Europace Advance Access originally published online on February 19, 2008
Europace 2008 10(4):419-424; doi:10.1093/europace/eun018
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'ABLATE AND PACE': STILL A VALID TREATMENT FOR AF
Long-term follow-up after radiofrequency catheter ablation for atrial fibrillation
1 Department of Cardiology, Athens Euroclinic, 9 Athanassiadou Street, Athens 11521, Greece; 2 Division of Cardiology, Virginia Commonwealth University School of Medicine and the Medical College of Virginia Hospital, Richmond, VA, USA
Manuscript submitted 22 November 2007. Accepted after revision 9 January 2008.
* Corresponding author. Tel: +30 210 6416600; fax: +30 210 6416661. E-mail address: dkatritsis{at}euroclinic.gr
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Abstract |
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Aims: Data on long-term follow-up of patients who have undergone catheter ablation for atrial fibrillation (AF) are very limited. This report aimed at presenting clinical outcome and AF-free survival after pulmonary vein (PV) isolation over an extended (>3 years) follow-up period.
Methods and results: Thirty-nine patients subjected to PV isolation for paroxysmal AF were followed-up for at least 3 years according to a strict protocol. Fourteen patients (35.8%) had one, 19 patients (50%) had two, and 6 patients (15.4%) had three ablation procedures. At end of follow-up (42.2 ± 6.0 months), 17 patients (43.5%) were completely free of AF or other atrial arrhythmia, and 26 patients (66.6%) had symptomatic improvement. The long-term success rate was 21.4% for patients subjected to a single ablation procedure, 52.6% for patients subjected to two catheter ablation procedures, and 66.7% for patients who underwent three ablation procedures (P = 0.094). There was also a trend for patients who underwent a combination of different ablation procedures (ostial, antral, and/or circumferential) to have a higher AF-free survival when compared with patients subjected to the same procedure (P-value for log-rank test = 0.036).
Conclusion: Catheter ablation does not eliminate paroxysmal AF in up to 56% of patients in the long term, despite the use of two or three ablation procedures in two-thirds of them. However, it confers symptomatic improvement in 67% of treated patients.
Key Words: Atrial fibrillation, Ablation, Long-term follow-up
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Introduction |
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Ostial ablation of pulmonary veins (PV) is an established therapeutic option for patients with paroxysmal atrial fibrillation (AF). According to published data, the procedure results in approximately 65–80% freedom from recurrent AF within the next 6–12 months, with 30–40% of patients having had two procedures.1
–5 Application of radiofrequency lesions outside the PV ostia including some or all of the antrum of the PVs, has increased ablation success, although reported values range widely from 54 to 91%.4–8
However, true long-term efficacy data for these procedures is limited, with most published studies having reported follow-up data for only 6–12 months. Few studies have provided follow-up data beyond 2 years,9–13 and in two of them9,10 concerns have been raised regarding a low (<40%) long-term success rate. To the best of our knowledge, no study has examined clinical outcome beyond 3 years after ablation. Thus, the long-term efficacy of PV ablation techniques is virtually unknown. In a recent worldwide survey on catheter ablation procedures for AF in clinical practice, only 6 out of 181 responding centres had follow-up data beyond 2 years.14 The aim, therefore, of this report is to present clinical outcome and AF-free survival after PV isolation over an extended (>3 years) follow-up period.
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Methods |
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Patients
The following patient recruitment criteria were adopted for this study:
- Patients with symptomatic, paroxysmal AF who underwent catheter ablation with attempted isolation of all pulmonary veins.
- Achievement of both entrance and exit block following ablation.
- Patients who had agreed to adhere to a strict follow-up protocol.
- Patients who underwent repeated ablation attempts for AF recurrence or ablation-induced atrial flutter or focal tachycardia were also included in the analysis, regardless of the methodology of ablation employed (ostial, antral, or circumferential lesions).
- Patients who fulfilled the above criteria and completed at least 3 years of follow-up were considered for final analysis.
Ablation techniques for atrial fibrillation
Left atrial (LA) ablation was performed by (i) segmental ostial PV isolation, (ii) antral ablation, (ablation at the PV–LA junction outside the ostium-guided by intracardiac echo), and (iii) circumferential ablation around the ostia of the PVs.
