Evaluation of T-wave memory after accessory pathway ablation in pediatric patients with Wolff-Parkinson-White syndrome.

BACKGROUND: T-wave memory (TWM) is a rare cause of T-wave inversion (TWI). Alterations in ventricular activation due to abnormal depolarization may cause repolarization abnormalities on the ECG, even if myocardial conduction returns to normal. These repolarization changes are defined as TWM. In our study, we aimed to determine the frequency of TWM development and the predictors affecting it in the pediatric population who underwent accessory pathway (AP) ablation due to Wolff-Parkinson-White (WPW) syndrome. METHODS: The data of patients with manifest AP who underwent electrophysiological studies and ablation between 2015 and 2021 were retrospectively analyzed. The study included 180 patients who were under 21 years of age and had at least one year of follow-up after ablation. Patients with structural heart disease, intermittent WPWs, recurrent ablation, other arrhythmia substrates, and those with less than one-year follow-up were excluded from the study. The ECG data of the patients before the procedure, in the first 24 h after the procedure, three months, and in the first year were recorded. The standard ablation technique was used in all patients. RESULTS: Postprocedure TWM was observed in 116 (64.4%) patients. Ninety-three patients (51.7%) had a right-sided AP, and 87 patients (48.3%) had a left-sided AP. The presence of posteroseptal AP was found to be significantly higher in the group that developed TWM. Of these patients, 107 (93.1%) patients showed improvement at the end of the first year. Preprocedural absolute QRS-T angle, postprocedural PR interval, and right posteroseptal pathway location were identified as predictors of TWM. CONCLUSION: The development of TWM is particularly associated with the right-sided pathway location, especially the right posteroseptal pathway location. The predictors of TWM are the preprocedural QRS-T angle, the postprocedural PR interval, and the presence of the right posteroseptal AP.

Permanent pacemaker implantation with hybrid endocardial perventricular approach in infancy: May be an alternative route in the absence of epicardial lead.

Despite the advancements in technology, establishing the optimal implantation technique for pediatric patients with a pacemaker (PM) indication remains challenging. Although the implantation of an epicardial PM is recommended, especially in children weighing less than 10 kg, transventricular placement of endocardial leads can be performed safely, offering a practical substitute for an epicardial pacing system, particularly in situations where a transvenous approach is unfeasible due to patient size, anatomical constraints or epicardial PM leads were not available as in our case.

Unmasking the uncommon: bidirectional ventricular tachycardia in two rare paediatric cardiomyopathies.

We present two exceptional cases of 14-year-old girls diagnosed with rare cardiomyopathies (left ventricular non-compaction, and arrhythmogenic right ventricular cardiomyopathy), both presenting with the unusual finding of bidirectional ventricular tachycardia.

High-density Mapping Catheter (Advisor™ HD Grid) Usage for Intra-atrial Reentrant Tachycardia Ablation in Children and Young Adult Patients with Congenital Heart Disease.

BACKGROUND: We aimed to share our experience of intra-atrial reentrant tachycardia mapping and ablation with a new grid-style multielectrode high-density mapping catheter (Advisor™ HD Grid) in pediatric and young adult patients with operated congenital heart disease. METHODS: All patients with operated congenital heart disease and intra-atrial reentrant tachycardia mapping with the new grid-style catheter between October 2019 and December 2022 were included (group 1), and the results were compared to those patients who operated with conventional catheter methods before this period (group 2). All procedures were performed using the EnSite Precision 3D mapping system (Abbott Laboratories, Abbott Park, Ill, USA) with a limited fluoroscopy approach. Data were evaluated retrospectively. RESULTS: In group 1 (n = 16; 9 male), the median age was 21 years (10-36), compared to 19 years (9-27) in group 2 (n = 10; 5 male). While irrigated radiofrequency ablation was pre-ferred in all patients, the median number of 15 lesions (8-38) in group 1 was significantly less than the median of 30 lesions (8-71) in group 2 (P =.027). The median procedure duration of 159 minutes (110-233) in group 1 was significantly shorter compared to 280 minutes (180-370) in group 2 (P <.05). Acute procedural success was achieved in all patients (16/16; 100%) in group 1 compared to 8/10 patients (80%) in group 2. During the median follow-up of 27 months (11-36), there was only 1 intra-atrial reentrant tachycardia recurrence in group 1 (1/16; 6.2%) and 2 recurrences (2/8; 25%) in group 2 during the median follow-up of 110 months (56-151). No complications related to the mapping catheter itself occurred. CONCLUSION: In the intra-atrial reentrant tachycardia ablation of children with congenital heart disease to increase procedural success and shorten the mapping duration, the utility of Advisor™ HD Grid mapping catheter seems to be a feasible alternative.

