Z Kardiol 94:280–286 (2005) DOI 10.1007/s00392-005-0215-4

M. Emmel N. Sreeram K. Brockmeier

Katheterablation bei junktional ektoper Tachykardie n Zusammenfassung Hintergrund Die idiopathische junktionale ektope Tachykardie ist eine bei Kindern seltene Arrhythmie. Wie mehrere Studien zeigten, ist eine medikamentöse Behandlung oft nicht erfolgreich und häufig muss man sich mit einer Verlangsamung der Tachykardie-Frequenz begnügen. Frühes Auftreten und häufiges Wiederkehren sind mit einer schlechten Prognose assoziiert. Patienten und Methode Drei konsekutive Kinder im Alter von 9, 7 und 12 Jahren mit einer junktional ektopen Tachykardie wurden mittels Radiofrequenz-Katheter-Ablation behandelt, nachdem Versuche einer medikamentösen Therapie zuvor keinen Effekt gezeigt hatten. Zunächst wurde das gesamte His-

Received: 30 June 2004 Accepted: 8 December 2004

Catheter ablation of junctional ectopic tachycardia in children, with preservation of atrioventricular conduction

Bündel wurde durch Mapping erfasst und im LocaLisa System markiert. Mittels intravenöser Isoprenalin-Infusion konnte die Arrhythmie leicht und reproduzierbar ausgelöst werden, so dass die ersten retrograden Signale während der Tachykardie erfasst und ebenfalls markiert werden konnten. Die Ablation erfolgte dann im Sinus-Rhythmus, im Bereich der zuvor bestimmten retrogaden Signale während der Tachykardie. Ergebnisse Mit diesem Vorgehen konnte bei den ersten beiden Patienten mit superoparaseptalem Ablationsort die Tachykardie erfolgreich beseitigt werden. Bei dem dritten Patienten war die junktional ektope Tachykardie auslösbar obwohl die retrograde Aktivierung der Vorhöfe nach Ablation in einer septalen Position des Trikuspidalklappenringes unterbunden war. Nach weiteren Ablationen in der superoparaseptalen Region, näher am His-Bündel, zeigte sich die Tachykardie nicht mehr auslösbar. Nach einer medianen Nachbeobachtungsperiode von 10 Monaten hatten die Patienten – trotz Beendigung jeglicher Medikation, keine weiteren Tachykardie-Ereignisse. Schlussfolgerung Die Radiofrequenz-Katheter-Ablation einer idiopathischen junktional ektopen Tachykardie ist unter Erhaltung der antegraden Überleitung möglich.

n Schlüsselwörter Idiopathische junktional ektope Tachykardie – Ablation n Summary Background Idiopathic junctional ectopic tachycardia is a rare arrhythmia in children. Several studies have demonstrated that drug therapy is often ineffective and sometimes the only achieved effect is rate control. Early presentation and frequent recurrence are associated with adverse outcome. Patients and methods Three consecutive children, aged 9, 7 and 12 years respectively, underwent radiofrequency catheter ablation for junctional ectopic tachycardia, after having failed antiarrhythmic drug therapy. The entire His bundle was plotted out and marked, using the Localisa navigation system. The arrhythmia was readily and repeatedly inducible using intravenous isoprenaline infusion and the site of earliest retrograde conduction during tachycardia could be assessed. Ablations were performed in sinus rhythm, empirically targeting the site of earliest retrograde conduction during tachycardia. Results This approach was successful in abolishing tachyarrhythmia in the first two patients, in whom the successful ablation site was located superoparaseptally. In the third patient, junctional ectopic tachycardia was

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Mathias Emmel Narayanswami Sreeram ()) Konrad Brockmeier Dept. of Paediatric Cardiology University Hospital of Cologne Joseph-Stelzmann-Straße 9 50924 Cologne, Germany Phone: +49-221/478 86301 Fax: +49-221/478 86302 E-Mail: [email protected]

