Download Atrial Arrhythmias After Single-Ring Isolation of the Posterior Left

Atrial Arrhythmias After Single-Ring Isolation of the
Posterior Left Atrium and Pulmonary Veins for
Atrial Fibrillation
Mechanisms and Management
Toon Wei Lim, MBBS, FRACP; Choon Hiang Koay, BSc, RN; Rebecca McCall, BVCDes;
Valerie A. See, BMedSci; David L. Ross, MBBS, FRACP; Stuart P. Thomas, PhD, FRACP
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Background—Single-ring isolation of the posterior left atrium is feasible, but the incidence and mechanisms of
postprocedural arrhythmias have not been described in detail.
Methods and Results—The first 100 consecutive patients (58.8⫾11.2 years old, 80 male) who underwent single-ring
isolation for atrial fibrillation (66 intermittent, 18 persistent, 16 long-standing persistent) were followed up for 9.1⫾4.5
months. Recurrences were diagnosed by clinical symptoms and Holter monitoring. Patients with recurrences of
sustained atrial arrhythmia ⬎3 months after the procedure were offered a repeat procedure and were studied to determine
the mechanisms of recurrence. Forty-six patients (46%) experienced sustained postprocedural atrial arrhythmias (35 had
atrial fibrillation, and 34 had atrial flutter). Of these, 34 required a second procedure 7.0⫾3.1 months after their initial
procedure. Reconnection of the posterior left atrium was seen in all patients with atrial fibrillation. Atrial flutter was
most commonly due to mitral isthmus-dependent macroreentry (n⫽8, cycle length 368⫾116 ms) or macroreentry
through 2 gaps in the ring of lesions (n⫽6, cycle length 328⫾115 ms). Posterior left atrium reisolation was achieved
at the second procedure in all patients. Atrial flutter was successfully ablated and rendered noninducible in all patients.
Six months after their last procedure, the Kaplan-Meier estimate of freedom from recurrence for all 100 patients was
81⫾5%.
Conclusions—Atrial fibrillation and atrial flutter recurrence is common after single-ring isolation. Reconnection of the
posterior left atrium and macroreentry are the common mechanisms. Repeat ablation results in satisfactory short-term
outcomes. (Circ Arrhythmia Electrophysiol. 2008;1:120-126.)
Key Words: atrium 䡲 fibrillation 䡲 catheter ablation 䡲 atrial flutter
C
ircumferentially wide antral pulmonary vein isolation,
with or without additional linear lesions, has been
adopted by many centers for treatment of atrial fibrillation
(AF). The reported success rates for ablation procedures
range from 48% to 88% for paroxysmal AF and 0% to 79%
for chronic AF after a single procedure.1– 6 Failure may be due
to recurrence of AF and atrial tachycardia due to macroreentry or focal mechanisms. Left atrial reentrant tachycardia has
been reported in 6% to 16% of patients with pulmonary vein
isolation.7,8
of patients undergoing circumferential pulmonary vein isolation with a ring around each ipsilateral vein pair. We
hypothesized that the new single-ring procedure may lead to
different patterns of arrhythmia recurrence. The purpose of
this study was to characterize arrhythmias occurring after the
single-ring procedure and determine the longer term efficacy
of catheter ablation for treatment of these procedures.
Methods
Clinical Perspective see p 126
Patient Population
Wide, electrically isolating percutaneous left atrial catheter ablation
was performed in 100 consecutive consenting patients with intermittent (66), persistent (18), or long-standing persistent (16) AF to
electrically isolate their pulmonary veins and PLA. No patients had
prior left atrial ablation.
Recently, we showed the feasibility of electrically isolating
the pulmonary veins and posterior left atrium (PLA) with a
single continuous ring of radiofrequency lesions.9 Short-term
clinical outcomes were similar to a historical control cohort
Received January 29, 2008; accepted April 18, 2008.
From the University of Sydney (T.W.L., D.L.R., S.P.T.); Department of Cardiology (T.W.L., C.H.K., V.A.S., D.L.R., S.P.T.), Westmead Hospital; and
Westmead Private Hospital (R.M.), Sydney, Australia.
Correspondence to Stuart P. Thomas, PhD, FRACP, Department of Cardiology, Westmead Hospital, Cnr Hawkesbury and Darcy Rds, Westmead, NSW
2145, Australia. E-mail [email protected]
© 2008 American Heart Association, Inc.
