How to perform encircling ablation of the left atrium HANDS ON

HANDS ON
How to perform encircling ablation of the left atrium
Carlo Pappone, MD, PhD, Vincenzo Santinelli, MD
From the Department of Cardiology, Electrophysiology and Cardiac Pacing Unit, San Raffaele Scientific Institute,
Milan, Italy.
The purpose of this article is to describe the technique
and results of circumferential pulmonary vein ablation
(CPVA) in patients with atrial fibrillation (AF) as currently
performed in Milan.1–14 Since a significant learning curve
still exists with the standard procedure, we have recently
developed a new system, called remote magnetic navigation
and ablation, which can be performed by less experienced
operators while at the same time still reducing complications.13 The results of our standard technique with manually
deflectable catheters are based on about 10,000 patients with
paroxysmal, persistent, or permanent AF, many of whom
have structural heart disease.1–12 At present, remote magnetic navigation and ablation has been performed safely in
about 200 patients with paroxysmal, persistent, or permanent AF.
Indications for AF ablation
Inclusion and exclusion criteria are listed in Table 1. We do
not exclude patients with mitral and/or aortic metallic prosthetic valves,6,11 and previous repair of atrial septal defects
is not an absolute contraindication for ablation.
Preablation preparation
All antiarrhythmic drugs are stopped ⬎5 half-lives before
ablation (amiodarone for ⬎3 months). Effective anticoagulation is obtained (international normalized ratio [INR] between 2 and 3), and in patients with permanent AF three or
more consecutive INR values between 2.5 and 3.5 are documented before ablation. A transesophageal echocardiography (TEE) is performed in all patients.
Anticoagulation protocol
Three days before the procedure, oral anticoagulant therapy
is stopped. The night before the procedure, heparin infusion
is started to achieve an activated clotting time (ACT) ranging from 200 to 250 seconds. Heparin is stopped 2 hours
before the ablation procedure to safely obtain vascular access and perform the transseptal puncture. After transseptal
puncture, heparin is restarted as an initial bolus (5,000 U),
followed by infusion or titrated with additional boluses to
maintain the target ACT (between 250 and 300 seconds or
between 300 and 350 seconds if evidence of smoke and/or
decreased velocity is noted at TEE). During the procedure,
Address reprint requests and correspondence: Carlo Pappone, M.D.,
Ph.D., F.A.C.C., Department of Cardiology, San Raffaele University
Hospital, Via Olgettina 60, 20132, Milan, Italy. E-mail address: carlo.
pappone.carlo@hsr.it.
we monitor the ACT every 20 minutes to the target ACT. At
the end of the procedure, protamine (15 mg) is injected to
achieve partial reversal of anticoagulation before sheath
removal. We remove all venous sheaths when ACT is ⬍200.
Heparin is administered intravenously for 24 hours, starting
3 hours after sheath removal at 1,000 U/hour without a
bolus. Thereafter, oral anticoagulant therapy is begun and
low molecular weight heparin is given for 3 days after
discharge. Anticoagulation is discontinued if sinus rhythm
(SR) is maintained for ⬎3 months without any episodes
of AF.
Navigation and mapping systems
Different navigation tools, such as an electroanatomic
mapping system (CARTO, Biosense-Webster) or the EnSite/NavX system (Endocardial Solution, St. Paul, MN) and
more recently a remote navigation system (Niobe II, Stereotaxis, St. Louis) with an integrated CARTO system are
used to determine the ablation catheter position relative to
the mapping electrodes. These technologies significantly
reduce fluoroscopic exposure. Intracardiac echocardiography has been very rarely used. No computer tomographic
scan or magnetic resonance imaging is usually performed
before ablation.
Radiofrequency (RF) ablation targets
Currently, we perform circumferential pulmonary vein (PV)
lesion lines to perform a point-by-point tailored distal disconnection of all PVs (Figures 1 and 2). Additional lesion
lines, including the mitral isthmus line, posterior lines, and
cavotricuspid isthmus, are also performed.4 During the procedure, we attempt to perform local vagal denervation by
eliciting and eliminating vagal reflexes.5 Inducibility of AF
is not routinely assessed.6
Standard circumferential PV ablation
At present, we are using an irrigated-tip ablation catheter
with a distal 3.5-mm tip (ThermoCool, Biosense-Webster)
to ensure lesion transmurality while minimizing risk of
perforation, particularly in the posterior lines.6 We still use
8-mm-tip catheters for cavotricuspid-isthmus ablation line.
