ELECTROPHYSIOLOGY
Radiofrequency ablation in children and adolescents: results in 154 consecutive patients
Herzzentrum Leipzig, University Hospital Leipzig, Leipzig, Germany
Manuscript submitted 21 August 2005. Accepted after revision 19 February 2006.
* Corresponding author: Department of Cardiology B, Skejby Hospital, Aarhus University Hospital, Brendstrupgaardsvej, DK-8200 Aarhus N, Denmark. Tel: +45 89 49 55 66; fax: +45 89 49 60 02. E-mail address: cosedis{at}dadlnet.dk
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Abstract |
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Aims The experience of using radiofrequency ablation (RFA) for the treatment of arrhythmias in children and adolescents is still limited. This study aimed to review the most recent results of RF ablation in children and adolescents in a highly experienced centre with access to both conventional techniques and non-fluoroscopic electroanatomic mapping (CARTO).
Methods and results A total of 154 consecutive patients younger than 19 years treated with RFA during the period 2000–04 were included. Numbers (%) or median (quartiles) are reported. Age was 15 (12–17) years, 70 (45%) were males. Five patients (3%) had congenital heart disease. RFA was successful in 147/154 patients (95%). Arrhythmia recurrence occurred in 11 patients (7%). Procedure time was 55 (35–90) min and fluoroscopy time was 8.8 (4–19) min. Number of RF applications was 4 (2–10) and number of RF applications >20 s was 2 (1–7). One patient (0.7%) had complicating high-grade atrioventricular block. CARTO was used in 18 RF ablation procedures (11%) performed in 15 patients.
Conclusion RF ablation can be undertaken in children and adolescents with a high success rate, few recurrences and complications, very short procedure times, and acceptable fluoroscopy times. Non-fluoroscopic electroanatomic mapping is helpful in selected patients.
Key Words: Radiofrequency ablation, Children, Adolescents, Fluoroscopy, CARTO
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Introduction |
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Radiofrequency (RF) ablation has become the treatment of choice for a variety of arrhythmias in children and adolescents1
since first reported in 1989.2 The success rate is high and the risk of severe complications is low.3–8 In previous studies, fluoroscopy time associated with the RF ablation procedures has been reported to be a mean of approximately 40 min.4,5,9,10 The risks for patients and medical personnel associated with this radiation exposure are low, but not negligible.11,12 It is well described that procedure and fluoroscopy times decrease and success rate increases with an increasing institutional experience.13 Furthermore, non-fluoroscopic, three-dimensional electroanatomic mapping systems have been developed to increase success rate of RF ablation and to reduce radiation exposure. At present, experience using such mapping systems in children and adolescents is limited.14–16 The aim of this study is to review the most recent results of RF ablation in children and adolescents in a highly experienced centre with access to both conventional techniques for catheter ablation and three-dimensional electroanatomic mapping (CARTO).
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Methods |
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A retrospective study was performed, reviewing files of consecutive patients younger than 19 years referred to the Department of Electrophysiology, Herzzentrum Leipzig, Germany, for RF ablation or electrophysiological evaluation during the period 2000–04. Data recorded were: age, gender, indication for RF ablation, arrhythmia, location of accessory pathway(s), concomitant structural heart disease, procedure time—defined as skin-to-skin time (min), fluoroscopy time (min), number of RF applications and number of RF applications >20 s, total RF ablation time (s), total RF energy (W), maximal temperature achieved (°C), whether RF ablation was successful, and reason if not successful, whether retrograde aortic or transseptal access was attempted, the use of CARTO-mapping, and complications. Indications for RF ablation were defined as paroxysmal tachycardia, tachycardia refractory to drug treatment, life-threatening arrhythmia, syncope, or left ventricular dysfunction. Arrhythmias were classified as Wolff–Parkinson–White (WPW) syndrome, concealed accessory pathway (AP), atrioventricular nodal re-entry tachycardia (AVNRT), permanent junctional reciprocating tachycardia, focal atrial tachycardia (FAT), atrial flutter, or ventricular tachycardia (VT). Location of AP was classified as left AP if left superior, superoposterior, posterior, inferoposterior, or left inferior, right AP if right superior, superoanterior, anterior, inferoanterior, or right inferior, and septal AP if superoparaseptal, inferoparaseptal, or septal.17
The RF ablation procedure including the initial electrophysiological study was performed under general anaesthesia or sedation with propofol in the majority of patients. On the basis of an individual judgment, no sedation or a light sedation with midazolam was chosen for some of the adolescents. All antiarrhythmic drugs were discontinued for at least five half-lives before the procedure. In general, three catheters (4–6F) were positioned at the right ventricular apex, His bundle region, and right atrium or coronary sinus using the left femoral vein approach for the electrophysiological study, which was done using standard protocols. An ablation catheter (6–7F, 4-mm tip) was typically introduced using the right femoral vein or artery approach. Mapping and ablation were performed using established methods. Energy delivered was 30–70 W, and temperature limit was individually set to 50–70°C using Osypka 300 HAT (Osypka, Rheinfelden, Germany) or Stockert (Cordis-Webster, Inc., Freiburg, Germany) RF generators. Biplane fluoroscopy was used. Long vascular sheaths were used to improve catheter stability if necessary. Heparin was used in case of access to the left side of the heart and for procedures of longer duration. The criteria for successful RF ablation were: complete conduction block of the AP's, also 10–30 min after ablation, non-inducibility of tachycardia after injection of catecholamines in patients with AVNRT, FAT, or VT, and conduction block in the critical channel in patients with atrial flutter. In patients with AVNRT, the presence of single atrioventricular nodal echo beats after RF ablation was accepted as a successful endpoint.