Circ Arrhythmia Electrophysiol is available at http://circep.ahajournals.org
120
DOI: 10.1161/CIRCEP.108.769752
Lim et al
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Figure 1. Isolation of all 4 pulmonary veins using a single ring of
ablation. The radiofrequency lesions are shown as red dots on
the volume-rendered computerized tomographic image. A, Left
posterior oblique view. B, Right anterior oblique cranial view. C,
Posterior–anterior view. D, Anterior–posterior caudal view with
clipping plane to display PLA: shows the ring of ablation encircling the posterior left atrial wall. LAA indicates left atrial
appendage; LIPV, left inferior pulmonary vein (light blue dots);
LSPV, left superior pulmonary vein (dark blue dots); RIPV right
inferior pulmonary vein (light green dots); and RSPV, right superior pulmonary vein (dark green dots).
Procedures
Procedures were performed under midazolam and fentanyl sedation10 or general anesthesia. Two transseptal punctures were performed, and long sheaths were used to position catheters in the left
atrium. A fixed curve braided sheath was used to position a circular
decapolar mapping catheter in the left atrium (Preface Multipurpose
and Lasso catheter, Biosense Webster, Diamond Bar, Calif). A
deflectable sheath (Ultimum Agilis, St Jude Medical, St Paul, Minn)
was used to direct an open irrigated 7F, 3.5-mm tip, deflectable
ablation catheter (Thermocool Navistar, Biosense Webster).
Mapping and ablation were guided by 3D rendering of the left
atrium created from a multislice computed tomographic image
integrated with the electroanatomic mapping system to guide ablation catheter navigation (CARTO Merge, Biosense Webster). Ablation sites were displayed on the rendered atrial surface.
Radiofrequency ablation power was limited to 40 W for the
septum, left free wall, and roof of the left atrium. Power was reduced
to 30 W during ablation of the PLA between the left and right
inferior pulmonary veins and was further reduced to 25 W when
ablation was required on the venous side of the ridge separating the
left-sided veins and the left atrial appendage. Temperature was
limited to 50°C. Ablation was continued at each site until the local
electrogram was abolished (reduced to ⬍0.05 mV) or for 30 seconds.
Ablation was applied at 2- to 5-mm intervals.
First Ablation Procedure: Single-Ring
PLA Isolation
The initial ablation procedure has been described in detail elsewhere.9 In brief, a single ring of ablation passed up the anterolateral
margin of the ridge separating the left-sided veins from the left atrial
appendage (Figure 1A). At the top of this ridge, it passed along the
superior margin of the left atrial appendage onto the left atrial roof
(Figure 1B). The roof was traversed, and the line continued down the
Atrial Arrhythmias After Single-Ring Isolation
121
interatrial septum between the septal puncture site in the foramen
ovale and the septal margin of the right pulmonary veins (Figure 1B).
It then passed below the right inferior pulmonary vein and back
across the PLA to below the left inferior pulmonary vein before
ascending up the lateral left atrium anterior to the left inferior
pulmonary vein to join the start of the line (Figure 1C).
By placing the circular mapping catheter sequentially in each of
the veins, it was possible, by comparison with a coronary sinus
reference electrogram, to determine which vein was activated first.
The activation sequence in the earliest vein indicated whether this
activation was coming from the adjacent segment of the ring of
lesions or the section of the posterior wall between the veins, where
there was uncertainty. The mapping catheter was placed on the
posterior wall, within the ring, and adjacent to the earliest vein to
determine the order of activation. Where the posterior wall was
activated first, point-by-point activation was used to identify the
earliest breakthrough in the roof or inferior line. Successful ablation
at the gap (earliest point of activation within the ring) isolated the
entire region within the ring (pulmonary veins and posterior wall) if
there was a single gap. When ⬎1 gap was present, ablation of the gap
caused delayed and altered activation within the ring. The mapping
process was repeated until all the gaps were abolished. The PLA and
pulmonary veins were considered isolated when 3 criteria were
fulfilled: (1) electrical activity was dissociated or absent within the
ring of ablation lesions during sinus rhythm, (2) pacing the PLA and
pulmonary veins did not capture the rest of the atria, and (3) pacing
from the coronary sinus catheter did not result in associated electrical
activity in the PLA or pulmonary veins.
