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β-Blocker therapy, specifically nadolol, is the recommended treatment for long QT syndrome (LQTS). Previous studies assessing maternal and fetal outcomes were published before the nadolol era.The purpose of this study was to examine contemporary maternal and fetal outcomes in the treatment of LQTS during pregnancy.We queried the Inherited Arrhythmia Database at Cleveland Clinic and identified all pregnant patients with LQTS from January 2001 through January 2020. Collected data included use and timing of β-blockers, maternal arrhythmic events, fetal growth restriction, neonatal hypoglycemia, and bradycardia.Among 68 live-birth pregnancies in 31 women with LQTS (mean age 29 ± 5.9 years; mean corrected QT interval 468 ± 39 ms), there were 5 arrhythmic events in 4 mothers. All arrhythmic events occurred in the postpartum period, and there were no arrhythmic events in patients taking β-blockers. In patients diagnosed with LQTS and treated with β-blockers (n = 27 [41%]), nadolol was the most commonly prescribed agent throughout pregnancy and the postpartum period (n = 16 [60%]). The rate of intrauterine growth restriction was not significantly different in fetuses exposed to β-blockers vs unexposed (P = .08). In the postnatal period, hypoglycemia was not seen and 1 patient in the exposure group had bradycardia.Arrhythmic events were only seen in the postpartum period in those not treated with β-blockers. Events occurred as late as 9 months postpartum. β-Blocker therapy, specifically nadolol, was not associated with a higher incidence of intrauterine growth restriction. Moreover, neonatal bradycardia was rare and hypoglycemia was not observed.

The study goal was to investigate electrocardiographic findings, including corrected QT interval (QTc), in patients aged 8 to 23 with eating disorders (EDs) at presentation, compared with an age-and sex-matched control population. We retrospectively reviewed 200 ED patients, and 200 controls. Blinded electrocardiograms (ECGs) were interpreted by an expert reader, and QT intervals corrected using the Bazett formula. Eating disorder patients were 89.5% female, with mean age 16.4 years and median percent median body mass index (BMI)-for-age (%mBMI)a of 91.1%. In ED patients, QTc was significantly shorter than controls (399.6 vs 415.0msec, P < .001). After adjusting for height, %mBMI, sex, magnesium level, and bradycardia, mean QTc duration in patients with anorexia nervosa-restricting subtype (AN-R) was significantly shorter than other ED patients ( P = .010). Higher %mBMI was associated with shorter QTc duration ( P = .041) after adjusting for height, magnesium, bradycardia, and Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) diagnosis. Within the ED group, no significant association was identified between QTc and medications, electrolytes, or inpatient status.

The Rhythmia™ system (Boston Scientific, Natick, MA, USA) facilitates the rapid acquisition of high-resolution electroanatomical and activation maps. However, there are limited data on its efficacy and safety in pediatric and adult congenital heart disease (CHD) patients. In a retrospective, observational cohort study, adult CHD and pediatric patients followed by pediatric cardiology underwent electrophysiologic study using the Rhythmia™ electroanatomic mapping system. Variables examined included the number of electroanatomical maps required, acquisition time, procedure time, fluoroscopy time, radiation dosage, and rate of recurrent arrhythmia. Twelve consecutive patients, including six male patients (50%), were included with an average age of 27.7 years (range: 11-64 years). Seven (58%) of these patients had a diagnosis of CHD [moderate complexity in two (17%) and great complexity in five patients (42%)] and 10 (83%) patients underwent ablation. A total of 37 high-density maps were created in 12 procedures, with a median of 8,140 mapping points, taking a median of 631 seconds. The median procedure time was 189.5 minutes. The median fluoroscopy time was 0.9 minutes, with eight (67%) patients receiving no fluoroscopy at all. Recurrence occurred in one patient (8%) over a median follow-up duration of 16 months (interquartile range: 12.8-17.3 months). No adverse periprocedural events were recorded. This study suggests the use of high-density electroanatomic mapping in adult CHD patients showed potential for rapid acquisition of highly detailed maps with minimal fluoroscopy time or risk of periprocedural events in the studied population.

