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How to select patients for atrial fibrillation ablation
Hakan Oral, MD, Fred Morady, MD
From the Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan.
The goals of therapy for atrial fibrillation (AF) are elimination of symptoms and improvement in quality of life;
prevention of complications such as thromboembolic events
and tachycardia-mediated cardiomyopathy; and, at least in
theory, improvement in survival.
From an evidence-based perspective, the primary benefit
of catheter ablation of AF has been demonstrated to be
improvement in symptoms and quality of life. Improvements in left atrial size, left ventricular ejection fraction, and
New York Heart Association (NYHA) functional class also
have been reported.1–3
Theoretically, maintenance of sinus rhythm after catheter
ablation should prevent thromboembolic events due to AF.
After catheter ablation of AF, left atrial transport function
may decrease by 30% in patients with paroxysmal AF and
improve in patients with chronic AF.4 Whether the improved transport function in patients with chronic AF and
the residual transport function in patients with paroxysmal
AF are sufficient to prevent left atrial thrombus formation is
unclear. No studies have demonstrated the long-term safety
of discontinuation of anticoagulation in patients with AF
who have remained in sinus rhythm after catheter ablation.
It is important to keep this in mind when considering the
option of catheter ablation in asymptomatic individuals with
AF who desire the procedure primarily because they would
like to avoid long-term anticoagulation with warfarin.
Although the original AFFIRM (Atrial Fibrillation Follow-Up Investigation of Rhythm Management) trial demonstrated equivalent survival in patients randomly assigned
to rate-control and rhythm-control strategies, a subsequent
post hoc on-treatment analysis demonstrated that sinus
rhythm was an independent predictor of improved
survival.5,6 Furthermore, a nonrandomized clinical registry
from a single center suggested that maintenance of sinus
rhythm after catheter ablation is associated with improvement in survival in patients with AF.7 In the AFFIRM trial,
sinus rhythm was maintained with antiarrhythmic drug therapy in a relatively small proportion of patients, and the
patient population was relatively old (mean age approximately 70 years) and, in general, not very symptomatic.
Address reprint requests and correspondence: Dr. Hakan Oral,
Division of Cardiovascular Medicine, University of Michigan, TC B1
140D, Electrophysiology, 1500 East Medical Center Drive, Ann Arbor,
Michigan 48109-0311.
E-mail address: [email protected].
Therefore, the results should not be extrapolated to younger
patients whose quality of life is impaired by symptomatic
AF. It should be kept in mind that a small annual survival
benefit of sinus rhythm over AF would much more likely
become clinically significant in younger patients followed
for 2 to 3 decades than in older patients followed for 3 to 5
years, as was the case in AFFIRM.
Factors influencing patient selection
The criteria used to select patients for an invasive procedure
are influenced by safety, efficacy, availability, the risk-tobenefit ratio of alternative treatment options, and patient
preference. From the societal perspective, the cost of the
procedure may influence selection criteria.
As the ablation strategies for eliminating AF continue to
evolve, the reported efficacy rates remain variable depending on whether AF had been paroxysmal or chronic, the
ablation strategy, the definition of a successful outcome, and
the methods and duration of surveillance to detect recurrences. These variables may explain the very wide range of
20% to 95% efficacy reported for catheter ablation of AF.
The standard definition of a successful outcome has been
maintenance of sinus rhythm in the absence of antiarrhythmic drug therapy. However, a marked decrease in AF burden and/or rhythm control with a previously ineffective
antiarrhythmic drug also may be clinically meaningful. It
should be noted that if extended ECG monitoring is performed, asymptomatic episodes may be detected and the
actual efficacy rates may be lower than reported.8
A worldwide survey reported a 6% incidence of major
complications for AF ablation procedures performed since
1995.9 A large proportion of the complications consisted of
pulmonary vein stenosis. As ablation strategies have
evolved toward antral or left atrial ablation away from the
ostia of the veins, the incidence of pulmonary vein stenosis
should continue to decrease. Pericardial tamponade, retroperitoneal hematoma, groin complications, and phrenic
nerve palsy remain major complications; however, these
operator-dependent complications should become infrequent as experience increases. Of particular concern are
thromboembolic complications and atrioesophageal fistulas.
Based on recent reports, the incidence of severe complications ranges from 1% to 2%. Thromboembolic events have
become infrequent with the use of aggressive periprocedural
anticoagulation regimens. Atrioesophageal fistulas are rare
1547-5271/$ -see front matter © 2006 Heart Rhythm Society. All rights reserved.
doi:10.1016/j.hrthm.2006.01.016
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(⬍0.5%) and should remain very infrequent with increased
awareness of the risk of esophageal injury. Various techniques for monitoring the position of the esophagus allow
improved safety when ablating along the posterior wall of
the left atrium.