Successful treatment of the focal ectopic atrial tachycardia in an infant with a single dose of ivabradin.

We report on a 12-month-old boy with an ectopic atrial tachycardia successfully treated with the ivabradine that acts on cardiac pacemaker cells by selectively inhibiting the If channel. The patient was diagnosed with supraventricular tachycardia in another centre, and multi-drug therapy was unsuccessful to restore sinus ryhthm, so he was sent to our hospital for catheter ablation. We stopped the medications the patient was taking and started using ivabradine. Sinus rhythm was restored 2 hours after ivabradine treatment was started.

Clinical Characteristics and Mid-term Follow-up in Children with Isolated Complete Atrioventricular Block.

BACKGROUND: Isolated complete atrioventricular block is a rare disease often associated with maternal autoantibodies. This study aimed to present the midterm data of patients at our clinic diagnosed with isolated complete atrioventricular block. METHODS: We evaluated 108 patients diagnosed with isolated complete atrioventricular block. Demographic data of the patients, electrocardiography, echocardiography, 24-hour Holter monitoring data, and follow-up and complications of the patients who underwent pacemaker implantation were evaluated retrospectively. RESULTS: The mean age of the patients at diagnosis was 5.51 ± 5.05 years. At the time of diagnosis, 74.8% of the patients had no symptoms associated with complete atrioventricular block. The most common symptom was fatigue. Pacemaker implantation was needed in 88 (81.4%) patients during follow-up. Significant bradycardia was the most common pacemaker implantation indication. The mean battery life was 5.41 ± 2.65 years. The battery replacement-free period of 68 patients who underwent pacemaker implantation and continued their follow-up was 4.18 ± 2.89 (0.1-10) years. Pacemaker-related complications developed in 8 patients during follow-up. Left ventricular dysfunction developed (dyssynchrony induced) in 3 patients at follow-up, and all were paced from the right ventricular anterior wall. Those patients underwent cardiac resynchronization therapy and their left ventricular dysfunction improved. CONCLUSION: Isolated complete atrioventricular block is a rare disease requiring careful clinical follow-up. Patients are often asymptomatic and significant bradycardia is the most common indication for pacemaker implantation. Left ventricular dysfunction is an important cause of morbidity, especially in patients with right ventricular anterior wall pacing. Physicians should be aware of left ventricular dysfunction during follow-up. Cardiac resynchronization therapy should be considered as a treatment option for left ventricular dysfunction.

A challenging catheter ablation of anteroseptal manifest accessory pathway from non-coronary aortic cusp in a paediatric patient.

Twelve-lead ECG of a child with Wolff-Parkinson-White syndrome and systolic dysfunction was consistent with the anteroseptal accessory pathway. The earliest atrial activation during electrophysiological study was found between the right anteroseptal region near the HIS. Multiple femoral tract right-sided cryotest lesions followed by radiofrequency catheter irrigated through the jugular vein route were unsuccessful. Then, non-coronary aortic cusp mapping and cryoablation were successfully performed with a retroartic approach.

A Rare Cause of Left Ventricular Dysfunction and Familial Dilated Cardiomyopathy in Children; Emery-Dreifuss Type 2: A Case Report.