A line of ablation was placed in the mitral isthmus joining the
single ring of ablation near the left inferior pulmonary vein to the
mitral annulus in 53 patients. The end point of ablation was
bidirectional conduction block across the line. This was demonstrated by pacing the coronary sinus catheter both septal to and
lateral to the ablation line. Conduction block across the line was
defined as a delay ⬎100 ms in conduction time and evidence of
reversal of activation sequence distal to the line of ablation.11 If an
epicardial connection was suspected, ablation was also performed in
the coronary sinus (25 W). A cavotricuspid isthmus line of ablation
was also performed in 90 patients.
Repeat Procedure
Patients in sinus rhythm at the start of the procedure were systematically checked for electrical isolation of the pulmonary veins and
the PLA as described earlier. Patients in AF at the start of the
procedure were electrically cardioverted to restore sinus rhythm. The
previously isolated region within the ring was mapped to identify
where the earliest activation was entering the PLA or pulmonary
veins as described above. These areas were ablated, and if ablation
resulted in isolation of the PLA or changed the site of earliest
activation to another part of the ring, the ablation sites were
considered a gap. Further gaps were mapped and closed with
additional ablation to reestablish electrical isolation of the PLA and
the pulmonary veins. Patients underwent rapid atrial pacing to induce
atrial flutter after completion of the ring of lesions. Any further atrial
flutters induced were characterized and ablated.
Patients in atrial flutter at the start of the repeat procedure were
studied by using activation mapping and entrainment to locate sites
suitable for ablation. Entrainment was performed in both atria to
determine whether the tachycardia was macroreentrant or focal and
to define whether the atrial flutter was right or left sided in origin.
Electroanatomic activation mapping was then performed, guided by
the entrainment mapping to confirm the mechanism of the
arrhythmia.
If needed, mitral isthmus ablations were performed as described
for the first procedure. The previous ring of lesions was checked for
gaps that were ablated as described earlier after successful ablation
and restoration of sinus rhythm.
Postprocedural Care and Long-Term Follow-Up
Patients were not routinely administered antiarrhythmic medications
after pulmonary vein isolation. Patients with symptoms suggestive of
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June 2008
recurrence were investigated by electrocardiography or Holter monitoring. A 3-month blanking period was applied to exclude early
recurrences that spontaneously resolved. Repeat procedures were
offered to patients experiencing a recurrence of atrial arrhythmia ⬎3
months after their first procedure. Patients who remained free of
symptomatic recurrences had 7-day Holter monitoring to look for
previously undetected atrial tachyarrhythmias at 6 months to identify
asymptomatic arrhythmias.
Analysis
Continuous variables are expressed as mean⫾SD. Kaplan-Meier analysis was used to determine the likelihood of atrial arrhythmia recurrence. The log-rank test and Cox regression analysis were used to
determine whether it was significantly affected by any patient or
procedural variables. P⬍0.05 was considered statistically significant.
The study was approved by the Sydney West Area Health Service
Human Ethics Committee, and all participants provided written
informed consent.
The authors had full access to the data and take responsibility for
the integrity of the data. All authors have read and agree to the
manuscript as written.
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Results
Patients
Between February 2006 and September 2007, 100 patients
underwent single-ring pulmonary vein isolation and were
followed up for 9.1⫾4.5 months. Their mean age was 58⫾11
years, and 80 were male. AF had been present for 7.4⫾7.1
years, and these patients had failed treatment with 2.4⫾1.2
antiarrhythmic medications. Twenty-three patients had concomitant structural heart disease. Mean left atrial size on 2D
echocardiography in the parasternal long-axis view was
42⫾7 mm. The PLA and pulmonary veins were successfully
isolated in 96 (96%) patients.
Recurrence After First Procedure
Recurrent atrial arrhythmia that was present ⬎3 months after
the first procedure occurred in 46 (46%) patients. Thirty-five
(35%) patients had recurrence of AF, and 34 (34%) patients
had recurrence of regular atrial tachycardia suggesting atrial
flutter or focal atrial tachycardia.
Repeat Procedure
A repeat procedure was performed on 34 patients with
arrhythmia recurrence 7.0⫾3.1 months after the initial procedure. The mean total procedure time was 251⫾63 minutes,
and mean total ablation time was 1444⫾980 seconds.
Electrophysiological Study Findings
At the start of the procedure, 21 (62%) patients were in sinus
rhythm, 1 (3%) was in AF, and 12 (35%) patients were in
organized atrial tachycardia. Mapping revealed that 30 (88%)
of 34 patients had breaches in the single ring of lesions that
led to resumption of electrical activity in the previously
isolated PLA, and 22 patients had ⬎1 gap (mean 2.8⫾1.6
gaps per patient).