Impedance is monitored continuously as it may increase
suddenly if thrombus forms on the catheter tip, and an
impedance map is also constructed.14 In our experience, a
much more useful indicator of thrombus formation is a
40%–50% reduction in the power delivered to reach target
temperature. If thrombus formation is suspected, catheter
1547-5271/$ -see front matter © 2006 Heart Rhythm Society. All rights reserved.
doi:10.1016/j.hrthm.2006.03.003
1106
Heart Rhythm, Vol 3, No 9, September 2006
Table 1
Inclusion criteria
● At least one weekly episode of paroxysmal AF
● At least one monthly episode of persistent symptomatic AF
● Permanent AF
● At least one failed antiarrhythmic drug
Exclusion criteria
● Age ⬎80 years
● Contraindications to anticoagulation
● Presence of cardiac thrombus
● Left atrial diameter ⱖ65 mm
● Life expectancy ⬍1 year
● Thyroid dysfunction
withdrawal from the left atrium (LA) without advancing the
transseptal sheath may be necessary to preserve transseptal
access. This avoids stripping any thrombus present on the
catheter tip as the catheter is withdrawn into the sheath,
which can result in systemic embolization. We normally
start by determining the location of all four major PVs and
the mitral annulus as anatomic landmarks for the EnSite/
NavX system (Figure 3) or the CARTO system and create
the map by entering each PV in turn. To locate PVs, we use
three criteria based on fluoroscopy, electrical activity, and
impedance.14 Entry into the vein is clearly identified as the
catheter leaves the cardiac shadow on fluoroscopy, the impedance usually rises above 140 –150 ⍀, and electrical
activity disappears. Because of the orientation of some veins
and the limitations of catheter shape, it can be difficult to
deeply enter some veins, but the impedance still rises when
the catheter is in the mouth of the vein. To better differentiate between PVs and LA, we use voltage criteria (fractionation of local bipolar electrogram) and impedance
(rise ⬎4 ⍀ above mean LA impedance) to define the PV
ostium. Clearly, the anatomic appearance on CARTO acts
as added confirmation of catheter entry into the PV ostium.
Figure 1 Schematic of CPVA strategy used to distally disconnect PVs
using point-by-point tailored lesions with substrate modification inside
encircled areas.
Figure 2
Panels 1– 4: On tailored ablation lines and within each of the
encircled areas, previous electrical activity (yellow arrows) completely
disappeared after ablation (blue arrows), which indicates distal electrical
disconnection and substrate modification.
The mapping and ablation procedures are performed by
using the CS atrial signal if the patient is in SR or the right
ventricular signal if the patient is in AF; these are the
synchronization triggers for CARTO. If spontaneous ventricular rates during AF are too low, we usually pace the
right ventricle at higher rates to increase the CARTO system
sampling rates. If the patient is in SR, we map during
continuous coronary sinus (CS) pacing to increase the refresh rate. The chamber geometry is reconstructed in real
time by interpolation of the acquired points. Usually, 100
points are required to create adequate maps of LA and PVs
and up to 200 points for accurate mapping of atrial tachycardia (AT). Local activation times can be used to create
activation maps, which are extremely important when attempting to ablate focal or macroreentrant ATs.4,6,8 –12
Figure 3 Posterior view of a NavX geometry showing a detailed postablation voltage map using this system (Endocardial Solutions). Tagged
ablation points (white circles) around the left- and right-sided PVs are
shown; continuous points joining the LSPVs and RSPVs and the LIPVs
and RIPVs with a mitral valve to the LIPV line (mitral isthmus line) are
depicted. The reference catheter is placed in the CS.