The non-fluoroscopic electroanatomic mapping system CARTO (Biosense Ltd, Tirat-HaCarmel, Israel) has been previously described in detail.18–20 In brief, the patient is placed in an ultra-low magnetic field. Using a magnetic field sensor incorporated in the ablation catheter tip, information about the precise position of the catheter tip is yielded, as well as catheter tip electrograms. Using computer technology, this information can be transferred into a three-dimensional electroanatomic map of the heart chamber(s) to guide the mapping and deliverance of RF ablation. In the present cohort, CARTO mapping was chosen initially or when conventional methods had failed based upon an individual patient evaluation.
After discharge, patients underwent follow-up by their referring cardiologist or general practitioner or in the hospital outpatient clinic.
Data analysis was performed using SPSS 9.0. Data are presented as mean±SD if normally distributed, and as median (quartiles) and ranges if not normally distributed. Not-normally distributed data were compared between groups using Mann–Whitney test or Kruskall–Wallis test as appropriate, P<0.05 is considered significant.
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Results |
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Patients
A total of 156 patients younger than 19 years were referred for RF ablation during the study period. In two of these patients, the parents refused RF ablation attempts after having been informed of an increased risk of atrioventricular block: a 9-year-old boy with a concealed AP in the His bundle (superoparaseptal) region and a 14-year-old girl with AVNRT, in whom temporary mechanical block was induced in the fast pathway of the AV node during catheter mapping. The results presented include data from the remaining 154 patients, in whom RF ablation was attempted. These patients underwent a total of 169 RF ablation procedures. The annual numbers of RF ablation procedures were 24, 35, 38, 31, and 41 in consecutive years from 2000 to 2004. Mean follow-up of the patients after RF ablation was 27±16 (range 1–60) months.
The patients are presented in Table 1. Median age was 15 (12–17) years, ranging from 0 to 18 years. Six patients (4%) were younger than 5 years and 16 patients (10%) were 5–9 years old at the time of RF ablation. Seventy patients (45%) were males. The primary indication for RF ablation was paroxysmal tachycardia in 145 patients (94%), tachycardia refractory to drug treatment in five patients, life-threatening arrhythmia in two patients, syncope in one patient, and left ventricular dysfunction in one patient. Six patients had more than one AP. Another three patients ablated for an AP additionally underwent successful RF ablation of the slow pathway due to inducible AVNRT during the ablation procedure. Three of the WPW patients had an atriofascicular AP (Mahaim fibre). Five patients had congenital heart disease, two with APs (complex disease with pulmonary valve atresia and corrected transposition of the great arteries, respectively) and three with atrial flutter (prior operation for atrial septal defect and mitral valve replacement, prior operation for ventricular septal defect, and prior corrective operation for tetralogy of Fallot, respectively).
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RF ablation procedures
A total of 169 RF ablation procedures was performed; 13 patients had a second RF ablation procedure and two patients underwent a third procedure. In three of the 10 patients who underwent an unsuccessful RF ablation procedure, success was obtained in a later procedure. Therefore, overall patient success was obtained in 147/154 (95%) patients. In three patients with WPW syndrome (n=2) and concealed AP, respectively, RF ablation was not technically possible. In four patients with WPW syndrome (n=2), concealed AP, and AVNRT, respectively, RF ablation was discontinued before success was achieved due to a high risk of AV block.
Twelve repeat procedures were undertaken in 11 patients (7%) with tachycardia recurrences after prior successful RF ablation, six in five patients with WPW syndrome, two in two patients with concealed AP, three in three patients with AVNRT, and one in a patient with FAT.
