Download Acute and long-term results of radiofrequency ablation of common

European Heart Journal (2003) 24, 956–962
Acute and long-term results of radiofrequency
ablation of common atrial flutter and the
influence of the right atrial isthmus ablation on
the occurrence of atrial fibrillation
Sebastian Schmieder, Gjin Ndrepepa, Jun Dong, Bernhard Zrenner,
Jürgen Schreieck, Michael A.E. Schneider, Martin R. Karch,
Claus Schmitt *
Deutsches Herzzentrum München and 1. Medizinische Klinik, Klinikum rechts der Isar,
Technische Universität München, Lazarettstrasse 36, D-80636 München, Germany
Received 3 December 2002; accepted 3 December 2002
KEYWORDS
Atrial flutter;
Atrial fibrillation;
Radiofrequency ablation
Aims The purpose of this study was to evaluate the acute success rate and long-term
efficacy of radiofrequency ablation of common type atrial flutter (AFL) by using a
standardised anatomical approach in a large series of patients and to assess the
influence of right atrial isthmus ablation on the occurrence of atrial fibrillation. There
are no large scale prospective or retrospective multicentre studies for radiofrequency
ablation of AFL.
Methods and results The study population consisted of 363 consecutive patients with
AFL (mean age 58±16 years, 265 men) who underwent radiofrequency ablation at the
inferior vena cava-tricuspid annulus (IVC-TA) isthmus using a standardised anatomic
approach. Bidirectional isthmus block at the IVC-TA was achieved in 328 patients
(90%). Following radiofrequency ablation, 343 patients (95%) were followed for a
mean of 496±335 days. During the follow-up period, 310 patients (90%) remained
free of AFL recurrences. Multivariate analysis identified five independent predictors
of AFL recurrence: fluoroscopy time (p<0.001), atrial fibrillation after AFL ablation
(p⫽0.01), lack of bidirectional block (p⫽0.02), reduced left ventricular function
(p⫽0.035) and right atrial dimensions (p⫽0.046). Atrial fibrillation occurrence was
significantly reduced after AFL ablation (112 in 343 patients, 33%) as compared to
occurrence of atrial fibrillation before radiofrequency ablation (198 in 363 patients,
55%, p<0.001).
Conclusion The current anatomical ablation approach for AFL and criteria for evaluation of the IVC-TA isthmus block is associated with an acute success rate of 90% and
a long-term recurrence rate of 10%. Radiofrequency ablation of common AFL results in
a significant reduction in the occurrence of atrial fibrillation.
© 2003 Published by Elsevier Science Ltd on behalf of The European Society of
Cardiology.
Introduction
* Corresponding author. Tel.: +49-89-1218-4025;
+49-89-1218-4593
E-mail address: [email protected] (C. Schmitt).
fax:
Typical atrial flutter (AFL) is a macroreentrant
supraventricular tachycardia whose reentry circuit
is entirely located in the right atrium.1,2 A recent
0195-668X/03/$ - see front matter © 2003 Published by Elsevier Science Ltd on behalf of The European Society of Cardiology.
doi:10.1016/S0195-668X(02)00846-1
Radiofrequency ablation of atrial flutter
population-based study have suggested that the
overall incidence of AFL is 88/100 000 personyears or 200 000 new cases in the US population annually.3 AFL is highly symptomatic in the
majority of patients4 and is associated with morbid
events such as tachycardic cardiomyopathy,5
thromboembolism,6–8 atrial stunning after therapeutic termination,9,10 inappropriate heart rate
during effort11 and marked reduction of exercise
tolerance especially in patients with advanced
structural heart disease.12 Radiofrequency current
application at the inferior vena cava-tricuspid
annulus (IVC-TA) isthmus evolved from an experimental technique to the therapy of choice for the
treatment of AFL. Earlier single centre radiofrequency studies reported a high initial success
rate but, on the other hand a relatively high recurrence rate of 11–25%.1,13,14 Clinical application of
the anatomical approach of radiofrequency ablation15 and development of criteria for evaluation of
bidirectional isthmus block16,17 transformed the
technique of ablation of AFL into a safe and effective means of therapy and improved substantially
the long-term results. However, the NASPE Prospective Catheter Ablation Registry for year 1998
reported an acute success of AFL ablation of 85.8%
and recurrence rates of 14.7%.18 Reasons for these
less favourable results as compared to the aforementioned studies were not known. On the other
hand, there are no large scale prospective or retrospective multicentre studies for radiofrequency
ablation of AFL.18
Thus, the purpose of this study was to evaluate
the acute success rate and long-term efficacy of
radiofrequency ablation of common type AFL by
using a standardised anatomical approach in a large
series of patients. A second objective of the study
was to assess the influence of isthmus ablation on
the occurrence of atrial fibrillation.