Emery-Dreifuss muscular dystrophy is one of a group of muscular dystrophies caused by a deficiency in genes encoding nuclear proteins (emerin, lamin A/C, nesprin). It progresses with joint contractures, muscular dystrophy, and cardiac involvement. Cardiac findings include dilated cardiomyopathy, conduction defects, and an associated increased risk of sudden cardiac death. We report the case of a young boy, aged 16, with lamin A/C gene mutation and dilated cardiomyopathy. From the patient's history, it was learned that his father and sister also had dilated cardiomyopathy and both died of heart failure. Cardiac resynchronization therapy implantation was planned in the follow-up of the patient due to progressive left ventricular dysfunction and left ventricular dyssynchrony. But the family did not accept this treatment option. The patient was placed on the heart transplant list. While waiting for a suitable donor, he died as a result of sudden cardiac arrest while he was being treated in the intensive care unit.

Clinical Course and Electrophysiological Characteristics of Permanent Junctional Reciprocating Tachycardia in Children.

BACKGROUND: In this study, we aimed to evaluate the clinical aspects, electrophysiological studies, and ablation results of permanent junctional reciprocating tachycardia in children. METHODS: The study comprised 29 pediatric patients diagnosed with permanent junctional reciprocating tachycardia between 2011 and 2021 in 2 pediatric electrophysiology centers. From the file records, the basic demographic characteristics of the patients, as well as electrocardiographic and echocardiographic findings, were acquired retrospectively. The medical treatment and responses of the patients throughout follow-up, as well as the electrophysiological study and ablation data of the patients who had electrophysiological study, were assessed. RESULTS: The mean age at diagnosis of the patients was 3.13 ± 4.43 (0-18) years and the mean weight was 18.22 ± 19.68 (3.8-94) kg. Eighteen patients (62.1%) were girls. Eleven patients (38%) developed tachycardia-induced cardiomyopathy. Tachycardia was incessant in 15 patients (51.7%). In total, 22 patients required 26 ablation procedures. Tachycardia-induced cardiomyopathy and multidrug-resistant tachycardia were the most prevalent indications for ablation. The right posteroseptal pathway was detected in 18 patients (81.8%). The acute procedure success rate was 100% (22/22). The recurrence rate was 18% (4/22) and 3 of them underwent successful ablation again. The overall success percentage was 95.4% (21/22). None of the patients had any complications. The mean follow-up period was 4.39 ± 3.05 years. CONCLUSION: Although permanent junctional reciprocating tachycardia is uncommon, it is often persistent, resistant to medical treatment, and associated with a substantial risk of tachycardia-induced cardiomyopathy. Catheter ablation can be performed on these patients at any age, with minimal risk of complications and a high success rate. It is crucial to keep monitor of the patients' recurrence.

Common Supraventricular and Ventricular Arrhythmias in Children.

The most common pediatric arrhythmias are tachycardias, and the most common type is supraventricular tachycardia, originating from or above the atrioventricular node and HIS bundle. Ventricular tachycardias are less common but more dangerous. Supraventricular tachycardias usually cause a narrow complex tachycardia unless there is a basal bundle branch block or rate-dependent aberration. A wide QRS tachycardia should be treated as ventricular tachycardias unless proven to be an supraventricular tachycardia with aberration. Diagnosis of both tachyarrhythmia types depends mainly on 12-lead electrocardiography. The most common supraventricular tachycardia type in newborns and infants is atrioventricular reentry tachycardia, related to manifest or concealed accessory pathways and in adolescent atrioventricular nodal reentry tachycardia, whereas focal atrial tachycardias consist of 10%-15% of supraventricular tachycardias during all ages. Supraventricular tachycardias have a low risk of morbidity, and ablation therapy is successful in most types with success rates over 90%. Ventricular tachycardias can be monomorphic or polymorphic, nonsustained or sustained, and can cause more hemodynamic instability than supraventricular tachycardias, requiring more close monitoring and urgent therapies. If hemodynamically unstable, synchronized cardioversion must be performed. Polymorphic ventricular tachycardias are very dangerous and often associated with primary ion channel defects (channelopathies), which can cause sudden cardiac death.

Electrocardiographic and electrophysiological characteristics of fasciculoventricular fibers in children.

