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Epicardial pacemaker implantation is the most common approach for small children requiring pacemaker implantation, though it is not free from complications. This article reviews the experience with endocardial pacemaker implantation, as an alternative approach, in children < or =10 kg at two centers. Thirty-nine children, median age 3.8 months (2 days-35 months), weight 4.6 kg (2.3-10 kg) underwent endocardial permanent pacing (VVI/R in 38, DDDR in 1). Indications for pacing were complete heart block (CHB) in 34 (congenital in 21, postsurgical in 12, congenitally corrected transposition of the great arteries 1), long QT syndrome in 3, and sinus bradycardia in 2 children. Two children with postsurgical CHB died 7 days and 3 weeks after implantation, respectively, due to heart failure and septicemia, despite appropriate pacemaker therapy. Over a median follow-up of 4.3 years (9 months-15.3 years), 12 patients underwent 18 generator replacements. Five patients were upgraded to physiological pacing. Ten patients underwent 12 ventricular lead advancements. Ventricular lead extraction was attempted 11 times in nine patients and succeeded 10 times. Two patients were converted to epicardial dual chamber systems. Two prepectorally placed generators required resiting due to threatened skin necrosis. Infective endocarditis on the lead, 9 months postimplant required removal of the system in one patient. The subclavian vein was found to be asymptomatically thrombosed in four patients. Endocardial permanent pacing is feasible and effective in children < or = 10 kg and an acceptable alternative to epicardial pacing. [ABSTRACT FROM AUTHOR]

Nonautomatic focal atrial tachycardia (NAFAT) is a rare and poorly understood arrhythmia either due to microreentry or triggered mechanism. NAFAT was defined as a focal atrial tachycardia which was inducible with pacing maneuvers in the electrophysiology lab. We reviewed the charts and EP study reports of all 38 patients with NAFAT, who underwent an EP study at our center between April 1994 and September 2000. Patients' were predominantly female (n = 31, 82%), aged 11-78 years (median 46). The mean age at presentation was 31 years (range 7-71 years). None of the patients had structural heart disease or had undergone prior heart surgery. Electroanatomic mapping (EAM) was performed in 22 patients and showed no scars in the atrium. A total of 45 foci were identified (range 1-3 foci/patient). Anatomically NAFAT foci were predominantly right atrial (n = 35) rather than left (n = 10). The NAFAT cycle length ranged from 270 to 490 (mean +/- SD; 380 +/- 69 ms) and was significantly lower in patients younger than 24 years of age. Ablation, attempted for 42 foci was successful in 33 (79%). The success rate in the EAM group was 20/25 foci (80%) compared to 13/18 (72%) in the non-EAM group. In conclusion, NAFAT is a rare arrhythmia which predominantly affects women with no other associated cardiac disease. It mainly occurs in the right atrium, affects all ages and is amenable to catheter ablation. [ABSTRACT FROM AUTHOR]

