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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

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

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

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.), Graphical abstract

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.

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.

Background Echocardiography is important in the follow-up of children with permanent pacemakers due to the risk for cardiomyopathy. However, the value of standard measurements is unclear in the setting of expected dyssynchrony caused by ventricular pacing. Objectives The study sought to assess and compare echocardiographic parameters of ventricular function in children with chronic ventricular pacing. Methods Echocardiographic studies of patients with normal cardiac anatomy and ventricular pacing for heart block were retrospectively evaluated for routine measurements of systolic and diastolic ventricular function. Results In 60 echocardiograms that were analyzed, fractional shortening (FS) had moderate correlation with ejection fraction (EF; R = 0.64, p Conclusions FS and EF are moderately correlated to each other and may both be appropriate in the evaluation of systolic function in chronically paced children. TDI values may be misleading, measuring low diastolic function despite normal LA area.

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

Implantation and maintenance of a permanent cardiac pacing system in children remains challenging due to small patient size, congenital heart defects and somatic growth. We are developing a novel epicardial micropacemaker for children that can be implanted on the epicardium within the pericardial space via a minimally-invasive technique. The key design configurations include a novel open-coiled lead in which living tissue replaces the usual polymeric support for the coiled conductor. To better understand and be able to predict the behavior of the implanted lead, we performed a radiographic image-based modeling study on a chronic animal test. We report a pilot study in which two mechanical dummy pacemakers with epicardial leads were implanted into an adult pig model via a minimally invasive approach. Fluoroscopy was obtained on the animal on Post-Operative Days #9, #35 and #56 (necropsy). We then constructed an analytic model to estimate the in vivo stress conditions on the open-coil lead based on the analysis of orthogonal biplane radiographic images. We obtained geometric deformation data of the implanted lead including elongation magnitudes and bending radii from sequenced films of cardiac motion cycles. The lead stress distribution was investigated on each film frame and the point of maximum stress (Mean Stress = 531.4 MPa; Alternating Stress = ± 216.4 MPa) was consistently where one of the leads exited the pericardial space, a deployment that we expected to be unfavorable. These results suggest the modeling approach can provide a basis for further design optimization. More animal tests and modeling will be needed to validate whether the novel lead design could meet the requirements to withstand ~200 million cardiac motion cycles over 5 years.

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.

We have developed a rechargeable fetal micropacemaker in order to treat severe fetal bradycardia with comorbid hydrops fetalis, a life-threatening condition in pre-term non-viable fetuses for which there are no effective treatment options. The small size and minimally invasive form factor of our design limit the volume available for circuitry and a power source. The device employs a fixed-rate and fixed-amplitude relaxation oscillator and a tiny, rechargeable lithium ion power cell. For both research and clinical applications, it is valuable to monitor the electrode-myocardium interface in order to determine that adequate pacemaker output is being provided. This is typically accomplished by observing the minimal stimulus strength that achieves threshold for pacing capture. The output of our simple micropacemaker cannot be programmatically altered to determine this minimal capture threshold, but a safety factor can be inferred by determining the refractory period for ventricular capture at a given stimulus strength. This is done by measuring the minimal timing between naturally occurring QRS complexes and pacing stimuli that successfully generate a premature ventricular contraction. The method was tested in a pilot study in four fetal sheep and the data demonstrate that a relative measure of threshold is obtainable. This method provides valuable real-time information about the electrode-tissue interface.

Dominic Abrams, MD, Sam Asirvatham, MD, Yaniv Bar-Cohen, MD, FAAP, FACC, FHRS, Andrew D. Blaufox, MD, FHRS, FACC, Bryan Cannon, MD, FHRS, John Clark, MD, Macdonald Dick, MD, FHRS, FACC, Anne Freter, MSN, FHRS, Naomi J. Kertesz, MD, FACC, FHRS, Joel A. Kirsh, MD, FRCP(C), FHRS, CEPS, John Kugler, MD, FAAC, FAAP, FAHA, Martin LaPage, MD, MS, FAAP, FHRS, CCDS, CEPS, Francis X. McGowan, MD, FAAP, Christina Y. Miyake, MD, Aruna Nathan, MBBS, FRCA, John Papagiannis, MD, FHRS, CEPS, Thomas Paul, MD, FHRS, FACC, Andreas Pflaumer, MD, FRACP, FCSANZ, CEPS, Allan C. Skanes, MD, FRCPC, William G. Stevenson, MD, FAHA, FHRS, FACC, Nicholas Von Bergen, Frank Zimmerman, MD, FAHA, FHRS