Pappone and Santinelli
Encircling Ablation of the Left Atrium
RF applications and energy setting
Once the main PVs and LA have been adequately reconstructed, RF energy is delivered to the atrial endocardium
with RF generator settings of 55– 65°C and a power limit of
100 W, but with irrigated catheters much less energy is
required (40 W-40°C). This is reduced in the posterior wall
to 35 W and 55°C to reduce risk of injury to the surrounding
structures.6,7 RF energy is applied continuously on the
planned circumferential lines as the catheter is gradually
dragged along the line. Continuous catheter movement, often in a to-and-fro movement over a point, helps keep
catheter tip temperature down because of passive cooling.
Successful lesion creation at each point is considered to
have taken place when the local bipolar voltage has decreased by 90% or to ⬍0.05 mV. On average, with
irrigated-tip catheters, a total of 15 seconds of RF is required. If the catheter position deviates significantly from
the planned line or falls into a PV, RF application is immediately terminated until the catheter is returned to a suitable
location. Circumferential ablation lines are usually created
starting at the lateral mitral annulus and withdrawing posterior and then anterior to the left-sided PVs, passing between the left superior PV (LSPV) and the LA appendage
(LAA) before completing the circumferential line on the
posterior wall of the LA. The “ridge” between the LSPV
and LAA may be identified by fragmented electrograms
from collision of activity from the LAA and LSPV/LA. The
appendage is identifiable by a significantly higher impedance (⬎4 ⍀ above LA mean) and a high-voltage local
bipolar electrogram, with characteristically organized activity in fibrillating patients. The right PVs are isolated in a
similar fashion, and then a posterior line connecting the two
circumferential lines is made to reduce the risk of macroreentrant ATs. Gaps are defined as breakthroughs in an
ablated area and identified by sites with single potentials
and by early local activation. Usually, we do not validate
circumferential lesions around PVs by pacing maneuvers.
Rather, we accurately validate the bipolar voltage abatement on lesions lines as well as within the encircled areas
(Figures 1 and 2) and perform a voltage remap, acquiring
new points on the existing geometry to give voltage measurements. This should characteristically show low voltage
(red) within the PV encircling lines (Figure 3). Completeness of lesion lines, particularly at the mitral isthmus, is
critical in preventing postablation macroreentrant LA tachycardias, which in the majority of cases are mitral-isthmus
dependent and incessant.4 The completeness of the mitral
isthmus line is demonstrated during CS pacing by endocardial and CS mapping by looking for widely spaced local
double potentials across the line of block and is confirmed
by differential pacing. In our experience, the minimum
double potential interval at the mitral isthmus during CS
pacing, after block is achieved, is between 150 and 300 ms,
depending on the atrial dimensions and the extent of scarring and lesion creation.4,6 After the planned lines of block
have been created, the LA is remapped, and the preablation
1107
and postablation activation maps are compared. Incomplete
block is revealed by impulse propagation across the line; in
such a case, further RF applications are given to complete
the line of block. We observe termination of AF during the
procedure in about one-third of patients. If AF does not
terminate during RF, then transthoracic cardioversion is
performed at the end of the procedure. If AF recurs immediately after cardioversion, then the completeness of the
lines is reassessed. Once SR is restored with either RF or
cardioversion, attempts to reinduce AF by rapid atrial pacing with and without isoproterenol infusion are only made
for investigational purposes in selected patients. We do not
isolate the superior vena cava for AF treatment. At present,
the CPVA procedure usually lasts approximately 1 hour,
including 20 minutes for pre-/postmapping and 40 minutes
for ablation.
Local vagal denervation
A recent target reported for the first time by our group in
Milan has been local vagal denervation.5,6 Potential vagal
target sites are identified during the procedure in more than
one-third of patients. Vagal reflexes are defined as sinus
bradycardia (⬍40 beats/min) or asystole, AV block, or
hypotension occurring within a few seconds of the onset of
RF application. If a reflex is elicited, RF energy is delivered
until such reflexes are abolished, or for up to 30 seconds.
The endpoint for ablation at these sites is termination of the
reflex, followed by sinus tachycardia or AF. Failure to
reproduce the reflexes with repeat RF is considered confirmation of denervation. Complete local vagal denervation is
defined by the abolition of all vagal reflexes.