OBJECTIVES: Fasciculoventricular fiber (FVF) that does not cause tachyarrhythmia is a rare form of ventricular preexcitation, which is important to distinguish from Kent fibers. Although, adenosine and some electrocardiographic features are important in the differentiation of Wolff Parkinson White (WPW) than FVF, a clear distinction may not always be possible without an electrophysiological study (EPS). In this study, we aimed to present the clinical and electrophysiological features of our pediatric patients with fasciculoventricular fiber. PATIENTS AND METHOD: Between October 2013 and September 2021, 565 patients who underwent electrophysiological studies due to ventricular preexcitation in our clinic were screened in the study, and 27 (4.7%) patients with fasciculoventricular fiber were included. The data of the patients were obtained from the file records using the electronic internet database system Filemaker® . Electrophysiological study age, weight, gender, symptom, and presence of congenital heart disease of the patients were obtained from the file records. Accessory pathway localization was evaluated according to the modified Arruda algorithm in pre-procedural electrocardiography. In addition, delta wave amplitudes were measured in the first 40 ms from the surface ECG. PR interval, QRS interval, and delta wave amplitude were recorded before and after ablation in patients with additional accessory pathways. Post-procedure values were included in the FVF group. RESULTS: The mean age of the patients was 11.47 ± 4.25 years. All 70.4% of the reasons for admission were symptoms such as palpitations and syncope. Two patients had hypertrophic cardiomyopathy and 1 patient had ccTGA. In the electrophysiological study, additional manifest WPW was found in 9 (33%) patients (3 patients with high risk, 6 patients with orthodromic supraventricular tachycardia), focal atrial tachycardia in a patient, and atrioventricular nodal reentry tachycardia in a patient. While the delta wave amplitude was found to be 2.56 ± 1.38(1-5.5) mm in the first 40 ms in surface electrocardiography in 9 patients with additional accessory pathway, it was found to be 1.64 ± 0.67(0.5-3) mm in the FVF group. There was no statistically significant difference between the 2 groups (p = .398). Delta wave amplitude > 3.5 mm was not detected in any patient with isolated FVF. Interestingly, delta wave amplitude was < 3.5 mm in 7 (78%) of 9 patients who were identified and ablated with an additional accessory pathway. Total 19 of the patients (59.3%) were adenosine-responsive (18 isolated FVF, 1 manifest AP+FVF adenosine-responsive. 8 patients with other manifest AP + FVF had no pre-procedural adenosine-asystole response, and all of them QRS were expanded). CONCLUSION: Although, the fasciculoventricular fibers themselves are not the cause of tachyarrhythmia, the accessory pathway and other tachyarrhythmia substrate frequency accompanying these cases are quite high (approximately 40%) in EPS. The delta wave characteristics of ablated patients are very similar to FVF patients. While all patients with isolated FVF were adenosine responsive, most of those with additional manifest WPW were unresponsive. Therefore, performing EPS in patients with suspected FVF based on surface ECG features seems to be important for the detection of additional tachyarrhythmias and risky accessory pathways.

Inappropriate shock delivery by an implantable cardioverter-defibrillator due to electrical interference with a refrigerator in a 4-year-old child.

We report a patient with long QT syndrome who received an inappropriate implantable cardioverter-defibrillator shock due to electrical interference from a refrigerator. This electrical interference was mistakenly detected as an episode of ventricular fibrillation and ended with an inappropriate delivery of shock without any warning symptoms before.

Prevalence of Jervell-Lange Nielsen syndrome in children with congenital bilateral sensorineural hearing loss.