Background: Current cohorts of patients with idiopathic ventricular fibrillation (IVF) primarily include adult-onset patients. Underlying causes of sudden cardiac arrest vary with age; therefore, underlying causes and disease course may differ for adolescent-onset vs adult-onset patients., Objective: The purpose of this study was to compare adolescent-onset with adult-onset patients having an initially unexplained cause of VF., Methods: The study included 39 patients with an index event aged ≤19 years (adolescent-onset) and 417 adult-onset patients from the Dutch Idiopathic VF Registry. Data on event circumstances, clinical characteristics, change in diagnosis, and arrhythmia recurrences were collected and compared between the 2 groups., Results: In total, 42 patients received an underlying diagnosis during follow-up (median 7 [2-12] years), with similar yields (15% adolescent-onset vs 9% adult-onset; P = .16). Among the remaining unexplained patients, adolescent-onset patients (n = 33) had their index event at a median age of 17 [16-18] years, and 72% were male. The youngest patient was aged 13 years. In comparison with adults (n = 381), adolescent-onset patients more often had their index event during exercise (P <.01). Adolescent-onset patients experienced more appropriate implantable cardioverter-defibrillator (ICD) therapy during follow-up compared with adults (44% vs 26%; P = .03). Inappropriate ICD therapy (26% vs 17%; P = .19), ICD complications (19% vs 14%; P = .41), and deaths (3% vs 4%; P = 1) did not significantly differ between adolescent-onset and adult-onset patients., Conclusion: IVF may occur during adolescence. Adolescent-onset patients more often present during exercise compared with adults. Furthermore, they are more vulnerable to ventricular arrhythmias as reflected by a higher incidence of appropriate ICD therapy., Competing Interests: Disclosures Dr Yap is a consultant for Boston Scientific; and has received lecture fees and research grants from Medtronic, Biotronik, and Boston Scientific. All other authors have no conflicts of interest to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Frequent premature ventricular contractions (PVCs) in children are usually considered benign. Symptoms and left ventricular dysfunction are indications for treatment with antiarrhythmic drugs., Objective: This study aimed to evaluate the efficacy of flecainide vs metoprolol in reducing PVCs in children., Methods: A randomized open-label crossover trial was conducted of children with a PVC burden of >15% on Holter monitoring successively treated with metoprolol and flecainide, or vice versa, with a drug-free interval of at least 2 weeks. Holter measurements were repeated before and after the start of the antiarrhythmic drug., Results: Sixty patients were screened; 19 patients could be included. Median age was 13.9 years (interquartile range, 5.5 years). Mean baseline PVC burden was 21.7% (n = 18; SD ± 14.0) before the start of flecainide and 21.2% (n = 17; SD ± 11.5) before the start of metoprolol. In a mixed model analysis, the estimated mean reduction in PVC burden was 10.6 percentage points (95% CI, 5.8-15.3) for flecainide and 2.4 percentage points (95% CI,2.7-7.5) for metoprolol, with a significant difference of 8.2 percentage points (95% CI, 0.86-15.46; P = .031). Exploratory analysis revealed that 9 of 18 patients treated with flecainide and 1 of 17 patients treated with metoprolol had a reduction to a PVC burden below 5%. No discriminating factors between flecainide responders and nonresponders were found; the mean plasma level was not significantly different (0.34 mg/L vs 0.52 mg/L; P = .277)., Conclusion: In children with frequent PVCs, flecainide led to a significantly greater reduction of PVC burden compared with metoprolol. Flecainide was effective in only a subgroup of patients, which appears to be unrelated to the plasma level., Competing Interests: Disclosures The authors have no conflicts of interest to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Aims: To evaluate the effect of electro-anatomical mapping on success rate and fluoroscopy time in ablation of supraventricular tachycardia substrates in a large group of children., Methods: Patients referred from multiple centres in the Netherlands and who received a first ablation for supraventricular tachycardia substrates in the Leiden University Medical Center between 2014 and 2020 were included in this retrospective cohort study. They were divided in procedures in patients with fluoroscopy and procedures in patients using electro-anatomical mapping., Results: Outcomes of ablation of 373 electro-anatomical substrates were analysed. Acute success rate in the fluoro-group (n = 170) was 95.9% compared to 94.5% in the electro-anatomical mapping group (n = 181) (p = 0.539); recurrence rate was 6.1% in the fluoro-group and 6.4% in the electro-anatomical mapping group (p = 0.911) after a 12-months follow-up. Redo-ablations were performed in 12 cases in the fluoro-group and 10 cases in the electro-anatomical mapping group, with a success rate of 83.3% versus 80.0%, resulting in an overall success rate of 95.9% in the fluoro-group and 92.8% in the electro-anatomical mapping group (p = 0.216) after 12 months. Fluoroscopy time and dose area product decreased significantly from 16.00 ± 17.75 minutes (median ± interquartile range) to 2.00 ± 3.00 minutes (p = 0.000) and 210.5 µGym 2 ± 249.3 to 32.9 µGym 2 ± 78.6 (p = 0.000), respectively. In the fluoro-group, four complications occurred (2.0%) and in the electro-anatomical mapping group no complications occurred., Conclusion: These results demonstrate that ablations of supraventricular tachycardia substrates in children remain a highly effective and safe treatment after the introduction of electro-anatomical mapping as a standard of care, while significantly reducing fluoroscopy time and dose area product.

Competing Interests: SAW has received a speaker fee from Biotronik and Daiichi Sankyo. GB has no conflicts of interest. JAEK has received a research grant from Medtronic. TBK has received a speaker fee from Abbott. SCY has received honoraria from Boston Scientific, Medtronic, Biotronik, and Acutus Medical; and research grants from Medtronic, Biotronik, and Boston Scientific.

