Severe cardiac conduction disease associated with titin gene mutation.

Heart block is rare in pediatrics with many possible causes. An association between complete heart block (CHB) and pathogenic titin (TTN) mutations have not been previously described. We report a 9-year-old female with history of leukodystrophy and family history of atrial fibrillation who presented with syncope and conduction abnormalities, including CHB. She underwent pacemaker implantation and genetic testing demonstrated a pathogenic TTN mutation likely responsible for her cardiac findings. Our case suggests an association between TTN mutations and conduction disease and emphasizes broadening gene testing in assessing these patients, especially when a family history is present.

Ectopic Atrial Tachycardia in Infants Following Congenital Heart Disease Surgery.

Although ectopic atrial tachycardia (EAT) is common following surgery for congenital heart disease (CHD), there are limited data regarding this arrhythmia. This study assessed risk factors and outcomes for patients less than one year of age with post-operative EAT. This was a retrospective analysis of infants undergoing CHD surgery from 2007 to 2020. Patients and surgeries with EAT were compared to controls without EAT. Out of 5372 infant CHD surgeries, EAT developed in 129 (2.5%). Compared to controls, the EAT cohort was younger (median 7 vs 85 days, p < 0.01), weighed less at time of surgery (3.3 vs 4.2 kg, p < 0.01), and was more likely to have DiGeorge syndrome (7.7% vs 3.0%, p < 0.01). Multivariate analysis revealed total anomalous venous connection (TAPVC) repair (odds ratio [OR] 2.8; 95% confidence interval 1.5-5.2), DiGeorge syndrome (OR 2.4; 1.1-5.2), Society of Thoracic Surgeons-European Association for Cardio-Thoracic surgery (STAT) category ≥ 4 (OR 2.1; 1.0-4.4), and longer cardiopulmonary bypass times (OR 1.1; 1.0-1.2) as independent risk factors for EAT. The onset of EAT occurred a median of 9 days (IQR 5-14 days) after CHD surgery. Antiarrhythmic treatment was initiated in 109/129 patients (84%) with propranolol (71%) and amiodarone (24%) the most commonly used medications. Although 15 (11.6%) patients did not survive to hospital discharge, EAT was not directly implicated in any deaths. EAT occurred after 2.5% of infant CHD surgeries. In addition to TAPVC repair, longer and more complex surgeries were associated with an increased the risk for the development of post-operative EAT.

Pediatric Electrophysiology Device Needs: A Survey from the Pediatric and Congenital Electrophysiology Society Taskforce on Pediatric-Specific Devices.

Background There are few US Food and Drug Administration (FDA)-approved devices specifically aimed at the pediatric patient with arrhythmia. This has led to a high off-label utilization of devices in this vulnerable population. The Pediatric and Congenital Electrophysiology Society (PACES), the international organization representing pediatric and congenital heart disease arrhythmia specialists, developed a task force to comprehensively address device development issues relevant to pediatric patients with congenital arrhythmia. Methods and Results As a first step, the taskforce developed a 26-question survey for the pediatric arrhythmia community to assess providers' understanding of the FDA approval process, specifically in regard to pediatric labeling. There were 92/211 respondents (44%) with a >90% completion rate. The vast majority of respondents believed there was a paucity of devices available for children (96%). More than 60% of respondents stated that they did not understand the FDA regulatory process and were not aware of whether the devices they used were labeled for pediatric use. Conclusions Pediatric electrophysiologists are keenly aware of the deficit of available pediatric devices for their patients. The majority do not understand the FDA approval process and could benefit from additional educational resources regarding this. A collaborative forum including PACES, FDA, patients and their families, and Industry would be an important next step in clarifying opportunities and priorities to serve this vulnerable population.

Pediatric Medical Device Development and Regulation: Current State, Barriers, and Opportunities.

