Authors: Mohammad Dalili, Mohammadreza Kargarfard, Avisa Tabib, Mahmood Sheikh Fathollahi, Pedro Brugada
Categories: Original Research Article, Ablation, Pediatric arrhythmias, Pediatric ventricular arrhythmias, Pediatric ventricular tachycardias
Source: Indian Pacing and Electrophysiology Journal
Authors: Mohammad Dalili, Mohammadreza Kargarfard, Avisa Tabib, Mahmood Sheikh Fathollahi, Pedro Brugada
The ablation of ventricular tachycardia, including premature ventricular contractions, is an approved, albeit infrequent procedure in pediatric patients. Data are scarce regarding the outcomes of this procedure. The purpose of this study was to share a high-volume center experience and patient outcomes for catheter ablation of ventricular ectopy and ventricular tachycardia in pediatric population.
Data were retrieved from the institutional data bank. Outcomes over time were evaluated, and procedural details were compared.
A total of 116 procedures were performed on 102 pediatric patients between July 2009 and May 2021 at the Rajaie Cardiovascular Medical and Research Center in Tehran, Iran. Ablation was not performed in 4 procedures (3.4%) due to high-risk substrates. Of the remaining 112 ablations performed, 99 (88.4%) were successful. However, one patient died due to a coronary complication. There were no significant differences observed in early ablation results based on patients' age, sex, cardiac anatomy, or ablation substrates (P > 0.05). Follow-up records were available for 80 procedures, and 13 (16.3%) of those experienced recurrence. During long-term follow-up, none of the variables mentioned above were statistically different between patients with or without arrhythmia recurrence.
The overall success rate of pediatric ventricular arrhythmia ablation is favorable. We found no significant predictor for the procedural success rate concerning acute and late outcomes. Larger multicenter studies are needed to elucidate the predictors and outcomes of the procedure.
Ventricular tachycardias (VTs) most often occur in patients with structural heart disease; but can also occur in the normal heart, so-called “idiopathic VTs” [1]. VTs are uncommon in childhood as attested to by a retrospective study reporting the incidence of 1.1 episodes per 100 000 childhood years [2]. The clinical features and prognoses of VTs depend on the type, the clinical category, age at onset, accurate diagnosis, and proper treatment [3]. Antiarrhythmic therapy in pediatric patients with ventricular arrhythmias is not significantly effective [4]. Catheter ablation is an approved and safe method to eliminate the different types of pediatric arrhythmias, including VTs [5,6]. The indications for VT ablation were re-emphasized by the PACES/HRS expert consensus statement [6], citing 2 principal indications for ventricular arrhythmia ablation in symptoms related to the arrhythmia and findings in favor of arrhythmia-induced cardiac failure.
This paper presents a review of the outcomes of 116 procedures, which includes 112 ablations for ventricular arrhythmias in 102 children under the age of 16. All procedures were conducted by a single team over 13 years at a single center.
Patient Population: Records of all consecutive patients who underwent catheter ablation for premature ventricular contractions (PVCs) or VTs between July 2009 and May 2021 were analyzed. All the procedures were performed at Rajaie Cardiovascular Medical and Research Center, an Iranian tertiary center of pediatric cardiology. In keeping with the center's policy, the study population consisted of children younger than 16 years.