Aims: In patients with catecholaminergic polymorphic ventricular tachycardia (CPVT), a rare inherited arrhythmia syndrome, arrhythmic events can be prevented by medication and lifestyle recommendations. In patients who experience breakthrough arrhythmic events, non-adherence plays an essential role. We aimed to investigate the incidence and potential reasons for non-adherence to medication and lifestyle recommendations in a large, international cohort of patients with CPVT., Methods and Results: An online multilingual survey was shared with CPVT patients worldwide by their cardiologists, through peer-recruitment, and on social media from November 2022 until July 2023. Self-reported non-adherence was measured using the validated Medication Adherence Rating Scale (MARS) and a newly developed questionnaire about lifestyle. Additionally, validated questionnaires were used to assess potential reasons for medication non-adherence. Two-hundred-and-eighteen patients completed the survey, of whom 200 (92%) were prescribed medication [122 (61%) female; median age 33.5 years (interquartile range: 22-50)]. One-hundred-and-three (52%) were prescribed beta-blocker and flecainide, 85 (43%) beta-blocker, and 11 (6%) flecainide. Thirty-four (17%) patients experienced a syncope, aborted cardiac arrest or appropriate implantable cardioverter defibrillator shock after diagnosis. Nineteen (13.4%) patients were exercising more than recommended. Thirty (15%) patients were non-adherent to medication. Female sex [odds ratio (OR) 3.7, 95% confidence interval (CI) 1.3-12.0, P = 0.019], flecainide monotherapy compared to combination therapy (OR 6.8, 95% CI 1.6-31.0, P = 0.010), and a higher agreement with statements regarding concerns about CPVT medication (OR 1.2, 95% CI 1.1-1.3, P < 0.001) were independently associated with non-adherence., Conclusion: The significant rate of non-adherence associated with concerns regarding CPVT-related medication, emphasizes the potential for improving therapy adherence by targeted patient education., Competing Interests: Conflict of interest: A.A.W. is a member of the scientific advisor board of ARMGO (unpaid) and a member of the scientific advisor board of Thryvv therapeutics (unpaid). E.J.B. is a consultant for Boston Scientific. M.J.A. has royalty/equity relationship with AliveCor, ARMGO, anumana, Pfizer, Trhyvv therapeutics. M.J.A. is a consultant for Abbott, Boston scientific, Daiichi Sankyo, Invitae, Tenaya Therapeutics, BioMarin Pharmaceutical, Bristol Myers Squibb, Illumina, Medtronic, and UpToDate. E.F. is supported by the Max’s foundation. All other authors report no disclosures., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Aim: This study aimed to investigate trends over time in pre-hospital factors for pediatric out-of-hospital cardiac arrest (pOHCA) and long-term neurological and neuropsychological outcomes. These have not been described before in large populations., Methods: Non-traumatic arrest patients, 1 day-17 years old, presented to the Sophia Children's Hospital from January 2002 to December 2020, were eligible for inclusion. Favorable neurological outcome was defined as Pediatric Cerebral Performance Categories (PCPC) 1-2 or no difference with pre-arrest baseline. The trend over time was tested with multivariable logistic and linear regression models with year of event as independent variable., Findings: Over a nineteen-year study period, the annual rate of long-term favorable neurological outcome, assessed at a median 2.5 years follow-up, increased significantly (OR 1.10, 95%-CI 1.03-1.19), adjusted for confounders. Concurrently, annual automated external defibrillator (AED) use and, among adolescents, initial shockable rhythm increased significantly (OR 1.21, 95% CI 1.10-1.33 and OR 1.15, 95% CI 1.02-1.29, respectively), adjusted for confounders. For generalizability purposes, only the total intelligence quotient (IQ) was considered for trend analysis of all tested domains. Total IQ scores and bystander basic life support (BLS) rate did not change significantly over time., Interpretation: Long-term favorable neurological outcome, assessed at a median 2.5 years follow-up, improved significantly over the study period. Total IQ scores did not significantly change over time. Furthermore, AED use (OR 1.21, 95%CI 1.10-1.33) and shockable rhythms among adolescents (OR1.15, 95%CI 1.02-1.29) increased over time., Competing Interests: Declaration of competing interest 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., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Sudden cardiac arrest (SCA) studies are often population-based, limited to sudden cardiac death, and excluding infants. To guide prevention opportunities, it is essential to be informed of pediatric SCA etiologies. Unfortunately, etiologies frequently remain unresolved. The objectives of this study were to determine paediatric SCA etiology, and to evaluate the extent of post-SCA investigations and to assess the performance of previous cardiac evaluation in detecting conditions predisposing to SCA. In a retrospective cohort (2002-2019), all children 0-18 years with out-of-hospital cardiac arrest (OHCA) referred to Erasmus MC Sophia Children's Hospital or the Amsterdam UMC (tertiary-care university hospitals), with cardiac or unresolved etiologies were eligible for inclusion. SCA etiologies, cardiac and family history and etiologic investigations in unresolved cases were assessed. The etiology of arrest could be determined in 52% of 172 cases. Predominant etiologies in children ≥ 1 year (n = 99) were primary arrhythmogenic disorders (34%), cardiomyopathies (22%) and unresolved (32%). Events in children < 1 year (n = 73) were largely unresolved (70%) or caused by cardiomyopathy (8%), congenital heart anomaly (8%) or myocarditis (7%). Of 83 children with unresolved etiology a family history was performed in 51%, an autopsy in 51% and genetic testing in 15%. Pre-existing cardiac conditions presumably causative for SCA were diagnosed in 9%, and remained unrecognized despite prior evaluation in 13%., Conclusion: SCA etiology remained unresolved in 83 of 172 cases (48%) and essential diagnostic investigations were often not performed. Over one-fifth of SCA patients underwent prior cardiac evaluation, which did not lead to recognition of a cardiac condition predisposing to SCA in all of them. The diagnostic post-SCA approach should be improved and the proposed standardized pediatric post-SCA diagnostics protocol may ensure a consistent and systematic evaluation process increasing the diagnostic yield., What Is Known: • Arrests in infants remain unresolved in most cases. In children > 1 year, predominant etiologies are primary arrhythmia disorders, cardiomyopathy and myocarditis. • Studies investigating sudden cardiac arrest are often limited to sudden cardiac death (SCD) in 1 to 40 year old persons, excluding infants and successfully resuscitated children., What Is New: • In patients with unresolved SCA events, the diagnostic work up was often incompletely performed. • Over one fifth of victims had prior cardiac evaluation before the arrest, with either a diagnosed cardiac condition (9%) or an unrecognized cardiac condition (13%)., (© 2023. The Author(s).)