Few medical devices are designed and marketed specifically for children. Instead, adult devices are often repurposed and used off-label in pediatrics. The innovation gap between pediatric and adult devices is complex and multifactorial. This review aims to summarize the medical device landscape, describe barriers to pediatric device development, and provide an update on current strategies to help overcome these limitations. Medical devices are regulated by the Food and Drug Administration. They are registered, cleared, or approved on the basis of a 3-tier risk classification system and a differentiated set of regulatory pathways. This includes some for products that receive special designations on the basis of specific aspects that warrant more rapid review and approval. Pediatric devices number only one-quarter of those developed for adults for multiple reasons. Clinically, innovators must adjust their products to address the smaller sizes, growth, and longer duration of use in children. Smaller sample sizes and population heterogeneity also challenge the ability to obtain sufficient safety data for regulatory submissions. Financial concerns stem from lower pediatric reimbursement rates coupled with a lack of nationally standardized coverage. There are a number of promising initiatives, including the Pediatric Device Consortia Program, Early Feasibility Studies, and the new System of Hospitals for Innovation in Pediatrics - Medical Devices. However, the gap will likely not be narrowed without broad cooperation across stakeholders from industry, academia, patient advocacy groups, health care providers, investors, payors, regulators, and Congress.

Third Trimester Fetal Heart Rates in Antibody-Mediated Complete Heart Block Predict Need for Neonatal Pacemaker Placement.

Congenital complete heart block (CCHB) affects 1 in 20,000 newborns. This study evaluates fetal and neonatal risk factors predictive of neonatal pacemaker placement in antibody-mediated complete heart block. The Children's Hospital Los Angeles institutional fetal, pacemaker, and medical record databases were queried for confirmed SSA/SSB cases of CCHB between January 2004 and July 2019. Cases excluded were those with a diagnosis beyond the neonatal period, diagnosis of a channelopathy, or if maternal antibody status was unknown. We recorded the gestational age (GA), birth weight (BW), fetal heart rates (FHRs) of the last echocardiogram before delivery, specific neonatal ECG and echocardiogram findings, age at pacemaker placement, and mortality. Of 43 neonates identified with CCHB, 27 had confirmed maternal antibody exposure. Variables associated with neonatal pacemaker implantation were FHRs < 50 bpm (p = 0.005), neonatal heart rates < 52 bpm (p = 0.015), and neonatal left ventricular fractional shortening (FS) percentages < 34% (p = 0.03). On multivariate analysis, FHR remained significant (p = 0.03) and demonstrated an increased risk of neonatal pacemaker placement by an odds ratio of 12.5 (95% CI 1.3-116, p = 0.05). The median GA at which the FHR was obtained was 34 weeks (IQR 26-35 weeks). Neonatal pacemaker placement was highly associated with a FHR < 50 bpm, neonatal HR < 52 bpm, and neonatal FS < 34%. FHRs at 34 weeks GA (IQR 26-35 weeks) correlated well with postnatal heart rates and were predictive of neonatal pacemaker placement.

Hypertrophic Cardiomyopathy in Adolescence: Application of Guidelines.

We present the course and management of an adolescent male with hypertrophic cardiomyopathy. The importance of family history, early screening, accurate evaluation of hypertrophy, and risk stratification for eligibility for a defibrillator in hypertrophic cardiomyopathy are emphasized. Learning points are seen in the light of new guidelines. (Level of Difficulty: Intermediate.).

Utility of Surveillance Ambulatory Rhythm Monitoring in the Pediatric Fontan Population.

