Summary
Background
Monomorphic ventricular tachycardia (MVT) is common in adults with repaired tetralogy of Fallot (TOF), and is associated with sudden cardiac death. Management of MVT is not defined, and results of catheter ablation (CA) are limited.
Aims
To evaluate long-term outcomes of MVT CA in repaired TOF.
Methods
Thirty-four patients (mean age 32 ± 10.3 years; 59% male) with repaired TOF underwent CA for symptomatic MVT between 1990 and 2012 in our centre; direct-current ablation (DCA) was used in 6%, radiofrequency followed by DCA in 29% and radiofrequency alone in 65%.
Results
Right ventricular (RV) dysfunction was present in 35% and left ventricular (LV) dysfunction in 21%. Mean numbers of clinical and induced MVTs were 1 and 2, respectively. Mean VT rate was 225 ± 95 bpm. Ablation targeted a single site (range 1–2), which was RV outflow tract in 85%. Primary success, defined as ventricular tachycardia (VT) termination during CA and final non-inducibility, was obtained in 82%. Seven patients (21%) required redo ablation in the first 3 months (before 2004; DCA). No death related to CA occurred. Mean follow-up time was 9.5 ± 5.2 years. Antiarrhythmic therapy was discontinued in 71%. There were two cases of sudden cardiac death and four VT recurrences. Freedom from death and arrhythmia recurrence was 94% at 5 years, 81% at 10 years and 70% at 20 years. Global survival was 91% at 20 years. Baseline LV ejection fraction < 60% was significantly associated with ventricular arrhythmia recurrence (hazard ratio 16.4, 95% confidence interval 1.8–147; P = 0.01).
Conclusions
CA can safely address macroreentrant MVT in repaired TOF patients with an acceptable long-term rate of recurrence in this high-risk population. Anatomical classification of isthmuses with electroanatomical mapping provides reproducible endpoints for CA. Attention should be given to LV systolic function in risk assessment and selection of candidates for implantable cardioverter-defibrillator.
Résumé
Contexte
Les tachycardies ventriculaires monomorphes (TVM) sont fréquentes chez les adultes ayant une tétralogie de Fallot réparée (TDFr) et sont associées à la survenue d’une mort subite (MS). Le traitement des TVMs n’est pas défini et les résultats de l’ablation par cathéter (AC) sont limités.
Objectifs
Evaluer les résultats à long-terme de l’AC des TVM dans la TDFr.
Méthodes
Trente-quatre patients (32 ± 10,3 ans ; 59 % hommes) ayant une TDFr ont eu une AC de TVM symptomatique entre 1990 et 2002. La fulguration seule a été utilisée chez 6 % des patients, la radiofréquence suivie de fulguration chez 29 % et la radiofréquence seule chez 65 %.
Résultats
Il existait une dysfonction ventriculaire droite (VD) chez 35 % et une dysfonction ventriculaire gauche (VG) au moins mineure chez 21 %. Le nombre moyen de TVMs cliniques et déclenchées était de 1 et 2 respectivement. La fréquence moyenne était de 225 ± 95 bpm. Il y a eu en moyenne un seul site d’ablation (de 1 à 2), qui était la voie d’éjection VD dans 85 %. Un succès primaire, défini par un arrêt de la TVM pendant le tir et une non-inductibilité finale a été obtenue dans 82 % des cas. Sept patients ont eu une ré-ablation dans les 3 premiers mois (avant 2004 et par fulguration). Aucun décès en rapport avec l’AC n’est survenu. La durée moyenne de suivi était de 9,5 ± 5,2 ans. Les traitements anti-arythmiques ont été arrêtés chez 71% des patients. Il y eut 2 MS et 4 récidives d’arythmies. La survie sans MS, récidive de TV et choc approprié était de 94 %, 81 % et 70 % à 5, 10 et 20 ans, respectivement. La survie totale était de 91 % à 20 ans. Une fraction d’éjection VG (FEVG) < 60 % était significativement associée aux récidives d’arythmie ventriculaire (HR 16,4, IC 95 % 1,8–147 ; p = 0,01).
Conclusions
L’AC est une technique fiable pour traiter les TVM par macro-réentrée dans la TDFr, avec une sécurité et un taux de récidive d’arythmies à long terme acceptables dans cette population à haut risque. L’identification des isthmes des TVM par cartographie électro-anatomique fournit une cible reproductible pour l’AC. Une attention particulière devrait être accordée à la fonction systolique du VG dans l’évaluation du risque rythmique et la sélection des candidats au défibrillateur automatique implantable.