Complication rates
Complications rates with standard CPVA (manually deflectable catheters) are shown in Table 2. Postablation LA tachycardias usually do not require a repeat of procedure, as most
resolve spontaneously within 5 months after the index procedure.4,6 Atrio-esophageal fistulas rarely occur but may be
dramatic and devastating.6,7 We recommend lower RF energy application when ablating on the LA posterior wall and
making the line on the posterior wall near to the roof of the
LA, where the LA is not in direct contact with the esophagus.6,7
Table 2
Complications after CPVA
%
●
●
●
●
●
●
●
●
0%
0.1%
0.03%
0.2%
0.1%
0.03%
0%
6%
Death
Pericardial effusion
Stroke
Transient ischemic attack
Tamponade
Atrio-esophageal fistula
Pulmonary vein stenosis
Left atrial tachycardia
1108
Heart Rhythm, Vol 3, No 9, September 2006
Remote circumferential PV ablation
We have recently developed a new technique (Niobe II, Stereotaxis) for remote circumferential PV ablation using a soft
magnetic catheter.13 The operator is positioned in a separate
control room, at a distance from the X-ray beam and the
patient’s body. A 4-mm magnetic catheter (NaviStar-RMT,
Biosense Webster, Inc.) is integrated with a newly developed electroanatomical mapping system (CARTO-RMT
mapping system). Additional magnets in the distal portion
of the device can be deflected in any desired direction and
steered by the magnetic navigation system. The catheter can
be softly advanced or retracted by a mechanical device
(Cardiodrive, Stereotaxis). All magnetic field vectors used
for each target navigation can be stored and, if necessary,
reapplied while the magnetic catheter is navigated automatically.
Remote mapping and ablation
A transseptal sheath positioned just proximal to the fossa
ovalis allows the greatest movement of the magnetic wire
catheter. After synchronizing with respiratory and cardiac
cycles, such as inspiration and end-diastolic period, a pair of
best-matched right anterior oblique/left anterior oblique
(RAO/LAO) images are transferred into the Navigant
screen as background references for orientation and navigation. Next a PV location is selected by a preset magnetic
field vector, and during navigation many points can be
simultaneously acquired by the NaviStar-RMT magnetic
catheter (Figure 4). Remote CPVA is usually performed
with a target temperature of 65°C and a power limit of
50 W. All ablation lines are performed by sequentially navigating to contiguous points with a single 5- to 10-second
application of RF current, which is able to achieve a ⬎90%
reduction in the bipolar electrogram amplitude (Figure 5).
The lesion line can be resent to and recorded on the fluo-
Figure 5
Post–remote ablation color-coded voltage remap of the LA is
shown. The lesion set includes circumferential lesions (red circles) around
the left- and right-sided PVs with additional posterior lines and the mitral
isthmus line.
roscopic image. Potential vagal target sites are also identified during the procedure as with the manual approach.
Sheath insertion and positioning of diagnostic catheters,
including the magnetic catheter, requires a few minutes
(min-max, 5–12 minutes). After crossing the atrial septum
and positioning the transseptal sheath, the operator leaves
the interventional room to perform mapping and ablation
from the control room. Based on our experience, remote
magnetic navigation and ablation to all targeted sites can be
safely and successfully achieved in all patients.
At the beginning of the learning curve, tip orientation
was frequently adjusted as the catheter was retracted and
advanced to access all PVs by using this sequence when
feasible: LSPV, left inferior PV (LIPV), right superior PV
(RSPV), and finally right inferior PV (RIPV). Afterward,
the mitral valve annulus and the LAA can be accessed by
selecting different field directions on NaviSphere. Finally,
we navigate the magnetic catheter in rapid sequence to the
posterior wall, roof, septal wall, and anterior wall.
Comparison of standard versus remote CPVA
Figure 4
Remote magnetic navigation with the Niobe II system (Stereotaxis). The figure shows remote navigation of a soft magnetic catheter on
the Navigant screen toward the LSPV (panel 1), LIPV (panel 2), RSPV
(panel 3), and RIPV (panel 4). A preset (as a stored vector, LSPV) was
selected from the preset list indicated on the right side of each panel and
then applied to the desired direction. RAO and LAO appear on the bottom
of each panel, and the virtual catheter is marked in yellow. On the top of
each panel, two anatomic images of the LA (NaviSphere) are depicted.