Our institution established a Fontan surveillance plan, which included ambulatory rhythm monitoring (ARM) at 6, 10, 13, 16 and 19 years old, for early detection of Fontan-associated complications. We conducted a retrospective chart review of Fontan patients followed at our institution 2014-2018 to determine the utility of surveillance ARMs. 139 ARMs from 83 patients were included. ARMs with supraventricular tachycardia, sinus node dysfunction, accelerated junctional rhythm, > 1st degree atrioventricular block, and complex ventricular ectopy were classified as positive for arrhythmia. Arrhythmias were occult if detected on surveillance ARM. The ARM indication was surveillance in 78 (56%) and clinically indicated in 61 (44%). 52 (37%) ARMs in 27 (33%) patients had an arrhythmia. There was no difference in the age of patients with and without arrhythmias [median 10.9 (6.5, 17.1 years) vs. 8.8 (7, 13.6 years), p = 0.5]. Clinically indicated ARMs more frequently demonstrated arrhythmias than surveillance ARMs (52% vs. 26%, p < 0.01). Compared to patients without arrhythmias, those with arrhythmias were more likely to be female (48% vs. 23%, p = 0.02), have a single right ventricle (46% vs. 19%, p < 0.01) and longer QRS duration on ECG [100 (91, 116 ms) vs. 94 (84, 104 ms), p = 0.046]. Patients with occult arrhythmias were less likely to have moderate to severe atrioventricular valvar regurgitation (0% vs. 46%; p = 0.04) or ventricular dysfunction (0% vs. 46%; p = 0.04) than those with clinical arrhythmia(s). Arrhythmia findings resulted in change in management for 16/52 (31%) ARMs. The findings suggest the frequent presence of arrhythmias on periodic ARMs in patients following the Fontan procedure regardless of symptomatic status.

Characteristics of antegrade-only accessory pathways in children and adolescents.

There is minimal data regarding antegrade-only accessory pathways in young patients. Given evolving recommendations and treatments, retrospective analysis of the clinical and electrophysiologic properties of antegrade-only pathways in patients <21 years old was performed, with subsequent comparison of electrophysiology properties to age-matched controls with bidirectional pathways. Of 522 consecutive young patients with ventricular pre-excitation referred for electrophysiology study, 33 (6.3%) had antegrade-only accessory pathways. Indications included palpitations (47%), chest pain (25%), and syncope (22%). The shortest value for either the accessory pathway effective refractory period or the pre-excited R-R interval was taken for each patient, with the median of the antegrade-only group significantly greater than shortest values for the bidirectional group (310 [280-360] ms versus 270 [240-302] ms, p < 0.001). However, the prevalence of pathways with high-risk properties (effective refractory period or shortest pre-excited R-R interval <250 ms) was similar in both study patients and controls (13% versus 21%) (p = 0.55). Sixteen patients had a single antegrade-only accessory pathway and no inducible arrhythmia. Six patients had Mahaim fibres, all right anterolateral with inducible antidromic reciprocating tachycardia. However, 11 patients with antegrade-only accessory pathways and 3 with Mahaim fibres had inducible tachycardia due to a second substrate recognised at electrophysiology study. These included concealed accessory pathways (7), bidirectional accessory pathways (5), and atrioventricular node re-entry (2). Antegrade-only accessory pathways require comprehensive electrophysiology evaluation as confounding factors such as high-risk conduction properties or inducible Supraventricular Tachycardia (SVT) due to a second substrate of tachycardia are often present.

Correction to: Life-threatening cardiac arrhythmias in congenital central hypoventilation syndrome.

The publisher regrets that in the original published version of this article, one of the author's name was incorrectly presented as "Yaniv Bar Cohen". The correct presentation should have been "Yaniv Bar-Cohen" and is now presented correctly in this article.

Life-threatening cardiac arrhythmias in congenital central hypoventilation syndrome.