CASE REPORT

M. Emmel et al. Catheter ablation of junctional ectopic tachycardia

inducible, despite abolishing retrograde atrial activation, in a septal location on the tricuspid valve annulus. Further ablations in the superoparaseptal region, closer to the His bundle, were successful in rendering tachyarrhythmia non-

inducible. Over a median followup of 10 months, none of the patients has had recurrence of arrhythmia, despite discontinuing all antiarrhythmic medications. Conclusions Radio frequency catheter ablation of junctional ectopic

Introduction Junctional ectopic tachycardia can occur as an idiopathic entity, or following cardiac surgery for congenital heart defects [3, 11, 16, 18]. The idiopathic form is rare and, when presenting in fetal life, infancy or childhood, is often resistant to antiarrhythmic drug therapy and in some patients the only achievable effect is rate control [2, 3, 10, 14, 17, 19]. Due to this the idiopathic form, especially when presenting early often carries a poor prognosis. Surgical, direct current, or radiofrequency catheter ablation of the atrioventricular node have been employed in the past, but have the disadvantage of requiring permanent pacemaker implantation [3, 18, 19]. More recently, successful catheter ablation of the ectopic focus has been reported, the majority of them as isolated case reports [8, 9, 12, 23, 24]. We present our experience with catheter ablation in three consecutive children.

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tachycardia is feasible with preservation of atrioventricular conduction. n Key words Idiopathic junctional ectopic tachycardia – ablation

The diagnosis of junctional ectopic tachycardia was made using previously established criteria [15]. Briefly, on the surface electrocardiogram junctional ectopic tachycardia is characterised by a normal QRS complex morphology tachycardia, with periods of atrioventricular dissociation. During electrophysiology study, junctional ectopic tachycardia was confirmed by excluding other tachyarrhythmia mechanisms or dual atrioventricular nodal physiology, by the inability to initiate or terminate the tachyarrhythmia by extrastimulation techniques but reproducible induction of tachyarrhythmia using isoproterenol infusion (0.03 lg/kg/minute) with the His bundle electrogram preceding ventricular activation, and by documenting periods of atrioventricular dissociation during tachyarrhythmia. Patient 1 had associated Ebstein’s anomaly of the tricuspid valve, while patients 2 and 3 had tachycardia-induced cardiomyopathy (left ventricular end-diastolic diameter > 97th centile for age, with left ventricular fractional shortening of < 30%). Informed consent was obtained prior to all procedures.

Patients and methods Electrophysiologic study and outcome Between January 1999 and April 2003, three consecutive children (2 male, 1 female), aged 9, 7 and 12 years respectively, were considered for catheter ablation of junctional ectopic tachycardia. The procedures had been performed in two institutions (University of Cologne, University of Utrecht) and each of them had been performed by the same electrophysiologist (N.S.). The first of these patients has been previously reported elsewhere [15]. All patients were symptomatic (headache, palpitations, dizziness, presyncope) with documented arrhythmia occurring on average between 2 to 3 times/week, usually related to exertion. The duration of arrhythmia ranged from 12 to 46 months. All had had trial of antiarrhythmic drug therapy (2 drugs in patient 1 and up to 3 drugs in patients 2 and 3), without success. Drug therapy consisted of beta blocker in combination with amiodarone (1 patient) or the above two medications together with verapamil (1 patient) or flecainide (1 patient).

All electrophysiologic studies were performed under general anesthesia, after antiarrhythmic drug therapy had been discontinued for one week prior to the study. The LocaLisa navigation system (Medtronic, USA) had been used in all 3 patients. A standard 7 French temperature-controlled ablation catheter with a 4 mm tip electrode (Medtronic USA) was used to map out the entire His bundle on the Localisa navigation system. This allowed reliable and continuous measurement of the distance between a given ablation site and the site of the proximal His-bundle recording (Fig. 1) [22]. Additional measures used to minimise the risk of permanent atrioventricular block included atrial overdrive pacing when an accelerated junctional rhythm occured during radiofrequency current application, and a gradual increase in power output from 5 W upto 50 W over 60 s, to achieve catheter-tip temperatures > 50 8C. In describing ablation sites, the nomenclature proposed by the