OBJECTIVE: Long QT syndrome (LQTS) is an inherited cardiac ion channel disorder (channelopathy) that is characterized by prolonged QT intervals on the electrocardiography (ECG) and possess the risk of sudden cardiac death (SCD). Jervell-Lange Nielsen syndrome (JLNS) is a specific subtype of LQTS that is accompanied by congenital sensorineural hearing loss, inherited autosomal recessively, and higher risk of SCD. In this study, we aimed to investigate JLNS prevalence in deaf children attending special schools for hearing loss, located in our province. METHODS: An ECG screening program was conducted in 6 special schools for children with hearing loss in Istanbul and a total of 440 students between 6 and 18 years old were included. Corrected QT interval (QTc) was calculated using the Bazett formula. Notably, 51 students, detected with any abnormal finding on ECG, were invited to our center for a comprehensive examination. RESULTS: A total of 8 patients were found with a prolonged QT interval. JLNS was diagnosed in 4 (0.9%) patients. In addition, 2 students had already been diagnosed with JLNS at another center earlier. The other 2 students, being siblings, were newly diagnosed with JLNS; and appropriate treatment was initiated. Genetic testing revealed a pathological homozygous mutation in KCNQ1 gene. The younger sibling (Case 1), who possessed a QTc of greater than 500 ms and a history of syncope, which was very suspicious for SCD, was implanted an implantable cardioverter-defibrillator. Propranolol treatment was initiated for both siblings. CONCLUSION: JLNS should be carefully considered and screened, especially in patients with a history of congenital deafness.

Clinical spectrum and long-term course of sustained ventricular tachycardia in pediatric patients: 10 years of experience.

OBJECTIVE: Pediatric ventricular tachycardias (VTs) have heterogeneous etiology and different clinical features. This study aimed to evaluate the clinical spectrum and long-term course of pediatric sustained VTs. METHODS: Patients diagnosed as having sustained VT between 2010 and 2020 were evaluated retrospectively. RESULTS: A total of 129 patients with VT were evaluated; 74 patients were male, and the median age was 12.5 years (0.25-18 years). Patients were grouped as having idiopathic VT (IVT) [n=85 (65.9%)], cardiomyopathy-associated VT (CMP-VT) [n=24 (18.6%)], catecholaminergic polymorphic VT [n=17 (13.2%)], and myocarditis-associated VT [n=3, (2.3%)]. Palpitations (n=61) and syncope (n=24) were the most common symptoms. VT originated from the right ventricle in 53.6% of the patients. Half of the patients underwent electrophysiological study, 64 patients received radiofrequency ablation therapy, and 29 patients had implantable cardiac defibrillators. During the follow-up, 70.4% of all patients had complete resolution, whereas 19 patients had a partial resolution and 23 patients (19.5%) had stable disease. Monomorphic VTs and VTs with left bundle bunch block were more thriving controlled (p=0.02 vs. p=0.04). In terms of long-term results, no statistical difference was found among the VT groups (p=0.39). Deaths were observed only in IVT (n=1) and CMP-VT (n=8) groups (p<0.001), and the overall mortality rate of pediatric sustained VT was observed at 6.9% in this study. CONCLUSION: VTs, which can cause sudden cardiac arrest, are potentially life-threatening arrhythmias. Identifying the heterogeneity of this VT and its peculiar characteristics would facilitate appropriate diagnosis and therapy.

Clinical and genetic characteristics and course of congenital long QT syndrome in children: A nine-year single-center experience.

OBJECTIVE: Long QT syndrome (LQTS) is an inherited primary arrhythmia syndrome associated with life-threatening ventricular arrhythmias and sudden death. This study aimed to report the clinical and genetic characteristics and outcomes of children diagnosed as having LQTS in a tertiary pediatric cardiology center in Turkey. METHODS: This was a retrospective review of pediatric patients diagnosed as having LQTS at our center from January 2011 to April 2020. RESULTS: A total of 145 patients (76 males) were included, with a mean age of 9.2±4.5 years and a mean weight of 35.7±18.5 kg; 38 (26.2%) were identified as having LQTS during family screening, whereas a significant proportion of patients were asymptomatic at presentation, 15 patients (10.3%) were diagnosed after previous cardiac arrest, and 26 patients (18%) had syncope. The mean Schwartz score was 4.5 points (range, 3-7.5 points). Furthermore, 107 patients (82%) were confirmed to have a pathogenic mutation for LQTS genes. All patients received beta-blockers. Implantable cardioverter-defibrillator insertion was performed in 34 patients (23.4%). Left or bilateral cardiac sympathetic denervation was performed in 9 patients (6.2%). Median follow-up time was 35.6±25.8 months. Five (3.4%) patients died during the follow-up. Statistical analyses of risk factors for major cardiac events revealed that the QTc was >500 ms and that T wave alternans, high Schwartz score, and Jervell and Lange-Nielsen syndrome were strong and significant predictors of cardiac events. CONCLUSION: LQTS has a variety of clinical manifestations. Patients' symptoms ranged between asymptomatic and sudden cardiac death (SCD). By raising the awareness of physicians regarding the disease, SCD might be prevented in the early period.