The study protocol was approved by the institutional ethics committee, and an informed consent form, including an agreement for publishing procedural results, was filled in and signed by the children's parents/legal custodians. Cardiac anatomy and function were assessed by echocardiography. Carefully detailed echocardiography was performed for all the patients before the procedure. Abnormal cardiac anatomy was defined as a present or repaired significant cardiac lesion (Table 1). Arrhythmia presentation was defined as PVCs or VTs based on the dominant arrhythmia by which the patient became a candidate for electrophysiology (EP) studies and ablations. Since multiple procedures were performed on some patients at different times, with varying ages, weights, symptoms, and cardiac functions, each patient was considered as a new "case" for each procedure for the purpose of statistical analysis.Table 1Summarized data on patients with abnormal cardiac structures in whom ablation was done.Table 1NoAge (years)Type of the structural anomalyArrhythmiaIndicationMapping systemArrhythmia mechanismAblation TargetEarly outcomeLate outcome, follow-up duration1.3.5DTGA, post arterial switchVTSymptomatic VT episodes, compromised cardiac functionCarto 3Focal automaticityNeopulmonary- old aortic root suture lineSuccessful ablationRecurrence after 1 year2.5.0DTGA, post arterial switchVTFast VTNAVX precisionFocal automaticityLinear lesion from RVOT mid-septal to Neopulmonary valveSuccessful ablationNo arrhythmia, 4 years3.5.0VSD repairPVCPVC + VTconventionalFocal automaticityRVOT AnteroseptalSuccessful ablationLost FU4.5.0LV tumorPVCFrequent palpitationNAVX precisionFocal automaticityMitral ring (posterior)Successful ablationNo arrhythmia, 7 years, the tumor partially regressed5.5.0aDTGA, post arterial switchVTSymptomatic VT episodes,NAVX precisionFocal automaticityNeopulmonary- old aortic root suture lineSuccessful ablationNo arrhythmia, 1 year6.12.0Repaired TOFVTFrequent palpitationconventionalFocal automaticityRV apico-septal areaSuccessful ablationNo arrhythmia, 7 years7.12.0VSD-PS repairPVCSymptoms, reduced EFNAVX precisionFocal automaticityRVOT mid-septalSuccessful ablationNo arrhythmia, 4 years8.13.0VSD repairVTPalpitation, Frequent PVCsconventionalReentryleft Posterior fascicleSuccessful ablationRecurrence after 1 month, controlled with verapamil, planned for re-ablation9.14.0large PA-LA fistula, occluded with devicePVCcompromised cardiac functionCarto 3Focal automaticityTricuspid ring (lateral)Successful ablationNo arrhythmia, 1 year10.15.0Repaired TOF, PVRVTsustained symptomatic VT episodesIntracardiac echocardiography + NAVX precisionFocal automaticityRVOT PosteroseptalSuccessful ablationNo arrhythmia, 4 yearDTGA = d-transposition of the great arteries; TOF = tetralogy of fallot; VSD = ventricular septal defect; LV = left ventricle; PS = pulmonary stenosis; PA = pulmonary artery; LA = left atrium; PVR = replaced pulmonary valve; VT = ventricular tachycardia; PVC = premature ventricular contraction; RVOT = right ventricular outflow tract.aThis case is the recurrence in case no 1.
Indications: The basic parameters for determining the indication for catheter ablation were the “patients’ symptoms” and “cardiac function”. Symptoms were grouped into 3 palpitations and mild chest pains were considered mild, sustained arrhythmias with syncope attacks necessitating hospital admission were deemed moderate, and symptoms needing emergency admission, cardioversion or cardiopulmonary resuscitation were regarded as severe. Cardiac function was mainly assessed with trans-thoracic echocardiography. A systemic ventricular ejection fraction (EF) above 55% was considered normal, between 40% and 55% mildly compromised, and less than 40% significantly compromised.
Fifty-two ablation procedures were performed for cases with PVCs as the dominant presentation. Among them, two cases had significantly compromised cardiac function. One case had a large pulmonary artery-left atrial fistula (Case 9, as shown in Table 1), while the other case had no structural anomaly but was found to have one major criterion (RV regional akinesia and RV ejection fraction of 37%) in favor of arrhythmogenic right ventricular cardiomyopathy. Both cases had mild symptoms.
Mildly compromised cardiac function was observed in 23 cases. Of them, 1 case had severe symptom, 7 had moderate symptoms, and 15 had mild symptoms. Twenty-seven cases had normal cardiac function; of them, 4 cases had moderate and the 23 others had mild symptoms. Holter monitoring had done for all PVC cases; the PVC counts were more than 10% (ranging from 10% to 52%) in all. All cases received at least one antiarrhythmic drug for several months without significant response, before the ablation.
A total of 60 ablation procedures were performed for sustained VT. Two ablation procedures were done for the same case with significantly compromised cardiac function although the patient was mildly symptomatic. Cardiac functions were mildly compromised in 13 cases; of them 8 had moderate and 5 had mild symptoms. Forty-five cases had normal cardiac functions; of them 1 case had severe, 30 cases had moderate, and 29 cases had mild symptoms.