Background
The population of adults with repaired congenital heart disease (CHD) is increasing . Tetralogy of Fallot (TOF) is the most common cyanotic CHD. Late ventricular arrhythmias are the leading cause of sudden cardiac death in adults with repaired TOF . Monomorphic ventricular tachycardia (MVT) is the most frequent form of ventricular arrhythmia, accounting for more than 80% of ventricular arrhythmias in patients with repaired TOF carrying an implantable cardioverter-defibrillator (ICD) . Several risk factors for sudden cardiac death in adults with repaired TOF have been identified, and are useful for selection of ICD candidates in a primary prevention setting , but lack predictive value, and might not be as relevant in the current era of early surgical repair. In the past decade, with the spread of electroanatomical mapping, important efforts have been made to characterize the anatomical basis of repaired TOF MVTs that seem to rely on the presence of scar tissue areas within the right ventricle (RV), corresponding to ventriculotomy or right ventricular outflow tract (RVOT) patch or ventricular septal defect patch. These scar areas create substrate for macroreentry, and MVT occurrence depends on their anatomical and electrophysiological properties, a finding that creates a path for individualized arrhythmic risk prediction in repaired CHD . However, less is known about the management of monomorphic ventricular tachycardias (VTs). Antiarrhythmic therapies and antitachycardia pacing lack efficacy , whereas ICDs do not prevent VT recurrence, and are associated with frequent complications and inappropriate therapies in this young population . Several small case series have suggested favourable outcomes after MVT catheter ablation (CA) in repaired CHD, with a VT-free long-term survival rate of 75–100% . To date, the largest series included 34 patients (eight with non-TOF CHD; seven with non-documented VT), and provided a limited follow-up of 46 months, hampering the evaluation of CA long-term efficacy . Here, we present the results of VT CA at 10 years in 34 patients with repaired TOF referred for symptomatic monomorphic VT.
Methods
Patients
We included 34 consecutive patients with surgical repair of TOF who underwent VT CA in our arrhythmia department between 1990 and 2012. Patients referred for preoperative electrophysiological study or who had other CHDs, such as pulmonary valvular stenosis or ventricular septal defect, were excluded. All patients had symptomatic VT, either sustained or non-sustained, but incessant on Holter electrocardiogram monitoring. Surgical repair of TOF was performed during an extended period ranging from 1962 to 1987, at a variable age, with or without previous palliative anastomosis, reflecting the evolution in surgical management of TOF. All ventricular septal defects were closed using a transventricular approach.
Electrophysiological study and endocardial mapping
Programmed ventricular stimulation was performed with three extrastimuli, at two drive cycle lengths of 600 and 400 ms, using a 6-Fr bipolar catheter placed at the right ventricular (RV) apex and the RVOT, until induction of sustained VT. When no VT could be induced, the same protocol was repeated under isoproterenol infusion. The induced VT was considered clinical when the 12-lead electrocardiogram morphology was identical to the documented VT with the same rate ± 20 bpm.
Endocardial mapping was performed during VT with a quadripolar ablation catheter under fluoroscopic guidance. The region of interest was identified by the presence of negative unipolar potentials (filter 0.05–500 Hz) and early bipolar potentials (presystolic or diastolic) to the surface electrocardiogram QRS complex. As described by Stevenson et al. , entrainment pacing identified slow-conduction zones corresponding to VT critical isthmus. When VT was not inducible ( n = 1), pacemapping was performed near the RVOT scar (<0.2 mV), and in the presence of late potentials during sinus rhythm. After 1999, electroanatomical mapping was used for 13 patients (CARTO ® , Biosense Webster Inc., Diamond Bar, CA, USA; and NavX™, St Jude Medical Inc., St. Paul, MN, USA). These systems allowed identification of scar areas corresponding to ventriculotomy, RVOT patch or ventricular septal defect, defined by a bipolar voltage < 0.5 mV. Dense scar was defined by a bipolar voltage < 0.1 mV with no capture by pacing. Activation mapping identified, as described , the earliest activation site and the VT mechanism (focal or macroreentry). Activation mapping also determined the isthmus type according to the anatomical classification of macroreentrant VT isthmuses in repaired TOF by Zeppenfeld et al. : isthmus 1 between the anterior tricuspid annulus and ventriculotomy or RVOT patch; isthmus 2 between the anterior pulmonary valve and ventriculotomy or RVOT patch; isthmus 3 between the posterior pulmonary valve and ventricular septal defect patch; and isthmus 4 between the ventricular septal defect patch and posterior tricuspid annulus.