Atrial Fibrillation
In total, 15 (44%) of the 34 patients who underwent a repeat
procedure had AF recurrence after their first procedure. They
all had gaps in their previous ring of isolating lesions
resulting in associated electrical activity in the PLA and
Figure 2. Schematic representation of breaches in ring of
lesions isolating the PLA. The numbers in brackets indicate the
number of patients who had breaches in each region. The sites
were reablated to achieve isolation of the PLA and pulmonary
veins. LAA indicates left atrial appendage; LIPV, adjacent to left
inferior pulmonary vein; LSPV, adjacent to left superior pulmonary vein; RIPV, adjacent to right inferior pulmonary vein; and
RSPV, adjacent to right superior pulmonary vein.
pulmonary veins. The gaps in the ring lesions were most
commonly seen in the roof and along the ridge between the
left-sided veins and the ostium of the left atrial appendage
(Figure 2). Conversely, none of the 4 patients who still had
intact isolation of the PLA had recurrence of AF after their
first procedure (see later). Ablation of gaps in the ring was
undertaken in the 30 patients who had reconnection of the
PLA. At the end of the procedure, there was successful
isolation of the PLA and pulmonary veins in all these
patients.
Regular Atrial Tachyarrhythmias Observed at
Repeat Procedure
Organized atrial tachycardia was present in 12 (35%) patients
at the start of the procedure and was inducible with rapid
atrial pacing or by catheter manipulation in another 6 (18%)
patients during the procedure. All of these 18 patients had
clinically documented organized atrial tachycardia after their
first procedure. Mapping of the atrial tachycardias showed
that 16 of them had organized left atrial tachycardias, while
the other 2 had typical cavotricuspid isthmus flutter. Atrial
flutter was not induced in 9 of 25 patients who had documented organized atrial tachycardia after their first procedure.
These 9 patients had gaps in the ring of lesions resulting in
reconnection of the PLA and pulmonary veins. These gaps
were closed at the repeat procedure. Five patients had ⬎1
form of organized left atrial tachycardia. Two patients had
both mitral annular reentrant tachycardia and ring breachdependent atrial flutter. Two other patients with ring breach
atrial flutter and a patient with mitral annular flutter also had
other forms of atrial flutter that were not sustained enough to
be mapped. These atrial flutters had cycle lengths that were
different from the flutters that were mapped in these patients,
and their mechanisms were unclear.
Mitral Annular Macroreentrant Atrial Flutter
Mitral annular atrial flutter was found in 8 (24%) patients
(Figure 3) with cycle lengths of 368⫾116 ms. Among the 34
patients who had a repeat procedure, 11 had an electrically
intact mitral isthmus line created at the first procedure, 10
patients had an incomplete mitral isthmus line, and 13
patients did not have any mitral isthmus ablation. Ablation
within the coronary sinus was not performed in any patients
Lim et al
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Figure 3. Anticlockwise mitral annular atrial flutter. Atrial flutter
recurred in this patient 13 months after the initial procedure. An
isochronal activation map was superimposed over a volumerendered computerized tomographic image. The broken line
represents the location of the ring of ablation lesions from the
previous procedure, and the white arrows indicate the direction
of activation propagation. Tachycardia cycle length was 250 ms.
A, Right anterior oblique view: The atrial flutter circuit propagates left to right over the anterior left atrium. B, Left anterior
oblique view: The circuit propagates around the mitral annulus
and is right to left inferiorly. C, Left posterior oblique view: Activation then goes inferior to superior through the left mitral isthmus. Brown spheres in this region represent ablation lesions
that terminated the atrial flutter. Delay over the left mitral isthmus was 170 ms after restoration of sinus rhythm. D, Posterior–
anterior view: The PLA and regions around the pulmonary veins
were still isolated from the first procedure and were electrically
silent. This is represented by gray areas in C and D. Abbreviations as shown in Figure 1.
at the first procedure. Reconnection across an electrically
intact mitral isthmus line created at the first procedure was
found in 5 of 11 patients, and all of these patients had mitral
annular atrial flutter at the repeat procedure. None of 6
patients who still had an intact mitral isthmus line had mitral
annular flutter. One of 10 patients who had an incomplete
mitral isthmus line and 2 of 13 patients who did not have a
mitral isthmus line ablated at the first procedure had mitral
annular atrial flutter at the second procedure.