Details of our ablation techniques have been described elsewhere.15,16 In brief, segmental ostial ablation of all PVs was accomplished with a 20 mm Lasso circular electrode (Cordis-Webster) as previously described.15 PV isolation endpoints was elimination of PV muscle conduction distal to the ablation site based on abolition or dissociation of distal PV potentials and demonstration of both entrance and exit block from each vein. Antral ablation was performed with the Lasso catheter positioned outside the PV ostium at the junction of PV–LA that was identified with the aid of intracardiac ultrasound.16 Endpoints were entrance and exit block. Circumferential ablation was performed, as a repeat procedure only, with the aid of electroanatomical mapping (Carto, Biosence-Webster) at a distance of 
1–2 cm from the ostia of the left and right PVs, aimed at a voltage reduction by >80% or a peak-to-peak bipolar electrogram <0.1 mV.16 If these endpoints were not achieved after 30 s of radiofrequency current application, the catheter was moved to the next site until completion of the circumferential lesions around the PV ostia was achieved.
Ablation procedures were performed with a conventional catheter with a 4 or 8 mm tip and 2.5 mm inter-electrode spacing (Cordis-Webster), at a preset electrical power of 30–40 W, aiming at a target temperature of 52°C for ostial ablation, or an irrigated-tip ablation catheter (infusions rates of 30 or 17 mL/min) with a 4 mm tip and 2.5 mm inter-electrode spacing (Cordis-Webster) electrical power of 30 W and aiming at target temperatures of 42°C or 46°C for antral and circumferential ablation, respectively.
Follow-up
As part of our routine AF ablation protocol, all patients were kept on amiodarone and warfarin for 6 weeks post-ablation. Patients were subjected to monthly clinical assessment and ambulatory electrocardiographic monitoring up to 1 year. Afterwards, clinic visits and electrocardiographic monitoring were arranged every 3 months. In case of persistent arrhythmia episodes, patients were instructed to obtain transtelephonic or electrocardiographic documentation of the underlying rhythm. In addition, all patients were encouraged to use transtelephonic monitoring with any episode of palpitations, even when their symptoms were not typical for recurrent AF. Patients were also instructed to maintain personal records with descriptions of every episode of symptomatic palpitations. A successful outcome over the follow-up period was defined as the lack of electrocardiographically recorded AF or atrial tachycardia or flutter,17 and no atrial arrhythmia on Holter or transtelephonic transmission after a 2-month blanking period. Patients were reviewed both by fellows who were blinded to treatment and at least two members of the ablation team. Paroxysmal AF was defined as recurrent AF that terminates spontaneously within seven days,17 documented on Holter, transtelephonic monitor or resting ECG. In addition, subjective symptomatic improvement by means of AF duration and frequency of episodes as perceived by patients was also registered.
Endpoints
The primary endpoint of the study was freedom from recurrent AF or other atrial arrhythmia such as atrial tachycardia and flutter after the last ablation procedure. Patients who had AF or other atrial arrhythmia relapse within the follow-up period after the initial ablation and refused to undergo a repeat ablation procedure were considered as failures. For patients who agreed to have a repeat ablation procedure after recurrence of AF, the first AF episode after the most recent procedure was considered as failure. All patients who developed an AF relapse earlier than 36 months after their initial ablation, continued to be followed for at least 36 months (36–58 months) in order to detect response to further ablation attempts as well as symptomatic improvement (secondary endpoint of the study).
Statistical analysis
Continuous variables were summarized as mean ± SD while categorical variables were reported as absolute and relative (%) frequencies. Associations between categorical variables were tested with the chi-square test or Fisher's exact test as appropriate. Associations between continuous and categorical variables were tested with Student's t-test and one-way analysis of variance (ANOVA). Kaplan–Meier curves were used to determine the probability of freedom from recurrent AF (or other atrial arrhythmia) during follow-up after the last procedure, and differences in AF-free survival were evaluated using the log-rank test. All reported P-values were based on two-sided tests and were compared with a significant level of 5%.
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Results |
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Patients
In total, 48 patients agreed to participate and provided a signed consent form. Of those 39 patients (81%), aged 51.9 ± 10.3 years, five (13%) females complied with follow-up criteria and were eventually recruited in our study. Clinical and procedural characteristics are presented in Table 1. Fourteen patients were subjected to one only ablation procedure, 19 patients had two, and six patients had three procedures. Initially, 90% of patients (35 patients) were subjected to ostial ablation and the other 10% (four patients) underwent antral ablation. In all cases, PV isolation was verified after the procedure. Twenty-five patients underwent a second ablation procedure: 14 (56%) of them were subjected to ostial, six (24%) to circumferential, and five (20%) to antral ablation. Circumferential ablation was the third ablation technique for five out of six patients (83%) who underwent a third ablation procedure; the remainder underwent antral ablation. For all first ablation attempts, a 4 mm tip catheter was used. Ablation of all PVs was attempted at first attempt, but it was not feasible in three patients who had AF recurrence. Two of them underwent a repeated circumferential ablation and the other had antral ablation. Apart from a case of pericardial effusion that did not require pericardiocentesis, no complications were encountered during the ablation procedures. Following ablation, six patients received no antiarrhythmic medications, whereas beta-blockers were administered to 29 patients. Flecainide, propafenone, sotalol, and dofetilide were given to one patient each.