CA
Direct-current ablation (DCA) alone ( n = 2) was performed between November 1990 and January 1992, using quadripolar USCI catheters (BARD, Murray Hill, NJ, USA) with 3 J/kg anodic shocks. From 1992 to 1996, ablation was achieved with 4 mm-tip catheters and 50 W radiofrequency generators ( n = 5). From 1997 to 2006, 8 mm-tip and/or 4 mm irrigated catheters and 150 W radiofrequency generators were used ( n = 16). From 2006 to 2012, all ablations were performed with 4 mm irrigated catheters ( n = 12), except for one procedure in 2010 with an 8 mm-tip ablation catheter. From 1993 to 2003, when radiofrequency alone failed to terminate VT, modified DCA (consisting of a double 160 J cathodic shock delivered by the ablation catheter) was performed under deep general anaesthesia and curarization ( n = 13). Final programmed ventricular stimulation was carried out after CA. Primary success was defined as VT termination during CA and inability of final programmed ventricular stimulation to induce any sustained VT without and with isoproterenol infusion. An indeterminate result was defined as the ability to induce a non-clinical sustained VT by programmed ventricular stimulation after CA, or when no VT was inducible at the beginning and end of the session. Failure was defined as the absence of VT termination by CA or by clinical VT inducibility at the end of the procedure.
Following the CA, patients were monitored in the cardiac intensive care unit for 48 hours, after which they were discharged from hospital if no complication had occurred.
Follow-up
Patients were referred to their primary cardiologist for follow-up. Control programmed ventricular stimulation was performed 7–30 days after CA in 19 patients. Control programmed ventricular stimulation was considered positive when any sustained VT was induced.
Need for redo CA in the first 3 months after CA for early clinical VT recurrence was not considered as VT recurrence during follow-up, and the beginning of the follow-up period was set as the date of the last ablation.
Long-term outcome was assessed retrospectively by inpatient visits, and was completed by telephone calls. VT recurrence was defined as recurrence of symptomatic VT, either sustained or unsustained, documented by Holter electrocardiogram monitoring, or the need for antitachycardia pacing therapy or the need for redo CA 3 months after the initial procedure.
Statistical analysis
The alpha risk value was set at 0.05. All statistical analyses were performed with IBM SPSS Statistics, version 23 (IBM Corp., Armonk, NY, USA). The log-rank test was used to compare survival of multiple groups. Univariate analyses were performed with the Cox proportional hazards model. The study was approved by our institutional review board.
Results
Patients
Thirty-four patients with repaired TOF underwent VT CA in our centre between 1990 and 2012. Patient characteristics are summarized in Table 1 . A transventricular approach was performed in every patient, and a RVOT patch was used in 94%. An abnormal coronary distribution was present in 18%. Among the 14 patients (41%) who underwent reintervention before CA, four had pulmonary valve replacement, two had pacemaker implantation and one had ICD implantation for VT secondary prevention. Two patients had undergone previous CA of atrial tachyarrhythmia. Fifteen patients (44%) were in New York Heart Association class II or more (mean 1.4 ± 0.6). The mean QRS complex duration was 169 ± 37 ms. Echocardiography showed RV dilatation in 47%, and RV systolic dysfunction in 35%. Accurate evaluation of RV systolic function was not available. Moderate-to-severe pulmonary regurgitation was present in 29%, and moderate-to-severe tricuspid regurgitation in 12%. RVOT aneurysm was observed in 8%. Mean left ventricular ejection fraction (LVEF) was 59 ± 8.6%. Among patients with LVEF < 60%, three had moderate aortic regurgitation, one had a residual ventricular septal defect, one had moderate mitral regurgitation and two had severe left ventricular (LV) systolic dysfunction (LVEF < 35%), in both cases related to myocardial infarction consecutive to surgical injury of an anomalous left anterior descending artery crossing the RVOT.
| Variable | |
|---|---|
| Patients | |
| Age at surgical correction | 5.4 years (3 months to 22.7 years) |
| Male sex | 20 (59) |
| Irregular TOF | 9 (24) |
| Transannular patch | 22 (65) |
| Previous palliative shunt | 12 (35) |
| Reoperation following surgical correction | 14 (41) |
| Previous ICD | 1 (3) |
| Antiarrhythmic therapy | 31 (91) |
| Amiodarone | 20 (59) |
| Beta-blocker | 17 (50) |
| Class I drug | 8 (24) |
| Sotalol | 4 (9) |
| QRS complex duration ≥180 ms | 10 (29) |
| RV systolic dysfunction | 12 (35) |
| Moderate to severe PR | 10 (29) |
| LVEF < 60% | 7 (21) |
| VT | |
| Age at first documented VT (years) | 27 ± 11.3 |
| >1 documented VT morphology | 16 (46) |
| VT rate (bpm) | 225 ± 95 |
| Poor clinical tolerance a | 20 (59) |
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