During the repeat procedure, an electrically insulating
mitral isthmus was successfully completed in all 8 patients
who had mitral annular flutter. Coronary sinus ablation was
required in 2 of these patients to achieve bidirectional block
across the line of ablation.
Gap-Related Macroreentrant Atrial Flutter
Left atrial flutter sustained by reentry through at least 2 gaps
in the ring was observed in 6 (18%) patients (Figure 4) with
cycle lengths of 328⫾115 ms. A gap in the ring was present
in either the septum (n⫽3) or the roof (n⫽3) in all patients,
together with another gap elsewhere in the ring. Activation in
these cases entered the ring through 1 gap and exited to the
remainder of the left atrium through a second breach in the
Atrial Arrhythmias After Single-Ring Isolation
123
Figure 4. Atrial flutter sustained by 2 gaps in the ring of ablation
lesions. Atrial flutter recurred in this patient 1 month after the
initial procedure and persisted. An isochronal activation map
was superimposed over a volume-rendered computerized tomographic image. The broken line represents the location of the
ring of ablation lesions from the previous procedure, and the
white arrows indicate the direction of activation propagation.
Tachycardia cycle length was 275 ms. A, Left posterior oblique
view: The atrial flutter circuit entered through a gap in the lateral
part of the ring and passed between the left-sided pulmonary
veins into the PLA before exiting through another gap in the ring
near the right inferior pulmonary vein. Brown spheres near the
left pulmonary veins represent ablation lesions that terminated
the atrial flutter but did not isolate the PLA. B, Right lateral view:
After termination of the atrial flutter, further ablation (red
spheres) near the right inferior pulmonary vein isolated the left
atrium. The yellow sphere marks the ablation site that resulted
in reisolation. C, Superior view: Activation over the roof of the
left atrium was from right to left. Hence the flutter circuit was a
figure-8 reentry using the region of the PLA within the single
ring as the common pathway. Abbreviations as shown in Figure
1.
ring. Ablation of these gaps terminated gap-related macroreentrant atrial flutter in all 6 patients.
Macroreentrant Right Atrial Flutter
Typical right atrial flutter, which was anticlockwise around
the tricuspid annulus and dependent on the cavotricuspid
isthmus, was observed in 2 (6%) patients. Of the 34 patients
who had a repeat procedure, cavotricuspid isthmus ablation
was performed at the previous procedure in 30 (88%) patients
and was unsuccessful in only 1 patient. This patient had right
atrial flutter, whereas the other had reconnection across a
previously ablated cavotricuspid isthmus.
Seven other patients had reconnection across their previously ablated cavotricuspid isthmus, but they did not have
inducible right atrial flutter. Right atrial flutter could not be
induced in any of the 21 patients who still had an electrically
intact cavotricuspid line or in the 4 patients who did not have
any cavotricuspid ablation at the previous procedure.
Irregular Conduction of AF Through a Ring Gap
A single patient had a different form of atrial tachycardia
characterized by irregular activation of the atria. There were
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Circ Arrhythmia Electrophysiol
June 2008
mate of atrial arrhythmia-free survival at 6 months after the
procedure was 81⫾5%.
Discussion
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Figure 5. Irregular conduction through a ring gap. This patient
had a recurrence 6 days after his first procedure that persisted.
A, Surface electrocardiogram demonstrated monomorphic P
waves with irregular P–P intervals (arrows). At the repeat procedure, a circular mapping catheter in the PLA showed fibrillation.
This was conducting out through a gap in his ring of lesions
near the right inferior pulmonary vein at irregular intervals. B,
Electrogram recording of PLA (circular mapping catheter) and
coronary sinus catheter. Ablation at the site of the gap in the
ring of lesions resulted in isolation of the fibrillating PLA and the
restoration of sinus rhythm in the rest of the heart as seen in the
coronary sinus catheter electrogram.
monomorphic P waves on the surface electrocardiogram, with
an isoelectric period separating each complex. Endocardial
recordings demonstrated disorganized irregular activation of
the myocardium within the ring of ablation lesions (PLA and
pulmonary veins) that was conducting irregularly out through
a single gap in the ring of ablation lesions (Figure 5).