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Fig. 1 Localisa map from patient 2. The His bundle electrogram recording sites are shown in light blue. The location of the coronary sinus is shown in green. A series of 5 closely related radiofrequency lesions have been placed in the anteroseptal area, in close proximity to the His bundle, to render junctional ectopic tachycardia noninducible. This was also the site of earliest retrograde atrial activation during tachyarrhythmia. The location of a temporary pacing electrode in the high right atrium is depicted in dark blue

joint Working Group of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology has been consistently used [4–6]. In patient 1, ablation was begun empirically in the septal region of the tricuspid valvular annulus, identical with slow pathway ablation for AV nodal reentrant tachycardia. Slow pathway potentials were not systematically sought. The application of radiofrequency lesions was then moved superiorly and progressively closer to the His bundle with successive current applications, thereby coming closer to the fast AV nodal pathway. The successful ablation site was located 5 mm from the proximal His bundle recording, and was also the site of earliest retrograde atrial activation during junctional ectopic tachycardia. Based on this experience, in patient 2, the site of earliest retrograde atrial activation during tachyarrhythmia was primarily targeted. This site was localised and mapped on the Localisa system, at a distance of 3 mm from the proximal His bundle recording, in the superoparaseptal position (Fig. 1). Radiofrequency current application at this site rendered junctional ectopic tachycardia noninducible. In patient 3, in whom the mapping and ablation procedure was performed in an identical fashion as with patient 2, retrograde atrial activation during tachyarrhythmia was located at the septal part of the tricuspid valve (Fig. 2 a). Serial radiofrequency current applications at this site abolished retrograde conduction, without terminating junctional ectopic tachy-

cardia (Fig. 2 b). Further radiofrequency lesions were then applied superoparaseptally, in a manner akin to fast pathway ablation in AV nodal reentrant tachycardia, at a distance of 3 mm from the proximal His electrogram site. The tachyarrhythmia was thereby rendered noninducible (Fig. 2 c). The number of radiofrequency lesions were 7, 5 and 15 respectively.

Follow-up All patients were discharged from hospital the following day, without antiarrhythmic medications. None of them had a measurable prolongation of the PQ interval on the surface ECG at discharge. Over a follow-up of 24 months, 10 months and 6 months, respectively, none of them has had recurrence of symptoms or of documented junctional ectopic tachycardia, or developed progressive atrioventricular block. Left ventricular dimensions and function have normalised in both patients with tachycardiainduced cardiomyopathy (fractional shortening of 35 and 38%, respectively).

Discussion Junctional ectopic tachycardia is characterised by an automatic focus in the atrioventricular junction. Previous reports have confirmed that in the idiopathic

M. Emmel et al. Catheter ablation of junctional ectopic tachycardia

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a

b Fig. 2 a Intracardiac recordings from patient 3 during junctional ectopic tachycardia. There is 1:1 retrograde conduction. The tip of the ablation catheter (MAP dist) is at the site of earliest retrograde atrial activation and demonstrates fused ventricular and atrial electrograms. This site was targeted initially for ablation. Three surface leads, I, II and V1 are shown. MAP mapping catheter; HRA high right atrium; RV dist/prox electrograms from the distal and proximal recording electrode pairs from a quadripolar catheter in the right ventricle. b Intracardiac recordings following septal ablation, at the site of

earliest retrograde ventriculoatrial conduction. Following radiofrequency current application, this recording confirms loss of retrograde conduction to the atria, but with inducibility of junctional ectopic tachycardia by isoprenaline. A constant His-Ventricle interval (His bundle potentials shown by arrows) is demonstrated in the distal electrode pair of the mapping catheter. This recording suggests that the tachycardia focus is anatomically separated from the site of retrograde conduction