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Characteristics of atrial fibrillation recurrences
Thirty-six patients (92%) developed recurrent AF at an average of 12.8 ± 9.4 months (range 3–42 months) after the initial ablation procedure (Figure 1). Twenty-two percent of these recurrences were within the third month after ablation, 22% occurred between 3 and 12 months, and the rest 56% were observed more than 12 months after the initial procedure. Twenty-five out of 36 patients with AF recurrence (69%) were subjected to a second ablation procedure. Among these, 15 patients (60%) developed a second AF or atrial arrhythmia recurrence at an average of 23.4 ± 9.2 months after the initial procedure or otherwise 8.5 ± 5.6 months after the second ablation. One patient had both AF recurrence and micro-reentrant atrial tachycardia at the ostium of the left superior PV following ostial ablation. He was subjected to mapping-guided ablation followed by circumferential ablation of all PVs. Another patient developed two non-sustained episodes of left atrial flutter following circumferential ablation but the arrhythmia disappeared 3 months after the procedure. The patient remained free of arrhythmia during follow-up and was considered a success. A third patient was found in left atrial flutter following a second antral ablation at the end of follow-up. He was considered a failure. In total, third catheter ablation was performed in 6 out of 15 patients (40%) who had a second arrhythmia recurrence, and two of them had a third AF recurrence after 12 and 10 months from the last ablation procedure.
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Clinical outcome
The long-term outcome of catheter ablation is shown in Figure 1 and Table 2. Patients have been followed for at least 36 months (average follow-up 42.2 ± 6.0 months, range 36–56 months). At the end of follow-up, 17 patients (43.5%) were free of AF. The long-term success rate was 21.4% for patients who underwent a single ablation procedure, 52.6% for patients subjected to two catheter ablations, and 66.7% for those subjected to three ablation techniques (P = 0.094).
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Considering symptomatic improvement by means of fewer AF episodes, 26 patients (66.6%) claimed symptomatic improvement. The rate of symptomatic improvement was statistically significantly higher among patients who underwent two or three catheter ablations when compared with those subjected to a single procedure (Table 2; P = 0.002).
Effect of multiple ablation procedures
Sinus rhythm without AF recurrence was maintained in three patients (21%) at 19.4 ± 10.6 months after a single procedure. Among patients subjected to a single ablation (14 patients), 93%, 43%, 28%, and 21% were free of AF recurrence at 12, 15, 18, and 24 months of follow-up, respectively (Figure 2). Among patients subjected to two ablation procedures (19 patients), 10 patients (52.6%) remained free from AF recurrence or other atrial arrhythmia at 14.1 ± 8.8 months after the second procedure, or otherwise 34.0 ± 11.2 months after the initial procedure. Kaplan–Meier analysis revealed that 89%, 59%, 52%, and 44% of patients were free of AF relapse at 6, 12, 18, and 24 months after the second procedure. Moreover, we found that among patients subjected to two catheter ablations, the success rate (percent of patients free of AF recurrence) was lower among those whose first recurrence had occurred within the first 3 months after the initial procedure (17%) when compared with those whose first recurrence had occurred after 3 months (77%, P = 0.013).
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An analysis including all 39 patients and the cumulative proportion of patients remaining free of AF over the follow-up period after the last procedure is depicted in Figure 3. At 6, 12, 18, and 24 months after the last procedure 92%, 73%, 42%, and 35% of patients were free of AF recurrence.
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Further analysis including only patients who underwent repeated ablations showed a trend for lower long-term success rate among patients who underwent the same kind of ablation in all attempts when compared with those in whom the second or third ablation was different than the initial procedure (75%, P-value for log-rank test = 0.036; Figure 4). In particular, at 6 and 12 months after the last catheter ablation, 83% and 46% of patients underwent the same procedure iteratively were free of AF recurrence, while 92% and 75% of patients underwent a combination of procedures were free of AF relapse, respectively.
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Discussion |
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There is substantial evidence that radiofrequency isolation of the pulmonary veins (PV), either by ostial or circumferential radiofrequency lesions, removes a potential source of arrhythmia that initiates AF. However, currently accepted success rates are usually based on limited follow-up periods without universal criteria for definition and identification of AF recurrences. Our series indicates that in the long-term, AF cannot be eradicated in at least half of the patients who are subjected to one or more ablation attempts.