This paper discusses the technical and safety requirements for cardiac pacing of a human fetus with heart failure and hydrops fetalis secondary to complete heart block. Engineering strategies to meet specific technical requirements were integrated into a systematic design and implementation consisting of a novel fetal micropacemaker, a percutaneous implantation system, and a sterile package that enables device storage and recharging maintenance in a clinical setting. We further analyzed observed problems on myocardial fixation and pacing lead fatigue previously reported in earlier preclinical trials. This paper describes the technical refinements of the implantable fetal micropacemaker to overcome these challenges. The mechanical performance has been extensively tested to verify the improvement of reliability and safety margins of the implantation system.

Pediatric medical devices cover a broad array of indications and risk profiles, and have helped to reduce disease burden and improve quality of life for numerous children. However, many of the devices used in pediatrics are not intended for or tested on children. Several barriers have been identified that pose difficulties in bringing pediatric medical devices to the market. These include a small market and small sample size; unique design considerations; regulatory complexities; lack of infrastructure for research, development, and evaluation; and low return on investment. In 2007, the Food and Drug Administration (FDA) created the Pediatric Device Consortia (PDC) Grants Program under the administration of the Office of Orphan Products Development. In 2018, the FDA awarded over US $30 million to five new PDCs. The West Coast Consortium for Technology & Innovation in Pediatrics (CTIP) is one of these PDCs and is centered at the Children’s Hospital Los Angeles. In February 2019, CTIP convened its primary stakeholders to discuss its priorities and activities for the new grant cycle. In this paper, we have presented a report of the summit proceedings to raise awareness and advocate for patients and pediatric medical device innovators as well as to inform the activities and priorities of other organizations and agencies engaged in pediatric medical device development.

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.

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.

Background Atrioventricular nodal reentrant tachycardia (AVNRT) typically occurs in adolescents and adults with limited data regarding AVNRT in young children. Methods All patients with AVNRT who underwent electrophysiology study and ablation between 2005 and 2012 were retrospectively studied. Patients were stratified by age

Although guidelines for routine follow-up of pacemakers and implantable cardioverter defibrillators (ICDs) are available for adults, minimal data supports their appropriateness in pediatrics and congenital heart disease. This study aimed to define current practices of cardiac rhythm device (CRD) follow-up among pediatric electrophysiologists. Pediatric and Congenital EP Society (PACES) members were surveyed regarding frequency of CRD in-person follow-up as well as transtelephonic monitoring (TTM) and remote monitoring (RM) practices. If home monitoring was used, the effect on in-person follow-up was also evaluated. A total of 106 PACES members responded to the survey. Uncomplicated pacemaker and ICD patients were both followed in-person at a median interval of 6 months (range 1-12 months). TTM was utilized by 67 % of responders (median interval 3 months; range 1-6 months), while RM was used by 87 % for pacemakers (median interval 3 months; range 1-6 months) and 92 % for ICDs (median interval 3 months; range 2 weeks-6 months). When TTM was used, 21 % of responders reduced their frequency of pacemaker clinic visits. In comparison, RM reduced the frequency of clinic visits for pacemakers and ICDs in 32 and 31 % of responders, respectively. Patient age was an independent factor in determining CRD follow-up for 49 % of responders. While CRD follow-up by pediatric electrophysiologists in general follows adult guidelines, individual practices widely vary. In contrast to published recommendations in adults, TTM and RM utilization does not reduce the frequency of in-person visits for the majority of pediatric electrophysiologists.

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.

In general, the prognosis is poor for pediatric patients who experience out-of-hospital (OOH) cardiac arrest, with survival rates of 12% to 29%.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.Retrospective analysis of OOH-VF patients19 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.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.In pediatric patients resuscitated from OOH-VF, a cardiovascular cause was identified in80%. 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.