Early postoperative arrhythmias in patients undergoing congenital heart surgery.

BACKGROUND: This study aims to evaluate early postoperative arrhythmias in children undergoing congenital cardiac surgery. METHODS: A total of 670 pediatric patients (355 males, 315 females; median age: 4 months; range, 1 day to 18 years) who underwent cardiac surgery due to congenital heart defects between December 2018 and November 2019 were included. The rate of postoperative arrhythmias, diagnosis, potential risk factors, and management strategies were evaluated. Multivariate regression analysis was used to identify significant factors of development of postoperative arrhythmias. RESULTS: Tachyarrhythmia was detected in 54 patients (8.1%), and the most common tachyarrhythmia was junctional ectopic tachycardia. Medical treatment was required in 25/38 (66%) of junctional ectopic tachycardia patients. Amiodarone was initiated in 18, dexmedetomidine in five, and flecainide + amiodarone in two of the patients. Different degrees of atrioventricular block were observed in 30 patients (4.5%). In 12 patients, permanent pacemakers were implanted during hospitalization. Age at the time of surgery under one-year-old, high inotropic scores, prolonged operation time, and high Aristotele"s scores were independent risk factors associated with early postoperative arrhythmia (p<0.05). The most common operations associated with early postoperative arrhythmia were left ventricular outflow tract, (6/20, 30%), complete atrioventricular septal defect (13/53, 24%), and tetralogy of Fallot (20/134, 14%) surgeries. CONCLUSION: Cardiac arrhythmias are common in the early period after congenital heart surgery in children. The diagnosis and frequency of arrhythmias may vary according to different surgical procedures.

Catheter ablation of focal atrial tachycardia in children using three-dimensional electroanatomic mapping system: a 6-year single-centre experience.

OBJECTIVE: This study demonstrates the clinical and electrophysiological details of catheter ablation conducted in children with focal atrial tachycardia using three-dimensional electroanatomic mapping systems. PATIENTS AND METHODS: Electrophysiological procedures were performed using the EnSite™ system. RESULTS: Between 2014 and 2020, 60 children (median age 12.01 years [16 days-18 years]; median weight 41.5 kg [3-98 kg]) with focal atrial tachycardia and treated with catheter ablation were evaluated retrospectively. Tachycardia-induced cardiomyopathy was developed in 15 patients (25%). Most of the focal atrial tachycardia foci were right-sided (75%), and more than one focus was found in four patients. Radiofrequency ablation was performed in 47 patients (irrigated radiofrequency ablation in seven cases), cryoablation in 9, and radiofrequency ablation and cryoablation in the same session in 4 patients. The median procedural time was 163.5 minutes (82-473 minutes). Fluoroscopy was used in 29 of (48.3%) patients (especially for left-side substrate) with a mean time of 8.6 ± 6.2 minutes. The acute success rate was 95%. The procedure failed in three patients, and recurrence was observed in 3.5% of patients (2/57) during a median follow-up of 17 months (2-69 months). The second ablation was performed in four cases, of which three were successful. Overall success rate was 96.6% with no major complications observed, except in one patient with minimal pericardial effusion. CONCLUSION: Catheter ablation seems to be an effective and safe treatment in focal atrial tachycardia. Electroanatomic mapping system can facilitate the ablation procedure and minimise radiation exposure.

Pulmonary hypertensive crisis: A potential reason for right ventricle and pacemaker lead failure.

Cardiac pacemakers have improved patient survival and quality of life, although malfunctions can be seen. We present the case of a girl with Seckel syndrome and congenital complete heart block. She had a single chamber permanent pacemaker in the right ventricle. When she referred us with a pulmonary hypertensive crisis (PHC), it was seen that the device was not pacing even in maximum threshold and pulse width values. After new epicardial lead implantation into the left ventricular apex, capture could be established again. For the cases presenting with capture failure, after eliminating lead-related problems and biochemical abnormalities, PHC should be kept in mind as a reason.