Procedure: Antiarrhythmic drugs were discontinued for at least 5 half-lives before the procedure. For children over approximately 20 kg of weight, the procedure was performed with sedation, achieved with a single dose of midazolam and fentanyl, and maintained via a propofol drip infusion. Patients weighing less than 20 kg underwent general anesthesia and mechanical ventilation. However, the weight range for decision-making as regards the type of sedation or general anesthesia was flexible and based on the patients' general characteristics and arrhythmia type, as well as the anesthesiologist's preference. For all the patients, except one, at least 3 vascular accesses were obtained. Two 5 or 6 Fr quadripolar diagnostic catheters were advanced to the right atrium (RA) and the right ventricle (RV), with the other access (5–8 Fr) used for advancing the ablation catheter. For cases in whom 3D mapping desired, except 3 cases weighing less than 20 kg, a coronary sinus catheter was also inserted for better geometry. Ablation of the right heart substrates were done via inferior caval vein access, and, for the left side substrates, except one case, retrograde trans-aortic access was used. The antegrade route was used for an infant towards ablating a VT/PVC arising from the anterolateral papillary muscle of mitral valve.
The mapping system was defined as 3D for procedures in which a type of 3D system (NavX or Carto) was used. Conventional fluoroscopy was labeled to those procedures in which the 3D systems were not used. Multipolar catheters were not used for mapping.
In the EP laboratory, conventional atrial and ventricular pacing protocols were used for arrhythmia induction and termination. The protocols included programmed pacing with different drive cycle lengths and up to 4 extra stimuli. If the arrhythmia was non-inducible with the abovementioned protocol, an isoproterenol infusion at doses ranging from 0.01 to 0.1 μg/kg/min was administered, and pacing protocols were repeated. High-risk conditions precluded ablation in some patients.
Conventional or cooled-tip catheters were used for ablation (EZ STEER®, Stinger™). For conventional catheters, targeted power of 30–35 W were used with the temperature target of 50–55°. In the case of cooled-tip catheters, targeted power set as 20–30 W, and the maximal energy targeted based on the impedance drop of 8–10 ohms.
Ablation target sites were chosen based on the earliest activation potential for automatic focuses and presystolic Purkinje potentials for reentrant fascicular ones. Pace-map was used as an adjunctive in the cases of automaticity. The non-inducible cases were not tried with pace mapping due to the doubts about accuracy. According to their anatomic locations and the arrhythmia mechanisms, the ablation target sites were grouped into 5 categories.•Focal PVCs/VTs with origins around the left ventricular (LV) outlet•Focal PVCs/VTs with origins around the RV outlet•Reentrant LV fascicular VTs•Focal PVCs/VTs with origins around the tricuspid valve or the RV body•Focal PVCs/VTs with origins around the mitral valve or the LV body
The protocol of VT induction, including double and triple extra-stimuli, without and with isoproterenol infusion was repeated after the ablation procedure. Ablation results were categorized as successful or unsuccessful. A successful result was defined as a procedure in which VTs and/or PVCs were completely terminated by radiofrequency (RF) application and could not be re-induced at that session using the above-mentioned VT induction protocol. Procedures in which VTs and/or PVCs persisted completely or partially despite RF application were considered unsuccessful. For all cases, arrhythmia induction protocols were done at least two times post RF application, the first time just after RF application, and the last one about 30 min thereafter. Failure to induce VT, even a nonsustained form was considered a success for the patients with VT. For PVC cases, lack of any PVC with the same morphology during about 30 min post-ablation targeted as the success.
All the cases were advised to return for outpatient visits at 1, 6, and 12 months and then yearly after the procedure. Cases whose follow-up records were not found beyond 1 month were considered lost to follow-up.
Recurrence was defined as the reappearance of arrhythmias during the follow-up period with the same characteristics as the ablated arrhythmia.