Other Atrial Tachycardia Mechanisms in Patients
With Intact Rings
Four patients were found to still have electrically isolated
posterior left atria and pulmonary veins, despite clinical
recurrence of atrial tachyarrhythmias. In these patients, AF
was not observed during follow-up after their first procedure
or during the repeat procedure. These patients only had
macroreentrant or focal tachycardias. Two patients had mitral
annular atrial flutter. One patient had long complex fractionated signals near the base of the left atrial appendage with
centrifugal activation of the left atrium from this site to the
rest of the atria. This pattern was thought to indicate localized
reentry in the left atrial roof outside the ring of ablation
lesions. The last patient had an apparently focal atrial
tachycardia arising from the ridge between the left atrial
appendage and the left superior pulmonary vein. Activation
from this region spread centrifugally to the rest of the left
atrium outside the ring of lesions. The mechanism of this
tachycardia was not clear, and local reentry could not be
excluded.
Follow-Up After Second Procedure
No patients had atrial tachyarrhythmias before discharge.
There were no significant complications associated with the
procedures. After a mean follow-up period of 5.6⫾4.1
months, 27 of 34 (79%) patients who underwent a redo
procedure remained free of atrial arrhythmias. On the basis of
follow-up since their last procedure, the Kaplan-Meier esti-
The main finding of this study is that approximately half of
the patients who underwent single-ring PLA isolation had
recurrence of an atrial arrhythmia, but a repeat procedure was
usually successful in reestablishing sinus rhythm. Single-ring
isolation of all pulmonary veins was followed by recurrence
of atrial flutter in a high proportion of patients. However,
these flutters had one of a small number of mechanisms and
could usually be identified and treated effectively. We found
at these repeat procedures that the reconnection of the
previously isolated PLA and pulmonary veins was seen in a
large majority of patients and that ablating any gaps in the
ring of lesions led to reisolation of these structures. Recurrent
macroreentrant atrial flutter was associated with discontinuity
in the ring or previous ablation lines in the mitral isthmus or
cavotricuspid isthmus. By reclosing these gaps, atrial flutter
was rendered noninducible, and short-term follow-up showed
that recurrence after a second procedure was uncommon.
Recurrent AF After Left Atrial Ablation and the
Role of PLA
In previous studies of catheter ablation for AF, recurrence of
atrial arrhythmias after a single percutaneous catheter ablation procedure, mostly AF, occurred in 12% to 85% of cases
and was more common in patients with persistent or permanent AF rather than intermittent AF.2– 6 Electrical reconnection in these studies was usually observed in patients who had
recurrence of AF after these procedures and was thought to be
the mechanism in most patients.5,6,12,13 The rate of AF
recurrence in our study (35%) was nearer the lower end of the
range reported in previous studies, for a cohort with a third of
patients who have persistent or long-standing persistent AF.
Reconnection of the previously isolated PLA and pulmonary
veins was seen in all patients with recurrent AF in the present
series. Moreover, AF did not recur in any of the 4 patients
whose pulmonary veins and PLA remained isolated. This
finding suggested that reconnection of the PLA was an
important factor in AF recurrence. The PLA has been
implicated in animal studies in the maintenance of AF.14,15
Mapping studies in patients with chronic AF have since
demonstrated rapid repetitive electrical activity in the
PLA.16,17 The PLA has also been shown to be a common site
for the initiation and maintenance of AF.18,19 Electrically
isolating this part of the left atrium may thus prevent the
initiation and perpetuation of AF.
Recurrent Atrial Flutter After Left Atrial Ablation
Left atrial flutter has been reported rarely after segmental
pulmonary vein isolation. Gerstenfeld et al20 found that
organized left atrial tachyarrhythmia recurred in 2.9% of
patients after this procedure, whereas AF recurred in 20%. At
repeat ablation, only 1 in 10 patients had macroreentrant atrial
flutter.
The incidence of left atrial flutters with pulmonary vein
antral isolation techniques was higher than that seen with
segmental pulmonary vein isolation at 11% to 14%.11,21
Lim et al
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Recurrent macroreentrant atrial arrhythmias were associated
with gaps in ablation lines.21,22 Despite this, the addition of
linear ablations in the roof or left mitral isthmus to this
procedure has been shown to reduce the recurrence of atrial
arrhythmias overall.11,21,23
Wide antral left atrial ablation with anatomic end points
aiming for substrate modification but without electrical isolation is also associated with postablation left atrial flutter
that is persistent in 4% to 16%.7,8,24 In patients who underwent a repeat procedure, mitral isthmus-dependent left atrial
flutter was the most common mechanism.8,25,26 Gaps in
previous ablation lines were thought to be responsible for
creating these reentry circuits.25,26
The rate of atrial flutter recurrence we observed in our
study was high compared with these previous studies at 34%.