Congenital central hypoventilation syndrome (CCHS) patients are at risk for life-threatening cardiac arrhythmias, and presentation is dependent on their PHOX2B gene mutation. We describe the presentation of life-threatening arrhythmias in our cohort of CCHS patients. We reviewed the records of 72 CCHS patients seen at CHLA from 2004 to 2018. Data collected included demographics, PHOX2B genotype, ventilatory support, clinical symptoms, ambulatory cardiac monitoring results, and presence of cardiac pacemaker. Sixteen of 72 patients had evidence of potential life-threatening cardiac arrhythmias. PHOX2B genotypes were 20/25 polyalanine repeat expansion mutation (PARM), 20/26 PARM, 20/27 PARM, 20/32 PARM, and c.245C > T non-polyalanine repeat mutation. 11/16 patients were ventilated during sleep only. Symptoms included syncope, dizziness, chest pain, tingling in the left arm, and palpitations. 15/16 patients had recorded ambulatory cardiac monitoring. 5/16 patients were symptomatic without significant sinus pauses. 12/16 patients had implantation of cardiac pacemakers. 9/12 had significant sinus pauses on ambulatory monitoring, and 7/12 patients were symptomatic.Conclusion: CCHS patients have potential life-threatening arrhythmias requiring cardiac pacemaker implantation. Many of these patients are symptomatic with significant sinus pauses on ambulatory monitoring. However, some symptomatic patients with no significant pauses on ambulatory monitoring may still require cardiac pacemaker implantation.What is Known:• CCHS patients are at risk for life-threatening sinus pauses and require cardiac pacemaker implantation.What is New:• CCHS patients regardless of PHOX2B genotype are at risk for significant sinus pauses. Many CCHS patients with significant sinus pause on ambulatory cardiac monitoring are symptomatic and most present with syncope. Some symptomatic patients do not have significant sinus pauses but may still require cardiac pacemaker implantation.

A comparison of oral flecainide and amiodarone for the treatment of recurrent supraventricular tachycardia in children.

BACKGROUND: Supraventricular tachycardia (SVT) in children can be difficult to treat when first-line therapies (beta-blockade or digoxin) are not effective. Both flecainide and amiodarone are used as second-line therapies. We sought to compare the efficacy and safety of flecainide and amiodarone in pediatric patients with recurrent SVT. METHODS: Pediatric patients treated with oral flecainide or oral amiodarone for SVT between 2006 and 2015 were studied. Tachycardia mechanisms included orthodromic reciprocating tachycardia (ORT), intra-atrial reentrant tachycardia (IART), and ectopic atrial tachycardia (EAT). Outcomes were classified as full success, partial success (requiring additional intervention), or failure. RESULTS: Seventy-four patients were included (median age 46 days, range 1 day to 19 years). Flecainide was used in 47 patients and amiodarone in 27 patients. Full success was achieved in 68% and 59%, respectively (P = 0.28). Partial success was achieved in 13% and 19%, respectively (P = 0.12). Treatment failed in 19% and 22%, respectively (P = 0.97). Ten crossover patients received the second medication after the first failed. Of five amiodarone-to-flecainide crossovers, four achieved success on flecainide alone. Of five flecainide-to-amiodarone crossovers, two achieved success. Minor adverse events occurred in 9% of flecainide and 22% of amiodarone patients (P = 0.16). No significant differences were seen by arrhythmia subtype (36 EAT, 28 ORT, 10 IART), congenital heart disease (n = 38), or age group (56 infants). CONCLUSIONS: Oral flecainide and amiodarone achieved meaningful arrhythmia control in 81% and 78% of pediatric patients with recurrent SVT, respectively. Those who failed amiodarone had encouraging outcomes when changed to flecainide.

Prenatal diagnosis and management of congenital complete heart block.

Congenital complete heart block (CCHB) is a life-threatening medical condition in the unborn fetus with insufficiently validated prenatal interventions. Maternal administration of medications aimed at decreasing the immune response in the fetus and beta-agonists intended to increase fetal cardiac output have shown only marginal benefits. Anti-inflammatory therapies cannot reverse CCHB, but may decrease myocarditis and improve heart function. Advances in prenatal diagnosis and use of strict surveillance protocols for delivery timing have demonstrated small improvements in morbidity and mortality. Ambulatory surveillance programs and wearable fetal heart rate monitors may afford early identification of evolving fetal heart block allowing for emergent treatment. There is also preliminary data suggesting a roll for prevention of CCHB with hydroxychloroquine, but the efficacy and safety is still being studied. To date, intrauterine fetal pacing has not been successful due to the high-risk invasive placement techniques and potential problems with lead dislodgement. The development of a fully implantable micropacemaker via a minimally invasive approach has the potential to pace fetal patients with CCHB and thus delay delivery and allow fetal hydrops to resolve. The challenge remains to establish accepted prenatal interventions capable of successfully managing CCHB in utero until postnatal pacemaker placement is successfully achieved.