Background: In severely affected patients with catecholaminergic polymorphic ventricular tachycardia, beta-blockers are often insufficiently protective. The purpose of this study was to evaluate whether flecainide is associated with a lower incidence of arrhythmic events (AEs) when added to beta-blockers in a large cohort of patients with catecholaminergic polymorphic ventricular tachycardia., Methods: From 2 international registries, this multicenter case cross-over study included patients with a clinical or genetic diagnosis of catecholaminergic polymorphic ventricular tachycardia in whom flecainide was added to beta-blocker therapy. The study period was defined as the period in which background therapy (ie, beta-blocker type [beta1-selective or nonselective]), left cardiac sympathetic denervation, and implantable cardioverter defibrillator treatment status, remained unchanged within individual patients and was divided into pre-flecainide and on-flecainide periods. The primary end point was AEs, defined as sudden cardiac death, sudden cardiac arrest, appropriate implantable cardioverter defibrillator shock, and arrhythmic syncope. The association of flecainide with AE rates was assessed using a generalized linear mixed model assuming negative binomial distribution and random effects for patients., Results: A total of 247 patients (123 [50%] females; median age at start of flecainide, 18 years [interquartile range, 14-29]; median flecainide dose, 2.2 mg/kg per day [interquartile range, 1.7-3.1]) were included. At baseline, all patients used a beta-blocker, 70 (28%) had an implantable cardioverter defibrillator, and 21 (9%) had a left cardiac sympathetic denervation. During a median pre-flecainide follow-up of 2.1 years (interquartile range, 0.4-7.2), 41 patients (17%) experienced 58 AEs (annual event rate, 5.6%). During a median on-flecainide follow-up of 2.9 years (interquartile range, 1.0-6.0), 23 patients (9%) experienced 38 AEs (annual event rate, 4.0%). There were significantly fewer AEs after initiation of flecainide (incidence rate ratio, 0.55 [95% CI, 0.38-0.83]; P =0.007). Among patients who were symptomatic before diagnosis or during the pre-flecainide period (n=167), flecainide was associated with significantly fewer AEs (incidence rate ratio, 0.49 [95% CI, 0.31-0.77]; P =0.002). Among patients with ≥1 AE on beta-blocker therapy (n=41), adding flecainide was also associated with significantly fewer AEs (incidence rate ratio, 0.25 [95% CI, 0.14-0.45]; P <0.001)., Conclusions: For patients with catecholaminergic polymorphic ventricular tachycardia, adding flecainide to beta-blocker therapy was associated with a lower incidence of AEs in the overall cohort, in symptomatic patients, and particularly in patients with breakthrough AEs while on beta-blocker therapy., Competing Interests: Disclosures A.W. is a consultant for ARMGO and LQT Therapeutics. S.S. is a consultant for Cardurion. M.J.A. is a consultant for Abbott, Boston Scientific, Bristol Myers Squibb, Daiichi Sankyo, Invitae, Medtronic, Tenaya Therapeutics, and UpToDate. M.J.A. and the Mayo Clinic are involved in an equity/royalty relationship with AliveCor, Anumana, Thryv Therapeutics, and Pfizer. However, none of these entities were involved in this study. S.P.E. is a consultant for UptoDate and has a relationship with Pfizer. S.C.Y. is a consultant for Boston Scientific and has received research grants from Medtronic and Biotronik. The other authors report no conflicts.

Sudden cardiac death is the most common mode of death during childhood and adolescence in hypertrophic cardiomyopathy, and identifying those individuals at highest risk is a major aspect of clinical care. The mainstay of preventative therapy is the implantable cardioverter-defibrillator, which has been shown to be effective at terminating malignant ventricular arrhythmias in children with hypertrophic cardiomyopathy but can be associated with substantial morbidity. Accurate identification of those children at highest risk who would benefit most from implantable cardioverter-defibrillator implantation while minimising the risk of complications is, therefore, essential. This position statement, on behalf of the Association for European Paediatric and Congenital Cardiology (AEPC), reviews the currently available data on established and proposed risk factors for sudden cardiac death in childhood-onset hypertrophic cardiomyopathy and current approaches for risk stratification in this population. It also provides guidance on identification of individuals at risk of sudden cardiac death and optimal management of implantable cardioverter-defibrillators in children and adolescents with hypertrophic cardiomyopathy.