A study that used a Markov model to assess the costeffectiveness of catheter ablation of AF compared with
pharmacologic rate-control or rhythm-control strategies
demonstrated that catheter ablation is cost-effective in
patients who are at moderate, but not low, risk for thromboembolic events.10 Because catheter ablation of AF may
not be cost-effective in many patients, society must be
willing to pay for procedures intended primarily to alleviate symptoms and improve quality of life.
Specific considerations
Symptomatic vs asymptomatic AF
Published studies on catheter ablation of AF have included
only, or mostly, patients with symptomatic AF, and the role
of catheter ablation in improving quality of life has been
well established in patients with symptomatic episodes of
AF. From an evidence-based perspective, catheter ablation
to eliminate AF in asymptomatic patients may not be appropriate until large, randomized, long-term studies become
available. However, despite the lack of data, asymptomatic
patients can be considered for catheter ablation if they are
young and/or have evidence of a possible tachycardia-mediated cardiomyopathy.
Failure of prior antiarrhythmic drug therapy vs
first-line therapy
Failure of two or more antiarrhythmic drugs was a selection
criterion in most of the initial reports on catheter ablation of
AF. In general, a trial of antiarrhythmic drug therapy usually is considered prior to catheter ablation. Drug therapy
may be effective at least in some patients and is noninvasive; therefore, it often is worth trying before considering
catheter ablation. However, it may not be necessary to
attempt multiple antiarrhythmic drugs prior to ablation. Primarily based on patient preference, it often may be reasonable to proceed with catheter ablation even after failure of
one antiarrhythmic drug.
In a pilot study, catheter ablation was found to have
better efficacy than antiarrhythmic drugs as first-line therapy in 70 drug-naive patients with paroxysmal AF.11 The
superior efficacy of ablative therapy also is evident from
many studies of patients who already did not respond to
multiple antiarrhythmic drugs. The choice of antiarrhythmic
drug therapy vs catheter ablation is influenced by a variety
Heart Rhythm, Vol 3, No 5, May 2006
of factors and should not simply be based on superior
efficacy.
Paroxysmal vs chronic AF
Initial attempts at focal pulmonary vein ablation and later
pulmonary vein isolation had very low clinical efficacy in
patients with chronic AF. As ablation strategies evolved to
include left atrial ablation to modify the electrophysiologic
substrate, clinical efficacy in patients with chronic AF has
improved markedly. A recent randomized study that used
daily transtelephonic monitoring demonstrated that 74% of
patients with chronic AF were in sinus rhythm with significant improvements in quality of life and left ventricular
ejection fraction and a decrease in left atrial size during
1-year follow-up.3 Antiarrhythmic drug therapy often has
very limited efficacy in patients with chronic AF. Patients
with chronic AF may be likely to benefit more from maintenance of sinus rhythm in the long term and should be
strongly considered for catheter ablation if they have not
responded to drug therapy.
Structural heart disease and prior cardiac surgery
Catheter ablation of AF has been performed successfully in
patients who have hypertensive heart disease, coronary artery disease with or without prior revascularization, and
atrial septal defect repair with a pericardial or synthetic
patch. The presence of structural heart disease was not an
independent predictor of recurrent AF in any of the published reports. However, these reports often were from a
single center and may not have had sufficient power. Data
on the safety and efficacy of catheter ablation in patients
with congenital heart disease (except for atrial septal defect), particularly in patients with hypertrophic cardiomyopathy, are insufficient.
The feasibility and clinical efficacy of left atrial catheter
ablation in patients with congestive heart failure (ejection
fraction ⬍0.45) have been demonstrated.1 Therefore, these
patients also may be considered for catheter ablation.
Patients with a prosthetic mitral valve can be particularly
challenging. A report from an experienced center demonstrated clinical efficacy of 73% and a complication rate of
2% in 23 patients who previously underwent mitral valve
replacement.12 However, caution should be exercised in
considering these patients for catheter ablation because of
the risk of catheter entrapment.
The feasibility and safety of transseptal catheterization in
patients who have undergone closure of a patent foramen
ovale or atrial septal defect with a percutaneous closure
device have not been reported.
Age
Catheter ablation of AF has been performed in patients as
young as 16 years up to those in their 80s. In prior reports,
Oral and Morady
Selection Criteria for Catheter Ablation of AF
age has not been identified as an independent predictor of
clinical success. However, it appears that although comparable efficacy often is achieved in older patients, the risk of
complications, particularly pericardial tamponade and
thromboembolic events, may be higher in elderly patients.