A 2-week-old infant with normal intracardiac anatomy presented to the emergency department in a hypertensive crisis with acute cardiac failure. Despite extensive evaluation, no underlying disease was found. The patient’s hypertension and cardiac dysfunction resolved after 1 week of supportive care in the PICU, and she was discharged within 2 weeks of presentation. The patient’s history revealed transplacental exposure to the α-adrenergic agonist methyldopa for 10 weeks before delivery. Her age at presentation and the self-limited nature of cardiac sequelae with complete resolution of cardiac dysfunction suggest withdrawal effects from this exposure. Whereas the rebound hypertensive effects of α-adrenergic agonists are well established in the adult population, this report shows an unusual adverse outcome of in utero exposure to methyldopa.

Background— Although retrograde decremental accessory pathways (DAPs) are thought to typically present as permanent junctional reciprocating tachycardia (permanent junctional reciprocating tachycardia), they may also be diagnosed unexpectedly during electrophysiology study. We aimed to compare the clinical and electrophysiological characteristics of patients with DAPs to an age-matched cohort with nondecremental accessory pathways. Methods and Results— We retrospectively studied pediatric patients (30 ms. Twenty-six patients with DAPs were compared with 73 controls (mean age at electrophysiology study 9.8±5.7 and 10.3±5.2 years, respectively [ P =nonsignificant]). Compared with controls, patients with DAPs had more frequent syncope (5/26 [19%] versus 3/73 [4%]; P =0.02) and ventricular dysfunction (6/26 [23%] versus 4/73 [6%]; P =0.04). Only 11 (42%) DAP patients manifested clinical permanent junctional reciprocating tachycardia, and these patients had more syncope (5/11 [45%] versus 0/15 [0%]; P P =0.001), and longer ventriculo-atrial times (mean maximum ventriculo-atrial times of 283±116 ms versus 208±42 ms; P =0.02) compared with those with DAPs without clinical permanent junctional reciprocating tachycardia. DAPs and controls had similar rates of acute ablation success (23/26 [89%] versus 67/73 [92%]; P =nonsignificant) and recurrences (1/23 [4%] versus 2/67 [3%]; P =nonsignificant). Conclusions— The majority of pediatric patients with DAPs do not present with clinical permanent junctional reciprocating tachycardia. DAPs are associated with more severe symptoms, but ablation outcomes are similar to those of age-matched controls.

Author(s): Roston, Thomas M; Haji-Ghassemi, Omid; LaPage, Martin J; Batra, Anjan S; Bar-Cohen, Yaniv; Anderson, Chris; Lau, Yung R; Maginot, Kathleen; Gebauer, Roman A; Etheridge, Susan P; Potts, James E; Van Petegem, Filip; Sanatani, Shubhayan | Abstract: BackgroundCatecholaminergic 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.MethodsThe 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 a Genomics (ACMG) criteria and structural mapping were used to predict the pathogenicity of variants (3D model of pig RyR2 in open-state).ResultsAmong 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.ConclusionsThis 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.

A Report from the Training and Credentialing Committee of the Pediatric and CongenitalElectrophysiology SocietyEndorsed by the Heart Rhythm SocietyCOMMITTEE MEMBERSEdward P. Walsh, MD, FHRS, ChairYaniv Bar-Cohen, MDAnjan S. Batra, MD, FHRS*Macdonald Dick II, MD, FHRSChristopher Erickson, MDFrank Fish, MDRobert M. Hamilton, MD

Left Ventricular Tachycardia in PediatricsIntroduction The aim of this study was to evaluate the clinical presentation and outcomes of pediatric patients with ventricular tachycardia (VT) originating from left heart structures. Methods and Results This international multicenter retrospective study including 152 patients (age 10.0 ± 5.1 years, 62% male), divided into those with fascicular VT (85%, 129/152) and nonfascicular LV VT (15%, 23/152). All patients had a normal heart structure or only a minor cardiac abnormality. Adenosine was largely ineffective in both groups (tachycardia termination in 4/74 of fascicular VT and 0/5 of nonfascicular LV VT). In fascicular VT, calcium channel blockers were effective in 80% (74/92); however, when administered orally, there was a 21% (13/62) recurrence rate. In nonfascicular LV VT, a variety of antiarrhythmic therapies were used with no one predominating. Ablation procedures were successful in 71% (72/102) of fascicular VT and 67% (12/18) of nonfascicular LV VT on an intention to treat analysis. Major complications occurred in 5 patients with fascicular VT and 1 patient with nonfascicular LV VT. After a follow-up period of 2 years (1 day to 15 years), 72% of all patients with fascicular VT were off medications with no tachycardia recurrence. One patient died of noncardiac causes. In nonfascicular LV VT, follow-up was 3.5 years (0.5–15 years), P = 0.38. A total of 65% of these patients were free from arrhythmias. Two patients died suddenly (P < 0.01). Conclusion The clinical course and outcomes of pediatric patients with fascicular VT and nonfascicular LV VT are varied. Catheter ablation procedures can be curative.