Initial results indicate that remote navigation and ablation is
a simple, safe, and useful system for AF ablation that does
not require a substantial learning curve because the endpoint
can be successfully reached in almost all patients undergoing such therapy. In the first patients, the procedure and
fluoroscopy times were long, which was due to the need to
visually confirm catheter location and stability during navigation and RF application. The procedure, which included
navigation and ablation, was done from the control room,
which reduced fluoroscopic exposure time for the operator.
The manual approach is operator-dependent, while the remote one is not, but it is dependent on a well-trained team.
Pappone and Santinelli
Encircling Ablation of the Left Atrium
1109
This may explain why the overall procedure time can be
longer in the remote group than in the control group, while
mapping times in both approaches are similar. Ablation
time to complete circumferential lesions around right-sided
PVs is shorter remotely, which indicates that there are no
challenging sites as with standard CPVA, thus avoiding
unnecessary RF energy applications.
present, then a repeat procedure is scheduled for 6 months
after the index procedure. During the repeat ablation procedure, an isthmus line for typical atrial flutter, LA mapping, and ablation of LA flutter or a touchup of the prior
ablation lines is performed. A maximum of three separate
ablation procedures per patient is allowed.
Follow-up and long-term efficacy of standard
and remote CPVA
1. Pappone C, Rosanio S, Oreto G, Tocchi M, Gugliotta F, Vicedomini G, Salvati
A, Dicandia C, Mazzone P, Santinelli V, Gulletta S, Chierchia S. Circumferential radiofrequency ablation of PV ostia. Circulation 2000;102:2619 –2628.
2. Pappone C, Oreto G, Rosanio S, Vicedomini G, Tocchi M, Gugliotta F, Salvati
A, Dicandia C, Calabro MP, Mazzone P, Ficarra E, Di Gioia C, Gulletta S, Nardi
S, Santinelli V, Benussi S, Alfieri O. Atrial electroanatomic remodeling after
circumferential radiofrequency PV ablation. Efficacy of an anatomic approach in
a large cohort of patients with AF. Circulation 2001;103:2539 –2544.
3. Pappone C, Rosanio S, Augello G, Gallus G, Vicedomini G, Mazzone P,
Gulletta S, Gugliotta F, Pappone A, Santinelli V, Tortoriello V, Sala S, Zangrillo
A, Crescenzi G, Benussi S, Alfieri O. Mortality, morbidity, and quality of life
after circumferential pulmonary vein ablation for atrial fibrillation: outcomes
from a controlled nonrandomized long-term study. J Am Coll Cardiol 2003;42:
185–197.
4. Pappone C, Manguso F, Vicedomini G, Gugliotta F, Santinelli O, Ferro A,
Gulletta S, Sala S, Sora N, Paglino G, Augello G, Agricola E, Zangrillo A,
Alfieri O, Santinelli V. Prevention of iatrogenic atrial tachycardia after ablation
of atrial fibrillation. A prospective randomized study comparing circumferential
pulmonary vein ablation with a modified approach. Circulation 2004;110:3036 –
3042.
5. Pappone C, Santinelli V, Manguso F, Vicedomini G, Gugliotta F, Augello G,
Mazzone P, Tortoriello W, Landoni G, Zangrillo A, Lang C, Tomita T, Mesas
C, Mastella E, Alfieri O. PV denervation enhances long-term benefit after
circumferential ablation for paroxysmal AF. Circulation 2004;109:327–334.
6. Pappone C, Santinelli V. The who, what, why, and how-to guide for circumferential pulmonary vein ablation. J Cardiovasc Electrophysiol 2004;15:1226 –
1230.
7. Pappone C, Oral H, Santinelli V, Vicedomini G, Lang CC, Manguso F,
Torracca L, Benussi S, Alfieri O, Hong R, Lau W, Hirata K, Shikuma N, Hall B,
Morady F. Atrio-esophageal fistula as a complication of percutaneous transcatheter ablation of AF. Circulation 2004;109:2724 –2726.