Methods
957
Table 1
Patient characteristics
Clinical characteristics
Valuea
Total number of patients
Females
Male: female ratio
Structural heart disease
Arterial hypertension
Coronary artery disease
Surgically corrected atrial septal defect
Prosthetic valve surgery
Dilated cardiomyopathy
Reduced left ventricular function (<50%)
Atrial fibrillation prior ablation
Antiarrhythmic therapy prior ablation
Atrial dimensions
Left atrial transverse diameter (mm)
Left atrial longitudinal diameter (mm)
Right atrial transverse diameter (mm)
Right atrial longitudinal diameter (mm)
Atrial flutter
Counterclockwise
Clockwise
Both types
363
98
2.7:1
261 (72)
188 (52)
93 (26)
30 (8)
25 (7)
13 (4)
97 (27)
198 (55)
288 (79)
a
40±7
55±9
40±8
54±8
298 (82)
52 (14)
14 (4)
Numbers in brackets show percentage.
paroxysmal in 176 patients and persistent in 22
patients. The first episodes suggestive of atrial
fibrillation were reported 50±49 months before
the ablation procedure. In 261 patients (72%) a
structural heart disease was found. Clinical characteristics of the patients are shown in Table 1.
Antiarrhythmic medications were withheld at least
five plasma half-lives before electrophysiological study except for amiodarone (23 patients).
Coumadine derivatives were stopped 2 days before
the procedure.
All patients underwent an initial clinical evaluation that included history, physical examination,
12-lead surface electrocardiogram, 24-h electrocardiographic monitoring, X-ray examination,
blood chemistry tests and two-dimensional
echocardiography with colour flow Doppler
measurements.
Study population
From October 1998 till June 2002, 363 consecutive
patients (mean age 58±16 years, range 2–86 years,
265 men) with common AFL who underwent radiofrequency ablation at our hospital were included
in this study. All patients had spontaneous AFL
episodes documented with 12-lead surface electrocardiogram (counterclockwise flutter in 298
patients, 82% and clockwise flutter in 52 patients,
14% and both types in 14 patients 4%). One hundred
and eighty-nine patients (55%) had a documented
history of atrial fibrillation. Atrial fibrillation was
Definition of arrhythmia
Electrocardiographic/electrophysiologic
criteria
of common type AFL were as follows: (1) typical surface electrocardiographic appearance for
counterclockwise and clockwise AFL, (2) counterclockwise or clockwise activation around the tricuspid annulus and (3) concealed entrainment
during pacing from the IVC-TA isthmus.2,19 Patients
with intra-atrial reentrant tachycardia following
reparative surgery for complex congenital heart
disease were excluded from this study.
958
Electrophysiological study
Before undergoing mapping/ablation procedure,
patients gave written informed consent. Three
electrode catheters were inserted from one or both
femoral veins and positioned in the right atrium and
the coronary sinus: one 20-polar catheter was positioned around the tricuspid annulus with the electrode pair 1/2 located in the low portion of the
lateral wall near the lateral entry of the IVC-TA
isthmus; one eight-polar mapping catheter was
inserted in the coronary sinus and a third catheter
was the ablation catheter. In 18 patients (5%), a
4-mm tip ablation catheter was used. In the
remaining patients, either an 8-mm tip (n⫽290,
85%) or cooled-tip ablation (n⫽55, 15%) catheters
were used. In the 2-year-old patient, 2.5 F mapping
catheters were used.
In those subjects who were not in AFL at the time
of electrophysiologic testing, programmed atrial
stimulation from the coronary sinus and high right
atrium was performed. During sustained AFL, activation sequence mapping was performed to define
the nature of arrhythmia. Entrainment mapping
was performed by pacing at the IVC-TA isthmus
with paced cycle length of 20–40 ms shorter than
the arrhythmia cycle lengths.