Procedure-related data are presented in Tables 2 and 3. For the whole population, median procedure time was 55 (35–90) min and median fluoroscopy time 8.8 (4–19) min. Both procedure time and fluoroscopy time were significantly lower in patients treated for AVNRT than in patients treated for WPW syndrome 40 (35–55) vs. 75 (45–115) min, and 5 (4–10) vs. 13 (6–25) min, respectively, both P<0.001, Mann–Whitney test. A median of four (2–10) RF applications were placed, two (1–7) of which exceeded 20 s (Table 2). Procedure time, fluoroscopy time, number of RF applications, and number of RF applications >20 s were significantly lower in RF ablation of left-sided APs than in ablation of right-sided and septal APs (P<0.01 each, Kruskall–Wallis test) (Table 3). Retrograde aortic access was achieved in 55 procedures (54 in RF ablation of AP's and one in ablation of VT), and transseptal puncture in eight procedures (six in RF ablation of AP's and two in ablation of FAT).
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Complications
One patient with WPW syndrome undergoing RF ablation of a superoparaseptal AP developed complicating acute third-degree AV block requiring implantation of a permanent pacemaker. This 17-year-old girl had frequent tachycardia episodes refractory to treatment with ß-blocker and class Ic antiarrhythmic drugs. Ablation of the AP was unsuccessful from the right side. Successful RF ablation was achieved from the left side using electroanatomic mapping. No other complications were recorded. No deaths occurred.
Electroanatomic mapping
The CARTO mapping system was used in a total of 18 RF ablation procedures (11%) performed in 15 patients (Table 4). In four patients (nos. 1, 2, 5, and 6), CARTO mapping was used after an initial unsuccessful attempt of RF ablation using conventional techniques in the same procedure. In the remaining 11 patients, a complex arrhythmia was expected, and CARTO mapping was chosen as the initial strategy. The arrhythmias and substrates in the patients treated using CARTO mapping are shown in Table 4. Three patients had recurrence after prior ablation (nos. 3, 4, and 8).
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Patient no. 4 had unsuccessful RF ablation twice in another centre before the first RF ablation in our institution. In the first procedure in our institution, successful RF ablation was achieved after transseptal puncture, CARTO mapping, and ablation in the left superior region, 1-cm atrial of the mitral annulus. The second procedure was performed 4 months later due to recurrent tachycardia and pre-excitation. CARTO mapping was used during orthodromic AVRT, and the earliest atrial activation was found at the ligament of Marshall between the left atrial appendage and the left inferior pulmonary vein. Ablation was unsuccessful with only transient effect. The CARTO map was lost due to patient movement, and the procedure was stopped. In the third RF ablation procedure, an identical activation could be demonstrated in the CARTO map, and an ablation line along the ligament of Marshall resulted in successful ablation (Figure 1). The patient is still without tachycardia recurrence after 12 months of follow-up. Patient no. 11 had incessant FAT. P-waves were positive in leads II, III, and aVF, negative in aVL and aVR, and isoelectric in lead I. CARTO mapping of the left atrium was done after transseptal puncture, and successful ablation was achieved between the orifice of the left atrial appendage and the superior mitral annulus. Three months later, a second CARTO procedure was performed after recurrence of the tachycardia, and success was achieved by RF ablation in the same region. No tachycardia recurrence has occurred after 4 years. In the remaining 13 patients, successful RF ablation was achieved in one CARTO procedure.
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Comparing procedure-related data between patients treated with CARTO and patients treated only with the use of conventional RF ablation techniques, both procedure and fluoroscopy times were longer in the CARTO group (P<0.001 and P<0.01, respectively, Mann–Whitney test), and more RF applications were placed in the CARTO group (P=0.005, Mann–Whitney test).
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Discussion |
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As documented in this study, RF ablation can be undertaken in children and adolescents with a high success rate, few recurrences and complications, very short procedure times, and acceptable fluoroscopy times. RF ablation using conventional techniques is feasible and without significant radiation exposure in most patients with common arrhythmias. In patients with complex arrhythmias such as FAT or atrial flutter as well as selected patients with APs, however, non-fluoroscopic electroanatomic mapping (CARTO) is helpful.