We found that mitral isthmus atrial flutters were frequently
seen, as found in previous studies. We also observed that
most of the recurrences were in patients who had undergone
mitral isthmus ablation in their last procedure but who had
reconnection across the line of ablation. In comparison, only
2 of 13 patients who did not have previous mitral isthmus
ablation had mitral annular atrial flutter. It is possible that
slow conduction across a recovered gap in the line predisposes to sustained atrial flutter. Further study will be required
to elucidate the role of mitral isthmus ablation in the context
of single-ring isolation of the PLA.
A second common mechanism of atrial flutter in this series
was reentry through 2 gaps in the single ring of lesions
(Figure 4). Mechanistically, this form of atrial flutter requires
at least 2 gaps in the ring to be sustained. Where the flutter is
dependent on 2 gaps, ablation of one of these gaps rendered
atrial flutter noninducible, but the PLA was not isolated
unless both gaps were closed by reablation. These macroreentrant flutters are due to recovery of conduction across the ring
of ablation lesions as these patients all had an electrically
isolating ring of lesions at the end of their previous procedure.
Gaps in the ring resulting in electrical reconnection were
most commonly seen in the roof line and also along the ridge
between the left atrial appendage and the left pulmonary
veins. This is not unexpected as we have previously noted
that these were the regions that were most difficult to isolate
in the initial procedure.9
Conclusions
Recurrence of atrial arrhythmias after single-ring isolation of
the PLA and pulmonary veins is usually associated with
reconnection across the ring of ablation lesions, resulting in
electrical activity in the PLA and pulmonary veins or reconnection across previous ablation lines in the mitral isthmus.
Left atrial flutter after this procedure is common, often due to
macroreentry involving discontinuity in linear lesions. These
recurrent atrial tachyarrhythmias are amenable to repeat
ablation, and the short-term outcomes are satisfactory.
Source of Funding
This research is funded by the Department of Cardiology, Westmead
Hospital.
Atrial Arrhythmias After Single-Ring Isolation
125
Disclosures
Drs Thomas and Ross are the principal investigators for a National
Health and Medical Research Council project grant titled “Circumvenous ablation for treatment of atrial fibrillation.” Dr Thomas has
also received honoraria from Johnson & Johnson. R. McCall is a
part-time employee of Biosense Webster. The remaining authors
report no conflicts.
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CLINICAL PERSPECTIVE
Atrial fibrillation (AF) ablation techniques continue to evolve in the quest for improved efficacy and safety. Recently,
procedures that isolate the posterior left atrium (PLA) and pulmonary veins have been proposed by several groups, as the
PLA has been implicated in the initiation and maintenance of AF and these procedures may also reduce esophageal
exposure to ablation. However, their efficacy and mechanisms of recurrence are unknown. We studied 100 patients with
AF (including 34 with persistent or long-standing persistent AF) who underwent en bloc single-ring isolation of the PLA
and pulmonary veins and were followed up for 9.1⫾4.5 months. Although recurrent atrial tachyarrhythmias were relatively
common (46%), particularly as organized atrial tachycardia (34%), a repeat procedure was usually successful and resulted
in a 6-month arrhythmia-free rate of 81%. At the repeat procedure, recovery of conduction into the previously isolated PLA
was observed in patients who had AF recurrence. Organized atrial tachycardia was due to a small number of mechanisms.
Mitral annular-dependent flutter was commonest and was frequently associated with reconnection across a previously
ablated mitral isthmus line. Flutter sustained by 2 gaps in the ring of lesions was next most common. Whether this
procedure is superior to other techniques is uncertain. The role of additional linear ablations (especially mitral isthmus
ablation, which potentially may be proarrhythmic) in this technique is also not clear. Both these issues are currently under
study.
Atrial Arrhythmias After Single-Ring Isolation of the Posterior Left Atrium and
Pulmonary Veins for Atrial Fibrillation: Mechanisms and Management
Toon Wei Lim, Choon Hiang Koay, Rebecca McCall, Valerie A. See, David L. Ross and Stuart
P. Thomas
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Circ Arrhythm Electrophysiol. 2008;1:120-126; originally published online January 1, 2008;
doi: 10.1161/CIRCEP.108.769752
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