Patients with Williams syndrome (WS) have a 25- to 100-fold higher risk of sudden death and prolonged heart rate-corrected QT (QTc). A recent study using the Fridericia formula for QT correction suggested that prolongation is principally an issue of heart rate. We used multiple published heart rate correction formulas to reevaluate the prevalence of QTc prolongation in our original dataset from our 2010 study at the Children's Hospital of Philadelphia. The ninety-eighth centile for QTc and corrected JT Interval (JTc) of the control population for each formula were used to set the threshold for prolongation. Prevalence comparison was done with Fisher's exact test. Predictors of longer QTc/JTc were assessed using linear regression models adjusting for age, gender, and heart rate. Adjusted odds of QTc/JTc prolongation were evaluated with conditional logistic regression models matched based on age and heart rate. There were 482 electrocardiograms from 188 patients with WS and 1,522 from normal controls. Patients with WS were younger, with higher heart rates and shorter RR and QRS intervals. WS was associated with longer QTc/JTc compared with controls. There were higher odds of prolonged QTc/JTc in patients with WS than controls using both Bazett and Fridericia formulas. In conclusion, this study confirms the higher prevalence of QTc prolongation in WS compared with controls and highlights the importance of setting appropriate formula-specific upper thresholds for QTc prolongation for accurate diagnosis.

BACKGROUND: Atrial fibrillation (AF) in healthy children and young adults is rare. Risk of recurrence and treatment efficacy are not well-defined. OBJECTIVE: To assess recurrence patterns and treatment efficacy in AF. METHODS: A retrospective multi-center cohort study including 13 congenital heart centers was facilitated by the Pediatric and Congenital Electrophysiology Society (PACES). Patients ≤ 21 years of age with documented AF from January 2004 to December 2018 were included. Demographics, family and clinical history, medications, electrophysiology study parameters and outcomes related to the treatment of AF were recorded and analyzed. Patients with contributory diseases were excluded. RESULTS: In 241 subjects (83% male, mean age at onset 16 years), AF recurred in 94 patients (39%) during 2.1 ± 2.6 years of follow-up. In multivariable analysis, predictors of AF recurrence were family history in a 1(st) degree relative under 50 years of age (OR 1.9, p=0.047) and longer PR interval in sinus rhythm (OR 1.1 per 10 ms, p=0.037). AF recurrence was similar whether patients began no treatment (39/125, 31%), began daily antiarrhythmic therapy (24/63, 38%) or had an ablation at any time (14/53, 26%; p = 0.39). Ablating non-AF substrate with supraventricular tachycardia improved freedom from AF recurrence (p=0.013). CONCLUSIONS: Recurrence of AF in the pediatric population is common and the incidence of recurrence was not impacted by “No Treatment”, “Medication Only” or “Ablation” treatment strategy. Ablation of pathways and other re-entrant targets was the only intervention that decreased AF recurrence in children and young adults.

While published guidelines are useful in the care of patients with long-QT syndrome, it can be difficult to decide how to apply the guidelines to individual patients, particularly those with intermediate risk. We explored the diversity of opinion among 24 clinicians with expertise in long-QT syndrome. Experts from various regions and institutions were presented with 4 challenging clinical scenarios and asked to provide commentary emphasizing why they would make their treatment recommendations. All 24 authors were asked to vote on case-specific questions so as to demonstrate the degree of consensus or divergence of opinion. Of 24 authors, 23 voted and 1 abstained. Details of voting results with commentary are presented. There was consensus on several key points, particularly on the importance of the diagnostic evaluation and of β-blocker use. There was diversity of opinion about the appropriate use of other therapeutic measures in intermediate-risk individuals. Significant gaps in knowledge were identified.