Radiofrequency ablation and isthmus block
evaluation
The anatomical approach with a goal of producing a
line of block between the tricuspid annulus and the
inferior vena cava was used for radiofrequency
ablation. The ablation catheter was steered under
fluoroscopic control and placed in the isthmus
region. The catheter was manoeuvred to approach
the tricuspid annulus (local electrogram reflecting
equally the atrial and ventricular signals) and then
withdrawn gradually from the tricuspid annulus
towards the inferior vena cava. If radiofrequency
ablation was performed during AFL episodes,
coincidence of local electrogram with the middle of
plateau (in counterclockwise flutter) or the downsloping part of the P waves (clockwise flutter) in
the inferior electrocardiographic leads served as
criteria for correct mid-isthmus positioning of the
ablation catheter.20 Radiofrequency energy was
delivered as a nonmodulated radiofrequency current at a frequency of 550 kHz between the tip of
the catheter and a skin patch placed under the left
shoulder for up to 60 s at a preset temperature
mode (60 °C). Ablation was considered successful
when the arrhythmia was no longer inducible and
the criteria for bidirectional isthmus conduction
block were observed.6,17 Provocative pacing and
S. Schmieder et al.
isthmus conduction testing were performed
immediately after and at 30–45 min after the last
radiofrequency delivery that resulted in isthmus
block. In the first series of the patients (120
patients) sequence activation criteria of the lateral
and posterior wall of the right atrium during pacing
from the coronary sinus and the low lateral wall
were used to test conduction in the post-ablation
isthmus. In patients ablated during the last 2 years,
sequence and local criteria (double potentials in
the isthmus region during pacing from the coronary
sinus and low lateral wall of the right atrium) for
isthmus block were applied. Transthoracic echocardiography was performed immediately following
ablation procedure to seek for eventual pericardial
effusion.
Post-ablation management and follow-up
Patients were discharged from hospital on treatment for the underlying heart disease. All
patients were discharged on oral anticoagulants
for 2 months. In patients with concomitant atrial
fibrillation oral anticoagulants were maintained.
Follow-up information was obtained at the time
of revisits at the ambulatory arrhythmia clinic or
by telephone contact with the patients or the
patients' private physicians at 3 months, 6 months,
1 year and then yearly after the ablation procedure. Whenever the patients had symptoms suggestive of arrhythmia they were advised to seek
consultation from the ambulatory arrhythmia clinic
or contact their physicians to evidence the eventual
arrhythmia relapse. In case of AFL recurrence,
the patients were hospitalised and reablation was
offered.
Statistical analysis
Data are presented as mean±SD, percentage or
range. Univariate comparisons between variables
were made by chi-square test for categorical variables and unpaired t-test for continuous variables.
Cumulative probability of freedom from AFL recurrence was calculated with the Kaplan–Meier
method. Multivariate analysis was performed with a
Cox proportional hazards model with stepwise
backward selection to identify independent factors
for AFL recurrence. Clinical and procedural variables that were subjected to the model were: age,
sex, left atrial dimensions, right atrial dimensions,
structural heart disease, left ventricular ejection
fraction, atrial fibrillation before ablation, atrial
fibrillation after ablation, achievement of bidirectional isthmus block, type of the ablation catheter,
Radiofrequency ablation of atrial flutter
fluoroscopy time and number of radiofrequency
current applications. A p<0.05 was considered
statistically significant
Results
Patient characteristics
Clinical characteristics of the patients are shown in
Table 1. Included in the study were patients with
ages from 2 to 86 years old. AFL was more frequent
in the age group of 55–75 years (225 patients, 62%).
Male patients predominated. Male-to-female ratio
was found to be 2.7:1. The most common structural
heart disease was arterial hypertension (188
patients, 52%) followed by coronary artery disease
(93 patients, 26%). In 102 patients no clinically
detectable structural heart disease was found. In
198 patients (55%) besides AFL, atrial fibrillation
episodes were documented before radiofrequency
ablation.
Electrophysiological data and acute ablation
results
At the time of electrophysiologic testing, 175
patients (48%) were in AFL and 162 patients presented with sinus rhythm (45%). In 70 of the
patients with sinus rhythm at the time of the electrophysiological procedure atrial pacing induced
AFL whereas in 93 patients (all of them with electrocardiographical documentation of spontaneous
episodes of sustained typical AFL) radiofrequency
ablation and testing of completeness of the isthmus
block were performed during coronary sinus pacing.