Data on EP studies and ablations were obtained from the institutional information system. The outpatient recording system was used to gather the follow-up data. The data are expressed as the mean ± the standard deviation (ranges) for numerical variables and are summarized as numbers (percentages) for categorical variables. The χ^2^ test or the Fisher exact test was utilized to compare the categorical variables across groups. The Student t-test was applied to compare the numerical variables across binary groups. The Shapiro–Wilk test was also employed to examine normal distribution in the numerical variables, and no statistical violations of normality assumption were found in any numerical variable (P > 0.05). For the statistical analyses, the statistical software SPSS version 22 (IBM, SPSS Inc, Chicago, IL, USA) was used. All P values were 2-tailed, with statistical significance defined by a P value equal to or less than 0.05.
Demographic Data: Between July 2009 and May 2021, a total of 116 procedures were conducted on 102 patients at the Rajaie Cardiovascular Medical and Research Center in Tehran, Iran. These included 4 diagnostic-only studies in 4 patients and 112 ablation procedures in 98 patients. The age range of the patients at the procedures was from 9 months to 16 years. Three ablations were done during infancy; 2 of them for the same case. Both infants had normal structural hearts and the VT origin was anterior papillary muscle of the mitral valve. Further details on these infants are summarized in Table 2. Cardiac structure was normal in the majority of the cases (90.5%), and cardiac function was normal in a sizable portion (62.9%), mildly compromised in approximately one-third, and significantly diminished in only a few. More than half of the cases had mild symptoms, about half showed moderate symptoms, and only 2 patients exhibited severe symptoms. VTs were a slightly more common presentation than PVCs (Table 3).Table 2Details on the ablation in the 2 infants included in the study.Table 2VariablesCase 1Case 2 (first time)Case 2 (second time)Age at the procedure12 months9.5 months12 monthsWeight at the procedure10.5 kg7 kgDrugs were tried beforeLidocaine, Procainamide, Verapamil, Amiodarone, Sotalol, Esmolol (the drugs were used alone and in different forms of combination)Amiodarone, Procainamide, Esmolol (the drugs were used alone and in combination)Flecainide, Verapamil, Sotalol, Amiodarone, Propranolol (the drugs were used alone and in combination)Indication for ablationIncessant VTReduced cardiac function, visual problem suspected to be a drug complicationReduced cardiac function,CathetersThree catheters (all 5F):1. Diagnostic quadripolar from RFV into RA,2. Diagnostic quadripolar from LFV into RV,3. Ablation from RFA into LVTwo 1. Diagnostic 5F quadripolar from LFV into RV,2. Ablation 7F from RFV into RA-PFO-LVThree 1. Diagnostic 5F quadripolar from RFV into RA,2. Diagnostic 5F quadripolar from LFV into RV,3. Ablation 7F from RFA into LVMapping systemConventional fluoroscopicConventional fluoroscopic3D NavX precisionFocusMV anterior papillary muscleMV anterior papillary muscleMV anterior papillary muscleEarly outcomeUnsuccessful ablation, the arrhythmia terminated with DC cardioversionSuccessfulSuccessfulComplicationNoneNoneNoneFollow upAfter the ablation, the arrhythmia could be controlled with combination of amiodarone, verapamil, propranolol, propafenone; after several months the drugs reduced to propafenone only, thereafter propafenone discontinued, the patient is in normal sinus rhythm within 5-years follow-upRecurrence after about 7 months, re-ablation was doneThe patient's condition was controlled with oral propranolol for 3 months to manage the cardiac failure, and then the medication was discontinued for the 4-year follow-up period. During multiple outpatient visits in the follow-up period, the patient's ventricular function returned to normal as documented by echocardiography.VT = ventricular tachycardia; RFV = right femoral vein; RA = right atrium, LFV = left femoral vein; RV = right ventricle; RFA = right femoral artery; LV = left ventricle; PFO = patent foramen ovale; MV = mitral valve.Table 3Demographic and arrhythmia characteristics of the study population, which included 102 patients who underwent a total of 116 procedures. The data were analyzed based on the number of procedures.Table 3VariablesDetailsNumber of procedures116 (100%)**Age (y)**9.71 ± 3.78 (0.8–16)Sex Male78 (67.2%) Female38 (32.8%)**Weight (kg)**38.00 ± 16.83 (8–82)**Height (cm)140.07 ± 24.65 (70–180)Body surface area (m^2^)**1.21 ± 0.37 (0.39–2.02)Cardiac Anatomy Normal105 (90.5%) Abnormal11 (9.5%)Cardiac Function Normal73 (62.9%) Mildly compromised38 (32.8%) Significantly compromised5 (4.3%)Symptom Mild61 (52.6%) Moderate53 (45.7%) Severe2 (1.7%)Presentation PVC53 (45.7%) VT63 (54.3%)Data are expressed as the mean ± the standard deviation (ranges) or numbers (percentages). PVC = premature ventricular contraction; VT = ventricular tachycardia.