1. Benjamin H. Hammond, MD* 2. Kenneth G. Zahka, MD* 3. Peter F. Aziz, MD* 1. *Department of Pediatric Cardiology, Cleveland Clinic Children’s, Pediatric Institute, Cleveland Clinic Foundation, Cleveland, OH * Abbreviations: ACC: : American College of Cardiology AED: : automated external defibrillator ARVC: : arrhythmogenic right ventricular cardiomyopathy CPVT: : catecholaminergic polymorphic ventricular tachycardia ECG: : electrocardiogram HCM: : hypertrophic cardiomyopathy ICD: : implantable cardioverter-defibrillator LQTS: : long QT syndrome LVNC: : left ventricular noncompaction cardiomyopathy LVOT: : left ventricular outflow tract RV: : right ventricle SADS: : sudden arrhythmic death syndrome SCA: : sudden cardiac arrest SCD: : sudden cardiac death TdP: : torsade de pointes VA: : ventricular arrhythmia VT: : ventricular tachycardia 1. There is a broad differential diagnosis to be considered in cases of sudden cardiac arrest, sudden cardiac death. 2. Timely diagnosis can circumvent progression to cardiac arrest in at-risk individuals. 3. All children should be screened and testing should be reserved for those with increased risk. After completing this article, readers should be able to: 1. Assess risk of sudden cardiac arrest/sudden cardiac death (SCA/SCD) with a screening history and physical examination. 2. Identify the mechanisms of distinct etiologies of SCA/SCD. 3. Recognize findings consistent with risk of SCA/SCD on a 12-lead electrocardiogram. 4. Address the concerns and questions of individuals and families after SCA/SCD. Sudden cardiac death (SCD) or sudden cardiac arrest (SCA) may occur in populations known to be at high risk or in individuals previously unrecognized to harbor underlying disease. This review focuses on the pediatrician’s role in identifying the latter group. SCA is a “severe malfunction or cessation of the electrical and mechanical activity of the heart, resulting in almost instantaneous loss of consciousness and collapse” that precedes SCD. (1) SCD is defined as rapid, unexpected death from cardiac causes that occurs within 1 hour of symptoms. (2) SCD that is known to be secondary to a primary arrhythmia is termed sudden arrhythmic death syndrome (SADS) . SCA is a common cause of death in adults, with the annual incidence estimated to be approximately 100 per 100,000, with variation seen with age, sex, and race. (3) These deaths are predominantly associated with coronary artery disease. In individuals younger than 18 years, SCA is much less common, with an estimated annual incidence of out-of-hospital cardiac arrest of 8.3 per 100,000 person-years. (4 …

Background Danon disease is a rare X-linked storage disorder characterized by hypertrophic cardiomyopathy leading to arrhythmias and heart failure. A preexcitation pattern on electrocardiogram (ECG) has been described in these patients, however, invasive studies to distinguish between Wolff-Parkinson-White syndrome syndrome and fasciculoventricular pathways (FVP) are limited. Objectives The purpose of this study was to delineate the electrophysiological cardiac abnormalities in patients with Danon disease and to describe the presence of FVP in this population. Methods We performed a retrospective study of all patients with a confirmed diagnosis of Danon disease presenting to a single center from May 2005 to May 2018. Baseline demographics, clinical characteristics, ECG findings, and electrophysiology study (EPS) results were collected. Results Ten patients with Danon disease (30% male, average age 17.4 years) were identified. Seven patients (70%) had tachyarrhythmias including five with atrial arrhythmias and six with nonsustained ventricular tachycardia. Preexcitation pattern on ECG was found in four (40%) patients. Of these, two underwent an EPS which confirmed the presence of an FVP. One patient underwent an adenosine challenge which supported a FVP. Implantable cardioverter defibrillator was placed in five patients for primary prevention with no patients receiving an appropriate discharge. Over a follow-up of 5.3 years, five underwent heart transplantation. Conclusions This study reports a high incidence of FVP in patients with Danon disease and preexcitation. It underscores an alternate etiology of preexcitation in this population which can potentially be diagnosed without invasive EPS testing. Future multicenter studies are needed to expand this experience.