Our results are in keeping with those reported by Cheema et al.10 and Solheim et al.9 Sanders et al.12 and Bertaglia et al.11 have reported better clinical outcomes but at shorter follow-up times and following combined ablation procedures. Sanders et al.12 have provided data on 27 patients with chronic AF who were subjected to PV and posterior left atrial isolation. Sinus rhythm was maintained without antiarrhythmic drugs in 12 patients (44%) at 23 months after a single procedure, and further in four patients (15%) at 12 months after a second procedure. Bertaglia et al.11 reported a success rate of 70% after 20 months of follow-up but the majority of their patients, apart from PV isolation, were also subjected to right atrial ablation and were kept on antiarrhythmic medication. Pappone et al.13 have provided data on long-term follow-up but the range was extremely diverse, 5–50 months. In this study, 120 out of 589 patients underwent a repeated procedure for recurrent AF, whereas 12 patients needed ablation for left atrial flutters. The number of patients free of AF in the absence of antiarrhythmic therapy is not clear in this study.
In the study of Cheema et al.,10 the single-procedure success rate after an average follow-up of 2 years was only 28%. In our study, 14 patients were followed for 42 months and only three (21%) were found asymptomatic without any recorded episodes of AF. A second ablation in 18 patients yielded a 55% success rate over a total 40-month follow-up after first ablation, while a third procedure was attempted in six patients with a 67% success rate over a 46-month total follow-up.
Our series had a considerably longer follow-up time than previous studies with relatively long-term results, and extensive use of transtelephonic monitoring. It is now known that 50% of patients are asymptomatic during at least one AF episode and transtelephonic monitoring will decrease AF-free survival by 15% at 3 months.18 A more vigorous follow-up method with implantable arrhythmia monitors19 might have revealed a higher recurrence rate. Having said that, it is important that symptomatic improvement was documented in 67% of ablated patients at the end of the follow-up period. It seems that catheter ablation does confer symptomatic improvement in patients with AF, but does not abolish all episodes of AF. These results required a second procedure in 48.7% of patients and a third procedure in 15.4% of patients. Repeat procedures in a considerable percentage of cases were of a different kind than the initial one. It seems that currently we do not have enough information to decide whether AF ablation is a curative or palliative procedure.
Recurrence of conduction in at least two PVs was detected in all patients who had a repeat ostial or antral ablation procedure, and the majority (84%) of our patients with AF relapses also demonstrated recurrence of conduction in all PVs. All our first ablation attempts have utilized 4 mm tip catheters and in three patients the right inferior PV could not be isolated. Several studies have related AF recurrence with recovery of PV conduction.20–26 However, permanent isolation of the PVs is not always a necessary condition for a successful outcome.20,21,27–30 In the series of Cappato et al.,20 no AF relapse was seen in 32% of patients despite late recurrence of conduction that occurred in up to 80% of ablated PVs. Lemola et al.30 detected recurrence of PV conduction following complete PV isolation in up to 95% of patients with AF recurrence, but this was not associated with a PV tachycardia. Perhaps, long-term clinical outcome following PV isolation should be interpreted within the context of the multi-factorial aetiology of AF.31 Both antral and circumferential ablation may result in substrate modification, the exact mechanism(s) of which still remains elusive. Apart from ectopic activity of the PV sleeves, several other mechanisms are implicated in the genesis and perpetuation of AF; thus, a single ablation technique is rather unlikely to offer a definitive therapy in all cases. Our data suggest that ostial ablation is less effective than antral or circumferential ablation. Although ostial ablation is associated with a very low long-term risk of proarrhythmia, we and most have abandoned it as the technique of choice for the treatment of AF. It is of interest that patients who were subjected to different ablation techniques, reported a better clinical outcome as well as symptomatic improvement.
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Study limitations |
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The main limitation of our study is the small number of our patients. It proved extremely difficult to recruit patients in a prospective way with the adopted inclusion criteria. Still, however, our report is the only series with a follow-up exceeding 3 years following the initial ablation procedure. Similar reports by investigators with bigger patient numbers are certainly needed before deciding about the true clinical efficacy of ablation procedures in patients with AF. Secondly, the use of different techniques with different ablation electrodes were unavoidably used following technological advances. This however is the usual approach in every day clinical practice.
In conclusion, extended follow-up of patients subjected to PV isolation revealed that 42 ± 6 months after the initial procedure, 67% experienced symptomatic improvement, but only 46% were free of AF recurrence. Almost half of the patients had a second ablation, while 15% required a third ablation procedure.
Conflict of interest: none declared.
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Supported by a research grant from the Cardiovascular Research Society, Athens, Greece.
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