Ablation Data: Ablation was not tried in 4 patients who were deemed high-risk for the procedure. Their conditions are summarized in Table 4. There were 9 cases with the ages of less than 2 years in whom ablation was done (Fig. 1). For the case mentioned in Fig. 1, an intracardiac cardioverter defibrillator was implanted due to the very high rate VTs and aborted sudden cardiac death.Table 4Characteristics of the high-risk patients on whom ablation was not tried.Table 4Case CharacteristicsArrhythmia DiagnosisReason for Avoiding AblationFollow-upA 6-year-old boy with palpitation episodes after ablation for left posterior fascicular VTsUpper septal VTsRisk of AV blockThis case was unresponsive to various combinations of medical therapy, including verapamil, flecainide, and propranolol, and was subsequently ablated at our center during a subsequent session. It has been classified as a fascicular VT and included in Table 5.A 5-year-old boy with palpitation, mildly reduced cardiac function, and frequent PVCsFocal PVCs with the focus near the RCA originRisk of coronary injuryComplete relief after several months of drug therapy with oral FlecainideA 5-year-old boy with a history of ToF correction and an episode of wide complex tachycardiasVTs from the RVOT originFast arrhythmias with a compromised hemodynamic conditionMedical therapy with Sotalol and ICD implantationA 6-year-old boy with palpitation and a history of viral myocarditisUpper septal VTsRisk of AV blockMedical therapy with oral FlecainideAV = atrioventricular; ICD = implantable cardioverter-defibrillator; PVC = premature ventricular contraction; RCA = right coronary artery; RVOT = right ventricular outflow tract; ToF = tetralogy of Fallot; VT = ventricular tachycardia.Fig. 1The illustration depicts successful radiofrequency ablation of hemodynamic compromising VT in an 18-months-old boy. the 12-lead ECG showing a rapid wide complex tachycardia with superior axis and right bundle branch block pattern. Cardiac magnetic resonance imaging showed hyper-trabeculation in the left ventricular apex. 3-D mapping with Ensite NavX precision showing the local activation times and the burn spots. fluoroscopic image showing the catheters' position at the time of ablation. the successful ablation signals recorded by the ablation catheter. the 12-lead ECG after successful ablation.Fig. 1
Three-dimensional mapping was used in 30 (26.8%) cases, one of them with zero-fluoroscopy using intracardiac echocardiography (Fig. 2). The case of zero-fluoroscopy procedure was done in a 15-year-old boy with a history of surgical repair of tetralogy of Fallot and metallic pulmonic valve. Intracardiac echocardiography (ICE) was performed using 9 F sheet and catheter inserted from the left femoral vein. One hundred twelve patients underwent catheter ablation. All ablations were done with radiofrequency energy. None of the patients required epicardial ablation. The procedure was acutely successful in 99 cases (88.4%). There were no significant differences in the acute success rate regarding the patients’ age, sex, cardiac anatomy, and ablation substrates (P > 0.05). ablation was done in 10 patients with abnormal cardiac structures. The details on these cases were summarized in Table 1. Even when the arrhythmia substrate classification was changed into larger cumulative groups (the right-sided vs the left-sided, the outlet vs the body, and the reentrant vs the automatic), no statistically significant differences were found (Table 