Congenital long QT syndrome (LQTS) is an inherited channelopathy that can manifest as sudden cardiac death in the absence of morphologic heart disease. Corrected QT interval (QTc) is typically calculated using Bazett’s formula of QTc = QT interval/√RR on the 12-lead electrocardiogram (ECG). Suspicion for the diagnosis of LQTS should be based upon a QTc exceeding 470 milliseconds (ms) in males and 480 ms in females. About 75–80% of patients with LQTS have identifiable genetic variants with variable penetrance. The most common subtype is LQT1 in which arrhythmia is triggered by exercise, particularly swimming. The less common subtypes are LQT2 and LQT3 in which arrhythmias are triggered by auditory stimuli and during sleep, respectively. The mainstay of treatment for LQTS is beta blockers which have been shown to reduce the risk of sudden cardiac death. Nadolol and propranolol have been demonstrated to have the best efficacy. Sports participation guidelines have become less restrictive as studies have demonstrated that episodes of sudden cardiac death are not as high as previously thought, particularly with avoidance of QT prolonging medications and adherence to proper medical treatment with beta blockers. It is crucial to review risk stratification with athletes with LQTS and utilize shared decision making to come to a consensus for sports participation on a case-by-case basis. Safety precautions at practices and games must be utilized such as having an AED on-site, avoidance of dehydration, and establishing an emergency action plan with the appropriate school/team officials.

Introduction: The safety of vigorous exercise for individuals with appropriately-treated LQTS remains unproven, and physical activity practices in this population have not been described. Methods: LIVE-LQTS prospectively enrolled individuals age 8-60 years with overt LQTS or gene mutation carriers. Participants (or parents, for children) answered surveys describing activity patterns. Vigorous exercise was defined as > 6 METS for > 60 hours per year. Clinical and demographic data were derived from medical record review. Results: Among 1554 participants, 804 (52%) reported exercising vigorously, 473 of these competitively, 577 (37%) exercising at moderate, and 173 (11%) at low levels. Seven percent of those working describe jobs more active than walking, including 10 in protective services and 19 in sports/coaching. Over 90% are genotype positive, 57% are phenotype positive at rest and an additional 16% have exercise-induced QT prolongation. Forty four percent have had documented ventricular arrhythmias or syncope. Eighty-four percent are appropriately treated with either beta-blockers, ICD, and/or sympathectomy, although among beta-blocked patients, only 60% are on the most effective agents. Among adults, BMI was significantly lower among the vigorous exercisers. Conclusion: While the high percentage of vigorous exercisers seen in this study may not represent all patients with LQTS due to self-selection for study participation, many patients with LQTS are engaged in vigorous exercise or competitive athletics. Prospective follow up of this cohort is ongoing and will determine safety of vigorous exercise through comparison of arrhythmic outcomes in vigorous exercisers vs moderate/low level exercisers.

The primary goal of this study was to evaluate the implant experience and midterm results of subcutaneous implantable cardioverter-defibrillators (S-ICDs) in pediatric patients and those with congenital heart disease.The S-ICD was developed to avoid the lead-related complications associated with transvenous systems. The absence of intravascular or intracardiac components offers potential advantages to pediatric patients and those with congenital heart disease.This international, multicenter, retrospective, standard-of-care study was conducted through the PediatricCongenital Electrophysiology Society. Complications at 30 and 360 days, inappropriate shocks, and delivery of appropriate therapy were assessed.The study included 115 patients with a median follow-up of 32 (19 to 52) months. Median age was 16.7 years (14.8 to 19.3 years), 29% were female, and 55% had a primary prevention indication. Underlying disease substrate was cardiomyopathy (40%), structural heart disease (32%), idiopathic ventricular fibrillation (16%), and channelopathy (13%). The complication rate was 7.8% at 30 days and 14.7% at 360 days. Overall, inappropriate shocks occurred in 15.6% of patients, with no single clinical characteristic reaching statistical significance. At implant, 97.9% of patients had successful first shock conversion with 96% requiring ≤65 J. Appropriate therapy was delivered to 11.2% of patients with an annual incidence of 3.9% and an acute first shock conversion success rate of 92.5%.This study found that in a heterogeneous population of pediatric patients and those with congenital heart disease, the S-ICD had comparable rates of complications, inappropriate shocks, and conversion efficacy compared with previously published studies on transvenous systems in similar populations.