The most important criteria for RF ablation in children and adolescents are success rates, complications, and a low rate of tachycardia recurrence. In the present cohort, 94% of the ablation procedures were acutely successful. Using more than one procedure, successful ablation was achieved in 95% of the patients. These success rates are similar to the rates recently reported from a large prospective multi-centre study8 and from the Pediatric Radiofrequency Ablation Registry.5 Also the rate of complicating high-grade AV block of less than 1% in this study is comparable to the best results reported in recent years.3–6,8,21 The patient who had inadvertent AV block in this study underwent RF ablation for a superoparaseptal AP. It is well known that RF ablation of APs in this region is associated with a higher risk of AV block.8,21 The majority of arrhythmia recurrences are observed within the first 6 months after initial RF ablation,6,22,23 and have been reported to occur in from 6% to as much as 20% of children and adolescents undergoing RF ablation.3,4,6,10 Therefore, the recurrence rate of 7% observed in the present cohort is similar to the lowest recurrence rates previously reported.6,10
The mean fluoroscopy times of 55–60 min reported in the early years of paediatric RF ablation22,24 have decreased to approximately 35–40 min in more recent reports.5,8,10 Fluoroscopy times have been found to be longer in RF ablation of APs than in RF ablation of AVNRT in previous studies4,5 as well as in this study. The fluoroscopy times observed in this study were markedly lower, both overall and for each of the common arrhythmias than previously reported. The reasons for these lower fluoroscopy times in our centre may be a combination of highly experienced operator in paediatric RF ablation, a definite aim at a low fluoroscopy time in every single procedure, and in part the use of non-fluoroscopic electroanatomic mapping in selected complex cases. Reducing fluoroscopy time is very important, especially in children and young individuals due to the health risks associated with radiation exposure. One hour of radiation exposure has been estimated to increase the risk of inducing a fatal cancer by 1% of the spontaneous risk.12 In our study, fluoroscopy time was less than 20 min in more than 75% of the RF ablation procedures (Table 2).
We had a median procedure time of 55 min, which is much shorter than the mean procedure times of 2.8 h to 206–213 min reported in recent large studies.8,10 One likely explanation of the short procedure time in our centre is the great experience in paediatric RF ablation. Furthermore, waiting time after RF ablation before the final electrophysiological testing is shorter in our centre than the 30–60 min or even longer used in most other centres.3,8,10 It should be noted, however, that no more arrhythmia recurrences were observed in the present cohort than in these centres.3,10 Shortening procedure time is not a major goal, and less important than reducing fluoroscopy time. However, shorter procedure times are associated with the advantages of shorter anaesthesia periods. Furthermore, a larger proportion of the adolescents may be treated with light sedation instead of anaesthesia if procedure time is short.
Both procedure and fluoroscopy times were significantly lower in this study than in prior studies.4,5,9,10 However, as described above, the main patient outcomes are as good as in studies with longer procedure and fluoroscopy times.
Compared with data from a recent large prospective study, the maximum temperature achieved and the numbers of RF applications in our study were similar.8 Total RF ablation time and RF energy have not been reported in previous reports. These data can be used as reference for future studies.
In our cohort, CARTO mapping was used for all three patients with presumed atypical atrial flutter and for three of the four patients with FAT. It is well described that CARTO mapping facilitates understanding of the tachycardia mechanisms in adult patients and children with incisional atrial flutter7,14,25 or FAT,26,27 and thereby may improve RF ablation success rates of these arrhythmias. This study supports that, in young patients with these arrhythmias, RF ablation can be performed with very low fluoroscopy times when CARTO mapping is used. The remaining CARTO procedures were used in patients with APs, typically when conventional techniques had failed in previous procedures or turned out to be unsuccessful and in patients with recurrences after prior RF ablation. It is likely that the use of CARTO mapping in these complex cases increased the success rates of RF ablation and reduced fluoroscopy times significantly. This is in accordance with previous studies, reporting that the use of CARTO mapping may improve success rates and reduce fluoroscopy times in selected patients undergoing RF ablation of right-sided APs16,28 as well as atriofascicular pathways.15 However, it was not a particular aim of this study to compare procedures using CARTO mapping with procedures using only conventional techniques. The true value of advanced electroanatomic mapping systems in RF ablation of the majority of arrhythmias remains to be established, most appropriately in randomized trials.
Study limitations
This study is retrospective in nature with all its inherent limitations. The results from a high-experience single centre study cannot automatically be generalized to be representative for other centres.
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Conclusion |
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RF ablation can be performed in children and adolescents with a high success rate, few recurrences and complications, very short procedure times, and acceptable fluoroscopy times. RF ablation using conventional techniques is feasible and without significant radiation exposure in most patients with common arrhythmias. In patients with complex arrhythmias such as FAT or atrial flutter as well as selected patients with APs, however, non-fluoroscopic electroanatomic mapping (CARTO) is helpful.
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Acknowledgements |
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J.C.N. was supported by grants from the Research Initiative of Århus University Hospital, Helga and Peter Kornings Foundation, August H. Jensen and Wife's Foundation, Elin Holms Foundation, the Danish Society of Cardiology, and the Association of Young Cardiologists.
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References |
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