateral-to-medial isthmus activation) combined with bifurcating ascending and descending activation on the RA free wall
(Figure 2C). Counterclockwise activation around the tricuspid annulus alone could be documented in another patient
with a Halo catheter, the second loop being demonstrated by
only a 3D electroanatomic map.
Tachycardia Transformation by Ablation
RF applications were delivered in the cavotricuspid isthmus
or at its lateral part. After a mean of 7⫾6 RF applications, the
flutter ECG changed abruptly into a dominant positive or
completely positive deflection flutter in inferior leads II, III,
aVF, and V6 with an inferiorly directed mean P-wave axis of
50⫾42°, a similar or identical cycle length (transformed cycle
length, 272⫾39 ms; change in cycle length, 13⫾11 ms;
range, 0 to 30 ms), and no intervening pause (Figures 1B and
2D). Less marked changes were seen in other leads: from
negative to positive in aVR and aVL, isoelectric to positive in
I, and various morphological changes in chest leads.
One patient (patient 4) had a second tachycardia with a
superior axis that was indistinguishable on the surface ECG
Shah et al
Figure-8 Intra-Atrial Reentry
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Figure 2. Another example of figure-8 tachycardia sequentially ablated at 2 isthmuses. A, 3D RA electroanatomic map (141 points)
during tachycardia with cycle length of 250 ms (mapped range of activation times, 4 to 254 ms). Color sequence shows complete loop
of unidirectional counterclockwise activation around tricuspid annulus (best seen on left in left anterior oblique [LAO] view), along with
simultaneous clockwise loop (similarly complete and unidirectional; thick black arrow) around the atriotomy incision (and also passing
around SVC) with double potentials represented by brown roundels and best seen in right anterior oblique [RAO] view. Both loops
could be mapped with duodecapolar catheter placed in RA as shown in B through D. B, During tachycardia, with catheter placed posterior (position 1) to atriotomy line of double potentials (block dots) as shown, apparently clockwise, ie, distal-to-proximal, activation
across catheter is noted. Scale bar⫽100 ms. C, When catheter is torqued counterclockwise so that it is now astride atriotomy line
(position 2 shown in accompanying cartoon), complete loop of clockwise activation on lateral wall (arrows) that spans the full cycle
length is recorded. Scale bar-100 ms. D, During ablation in lateral cavotricuspid isthmus (stars), baseline surface ECG (Pre) shown on
left is transformed from superior to inferior P-wave axis and without any change in cycle length, but catheter posterior to atriotomy line
(position 1) does not record any change in activation. This remaining tachycardia was successfully ablated by RF delivery between
lower end of atriotomy and IVC (crosses). Scale bar⫽250 (right) and 1000 (left) ms. E, Complete block of this second isthmus was documented by stimulating posterior to atriotomy line (see designator), with catheter positioned anterior to atriotomy line recording completely descending activation. Note that stimulus to low anterolateral RA activation time is 240 ms and nearly same as tachycardia
cycle length. tv indicates tricuspid valve; prx, proximal; and dst, distal.
from the presenting flutter except for its cycle length;
sequential mapping of the isthmus also revealed lateral-tomedial activation. Ablation in the isthmus again produced a
transformation to a different inferior-axis flutter (see below).
The transformed inferior-axis flutters were mapped with
the 3D electroanatomic system in 4 cases (87⫾5 points), and
2 circuits were documented with a Halo catheter complemented by sequential mapping. Convergent bystander activation of the cavotricuspid isthmus by colliding wave fronts
from 2 directions was demonstrated in all cases (Figure 1C).
Five of the inferior-axis flutters were the result of a clockwise
single-loop reentry circuit around the atriotomy scar. The 3D
electroanatomic mapping revealed descending activation of
the interatrial septum (Figure 1C). The sixth inferior-axis
flutter in patient 4, however, was due to counterclockwise
activation around the atriotomy scar.
Ablation of the Second Loop
Successful ablation of all the inferior-axis flutter morphologies was performed by delivering additional RF energy
(12⫾15 applications) at a second isthmus in each patient—in
4 formed by the end of the atriotomy scar and the nearest
great caval vein, the IVC—and in 1 patient between the lower
end of the atriotomy scar and the superior tricuspid annulus
(patient 5).
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Figure 2B
Procedural Outcome
During sinus rhythm, complete cavotricuspid isthmus block was
verified in all patients, and block was achieved across the second
isthmus between the lower end of the atriotomy scar and the IVC or
the tricuspid annulus in 2 patients (Figure 2E). Despite multiple
attempts, block could not be achieved in the isthmus between the
lower end of the atriotomy scar and the superior tricuspid annulus in
1 patient. Block in the second isthmus was not verified in the other
2 patients. After a follow-up of 19⫾6 months (without antiarrhythmic drugs), there were no recurrences.
Shah et al
Figure-8 Intra-Atrial Reentry
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Figure 2D
Discussion
This article describes the characteristics of dual-loop, figure-8
atrial reentry. All occurred in patients previously operated on
for surgical closure of an ostium secundum atrial septal defect
and required ablation of 2 isthmuses to be curative.
Circuit Characteristics
Double-loop figure-8 activation characteristically involved
counterclockwise activation around the tricuspid valve and
clockwise activation around the atriotomy, with activation
from both loops coalescing into a common pathway anterior
to it. In 1 case, both loops were counterclockwise, although
other variations, including clockwise loops and ⬎2 loops, are
also possible.12
The simultaneous coexistence of both loops was proved by
comprehensive 3D mapping and transformation to a singleloop circuit with appropriately targeted RF application. Entrainment mapping was not systematically performed to avoid
terminating or transforming the tachycardia or inducing atrial
fibrillation (which could be considered a limitation). However, in view of the ⱕ30-ms change in cycle length after
transformation in 1 case, discordant postpacing intervals in
the 2 loops may also be possible. Transection of 1 loop
(peritricuspid) allowed unopposed atrial activation by the
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other loop (periatriotomy) to be evident on the surface ECG.