The study objective was to determine the predictors of new-onset arrhythmia among infants with single-ventricle anomalies during the post-Norwood hospitalization and the association of those arrhythmias with postoperative outcomes (ventilator time and length of stay) and interstage mortality.After excluding patients with preoperative arrhythmias, we used data from the Pediatric Heart Network Single Ventricle Reconstruction Trial to identify risk factors for tachyarrhythmias (atrial fibrillation, atrial flutter, supraventricular tachycardia, junctional ectopic tachycardia, and ventricular tachycardia) and atrioventricular block (second or third degree) among 544 eligible patients. We then determined the association of arrhythmia with outcomes during the post-Norwood hospitalization and interstage period, adjusting for identified risk factors and previously published factors.Tachyarrhythmias were noted in 20% of subjects, and atrioventricular block was noted in 4% of subjects. Potentially significant risk factors for tachyarrhythmia included the presence of modified Blalock-Taussig shunt (P = .08) and age at Norwood (P = .07, with risk decreasing each day at age 8-20 days); the only significant risk factor for atrioventricular block was undergoing a concomitant procedure at the time of the Norwood (P = .001), with the greatest risk being in those undergoing a tricuspid valve procedure. Both tachyarrhythmias and atrioventricular block were associated with longer ventilation time and length of stay (P .001 for all analyses). Tachyarrhythmias were not associated with interstage mortality; atrioventricular block was associated with mortality among those without a pacemaker in the unadjusted analysis (hazard ratio, 2.3; P = .02), but not after adding covariates.Tachyarrhythmias are common after the Norwood procedure, but atrioventricular block may portend a greater risk for interstage mortality.

Background— Supraventricular tachycardia (SVT) is one of the most common conditions requiring emergent cardiac care in children, yet its management has never been subjected to a randomized controlled clinical trial. The purpose of this study was to compare the efficacy and safety of the 2 most commonly used medications for antiarrhythmic prophylaxis of SVT in infants: digoxin and propranolol. Methods and Results— This was a randomized, double-blind, multicenter study of infants P =0.25). No first recurrence occurred after 110 days of treatment. The 6-month recurrence-free status was 79% for patients on digoxin and 67% for patients on propranolol ( P =0.34), and there were no first recurrences in either group between 6 and 12 months. There were no deaths and no serious adverse events related to study medication. Conclusions— There was no difference in SVT recurrence in infants treated with digoxin versus propranolol. The current standard practice may be treating infants longer than required and indicates the need for a placebo-controlled trial. Clinical Trial Registration Information— http://clinicaltrials.gov ; NCT-00390546.

We are developing a cardiac pacemaker with a small, cylindrical shape that permits percutaneous implantation into a fetus to treat complete heart block and consequent hydrops fetalis, which can otherwise be fatal. The device uses off-the-shelf components including a rechargeable lithium cell and a highly efficient relaxation oscillator encapsulated in epoxy and glass. A corkscrew electrode made from activated iridium can be screwed into the myocardium, followed by release of the pacemaker and a short, flexible lead entirely within the chest of the fetus to avoid dislodgement from fetal movement. Acute tests in adult rabbits demonstrated the range of electrical parameters required for successful pacing and the feasibility of successfully implanting the device percutaneously under ultrasonic imaging guidance. The lithium cell can be recharged inductively as needed, as indicated by a small decline in the pulsing rate.