8. Pappone C, Santinelli V. Atrial fibrillation ablation: state of the art. Am J
Cardiol 2005;96:59L– 64L.
9. Pappone C, Santinelli V. Atrial fibrillation ablation: a realistic alternative to
pharmacologic therapy. Nat Clin Pract Cardiovasc Med 2005;2:608 – 609.
10. Pappone C, Santinelli V. Towards a unified strategy for atrial fibrillation ablation? Eur Heart J 2005;26:1687–1688.
11. Lang CC, Santinelli V, Augello G, Ferro A, Gugliotta F, Gulletta S, Vicedomini
G, Mesas C, Paglino G, Sala S, Sora N, Mazzone P, Manguso F, Pappone C.
Transcatheter radiofrequency ablation of atrial fibrillation in patients with mitral
valve prostheses and enlarged atria: safety, feasibility, and efficacy. J Am Coll
Cardiol 2005;45:868 – 872.
12. Mesas CE, Pappone C, Lang CC, Gugliotta F, Tomita T, Vicedomini G, Sala S,
Paglino G, Gulletta S, Ferro A, Santinelli V. Left atrial tachycardia after
circumferential pulmonary vein ablation for atrial fibrillation: electroanatomic
characterization and treatment. J Am Coll Cardiol 2004;44:1071–1079.
13. Pappone C, Vicedomini G, Manguso F, Gugliotta F, Mazzone P, Gulletta S, Sora
N, Sala S, Marci A, Augello G, Rivolsi L, Santagostino A, Santinelli V. Robotic
magnetic navigation for atrial fibrillation ablation. J Am Coll Cardiol 2006;47:
1390 –1400.
14. Lang CC, Gugliotta F, Santinelli V, Mesas C, Tomita T, Vicedomini G, Augello
G, Gulletta S, Mazzone P, De Cobelli F, Del Maschio A, Pappone C. Endocardial impedance mapping during circumferential pulmonary vein ablation of
atrial fibrillation differentiates between atrial and venous tissue. Heart Rhythm
2006;3:171–178.
Patients are supplied with a transtelephonic event recorder
for at least 1 year after the ablation and are requested to send
recordings weekly, irrespective of the presence or absence
of symptoms. We arrange clinical assessment, Transthoracic echocardiography (TTE) and 24-hour ambulatory recordings 1, 3, 6, and 12 months after the procedure. Because
a large minority of patients have early recurrence of AF
after ablation, many patients are prescribed antiarrhythmic
drugs. Long-term efficacy of standard CPVA is ⬎90% for
patients with paroxysmal or persistent AF and ⬎80% for
permanent AF. In patients with paroxysmal AF and local
vagal denervation, the long-term success rate is close to
100%. Early recurrences of AF usually occur within the first
2 months after the index procedure, but in half of cases they
are a transient phenomenon that do not require a repeat
procedure. After ablation, the follow-up management depends on the clinical and echocardiographic characteristics
of the patient population. In patients with LA diameter
(LAD) ⬎55 mm and permanent AF, we prescribe oral
amiodarone at a total dose of 200 mg, 5 days a week for 30
days, and then 100 mg, 5 days a week for the following 30
days. If TTE performed at 2 months shows a decrease in
LAD ⬎35 mm associated with improved atrial transport
function and persistent SR documented by daily transtelephonic recordings, amiodarone is replaced by oral sotalol
(120 mg daily for 30 days). Usually, sotalol is discontinued
after 30 days if SR persists. Angiotensin receptor (ATR)
blockers usually are withdrawn 90 days after procedure but
are maintained in patients who were undergoing ATR
blocker therapy before the procedure. In patients with LAD
between 40 and 55 mm and paroxysmal AF, we prescribe
sotalol 40 mg twice daily and flecainide 50 mg twice daily
for 30 days. If the LAD decreases after this period, the
patient continues taking sotalol for another 30 days. In
patients with LAD ⬍40 mm and paroxysmal AF, we prescribe sotalol 40 mg daily for 30 days. If recurrence of
persistent AF or monthly episodes of symptomatic paroxysmal AF occur beyond the first month after ablation or
incessant highly symptomatic left or right atrial flutter is
References