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Fig. 2 c Intracardiac recordings during sinus rhythm, from the successful ablation site located superoseptally. The mapping catheter shows a small, but distinct His bundle potential (arrows)

form of junctional ectopic tachycardia antiarrhythmic drug therapy is often suboptimal, and may only achieve rate control, without termination of tachyarrhythmia [2, 14, 17, 19]. Thus, it carries a poor prognosis, with upto 35% mortality being reported in the series of Villain [19]. As has been emphasised previously, this report consisting of the largest series of patients with junctional ectopic tachycardia was a multicenter study, and describes 26 patients seen over a period of 17 years [20]. Despite the use of newer antiarrhythmic agents, often in combination, arrhythmia control is difficult to achieve, and cardiomyopathy or death as a result of the arrhythmia have been reported [2, 7, 17, 20]. As the arrhythmia appears to be resproducibly inducible during exercise (or with the use of isoproterenol infusion) initial therapy with a beta blocker appears to be logical. Not unusually, other medications often have to be deployed. In the collaborative study, amiodarone was useful in achieving partial or complete control of the tachyarrhythmia in upto 70% of patients [19]. Data documenting successful medical therapy using other antiarrhythmic agents either singly or in combination are scarce, and often anecdotal [20]. Abnormalities in the anatomy of tha atrioventricular node have been described in postmortem specimens of patients dying from JET, including abnormal location of the atrioventricular node within the central fibrous body, split atrio-

ventricular nodes and dual atrioventricular nodes [1]. Such anatomic abnormalities may conceivably have been present in patient 1, who had coexisting Ebstein’s anomaly. In patient 3, we initially unsuccessfully targeted the site of earliest retrograde ventriculoatrial conduction during tachyarrhythmia. Subsequently, the fast AV nodal pathway was targeted, with a successful outcome. This patient did not demonstrate evidence for dual AV nodal physiology. This approach does indeed carry a risk of permanent AV block. This case also clearly confirmed that ventriculoatrial activation may occur at an anatomically discrete site from the tachyarrhythmia focus. The treatment modalities described for junctional ectopic tachycardia include atrioventricular node ablation followed by permanent pacemaker implantation, or specific targeting of the arrhythmia focus. Hamdan et al. reported successful ablation of junctional ectopic tachycardia, with preservation of AV conduction in 6 of 6 patients under the age of 18 years [12]. In patients with ventriculoatrial conduction during tachyarrhythmia, they targeted the earliest site of retrograde activation for ablation, with good success. In our own series, this approach rendered junctional ectopic tachycardia noninducible in patients 1 and 2. In patient 1, we began RF lesion application targeting the putative slow AV nodal pathway, but subsequently targeted the site of retro-

M. Emmel et al. Catheter ablation of junctional ectopic tachycardia

grade ventriculoatrial conduction, at a superoseptal location on the tricuspid valve annulus, with success. In patient 3, however, abolition of retrograde ventriculoatrial conduction was possible by lesion application septally, without interrupting the tachyarrhythmia. Additional radiofrequency lesions closer to the superoparaseptal location, in close proximity to the His bundle were required to abolish junctional ectopic tachycardia. This confirms previous speculation that different loci in the atrioventricular nodal region may account for retrograde conduction versus junctional ectopic tachycardia initiation. Accelerated junctional rhythm during radiofrequency lesion application was observed over a relatively wide area, and was not predictive of the successful ablation site in patients 2 and 3. When accelerated junctional rhythm was observed during radiofrequency ablation, overdrive atrial pacing was employed to confirm integrity of atrioventricular conduction. Apart from continuously monitoring ablation catheter loca-

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tion in relation to the His bundle, radiofrequency energy was carefully titrated, starting at 5 W and increasing gradually upto 50 W, to achieve tissue temperatures > 50 8C. This approach has been shown to improve safety of slow pathway modification in patients with atrioventricular nodal reentrant tachycardia also [9]. An alternative technique for junctional ectopic tachycardia ablation could be the use of cryoablation, with prior ice-mapping of target sites, in order to minimise the risk of permanent atrioventricular block. All patients were discharged 24 hours following ablation, and none has shown progressive PQ interval prolongation, or late atrioventricular block at follow-up [16]. In conclusion, selective ablation of the tachycardia focus, with preservation of normal atrioventricular conduction is feasible in children with junctional ectopic tachycardia. The use of an accurate electroanatomic mapping system may improve savety of the procedure.

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