Assessment of the risk for sudden cardiac death (SCD) after surgery for congenital heart disease (CHD) remains a difficult challenge. In the study of this problem, the focus has evolved from concern regarding late-onset heart block to a subsequent focus on ventricular and reentrant atrial arrhythmias, with the most recent emphasis on ventricular dysfunction and heart failure. Sudden cardiac death in CHD patients has been studied most extensively in tetralogy of Fallot. More than 30 risk factors have been proposed, with age at repair, QRS duration, right ventricular enlargement, and left ventricular dysfunction considered the most predictive risk factors. Additionally, SCD has been studied in patients with atrial repair for transposition of the great arteries, left heart obstructive lesions, and to a limited extent, patients with univentricular physiology. This review discusses current risk factors for SCD in CHD and the limited positive predictive value of any individual factor. The emphasis is on contemporary patients with CHD, who differ markedly from those who had repair of CHD decades earlier. This is characterized by complete repairs during the neonatal period, improved physiologic outcomes, and extended survival of patients with complex forms of CHD. Therefore, earlier data and conclusions may not be relevant to newer generations of patients with CHD. According to current perspectives, systemic ventricular dysfunction becomes a major risk factor beyond the age of 20 years. The first symptomatic arrhythmia may result in SCD, and defibrillators are increasingly implanted despite the lack of risk stratification criteria. The large number of potential risk factors and therapeutic options, in contrast to the low incidence of actual events, results in a difficult clinical challenge in the assessment of the risk for SCD in the individual patient with CHD.

Supraventricular tachycardia (SVT) is the most common arrhythmia in children and is especially common in infants. SVT is typically thought of as an acute condition; however, if unrecognized, a persistent tachyarrhythmia can progress to a state of cardiac contractile dysfunction known as tachycardia-induced cardiomyopathy. A high index of suspicion for an underlying arrhythmia is needed in the workup of any patient with new onset heart failure, and the 12-lead electrocardiogram can aid in the diagnosis. While this may be a rare cause of dilated cardiomyopathy and heart failure in children, the condition is usually reversible and should be considered in infants and young children.

Objectives To determine the outcomes of medical management, pacing, and catheter ablation for the treatment of nonpost-operative junctional ectopic tachycardia (JET) in a pediatric population. Background Nonpost-operative JET is a rare tachyarrhythmia that is associated with a high rate of morbidity and mortality. Most reports of clinical outcomes were published before the routine use of amiodarone or ablation therapies. Methods This is an international, multicenter retrospective outcome study of pediatric patients treated for nonpost-operative JET. Results A total of 94 patients with JET and 5 patients with accelerated junctional rhythm (age 0.8 year, range fetus to 16 years) from 22 institutions were identified. JET patients presenting at age ≤6 months were more likely to have incessant JET and to have faster JET rates. Antiarrhythmic medications were utilized in a majority of JET patients (89%), and of those, amiodarone was the most commonly reported effective agent (60%). Radiofrequency ablation was conducted in 17 patients and cryoablation in 27, with comparable success rates (82% radiofrequency vs. 85% cryoablation, p = 1.0). Atrioventricular junction ablation was required in 3% and pacemaker implantation in 14%. There were 4 (4%) deaths, all in patients presenting at age ≤6 months. Conclusions Patients with nonpost-operative JET have a wide range of clinical presentations, with younger patients demonstrating higher morbidity and mortality. With current medical, ablative, and device therapies, the majority of patients have a good clinical outcome.

A previously healthy 11-year-old girl was transferred to our facility with fevers, polyarthralgias, abdominal pain, tachypnea, palatal ulcers, petechiae on the dorsal feet, and vesicular rash on the extensor elbows. Two weeks earlier, she was treated with 3 days of cephalexin and penicillin for cellulitis of the left foot, followed by a week of oral clindamycin. She had persistent arthralgias and later developed abdominal pain, tachypnea, and hypoxia, for which she was admitted to an outside hospital 3 days before transfer to our facility. At the outside hospital, she had extensive laboratory and imaging studies, including chest computed tomography, which showed bilateral peripheral opacification, and she was started on vancomycin and ampicillin/sulbactam for presumed pneumonia. Her antibiotics were subsequently changed to ceftriaxone and azithromycin and then discontinued on arrival at our facility. The patient’s infectious workup included multiple negative blood cultures, viral studies, and serologies. A screening echocardiogram performed on the second day of her admission at our hospital showed normal …

The use of pacemakers and implantable cardioverter-defibrillators (ICDs) in infants, children, and patients with congenital heart disease presents unique challenges and considerations. They include uncommon indications for device implantation, innovative approaches to lead implantation and configuration, and age-dependent and disease-specific aspects of device programming. In this review, the current indications for pacemaker and ICD implantation in young patients are discussed, followed by consideration of the approaches to lead and device placement in very small patients and those with complex congenital heart disease, in whom unique problems may be encountered. The limitations of programmability of current pacemakers and ICDs when used in young patients are discussed, followed by an analysis of long-term device follow-up and potential late complications.