Background: Insight into type 5 long QT syndrome (LQT5) has been limited to case reports and small family series. Improved understanding of the clinical phenotype and genetic features associated with rare KCNE1 variants implicated in LQT5 was sought through an international multicenter collaboration. Methods: Patients with either presumed autosomal dominant LQT5 (N = 229) or the recessive Type 2 Jervell and Lange-Nielsen syndrome (N = 19) were enrolled from 22 genetic arrhythmia clinics and 4 registries from 9 countries. KCNE1 variants were evaluated for ECG penetrance (defined as QTc >460 ms on presenting ECG) and genotype-phenotype segregation. Multivariable Cox regression was used to compare the associations between clinical and genetic variables with a composite primary outcome of definite arrhythmic events, including appropriate implantable cardioverter-defibrillator shocks, aborted cardiac arrest, and sudden cardiac death. Results: A total of 32 distinct KCNE1 rare variants were identified in 89 probands and 140 genotype positive family members with presumed LQT5 and an additional 19 Type 2 Jervell and Lange-Nielsen syndrome patients. Among presumed LQT5 patients, the mean QTc on presenting ECG was significantly longer in probands (476.9±38.6 ms) compared with genotype positive family members (441.8±30.9 ms, P P =0.001). Event incidence did not differ significantly for Type 2 Jervell and Lange-Nielsen syndrome patients relative to the overall heterozygous cohort (10.5% [2/19]; HR 1.7 [95% CI, 0.3–10.8], P =0.590). The cumulative prevalence of the 32 KCNE1 variants in the Genome Aggregation Database, which is a human database of exome and genome sequencing data from now over 140 000 individuals, was 238-fold greater than the anticipated prevalence of all LQT5 combined (0.238% vs 0.001%). Conclusions: The present study suggests that putative/confirmed loss-of-function KCNE1 variants predispose to QT prolongation, however, the low ECG penetrance observed suggests they do not manifest clinically in the majority of individuals, aligning with the mild phenotype observed for Type 2 Jervell and Lange-Nielsen syndrome patients.

NKX2-5 is a cardiac homeobox gene that is pivotal in the development of the myocardium and conduction system.1 Cardiac structural abnormalities and conduction disturbances have been described in the pediatric population with NKX2-5 mutations in recent years.2 Of the structural abnormalities, atrial septal defect (ASD) is the signature phenotype, although conotruncal defects, systemic and pulmonary outflow obstructions, and cardiomyopathies have also been reported.3, 4 Additionally, sudden death has been reported in patients with these mutations.5 Adult literature has demonstrated the presence of NKX2-5 mutations in patients with lone atrial fibrillation presenting in their early 40s.6 However, there are no current reports of patients with NKX2-5 mutations presenting with atrial fibrillation in teenage years or young adulthood. A recent study described the presence of ventricular tachycardia found incidentally on a pacemaker check in a patient with a strong family history of sudden death and NKX2-5 mutations.7 We previously published a paper describing a novel mutation in the NKX2-5 gene in a family with a history of sudden death.8 Our initial report described 2 male siblings with familial NKX2-5 mutation who had congenital heart defects, left ventricular noncompaction cardiomyopathy, and bradyarrhythmias as children. We now present an update on these 2 patients as young adults who went on to develop tachyarrhythmias prompting implantable cardioverter defibrillator (ICD) therapy, highlighting the importance of maintaining a high index of suspicion and considering increased surveillance for potentially dangerous rhythm abnormalities in this patient population.