Cryoablation with an 8-mm tip catheter for typical AVNRT in children: a single center 5-year experience.

BACKGROUND: In children with typical atrioventricular nodal reentrant tachycardia (tAVNRT), cryoablation is preferred over radiofrequency ablation (RFA) because of its safety profile and acceptable long-term success rates. In this study, we have assessed the utility of 8-mm tip cryocatheters for tAVNRT ablation in our center. METHODS: All pediatric AVNRT patients who underwent cryoablation with an 8-mm tip cryocatheter in our center between 2013 and 2018 were included. EnSite™ (St. Jude Medical Inc., St. Paul, MN, USA) was used in all patients. RESULTS: A total of 120 patients (64 females, 53%) were included in this study, and the mean age was 13.9 years with a standard deviation of 2.5 years. Eleven patients (9.1%) had structural heart disease, and 12 patients (10%) had additional arrhythmia substrate. The mean number of effective cryolesions was 8 with a standard deviation of 2.3. Fluoroscopy was used in three patients (2.5%). There were minor complications in only four patients (3.3%)-transient first-degree atrioventricular block or transient incomplete right bundle branch block. Acute success rate of cryoablation was 108/120 (90%). In twelve patients, cryoablation was suboptimal, or it failed. The procedure was completed successfully with RFA in the same session in ten patients. Overall acute success rate of ablation (Cryo ± RFA) was 98.5%. During a mean follow-up period of 24.6 months with a standard deviation of 11.3 months, three patients had recurrence (2.5%). Time between the beginning of the effective cryolesion and termination of AVNRT was found associated with acute success of cryoablation (p = 0.013). CONCLUSIONS: Cryoablation of AVNRT with an 8-mm tip catheter in children appears to be safe, with an acceptable acute success rate and a low recurrence rate. A faster termination of AVNRT during the cryolesion, slowing down before ending with atrioventricular block, is a good indicator for acute success.

Clinical characteristics of hypertrophic cardiomyopathy in children: An 8-year single center experience.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is the second most common pediatric cardiomyopathy. Although there is a large body of literature about HCM in adults, there is limited information on HCM in childhood. We evaluated various aspects of pediatric HCM patients treated at our center. METHODS: We identified 152 pediatric patients with HCM between October 2011 and October 2019. Clinical history, invasive (ICD, pacemaker, electrophysiologic study, catheter ablation therapy) and non-invasive (ECG, holter moniterization, echocardiography, cardiac MR, genetic study, medicam treatment) data were collected and evaluated. RESULTS: The mean ± standard deviation age of patients was 8.9 ± 5.7 years (1 month-18 years) and 67.8% were male. The most frequent clinical symptoms were murmur and palpitations. Three cases (2%) had aborted sudden death as the first manifestation of HCM. Of these patients, 120 (78.9%) had non-syndromic HCM and 32 (27.2%) had syndromic HCM. Asymmetric septal hypertrophy was common (48.3%) in the non-syndromic group, whereas concentric hypertrophy was common (56.2%) in syndromic group. Left ventricular outflow tract obstruction (LVOTO) occurred in 39 (25.6%) patients. Nine (5.9%) patients underwent electrophysiologic study and/or ablation and 16 patients underwent surgical intervention. Implantable cardioverter defibrillator (ICD) insertion was performed in 38 patients (26 transvenous, 12 epicardial). ICDs were inserted in three (7.9%) patients for secondary prevention; in the remaining patients (92.1%) the devices were placed for primary prevention. Mean SD follow-up time was 27.1 ± 22 months. Five (3.3%) patients died during the follow-up. No patient had heart transplantation or a long-term assistive device. CONCLUSION: The etiology of HCM is heterogeneous and present at any age. It is important to determine the timing of surgery and potential risks for sudden cardiac arrest. As most cases of HCM are familial, evaluation of family members at risk should be a routine component of clinical management.