The long QT syndrome (LQTS) is characterized by electrocardiographic abnormalities and a high incidence of syncope and sudden cardiac death (SCD). The diagnosis is suggested when ventricular repolarization abnormalities result in prolongation of the corrected QT interval. When LQTS is suspected, genetic screening may identify a specific long QT subtype and provide guidance for appropriate therapy. Treatment depends on the relative risk of SCD, which is increased with longer QT durations, prior cardiac events, and a family history of SCD. beta Blockers are considered the initial treatment of choice, with implantable cardioverter-defibrillator (ICD) therapy warranted in high-risk patients. In patients with frequent ICD shocks or in those at high risk for SCD where ICD placement cannot be performed, cardiac pacing and/or left cardiac sympathetic denervation may be indicated.

Background Cryoablation may offer advantages over radiofrequency (RF) ablation for certain arrhythmia substrates, such as septal accessory pathways (APs). Data for young patients, especially regarding recurrence risk, require expansion. Objectives The purpose of this study was to study institutional outcomes for cryoablation of APs located in potentially difficult septal regions for children and young adults. Methods Cryoablation was attempted in 35 young patients (mean age 15.6 years) with 37 APs that were either close to normal conduction tissues or inside the coronary venous system. Outcomes were compared with previously published institutional data for RF ablation at these same locations. Results Acute cryoablation success was achieved for 29 (78%) of 37 APs. Apart from permanent PR prolongation in one case and right bundle branch block in one other, there were no detrimental effects on normal conduction. At median follow-up of 207 days (range 2–695 days), AP conduction recurred for 13 (45%) of 29 ablated APs. Younger patient age and midseptal AP location correlated with higher likelihood of recurrence. Acute success rates for cryoablation were similar to RF ablation in our laboratory, but recurrence rates were significantly higher ( P Conclusion Cryoablation yields acute success rates comparable with RF ablation for difficult septal APs in young patients. The risk of AP recurrence appears higher after cryoablation, although safety benefits may provide suitable compensation for this deficiency. Methods for creating more effective cryoablation lesions need to be explored.

Yaniv Bar-Cohen, MD, FHRS, Gerald E. Loeb, MD, Jay D. Pruetz, MD, Michael J. Silka, MD, Catalina Guerra, DVM, Adriana N. Vest, BE, Li Zhou, MS, Ramen H. Chmait, MD From the Division of Cardiology, Children’s Hospital Los Angeles; and Keck School of Medicine, University of Southern California, Los Angeles, CA, Department of Biomedical Engineering, University of Southern California, Los Angeles, California, C.W. Steers Biological Resources Center, Los Angeles Biomedical Research Institute, Harbor–University of California, Los Angeles, Torrance, California, and Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, Los Angeles, California.

Background: In general, the prognosis is very poor for pediatric patients who experience out-of-hospital (OOH) cardiac arrest. This study describes the causes and outcomes of a subset of pediatric patients who experienced OOH cardiac arrest due to documented ventricular fibrillation (VF) and who had

A miniaturized, self-contained pacemaker that could be implanted with a minimally invasive technique would dramatically improve the survival rate for fetuses that develop hydrops fetalis as a result of congenital heart block. We are currently validating a device that we developed to address this bradyarrhythmia. Preclinical studies in a fetal sheep model are underway to demonstrate that the device can be implanted via a minimally invasive approach, can mechanically withstand the harsh bodily environment, can induce effective contractions of the heart muscle with an adequate safety factor, and can successfully operate for the required device lifetime of three months using the previously-developed closed loop transcutaneous recharging system.