This novel mechanism of transformation of a reentrant
tachycardia ECG may also be considered the gold standard
test for a true figure-8 reentry circuit in which the remaining
loop is capable of independent stability as opposed to a
figure-8 activation pattern.5
Complete figure-8 circuits were first described by El Sherif
et al,5 who mapped ventricular arrhythmias resulting from
figure-8 activation patterns in the surviving epicardium 3 to 5
days after ligation of the left anterior descending artery in
dogs. The 2 loops rotated around 2 separate arcs of functional
block with a common channel of slow conduction. These
lines of block were attributed to spatial inhomogeneities in
repolarization and anisotropic myocardial properties. A cryothermal probe terminated the tachycardia only when applied
to the common channel. Similar figure-8 ventricular circuit–
based arcs of functional block have been mapped intraoperatively in patients with ischemic heart disease.6,7 Figure-8
atrial circuits have also been epicardially mapped in a canine
sterile pericarditis model, again around lines of functional
block.13
The figure-8 circuits (as well as the variant double-loop
circuit) described in this article differ because activation
revolved in the form of 2 loops around anatomic and fixed
obstacles: the atriotomy scar in the free RA wall and the
tricuspid valve annulus. This permitted the dual-loop
reentrant circuit to function stably as a symbiotic arrhythmia and as a single-loop arrhythmia (resulting from the
parent arrhythmia) by sectioning of the other loop. This
tachycardia transformation could be considered a variant
of Mines’ test for verifying the reentrant nature of each the
circuit’s constituent loops. The common channel between
the 2 also did not behave like the slowest part of the
circuit. The isthmuses themselves resulted from an atriotomy adjacent to multiple anatomical defects—the IVC
and tricuspid valve—in the RA.
ECG Recognition
All patients presented with a typical-flutter ECG pattern
with no features distinguishing this type of dual-loop
figure-8 reentry circuit from typical counterclockwise
isthmus-dependent flutter. All had undergone surgery for
ostium secundum atrial septal defect closure representing
30% of a consecutive cohort (5 of 15). Such reentry might
also probably be seen after a similar atriotomy for other
forms of heart disease and in both atria. The small or
nonexistent change in flutter cycle length after transection
of the peritricuspid loop indicates the requirement of an
appropriately long and freely hanging (not extending to the
IVC or tricuspid valve annulus) atriotomy with or without
a zone of slow conduction at its periphery to permit
matching activation times around the atriotomy and tricuspid valve. After transection of 1 loop, the cycle length of
the remaining loop (and therefore of the tachycardia)
changed slightly in 4 of 6 instances, probably as a result of
the loss of the modulating effect of the ablated loop.
Despite the simultaneous coexistence of an additional
circuit loop and posterior RA activation that was significantly different from that in typical flutter,10 the ECG was
indistinguishable from that of typical flutter, indicating
that simultaneous periatriotomy loop activation is not
clearly evident on the surface ECG and that similarly
posterior RA activation in typical flutter may not contribute to the surface ECG tracing. The role of the crista
terminalis in these arrhythmias is unclear, although in each
case the center of the RA free wall loop (the atriotomy)
was in an anatomic position that was clearly distinct
(lateral and anterior) from that expected of the crista
terminalis. Additionally, activation in this region during
tachycardia was parallel to the long axis of the crista
terminalis, thus masking any marker double potentials.
Mapping in sinus rhythm confirmed the position and fixed
nature of the atriotomy line of block in 3 patients.
The double-loop mechanism was revealed on ECG only
by transection of 1 loop. The ECG transformation was
instantaneous and without an intervening pause, which
might suggest termination followed by induction. The
mapping of transformation of a superior-axis negativedeflection flutter (in inferior leads) to a positive-deflection
flutter (inferior P-wave axis) with a periatriotomy reentry
circuit indicates that the polarity change on the surface
ECG is associated with altered septal activation from
caudocranial to craniocaudal and possibly a similar change
in left atrial activation. In all the above cases, ablation was
begun in the cavotricuspid isthmus; however, if we had
begun by ablating the IVC-atriotomy isthmus, in all
likelihood no significant surface ECG changes would have
occurred because the resulting change in atrial activation
would be limited to only a part of the lateral and posterior
RA, which appears to be silent on the ECG.
Ablation
The dual-loop reentry circuit required ablation at 2 distinct
isthmuses. Although theoretically ablation of the common
corridor between the atriotomy scar and the tricuspid annulus
represents a more parsimonious approach, catheter stability in
this region is a major problem. Moreover, ablation of this
corridor would not be expected to be effective in the event of
a single-loop typical-flutter circuit or a counterclockwise
double-loop circuit; therefore, such an ablation strategy
would require prior recognition of a figure-8 circuit by
detailed intracardiac mapping.
Conclusions
A specific type of figure-8 reentry circuit involving simultaneously the atriotomy scar and the tricuspid valve can be
encountered in post–atrial septal defect surgical closure
patients with apparently typical atrial flutter. Ablation of the
cavotricuspid isthmus transects the peritricuspid loop and
leaves a single periatriotomy loop tachycardia, producing an
instantaneous change in the ECG pattern, which requires
ablation in a second isthmus.
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Dual-Loop Intra-Atrial Reentry in Humans
Dipen Shah, Pierre Jaïs, Atsushi Takahashi, Meleze Hocini, Jing Tian Peng, Jacques Clementy
and Michel Haïssaguerre
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Circulation. 2000;101:631-639
doi: 10.1161/01.CIR.101.6.631
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