In 22 patients with persistent atrial fibrillation,
internal cardioversion was performed before the
ablation procedure. In patients with spontaneous
or induced counterclockwise and clockwise AFL
the cycle lengths were 239±27 and 241±42 ms
(p⫽0.80), respectively.
Radiofrequency ablation at the IVC-TA was
attempted in all patients. Criteria for bidirectional
block were achieved in 328 patients (90%). Mean
fluoroscopy time was 28±21 min. Mean number of
radiofrequency applications was 22±17 deliveries.
In 35 patients (10%), despite more radiofrequency
applications (40±20 vs. 21±17, p<0.001) or longer
fluoroscopy times (56±34 vs. 27±20 min, p<0.001)
as compared to successfully ablated patients, criteria for bidirectional block could not be achieved.
Complications
In nine patients (nearly 3%) procedure-related complications were observed. In four patients, femoral
959
artery-to-femoral vein fistulas were documented.
In two patients, acute complete atrioventricular
conduction block was produced during isthmus
ablation for which dual-chamber pacemakers were
implanted. One patient collapsed 10 days after
ablation procedure and complete atrioventricular
conduction block was documented. The patient was
resuscitated and a VVI pacemaker was implanted.
The patient died 3 months later due to progression of congestive heart failure. In two patients
slight pericardial effusion was detected by transthoracic echocardiography. No pericardial puncture was applied and no other clinical events were
observed.
Medications at discharge
Following the radiofrequency ablation patients
were discharged on the following antiarrhythmic
regimen: beta blockers (291 patients), amiodarone
(10 patients) and flecainide (one patient). No
statistical differences were observed between
antiarrhythmic therapy before (288 patients, 79%)
and after ablation (302 patients, 83%, p⫽0.18).
All patients were discharged on coumadine
derivatives. In patients without AFL recurrences,
coumadine derivatives were stopped after 2 months
of follow-up. In patients with atrial fibrillation episodes (112 patients, see below) coumadine derivatives were maintained. Angiotensin-converting
enzyme inhibitors, diuretics and digitalis were
prescribed in 166, 118 and 20 patients, respectively. Aspirin was prescribed in 85 patients after
discontinuation of coumadine derivatives.
Follow-up results
Three hundred and forty-three patients (95% of the
study population) were followed for a mean of
496±335 days. Twenty patients were lost during
follow-up. During this time interval six patients
died. Two patients died due to malignancies (one
breast cancer and one lung cancer). Three patients
with advance heart disease died due to progression
of congestive heart failure including one patient
with an implanted internal cardioverterdefibrillator. One patient with pemphigus vulgaris
died due to multi-organ failure. During the
follow-up period, 310 patients (90%) were free of
AFL recurrences. In 33 patients (10%) recurrences
of typical AFL occurred and were reablated. Four
patients underwent a third ablation procedure.
Recurrences occurred in nine of 35 patients (26%)
in whom no criteria for bidirectional isthmus
block were achieved and 24 of 328 patients (7%)
960
Fig. 1 Kaplan–Meyer cumulative probability of survival free of
AFL recurrence during follow-up.
with bidirectional isthmus block (p⫽0.002).
Kaplan–Meyer analysis revealed that the majority
of recurrences occurred in the first months following the ablation procedure (Fig. 1). Multivariate
analysis identified five independent predictors of
AFL recurrence: fluoroscopy time (p<0.001), atrial
fibrillation after ablation (p⫽0.01), lack of bidirectional block (p⫽0.02), reduced left ventricular
function (p⫽0.035) and right atrial dimensions
(p⫽0.046).
Atrial fibrillation after AFL ablation
As compared with atrial fibrillation episodes before
the radiofrequency ablation, the incidence of atrial
fibrillation after the flutter ablation was reduced
significantly (112 patients, 33%) as compared to
occurrence of atrial fibrillation before radiofrequency ablation (198 in 363 patients, 55%,
p<0.001). Proportions of the patients with atrial
fibrillation before and after radiofrequency
ablation are shown in Fig. 2.
Discussion
This study evaluated the efficacy of radiofrequency
ablation for treatment of AFL in a large series of
patients analysed retrospectively. Since, a standard anatomical approach and criteria for evaluation
of isthmus block were used in all patients, results
of this study reflect the therapeutic power of a
mature and standardised radiofrequency ablation
approach for this arrhythmia.