Inherited ion channelopathies have come to the forefront as a significant cause of sudden cardiac death (SCD) in pediatric patients with structurally normal hearts. Implantable cardioverter-defibrillator (ICD) placement can be a life-saving primary preventative therapy, but because of actors inherent in the pediatric population, careful thought must be given to the specific indications for placement in each patient. The most common inherited ion channelopathies are long QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia. All have the potential to cause SCD. However, thanks to current research, more is now known about the range of phenotypes present within each disorder and also the benefits that medical therapy can provide. Risk stratification can allow clinicians to best predict which patients may most benefit from a primary preventative ICD while at the same time avoid placement in the larger group who may remain asymptomatic with the aid of medical therapy or even simply observation.

Sudden cardiac death in the young (SCDY) spans gender, race, ethnicity, and socioeconomic class. The loss of any pediatric patient is a matter of national and international public health concern, and focused efforts should be aimed at preventing these burdensome tragedies. Prepared by members of the Cardiac Safety Research Consortium, this White Paper summarizes and reports the dialogue at the second Think Tank related to the issues and the proposed solutions for the development of a national resource for screening and prevention of SCDY. This Think Tank, sponsored by the Cardiac Safety Research Consortium and the United States Food and Drug Administration, convened on February 18, 2016, in Miami, FL, to identify and resolve the barriers that prevent early identification of patients at risk for SCDY. All potential stakeholders including national and international experts from industry, medicine, academics, engineering, and community advocacy leaders had an opportunity to share ideas and collaborate.

Objectives This study sought to characterize risk in children with Wolff-Parkinson-White (WPW) syndrome by comparing those who had experienced a life-threatening event (LTE) with a control population. Background Children with WPW syndrome are at risk of sudden death. Methods This retrospective multicenter pediatric study identified 912 subjects ≤21 years of age with WPW syndrome, using electrophysiology (EPS) studies. Case subjects had a history of LTE: sudden death, aborted sudden death, or atrial fibrillation (shortest pre-excited RR interval in atrial fibrillation [SPERRI] of ≤250 ms or with hemodynamic compromise); whereas subjects did not. We compared clinical and EPS data between cases and subjects. Results Case subjects (n = 96) were older and less likely than subjects (n = 816) to have symptoms or documented tachycardia. Mean age at LTE was 14.1 ± 3.9 years of age. The LTE was the sentinel symptom in 65%, consisting of rapidly conducted pre-excited atrial fibrillation (49%), aborted sudden death (45%), and sudden death (6%). Three risk components were considered at EPS: SPERRI, accessory pathway effective refractory period (APERP), and shortest paced cycle length with pre-excitation during atrial pacing (SPPCL), and all were shorter in cases than in control subjects. In multivariate analysis, risk factors for LTE included male sex, Ebstein malformation, rapid anterograde conduction (APERP, SPERRI, or SPPCL ≤250 ms), multiple pathways, and inducible atrial fibrillation. Of case subjects, 60 of 86 (69%) had ≥2 EPS risk stratification components performed; 22 of 60 (37%) did not have EPS-determined high-risk characteristics, and 15 of 60 (25%) had neither concerning pathway characteristics nor inducible atrioventricular reciprocating tachycardia. Conclusions Young patients may experience LTE from WPW syndrome without prior symptoms or markers of high-risk on EPS.