Brugada syndrome (BrS) is a rare inherited arrhythmia syndrome. Affected children may experience life-threatening symptoms, mainly during fever. The percentage of SCN5A variant carriers in children is higher than in adults. Current diagnostic and follow-up policies for children with (a family history of) BrS vary between centres. Here, we present a consensus statement based on the current literature and expert opinions to standardise the approach for all children with BrS and those from BrS families in the Netherlands. In summary, BrS is diagnosed in patients with a spontaneous type 1 electrocardiogram (ECG) pattern or with a Shanghai score ≥ 3.5 including ≥ 1 ECG finding. A sodium channel-blocking drug challenge test should only be performed after puberty with a few exceptions. A fever ECG is indicated in children with suspected BrS, in children with a first-degree family member with definite or possible BrS according to the Shanghai criteria with a SCN5A variant and in paediatric SCN5A variant carriers. In-hospital rhythm monitoring during fever is indicated in patients with an existing type 1 ECG pattern and in those who develop such a pattern. Genetic testing should be restricted to SCN5A. Children with BrS and children who carry an SCN5A variant should avoid medication listed at www.brugadadrugs.org and fever should be suppressed. Ventricular arrhythmias or electrical storms should be treated with isoproterenol infusion., (© 2022. The Author(s).)

Catheter ablation (CA) is an important treatment option for ventricular arrhythmias (VA) in pediatric cardiology. Currently, various CA techniques are available, including remote magnetic navigation (RMN)-guided radiofrequency (RF) ablation. However, no studies evaluate RMN-guided ablative therapy outcomes in children with VA yet. This study aimed to compare procedural and long-term outcomes between RMN-guided and manual (MAN)-guided VA ablation in children. This single-center, retrospective study included all CA procedures for VA performed in children with or without structural heart disease from 2008 until 2020. Two study groups were defined by CA technique: RMN or MAN. Primary outcome was recurrence of VA. Baseline clinical, procedural and safety data were also evaluated. This study included 22 patients, who underwent 30 procedures, with a median age of 15 (IQR 14-17; range 1-17) years and a mean weight of 57 ± 20 kg. In total, 14 procedures were performed using RMN and 16 using MAN (22 first and 8 redo procedures). Regarding first procedures, recurrence rates were significantly lower in RMN compared to MAN (20% versus 67%, P = 0.029), at a mean follow-up of 5.2 ± 3.0 years. Moreover, fluoroscopy dosages were significantly lower in RMN compared to MAN [20 (IQR 14-54) versus 48 (IQR 38-62) mGy, P = 0.043]. In total, 20 patients (91%) were free of VA following their final ablation procedure. This is the first study to investigate the use of RMN in pediatric VA ablation. RMN showed improved outcomes compared to MAN, resulting in lower VA recurrence and reduced fluoroscopy exposure., (© 2022. The Author(s).)

Early post-operative sinus node dysfunction (SND) is common in paediatric patients undergoing surgical correction of congenital heart defects (CHD). At present, the pathophysiology of these arrhythmias is incompletely understood. In this case series, we present three paediatric patients in whom we performed intraoperative epicardial mapping and who developed early post-operative SND. All patients had either an inferior or multiple sinoatrial node (SAN) exit sites, in addition to extensive conduction disorders at superior and inferior right atrium. Our findings contribute to the hypothesis that pre-existing alterations in SAN exit sites in combination with atrial conduction disorders may predispose paediatric patients with CHD for early post-operative SND. Such insights in the development of arrhythmias are crucial as it may be the first step in identifying high-risk patients., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery.)

Background: Symptomatic children with catecholaminergic polymorphic ventricular tachycardia (CPVT) are at risk for recurrent arrhythmic events. β-Blockers decrease this risk, but studies comparing individual β-blockers in sizeable cohorts are lacking. We aimed to assess the association between risk for arrhythmic events and type of β-blocker in a large cohort of symptomatic children with CPVT., Methods: From 2 international registries of patients with CPVT, RYR2 variant-carrying symptomatic children (defined as syncope or sudden cardiac arrest before β-blocker initiation and age at start of β-blocker therapy <18 years), treated with a β-blocker were included. Cox regression analyses with time-dependent covariates for β-blockers and potential confounders were used to assess the hazard ratio (HR). The primary outcome was the first occurrence of sudden cardiac death, sudden cardiac arrest, appropriate implantable cardioverter-defibrillator shock, or syncope. The secondary outcome was the first occurrence of any of the primary outcomes except syncope., Results: We included 329 patients (median age at diagnosis, 12 [interquartile range, 7-15] years, 35% females). Ninety-nine (30.1%) patients experienced the primary outcome and 74 (22.5%) experienced the secondary outcome during a median follow-up of 6.7 (interquartile range, 2.8-12.5) years. Two-hundred sixteen patients (66.0%) used a nonselective β-blocker (predominantly nadolol [n=140] or propranolol [n=70]) and 111 (33.7%) used a β1-selective β-blocker (predominantly atenolol [n=51], metoprolol [n=33], or bisoprolol [n=19]) as initial β-blocker. Baseline characteristics did not differ. The HRs for both the primary and secondary outcomes were higher for β1-selective compared with nonselective β-blockers (HR, 2.04 [95% CI, 1.31-3.17]; and HR, 1.99 [95% CI, 1.20-3.30], respectively). When assessed separately, the HR for the primary outcome was higher for atenolol (HR, 2.68 [95% CI, 1.44-4.99]), bisoprolol (HR, 3.24 [95% CI, 1.47-7.18]), and metoprolol (HR, 2.18 [95% CI, 1.08-4.40]) compared with nadolol, but did not differ from propranolol. The HR of the secondary outcome was only higher in atenolol compared with nadolol (HR, 2.68 [95% CI, 1.30-5.55])., Conclusions: β1-selective β-blockers were associated with a significantly higher risk for arrhythmic events in symptomatic children with CPVT compared with nonselective β-blockers, specifically nadolol. Nadolol, or propranolol if nadolol is unavailable, should be the preferred β-blocker for treating symptomatic children with CPVT.