Catecholaminergic polymorphic ventricular tachycardia patients with multiple genetic variants in the PACES CPVT Registry.

BACKGROUND: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is often a life-threatening arrhythmia disorder with variable penetrance and expressivity. Little is known about the incidence or outcomes of CPVT patients with ≥2 variants. METHODS: The phenotypes, genotypes and outcomes of patients in the Pediatric and Congenital Electrophysiology Society CPVT Registry with ≥2 variants in genes linked to CPVT were ascertained. The American College of Medical Genetics & Genomics (ACMG) criteria and structural mapping were used to predict the pathogenicity of variants (3D model of pig RyR2 in open-state). RESULTS: Among 237 CPVT subjects, 193 (81%) had genetic testing. Fifteen patients (8%) with a median age of 9 years (IQR 5-12) had ≥2 variants. Sudden cardiac arrest occurred in 11 children (73%), although none died during a median follow-up of 4.3 years (IQR 2.5-6.1). Thirteen patients (80%) had at least two RYR2 variants, while the remaining two patients had RYR2 variants plus variants in other CPVT-linked genes. Among all variants identified, re-classification of the commercial laboratory interpretation using ACMG criteria led to the upgrade from variant of unknown significance (VUS) to pathogenic/likely pathogenic (P/LP) for 5 variants, and downgrade from P/LP to VUS for 6 variants. For RYR2 variants, 3D mapping using the RyR2 model suggested that 2 VUS by ACMG criteria were P/LP, while 2 variants were downgraded to likely benign. CONCLUSIONS: This severely affected cohort demonstrates that a minority of CPVT cases are related to ≥2 variants, which may have implications on family-based genetic counselling. While multi-variant CPVT patients were at high-risk for sudden cardiac arrest, there are insufficient data to conclude that this genetic phenomenon has prognostic implications at present. Further research is needed to determine the significance and generalizability of this observation. This study also shows that a rigorous approach to variant re-classification using the ACMG criteria and 3D mapping is important in reaching an accurate diagnosis, especially in the multi-variant population.

Minimally Invasive Implantation of a Micropacemaker Into the Pericardial Space.

BACKGROUND: Permanent cardiac pacemakers require invasive procedures with complications often related to long pacemaker leads. We are developing a percutaneous pacemaker for implantation of an entire pacing system into the pericardial space. METHODS: Percutaneous micropacemaker implantations were performed in 6 pigs (27.4-34.1 kg) using subxyphoid access to the pericardial space. Modifications in the implantation methods and hardware were made after each experiment as the insertion method was optimized. In the first 5 animals, nonfunctional pacemaker devices were studied. In the final animal, a functional pacemaker was implanted. RESULTS: Successful placement of the entire nonfunctional pacing system into the pericardial space was demonstrated in 2 of the first 5 animals, and successful implantation and capture was achieved using a functional system in the last animal. A sheath was developed that allows retractable features to secure positioning within the pericardial space. In addition, a miniaturized camera with fiberoptic illumination allowed visualization of the implantation site before electrode insertion into myocardium. All animals studied during follow-up survived without symptoms after the initial postoperative period. CONCLUSIONS: A novel micropacemaker system allows cardiac pacing without entering the vascular space or surgical exposure of the heart. This pericardial pacemaker system may be an option for a large number of patients currently requiring transvenous pacemakers but is particularly relevant for patients with restricted vascular access, young children, or those with congenital heart disease who require epicardial access.

Pediatric survivors of out-of-hospital ventricular fibrillation: Etiologies and outcomes.