In one series, although the efficacy of left atrial catheter
ablation was similar among patients with AF who were ⱕ70
years and ⬎70 years, the incidence of tamponade and
thromboembolic events was four times higher in patients
who were ⬎70 years than in patients who were ⱕ70
years.13
Although the findings of AFFIRM suggest that rate
control may be preferable in older patients, it is important
to recognize that sinus rhythm could be maintained in
only a small group of patients with AF. Furthermore,
despite their age, some older patients may lead very
active lifestyles and may be debilitated by symptomatic
AF even in the presence of adequate rate control. Therefore, therapy should be carefully individualized in older
patients, taking into consideration their overall physical
health, lifestyle preferences, longevity, and risk of complications.13
Left atrial size and duration of AF
Because most reports on catheter ablation of AF included a
relatively small number of patients from a single center,
multivariate analyses either were not performed or may not
have had sufficient power to identify all predictors of a
successful outcome after catheter ablation. However, based
on a few series, a left atrial diameter ⬍50 to 55 mm predicts
a higher probability of a successful outcome. A dilated left
atrium is likely to be associated with substantial electroanatomic remodeling, and this may decrease the probability of
a successful outcome.
A long duration of AF from the time of first diagnosis in
patients with chronic AF may be associated with a higher
probability of recurrent AF after ablation. A longer duration
of AF may result in marked left atrial electroanatomic
remodeling and left atrial enlargement. However, a cutoff
value for the duration of AF has not been reported. In
patients with paroxysmal AF who have not progressed to
chronic AF, the duration of AF does not appear to be a
predictor of outcome.
Surgical ablation
In patients with AF who require cardiac surgery for
another problem, such as coronary artery disease or mitral valve disease, concomitant intraoperative therapy for
AF is appropriate. In patients who do not require concomitant open heart surgery, no data are available on
whether surgical ablation should be considered instead of
catheter ablation or after one or more failed attempts at
catheter ablation.
617
Specific recommendations on how to select
patients with AF for catheter ablation
Ideal candidate
The ideal candidate for catheter ablation of AF has symptomatic episodes of paroxysmal or chronic AF, has not
responded to one or more antiarrhythmic drugs, does not
have severe comorbid conditions or significant structural
heart disease, is younger than 65 to 70 years, has a left atrial
diameter ⬍50 to 55 mm, and, for chronic AF, has had AF
for ⬍5 years.
Relative and absolute contraindications
Complications of catheter ablation may have catastrophic
outcomes in certain types of patients. They include individuals with severe obstructive carotid artery disease, severe
cardiomyopathy with a low ejection fraction, severe aortic
stenosis, nonrevascularized left main or three-vessel coronary artery disease, severe pulmonary arterial hypertension,
or hypertrophic cardiomyopathy with severe left ventricular
outflow tract obstruction. Another relative contraindication
may be a history of major lung resection because of the
severe impact of pulmonary vein stenosis on a remaining
pulmonary vein.
Because the risk of thromboembolic events both during
the procedure and in the early postoperative period may be
prohibitive in the absence of systemic anticoagulation, patients who cannot be anticoagulated both during and for at
least 2 months after the ablation procedure should not be
considered for catheter ablation of AF. Ablation should not
be performed in patients who have a left atrial appendage
thrombus or a recently implanted left atrial appendage occlusion device.
Surgical intervention can be lifesaving should a severe
mechanical complication, such as rupture or massive perforation of the heart or catheter entrapment, occur. Therefore, catheter ablation of AF should not be performed,
particularly in higher-risk patients such as the elderly, if
surgical backup is not readily available.
Catheter ablation of AF should not be performed in
patients who are scheduled to undergo cardiac surgery for
another indication when surgical ablation of AF also can be
performed.
Catheter ablation of AF is likely to be of little or no
benefit in patients with end-stage cardiomyopathy or massive enlargement of the left atrium (⬎6 cm); or who have
severe mitral regurgitation or stenosis and are deemed inappropriate candidates for valvular intervention.
Conclusion
A variety of ablation strategies have been reported to result
in favorable clinical outcomes with a relatively small risk of
618
severe complications, although the vast majority of the
published experience comes from high-volume centers. The
procedure remains complicated, technically challenging,
and lengthy. The criteria used to select patients for catheter
ablation should always be individualized because the genesis of AF is multifactorial, AF patients are a heterogeneous
population, and the ablation strategies and clinical outcomes
vary among centers.
Heart Rhythm, Vol 3, No 5, May 2006
7.
8.
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