5). The arrhythmia focus was around the papillary muscles in 9 cases; 5 cases around mitral antero-lateral papillary muscle, 1 case around mitral postero-medial papillary muscle, and 3 cases around tricuspid anterior papillary muscle. Ablation procedure was successful in 7 cases; of them, 4 cases experienced recurrence (see Table 6).Fig. 2The illustration depicts successful, zero-fluoroscopy radiofrequency ablation of PVC and VT runs in a 15-year-old boy with a history of surgical repair of tetralogy of Fallot. the 12-lead baseline ECG showing surgically induced right bundle branch block, and inferior axis VT runs. the chest radiogram, note the metallic pulmonary valve (On-X 25). intracardiac echocardiography view showing the ablation catheter position beneath the prosthetic valve. 3-D mapping with Ensite NavX precision showing the local activation times and the burn spots. the successful ablation signals. the 12-lead ECG after successful ablation.Fig. 2Table 5Early ablation results in different categories. The data were analyzed based on the number of procedures.Table 5VariablesSuccessfulUnsuccessfulTotalP valueNo of procedures99 (88.4%)13 (11.6%)112 (100%)Age (y)9.82 ± 3.7110.15 ± 4.309.86 ± 3.760.762Sex0.126 Male68 (91.9%)6 (8.1%)74 Female31 (81.6%)7 (18.4%)38Weight (kg)38.52 ± 16.9039.27 ± 16.6138.61 ± 16.800.880Height (cm)140.92 ± 24.59140.46 ± 26.25140.87 ± 24.660.950BSA1.22 ± 0.371.23 ± 0.381.22 ± 0.370.937Cardiac Anatomy0.602 Normal89 (87.3%)13 (12.7%)102 Abnormal10 (100%)010Cardiac Function0.999 Normal63 (87.5%)9 (12.5%)72 Mildly compromised32 (88.9%)4 (11.1%)36 Significantly compromised4 (100%)04Symptom0.999 Mild53 (88.3%)7 (11.7%)60 Moderate44 (88.0%)6 (12.0%)50 Severe2 (100%)02Mapping System0.342 Conventional69 (86.3%)11 (13.8%)80 3D30 (93.8%)2 (6.3%)32Ablation Catheter0.699 Conventional RF82 (89.1%)10 (10.9%)92 Cool-tip RF17 (85.0%)3 (15.0%)20Ablation Substrates *(by definite arrhythmia focus and mechanism)*0.540LVOT27 (84.4%)5 (15.6%)32RVOT31 (88.6%)4 (11.4%)35Fascicular25 (96.2%)1 (3.8%)26TV/RV9 (81.8%)2 (18.2%)11MV/LV7 (87.5%)1 (12.5%)8Ablation Substrate *(by cumulative arrhythmia focus considering the mechanism)*0.320Outlets58 (86.6%)9 (13.4%)67Inlets and body16 (84.2%)3 (15.8%)19Fascicular25 (96.2%)1 (3.8%)26Ablation Substrate *(by cumulative arrhythmia focus irrespective of the mechanism)*0.692Right-sided40 (87.0%)6 (13.0%)46Left-sided59 (89.4%)7 (10.6%)66Ablation Substrate (by arrhythmia mechanism)0.293Reentrant25 (96.2%)1 (3.8%)26Automatic74 (86.0%)12 (14.0%)86BSA = body surface area; LV = left ventricle; LVOT = left ventricular outflow tract; MV = mitral valve; RF = radiofrequency; RV = right ventricle; RVOT = right ventricular outflow tract; TV = tricuspid valve.Table 6Late outcomes of the study population. The data were analyzed based on the number of procedures.Table 6VariablesNo recurrenceRecurrenceTotalP valueNo of Patients67 (83.8%)13 (16.3%)80 (100%)Age (y)9.72 ± 3.468.94 ± 5.589.60 ± 3.850.634Sex0.326 Male48 (87.3%)7 (12.7%)55 Female19 (76.0%)6 (24.0%)25Weight (kg)37.79 ± 15.6331.99 ± 17.6836.85 ± 16.010.234Height (cm)141.21 ± 22.36127.69 ± 34.65139.01 ± 25.010.198BSA1.21 ± 0.341.05 ± 0.451.18 ± 0.360.151Cardiac Anatomy0.634 Normal60 (84.5%)11 (15.5%)71 Abnormal7 (77.8%)2 (22.2%)9Cardiac Function0.222 Normal41 (85.4%)7 (14.6%)48 Mildly compromised24 (85.7%)4 (14.3%)28 Significantly compromised2 (50.0%)2 (50.0%)4Symptom0.553 Mild33 (78.6%)9 (21.4%)42 Moderate32 (88.9%)4 (11.1%)36 Severe2 (100%)02Mapping System0.115 Conventional47 (88.7%)6 (11.3%)53 3D20 (74.1%)7 (25.9%)27Ablation Catheter0.717 Conventional RF54 (84.4%)10 (15.6%)64 Cool-tip RF13 (81.3%)3 (18.8%)16Ablation Substrates**0.323LVOT14 (82.4%)3 (17.6%)17RVOT23 (92.0%)2 (8.0%)25Fascicular19 (86.4%)3 (13.6%)22TV/RV6 (66.7%)3 (33.3%)9MV/LV5 (71.4%)2 (28.6%)7BSA = body surface area; LV = left ventricle; LVOT = left ventricular outflow tract; MV = mitral valve; RF = radiofrequency; RV = right ventricle; RVOT = right ventricular outflow tract; TV = tricuspid valve.