Background: Catheter ablation (CA) is the first-choice treatment for tachyarrhythmia in children. Currently available CA techniques differ in mechanism of catheter navigation and energy sources. There are no large studies comparing long-term outcomes between available CA techniques in a pediatric population with atrioventricular reentry tachycardia (AVRT) or atrioventricular nodal reentry tachycardia (AVNRT) mechanisms., Objective: This study aimed to compare procedural and long-term outcomes of remote magnetic navigation-guided radiofrequency (RF) ablation (RMN), manual-guided RF ablation (MAN) and manual-guided cryoablation (CRYO)., Methods: This single-center, retrospective study included all first consecutive CA procedures for AVRT or AVNRT performed in children without structural heart disease from 2008 to 2019. Three study groups were defined by the ablation technique used: RMN, MAN or CRYO. Primary outcome was long-term recurrence of tachyarrhythmia., Results: In total, we included 223 patients, aged 14 (IQR 12-16) years; weighting 56 (IQR 47-65) kilograms. In total, 108 procedures were performed using RMN, 76 using MAN and 39 using CRYO. RMN had significantly lower recurrence rates compared to MAN and CRYO at mean follow-up of 5.5 ± 2.9 years (AVRT: 4.3% versus 15.6% versus 54.5%, P < 0.001; AVNRT: 7.7% versus 8.3% versus 35.7%, P = 0.008; for RMN versus MAN versus CRYO respectively). In AVNRT ablation, RMN had significantly lower fluoroscopy doses compared to CRYO [30 (IQR 20-41) versus 45 (IQR 29-65) mGy, P = 0.040)., Conclusion: In pediatric patients without structural heart disease who underwent their first AV(N)RT ablation, RMN has superior long-term outcomes compared to MAN and CRYO, in addition to favorable fluoroscopy doses., Competing Interests: 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., (© 2021 The Authors.)

Introduction: Shockable rhythm following pediatric out-of-hospital cardiac arrest (pOHCA) is consistently associated with hospital and short-term survival. Little is known about the relationship between shockable rhythm and long-term outcomes (>1 year) after pOHCA. The aim was to investigate the association between first documented rhythm and long-term outcomes in a pOHCA cohort over 18 years., Methods: All children aged 1 day-18 years who experienced non-traumatic pOHCA between 2002-2019 and were subsequently admitted to the emergency department (ED) or pediatric intensive care unit (PICU) of Erasmus MC-Sophia Children's Hospital were included. Data was abstracted retrospectively from patient files, (ground) ambulance and Helicopter Emergency Medical Service (HEMS) records, and follow-up clinics. Long-term outcome was determined using a Pediatric Cerebral Performance Category (PCPC) score at the longest available follow-up interval through august 2020. The primary outcome measure was survival with favorable neurologic outcome, defined as PCPC 1-2 or no difference between pre- and post-arrest PCPC. The association between first documented rhythm and the primary outcome was calculated in a multivariable regression model., Results: 369 children were admitted, nine children were lost to follow-up. Median age at arrest was age 3.4 (IQR 0.8-9.9) years, 63% were male and 14% had a shockable rhythm (66% non-shockable, 20% unknown or return of spontaneous circulation (ROSC) before emergency medical service (EMS) arrival). In adolescents (aged 12-18 years), 39% had shockable rhythm. 142 (39%) of children survived to hospital discharge. On median follow-up interval of 25 months (IQR 5.1-49.6), 115/142 (81%) of hospital survivors had favorable neurologic outcome. In multivariable analysis, shockable rhythm was associated with survival with favorable long-term neurologic outcome (OR 8.9 [95%CI 3.1-25.9])., Conclusion: In children with pOHCA admitted to ED or PICU shockable rhythm had significantly higher odds of survival with long-term favorable neurologic outcome compared to non-shockable rhythm. Survival to hospital discharge after pOHCA was 39% over the 18-year study period. Of survivors to discharge, 81% had favorable long-term (median 25 months, IQR 5.1-49.6) neurologic outcome. Efforts for improving outcome of pOHCA should focus on early recognition and treatment of shockable pOHCA at scene., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Aims: Sudden death and aborted sudden death have been observed in patients with biallelic variants in TECRL. However, phenotypes have only begun to be described and no data are available on medical therapy after long-term follow-up., Methods and Results: An international, multi-centre retrospective review was conducted. We report new cases associated with TECRL variants and long-term follow-up from previously published cases. We present 10 cases and 37 asymptomatic heterozygous carriers. Median age at onset of cardiac symptoms was 8 years (range 1-22 years) and cases were followed for an average of 10.3 years (standard deviation 8.3), right censored by death in three cases. All patients on metoprolol, bisoprolol, or atenolol were transitioned to nadolol or propranolol due to failure of therapy. Phenotypes typical of both long QT syndrome and catecholaminergic polymorphic ventricular tachycardia (CPVT) were observed. We also observed divergent phenotypes in some cases despite identical homozygous variants. None of 37 heterozygous family members had a cardiac phenotype., Conclusion: Patients with biallelic pathogenic TECRL variants present with variable cardiac arrhythmia phenotypes, including those typical of long QT syndrome and CPVT. Nadolol and propranolol may be superior beta-blockers in this setting. No cardiac disease or sudden death was present in patients with a heterozygous genotype., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2020. For permissions, please email: journals.permissions@oup.com.)