S. Schmieder et al.
Fig. 2 Proportions of the patients with atrial fibrillation before
and after radiofrequency ablation for AFL. Black and white bars
show the total number of patients and the patients with atrial
fibrillation, respectively.
Acute results of radiofrequency ablation of
AFL
Our study showed that radiofrequency ablation at
the IVC-TA isthmus results in a high acute success
rate of 90%. In 10% of patients, despite more radiofrequency current deliveries, we were unable to
achieve a complete isthmus block. These data
coincide with a recent study by Jais et al. who
found that in 7.6% of the patients conventional
radiofrequency ablation failed to create a complete isthmus block.21 Reasons for failure to produce a complete isthmus block are unclear.
However, several factors might be responsible.
First, anatomic factors (thicker isthmus myocardium or an isthmus geometry which prevents
a close catheter tissue contact throughout the
isthmus entirety) should be considered.21,22 The
fact that Jais et al. succeeded in producing complete isthmus block using an irrigated-tip catheter
which results in deeper lesions supports the
importance of this factor.21 Second, with the use
of conventional mapping technique the possibility
of rapid conduction around the posterior aspect of
the inferior vena cava23 cannot be excluded.
In the latter situation, the completeness of the
isthmus block cannot be evaluated.
Long-term results of radiofrequency
ablation of AFL
During a mean follow-up of 496±335 days, 10% of
the patients developed recurrences of AFL. Interestingly, these data coincide with two recent
studies which included a relatively large number of
Radiofrequency ablation of atrial flutter
patients.18,24 In a series of 200 patients with common AFL Fischer et al. reported a recurrence rate
of AFL of 15.5% after a mean of follow-up of 24±9
months.24 In the 1998 NASPE Prospective Catheter
Ablation Registry, Scheinman and Huang18 reported
a similar recurrence rate of 14.8%. Several other
studies, in which conduction through the isthmus
region was verified with electroanatomic mapping,
have demonstrated resumption of the transisthmus conduction following radiofrequency ablation for cure of AFL.25,26 From these studies and
the present one, it seems that isthmus conduction
resumed in nearly 7% of patients with AFL in whom
an acute isthmus bidirectional block has been evidenced by the current criteria. Although, the exact
factors that favour the resumption of the conduction through acutely ablated isthmus are not clear,
the possible role of acute ischaemia and oedema
caused by radiofrequency ablation27 might be considered as factors that participate in acute interruption of the trans-isthmus conduction, masking
the presence of still viable isthmus myocardium.
Since these factors fade gradually after acute
damage, viable myocardium at the isthmus might
restore capacity for conduction. Improvement of
isthmus conduction with isoproterenol underscores
the importance of these factors.28 Furthermore,
details of isthmus remodelling following radiofrequency ablation for AFL are obscure. Our study
showed that multiple factors like those that reflect
the severity of the structural heart disease (left
ventricular function and atrial dimensions), trigger
factors (atrial fibrillation after ablation) and procedural parameters (longer procedures and failure
to achieve bidirectional isthmus block) were independent predictors for AFL recurrences following
radiofrequency ablation.
Incidence of atrial fibrillation before and
after ablation
A close link between AFL and fibrillation has been
demonstrated from Holter monitoring29,30 and electrophysiologic studies.31–33 In patients with AFL a
high incidence of atrial fibrillation has been
reported16,24,34–36 which might be explained with
more advanced heart disease as compared with
patients with flutter episodes only. However,
the impact of AFL ablation on the incidence of
atrial fibrillation is complex and still an issue of
debate.35,37 Previous studies have suggested the
importance of right AFL for induction of atrial fibrillation.38 A possible reduction in the atrial fibrillation episodes after radiofrequency ablation
of AFL have been suggested by small-number
961
studies.39,40 Our data gathered from a large number
of patients show that radiofrequency ablation
of AFL reduces significantly the incidence of atrial
fibrillation and stress the fact that regular
supraventricular rhythms do play a role in
precipitation of atrial fibrillation.
Conclusions
The current anatomical ablation approach and set
of criteria to assess post-ablation isthmus block is
associated with an acute success rate of 90% and
long-term recurrence rate of 10%. Radiofrequency
ablation of common AFL results in a significant
reduction of incidence of atrial fibrillation.
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