Complications: One of the successful cases experienced an early VTs with the ablation target within the left coronary cusp about 5 mm far from the ostium of the left main coronary artery. Ablation was done using NavX 3D system. The left main coronary artery (LMCA) was tagged with the 3D system as it was inadvertently entered during mapping. Aortic root angiography confirmed the location of the left main coronary artery. After successful ablation, since the electrocardiogram was normal a repeat aorto or coronary angiography was not done. As the child experienced ventricular fibrillation and cardiac arrest in recovery room, an emergent angiography was done which confirmed total occlusion in the left main coronary artery. Coronary balloon angioplasty was performed emergently. Nonetheless, the successful coronary re-opening and extracorporeal membrane oxygenation failed to rehabilitate the child, who expired after 1 day. While no RF energy was applied within the coronary artery, it is not clear that the damage happened because of the catheter trauma or RF application near the ostium of LMCA. The other possible complications including bundle branch block, atrioventricular block, pericardial effusion, and vascular damages were not seen in any case.
Follow-up Data: Follow-up records beyond 1 month after ablation were found in 80 cases. At follow up a detailed history was taken and 24 h Holter was done. The median follow-up time was approximately 5 years. Thirteen patients (16.3%) experienced recurrence. None of the variables was statistically different between the 2 groups of recurrence and no recurrence (P > 0.05) (Table 5). The outcome pathways of the study population are summarized in Fig. 3.Fig. 3The image shows the outcome pathways of the 116 procedures that were conducted on 102 pediatric patients with ventricular tachycardia or premature ventricular contractions. For the purpose of statistical analysis, each patient was considered as a new "case" for each procedure. The number of cases in each category is indicated in parentheses.Fig. 3
This single-center study presents an evaluation of VT ablation outcomes in pediatric patients.
The major concern in catheter ablation in pediatric patients is procedural safety [7]. Several reports have confirmed the safety of VT catheter ablation in the pediatric population [[8], [9], [10], [11]]. Most reports include idiopathic VT and common reentrant fascicular forms. We decided against ablation in 4 patients due to the high-risk property of the arrhythmia; nevertheless, we performed the procedure on a 13-year-old boy who weighed 83 kg. In the latter case, although the ablation procedure was successful, total occlusion in the left main coronary artery was observed early after the procedure. Unfortunately, the patient died despite a successful coronary balloon angioplasty and resuscitation efforts. This catastrophic case should serve as a stark warning that patient size cannot confer protection against serious complications.