The aim of the study is to compare the efficacy of flecainide, beta-blockers, sotalol, and verapamil in children with frequent PVCs, with or without asymptomatic VT. Frequent premature ventricular complexes (PVCs) and asymptomatic ventricular tachycardia (VT) in children with structurally normal hearts require anti-arrhythmic drug (AAD) therapy depending on the severity of symptoms or ventricular dysfunction; however, data on efficacy in children are scarce. Both symptomatic and asymptomatic children (≥ 1 year and < 18 years of age) with a PVC burden of 5% or more, with or without asymptomatic runs of VT, who had consecutive Holter recordings, were included in this retrospective multi-center study. The groups of patients receiving AAD therapy were compared to an untreated control group. A medication episode was defined as a timeframe in which the highest dosage at a fixed level of a single drug was used in a patient. A total of 35 children and 46 medication episodes were included, with an overall change in PVC burden on Holter of -4.4 percentage points, compared to -4.2 in the control group of 14 patients. The mean reduction in PVC burden was only significant in patients receiving flecainide (- 13.8 percentage points; N = 10; p = 0.032), compared to the control group and other groups receiving beta-blockers (- 1.7 percentage points; N = 18), sotalol (+ 1.0 percentage points; N = 7), or verapamil (- 3.9 percentage points; N = 11). The efficacy of anti-arrhythmic drug therapy on frequent PVCs or asymptomatic VTs in children is very limited. Only flecainide appears to be effective in lowering the PVC burden.

Patients with congenital heart disease (CHD) are prone to develop atrial and ventricular arrhythmias. Multiple factors throughout life contribute to arrhythmogenicity substrate such as (i) (longstanding) volume and/or pressure overload, (ii) scar tissue, (iii) ageing-related structural remodelling, (iv) cardiovascular risk factors and (v) tachycardia-induced remodelling. At present, it is unknown whether, and to what extent, paediatric patients with CHD have atrial or ventricular conduction disorders early in life and whether there is a correlation between duration of volume/pressure overload and extensiveness of conduction disorders. To investigate this, we initiated high-resolution intraoperative epicardial mapping in paediatric patients with CHD undergoing primary open-heart surgery., (© The Author(s) 2020. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