BACKGROUND: In general, the prognosis is poor for pediatric patients who experience out-of-hospital (OOH) cardiac arrest, with survival rates of 12% to 29%. OBJECTIVE: The purpose of this study was to describe the causes and outcomes of pediatric patients with documented ventricular fibrillation (VF) at resuscitation from OOH cardiac arrest with sustained return of spontaneous circulation after defibrillation and survival to hospital admission. METHODS: Retrospective analysis of OOH-VF patients <19 years of age evaluated between 2004 and 2016 was performed. Primary outcome measures included demographics, arrest and resuscitation parameters, cardiac diagnoses, survival, and neurologic outcome. RESULTS: Forty-five patients fulfilled study criteria (median age 12 years; range 2 months to 18 years). Cardiac arrest occurred in public in 68% of cases, with bystander cardiopulmonary resuscitation in 42% before arrival of emergency medical services. All patients underwent defibrillation (1-6 shocks) with return of spontaneous circulation and survival to hospital admission. Underlying etiologies were primary electrical disease (33%), cardiomyopathy (27%), congenital heart disease (11%), other (13%), and unknown (16%). Before arrest, 40% of patients had a cardiac diagnosis and 26% had symptoms. Ultimately, 40 of 45 patients (89%) survived resuscitation to hospital discharge. During 72 ± 37 months of follow-up, 38% of survivors had a normal neurologic outcome, whereas 32% had mild neurologic impairment and 30% had moderate-to-severe neurologic impairment. CONCLUSION: In pediatric patients resuscitated from OOH-VF, a cardiovascular cause was identified in >80%. Regardless of cause, survival and neurologic prognosis appear improved compared to patients with asystole or pulseless electrical activity. These findings support early rhythm assessment and advanced cardiopulmonary resuscitation protocols in pediatric cardiac arrest victims.

The clinical and genetic spectrum of catecholaminergic polymorphic ventricular tachycardia: findings from an international multicentre registry.

Aims: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an ion channelopathy characterized by ventricular arrhythmia during exertion or stress. Mutations in RYR2-coded Ryanodine Receptor-2 (RyR2) and CASQ2-coded Calsequestrin-2 (CASQ2) genes underlie CPVT1 and CPVT2, respectively. However, prognostic markers are scarce. We sought to better characterize the phenotypic and genotypic spectrum of CPVT, and utilize molecular modelling to help account for clinical phenotypes. Methods and results: This is a Pediatric and Congenital Electrophysiology Society multicentre, retrospective cohort study of CPVT patients diagnosed at <19 years of age and their first-degree relatives. Genetic testing was undertaken in 194 of 236 subjects (82%) during 3.5 (1.4-5.3) years of follow-up. The majority (60%) had RyR2-associated CPVT1. Variant locations were predicted based on a 3D structural model of RyR2. Specific residues appear to have key structural importance, supported by an association between cardiac arrest and mutations in the intersubunit interface of the N-terminus, and the S4-S5 linker and helices S5 and S6 of the RyR2 C-terminus. In approximately one quarter of symptomatic patients, cardiac events were precipitated by only normal wakeful activities. Conclusion: This large, multicentre study identifies contemporary challenges related to the diagnosis and prognostication of CPVT patients. Structural modelling of RyR2 can improve our understanding severe CPVT phenotypes. Wakeful rest, rather than exertion, often precipitated life-threatening cardiac events.

Cardiac Resynchronization Therapy in Pediatrics.

Cardiac resynchronization therapy (CRT) has proven to be a powerful and effective tool in the treatment of adults with severe dilated or ischemic cardiomyopathy. A substantial portion of the adult heart failure population has severely depressed systolic function, heart failure symptoms, QRS prolongation, and left bundle branch block. Indications for CRT in adults are commonly focused on these characteristics. However, pediatric patients represent a heterogeneous group with many etiologies of heart failure and anatomic variants, with most of them not fitting the typical adult CRT criteria. The heterogeneity of the pediatric population has hindered the identification of ideal candidates for CRT, but initial experience with CRT in various groups of pediatric patients has been encouraging. This article reviews indications for and outcomes of CRT in pediatric and congenital heart disease patients.