Our success rate of 88.4% is very close to that reported by Oomen et al. [12], who achieved a procedural ablation success rate of 89% in 147 ablations on 131 adult patients with idiopathic ventricular arrhythmias. Several other studies have shown ablation success rates of over 80% for symptomatic idiopathic PVCs/VTs [[13], [14], [15], [16]]. All these data underscore the high efficacy of the procedure among adult patients. Our findings demonstrated no significant difference in the outcome between pediatric and adult patients. In our study, of the 4 patients aged less than 2 years; one of them had LV noncompaction with VT arising from the same region.
During a median follow-up of 5 years, we observed an approximate arrhythmia recurrence rate of 16%. While numerous investigations have reported short- and midterm follow-up results concerning VT ablation in adults, the literature contains a dearth of information on such results in pediatric patients. Schleberger et al. [17] reported the outcome of the catheter ablation of non-reentrant ventricular arrhythmias in patients with and without structural heart disease. During a follow-up period of 34.7 ± 15.1 months, they reported the need for re-ablation in 22.5% and 15.6% of the cases with and without structural heart disease, respectively. Our study included 11 cases with structural anomalies of the heart. Ablation was not tried in 1 case due to the very fast and hemodynamically compromising arrhythmia which did not allow careful study and mapping (Table 4). Ten ablation procedures were done for cases with structural anomalies (Table 1). Except one case with LV benign tumor, the other cases had the history of surgical repair and/or trans-catheter interventions for their cardiac structural anomalies. Encouraging results in this group could be a confirmation for effectiveness of VT ablation in pediatric patients with repaired cardiac anomalies, and, needless for implanting cardioverter-defibrillators in these selected cases.
Intracardiac echocardiography is a useful tool for targeting the ventricular arrhythmias, especially, in the case of papillary muscle substrates [18]. The main limitation of ICE catheter for using in small children is its relative large caliber (9 Fr). We did just one case (Table 1, case 10) using ICE. Using ICE could probably enhance the results of the catheter ablation, especially, in the cases with papillary muscle substrates.
Vaseghi et al. [19] reported the outcome of VT catheter ablation according to etiology in nonischemic heart disease on 780 adult patients. Based on their results, in a mean follow-up of 12.8 months, VTs recurred in 318 patients (41%) and death occurred in 137 (18%). Wu et al. [9] reported VT recurrence in 6 out of 53 pediatric cases (11%) during a mean follow-up of 29.2 ± 21.7 months.
Chiming in with many recent studies, we could not find statistical differences in acute and long-term outcomes of VT catheter ablation between different age groups or those with different arrhythmia substrates, which could be a consequence of high success rates and low recurrence rates in patients undergoing the procedure [9,17,19].
Ablation of VTs in the pediatric population is effective. The high success rate and the low complication rate statistically preclude the determination of the predictors of unsuccessful and recurrent cases. Larger multicenter studies are needed to elucidate the predictors and outcomes of the procedure. We recommend post-procedural aortography after the ablation of arrhythmia substrates within the aortic cups for ruling out coronary or valvar complications.
A major concern in patients with automatic tachycardias, including some forms of VTs, is non-inducibility. We could not evaluate the effect of general anesthesia, by which, some of our procedures were done. The present study does not present data regarding non-inducible cases. Some previous investigations have discussed the inducibility of VTs in adult patients [[20], [21], [22]]; nonetheless, we could not access such data on pediatric patients.
Although 3D mapping is the preferred method for ablation in most VTs in the pediatric population, we opted to perform some of the procedures using conventional fluoroscopy for mapping and ablation. Another limitation of our report is lacking on the number of RF-induced lesions in each case and the durations of RF application.
The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.
All authors contributed to the study conception and design.
Mohammad Dalili: Study design, doing the procedures, drafting of the manuscript.
Avisa Tabib: Drafting of the manuscript, correspondence for article requirements.
Mohammadreza Kargarfard: Cooperation in drafting of the manuscript, and data gathering.
Mahmood Sheikhfathollahi: Analysis and interpretation of data.
Pedro Brugada: Revising the manuscript critically for important intellectual content.
All authors read and approved the final manuscript.
The study protocol was approved by the Rajaie Cardiovascular Medical and Research Center ethics committee.
Written informed consent, including an agreement for publishing procedural results, was obtained from the parents/legal custodians.
The authors have no relevant financial or non-financial interests to disclose. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.