Background— Catecholaminergic polymorphic ventricular tachycardia is an uncommon, potentially lethal, ion channelopathy. Standard therapies have high failure rates and little is known about treatment in children. Newer options such as flecainide and left cardiac sympathetic denervation are not well validated. We sought to define treatment outcomes in children with catecholaminergic polymorphic ventricular tachycardia. Methods and Results— This is a Pediatric and Congenital Electrophysiology Society multicenter, retrospective cohort study of catecholaminergic polymorphic ventricular tachycardia patients diagnosed before 19 years of age. The cohort included 226 patients, including 170 probands and 56 relatives. Symptomatic presentation was reported in 176 (78%). Symptom onset occurred at 10.8 (interquartile range, 6.8–13.2) years with a delay to diagnosis of 0.5 (0–2.6) years. Syncope ( P P P =0.008) occurred more often in probands. β-Blockers were prescribed in 205 of 211 patients (97%) on medication, and 25% experienced at least 1 treatment failure event. Implantable cardioverter defibrillators were placed in 121 (54%) and was associated with electrical storm in 22 (18%). Flecainide was used in 24% and left cardiac sympathetic denervation in 8%. Six deaths (3%) occurred during a cumulative follow-up of 788 patient-years. Conclusions— This study demonstrates a malignant phenotype and lengthy delay to diagnosis in catecholaminergic polymorphic ventricular tachycardia. Probands were typically severely affected. β-Blockers were almost universally initiated; however, treatment failure, noncompliance and subtherapeutic dosing were often reported. Implantable cardioverter defibrillators were common despite numerous device-related complications. Treatment failure was rare in the quarter of patients on flecainide. Left cardiac sympathetic denervation was not uncommon although the indication was variable.

Previous in vivo studies have shown that transcutaneous ultrasound enhances clot dissolution in the presence of either streptokinase or microbubbles. However, ultrasound-induced skin damage has been a major drawback. The objective was to evaluate the effect of a cooling system to prevent the skin damage that has heretofore been associated with transcutaneous low-frequency, high-intensity ultrasound clot dissolution. After thrombi were induced in both iliofemoral arteries in 15 rabbits, streptokinase (25,000 U/kg) was given intravenously and dodecafluoropentane was injected slowly (2 mL/15 min) through an infusion catheter into the abdominal aorta. One iliofemoral artery was randomized to receive ultrasound treatment, and the contralateral artery was treated as a control (receiving streptokinase and dodecafluoropentane alone). In six rabbits (group 1), the skin below the ultrasound transducer was protected by the use of a balloon cooling system, and in the other nine rabbits (group 2), ultrasound was used without a cooling system. Seven of nine (78%) arteries treated without the cooling system, and six of six (100%) arteries treated with the cooling system were angiographically recanalized after ultrasound + streptokinase + dodecafluoropentane treatment. Thermal damage was present in the skin and soft tissues of all nine rabbits treated without a cooling system. However, the skin and soft tissues were grossly and histologically normal in the six rabbits in which the transcutaneous ultrasound was used with the cooling system. Low-frequency, high-intensity ultrasound energy can be delivered transcutaneously for clot dissolution without concomitant tissue damage when coupled with the use of a cooling system to prevent thermal injury.

We are developing a self-contained cardiac pacemaker with a small, cylindrical shape (~3 × 20 mm) that permits it to be implanted percutaneously into a fetus to treat complete heart block and consequent hydrops fetalis, which is otherwise fatal. The device uses off-the-shelf components including a rechargeable lithium cell and a highly efficient relaxation oscillator encapsulated in epoxy and glass. A corkscrew electrode made from activated iridium can be screwed into the myocardium, followed by release of the pacemaker and a short, flexible lead entirely within the chest of the fetus to avoid dislodgement from fetal movement. The feasibility of implanting the device percutaneously under ultrasonic imaging guidance was demonstrated in acute adult rabbit experiments.

We are developing a cardiac pacemaker that is designed to be implanted percutaneously into a fetus to treat complete heart block and consequent hydrops fetalis, which is otherwise fatal. One of the most significant considerations for this device is the technical challenges presented by the battery and charging system. The size of the device is limited to about 3 mm in diameter; batteries on this scale have very small charge capacities. The smaller capacity means that the device needs to be designed so that it uses as little current as possible and so that its battery can be recharged wirelessly. We determined the pacing thresholds for a simple relaxation oscillator that can be assembled from discrete, surface mount components and analyzed the power consumption of the device given different electrode configurations and stimulus parameters. An inductive recharging system will be required for some patients; it is feasible within the package constraints and under development.