This study sought to investigate whether pediatric patients with congenital heart disease (CHD) already have atrial conduction disorders early in life. The authors conducted first-in-children epicardial mapping in 10 pediatric patients with CHD undergoing primary open heart surgery. Areas of conduction delay (CD) and block (CB) were present in all patients and were particularly observed at Bachmann's bundle (CD: 4.9%; CB: 2.3%), followed by the right atrium (CD: 3.7%; CB: 1.6%) and, to a lesser degree, the left atrium (CD: 1.8%; CB: 1.0%). Conduction abnormalities may by aggravated over time (e.g., aging, residual lesions, or valvular dysfunction), predisposing these patients to atrial arrhythmias early in life., Competing Interests: Author Disclosures The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Risk stratification in catecholaminergic polymorphic ventricular tachycardia remains ill defined. Heart rate recovery (HRR) immediately after exercise is regulated by autonomic reflexes, particularly vagal tone, and may be associated with symptoms and ventricular arrhythmias in patients with catecholaminergic polymorphic ventricular tachycardia. Our objective was to evaluate whether HRR after maximal exercise on the exercise stress test (EST) is associated with symptoms and ventricular arrhythmias., Methods: In this retrospective observational study, we included patients ≤65 years of age with an EST without antiarrhythmic drugs who attained at least 80% of their age- and sex-predicted maximal HR. HRR in the recovery phase was calculated as the difference in heart rate (HR) at maximal exercise and at 1 minute in the recovery phase (ΔHRR1')., Results: We included 187 patients (median age, 36 years; 68 [36%] symptomatic before diagnosis). Pre-EST HR and maximal HR were equal among symptomatic and asymptomatic patients. Patients who were symptomatic before diagnosis had a greater ΔHRR1' after maximal exercise (43 [interquartile range, 25-58] versus 25 [interquartile range, 19-34] beats/min; P <0.001). Corrected for age, sex, and relatedness, patients in the upper tertile for ΔHRR1' had an odds ratio of 3.4 (95% CI, 1.6-7.4) of being symptomatic before diagnosis ( P <0.001). In addition, ΔHRR1' was higher in patients with complex ventricular arrhythmias at EST off antiarrhythmic drugs (33 [interquartile range, 22-48] versus 27 [interquartile range, 20-36] beats/min; P =0.01). After diagnosis, patients with a ΔHRR1' in the upper tertile of its distribution had significantly more arrhythmic events as compared with patients in the other tertiles ( P =0.045)., Conclusions: Catecholaminergic polymorphic ventricular tachycardia patients with a larger HRR following exercise are more likely to be symptomatic and have complex ventricular arrhythmias during the first EST off antiarrhythmic drug.

Objective: Outcomes after surgical repair of complete atrioventricular septal defect (cAVSD) have improved. With advancing age, the risk of development of dysrhythmias may increase. The aims of this study were to (1) examine development of sinus node dysfunction (SND), atrial and ventricular tachyarrhythmias, and (2) study progression of atrioventricular conduction abnormalities in young adult patients with repaired cAVSD., Study Design: In this retrospective multicenter study, 74 patients (68% female) with a cAVSD repaired in childhood were included. Patients' medical files were evaluated for occurrence of SND, atrioventricular conduction block (AVB), atrial and ventricular tachyarrhythmias., Results: Median age at repair was 6 months (interquartile range 3-10) and median age at last follow-up was 24 years (interquartile range 21-28). SND occurred after a median of 17 years (interquartile range 11-19) after repair in 23% of patients, requiring pacemaker implantation in two patients (12%). Regular supraventricular tachycardia was observed in three patients (4%). Atrial fibrillation and ventricular tachyarrhythmias were not observed. Twenty-seven patients (36%) had first-degree AVB, which was self-limiting in 16 (59%) and persistent in 10 (37%) patients. One patient developed third-degree AVB 7 days after left atrioventricular valve replacement. Spontaneous type II second-degree AVB occurred in a 28-year-old patient. Both patients underwent pacemaker implantation., Conclusions: Clinically significant dysrhythmias were uncommon in young adult patients after cAVSD repair. However, three patients required pacemaker implantation for either progression of SND or spontaneous type II second-degree AVB. Longer follow-up should point out whether dysrhythmias will progress or become more prevalent with increasing age., (© 2018 The Authors. Congenital Heart Disease Published by Wiley Periodicals, Inc.)

Aim: Evaluation of long-term outcome of transvenous pacemaker (PM) implantation in infants., Methods and Results: A retrospective analysis of all transvenous PM implantations in infants <10 kg between September 1997 and October 2001 was made. Indications for PM implantation, age at implantation, and determinants of long-term outcome including cardiac function, PM function, and PM (system) complications were noted. Seven patients underwent transvenous VVI(R) PM implantation. Median age at implantation was 3 days (range: 1 day to 14 months), median weight 3.5 kg (range: 2.3-8.7 kg), and median follow-up 14 years (range: 12.3-16.3 years). Pacemaker indications were congenital complete atrioventricular block (n = 4), long QT syndrome with heart block (n = 2), and post-operative complete atrioventricular block with sinus node dysfunction (n = 1). No procedural complications were noted. Today all patients are alive and symptom free with good PM and cardiac function. Two patients underwent PM generator relocation for imminent skin necrosis and skin traction. Two patients suffered from asymptomatic left subclavian vein occlusion and developed thrombosis on the PM electrode. Three patients were converted to an epicardial PM system, due to atrial perforation after upgrading procedure (n = 1), syncope with need for implantable cardioverter defibrillator implantation (n = 1), and systolic dysfunction with development of dilated cardiomyopathy, which normalized under cardiac resynchronization therapy pacing (n = 1). Two patients needed atrioventricular (AV) valve repair for severe insufficiency. Two patients underwent repositioning of dysfunctional PM leads. In five patients, transvenous leads were removed. Indications were elective lead replacement (n = 1), atrial perforation (n = 1), and switch to an epicardial system (n = 3)., Conclusion: Transvenous PM implantation in infants (<10 kg) is associated with a high incidence of vascular occlusion, thrombosis, and severe atrioventricular valve regurgitation during long-term follow-up. We advocate an epicardial approach for PM implantation in small children., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.)