Background/Purpose: Many young patients with congenital heart disease (CHD), cardiomyopathies or inherited arrhythmia syndromes are at an increased risk for sudden cardiac death (SCD). These patients have been restricted from sports participation to various degrees given the perceived risk. We sought to determine the prevalence of counseling about sports participation by pediatric cardiologists, the effectiveness of counseling, the adherence to published recommendations and the rate of participation in sports by young patients with heart disease. Methods: Using a cross-sectional research model, we gave IRB-approved surveys about sports participation to patients age 6 to …

Little is known about lone atrial fibrillation (AF) in pediatrics and its risk factors due to low prevalence. We sought to determine risk factors and estimate recurrence rates in children with lone AF using a large clinical database. Using the Explorys clinical database, we retrospectively identified patients who were below 20 years of age at the time of their AF diagnosis. Patients with congenital heart disease, cardiomyopathy, prior open heart surgery, or thyroid disease were excluded. Out of 7,969,230 children identified, 1910 had AF and 1570 met the definition of lone AF. The prevalence of lone AF was 7.5 per 100,000 children. In comparison to young children (0-4 years), risk for lone AF increased with age (adjusted odds ratio (aOR) 1.2 [95% CI 0.9-1.5, P = 0.21] in those 5-9 years, aOR 1.7 [95% CI 1.3-2.1, P

Implantable loop recorders are commonly used to sense arrhythmias. The purpose of this study is to assess the P- and R-wave amplitudes at implantation (I) and follow-up (F) following insertion of the Reveal LINQ™ Insertable Cardiac Monitor (Medtronic, Minneapolis, MN) in an institutional review board-approved, multicenter study performed on pediatric patients younger than 18 years old. Collected data included demographics, presence of congenital heart disease (CHD), P- and R-wave-sensed amplitude at I and F, and the method of implant (i.e. mapping or standard.) P waves were manually measured and R-wave sensing was recorded by the device. A total of 87 patients had a Reveal LINQ™ (Medtronic, Minneapolis, MN) device implanted; the mean patient age was 11.8 years (0.5 years to 18 years) with 48% of patients being female and 19% of patients having CHD; mapping was used in 43% of patients. The Reveal LINQ™ (Medtronic, Minneapolis, MN) experienced no change in average sensed R-wave amplitude at either I or F (1.28 mV vs 1.26 mV, p = NS). There was no difference in sensed R-wave amplitude noted with or without mapping used at I (1.29 mV vs 1.26 mV, p = NS) or F (1.48 mV vs 1.18 mV, p = NS). Additionally, no difference could be found in R-wave sensing of patients with CHD or without CHD at I (1.26 mV vs 1.4 mV, p = NS) or F (1.32 mV vs 1.32 mV, p = NS). R-wave sensing trended towards being inversely proportional to patient body surface area (BSA) (p = NS). P waves were detected on 48% of tracings in all patients at I and/or F, irrespective of whether the Reveal LINQ™ (Medtronic, Minneapolis, MN) device was placed with mapping. The R wave was (0.37-3.5 mV) at I and (0.3-3 mV) (p = NS) at F when P waves were detected. From these results, it can be said that the Reveal LINQ™ Insertable Cardiac Monitor (Medtronic, Minneapolis, MN) has an excellent ability to sense R-wave amplitude in pediatric patients. No significant difference in the sensing ability of the device could be identified with respect to the presence of CHD, use of mapping or BSA. P waves tended to be identified when there was a higher baseline R-wave amplitude.

Abrupt loss of ventricular preexcitation on noninvasive evaluation, or nonpersistent preexcitation, in Wolff-Parkinson-White syndrome (WPW) is thought to indicate a low risk of life-threatening events.The purpose of this study was to compare accessory pathway (AP) characteristics and occurrences of sudden cardiac arrest (SCA) and rapidly conducted preexcited atrial fibrillation (RC-AF) in patients with nonpersistent and persistent preexcitation.Patients 21 years or younger with WPW and invasive electrophysiology study (EPS) data, SCA, or RC-AF were identified from multicenter databases. Nonpersistent preexcitation was defined as absence/sudden loss of preexcitation on electrocardiogram, Holter monitoring, or exercise stress test. RC-AF was defined as clinical preexcited atrial fibrillation with shortest preexcited R-R interval (SPERRI) ≤ 250 ms. AP effective refractory period (APERP), SPERRI at EPS , and shortest preexcited paced cycle length (SPPCL) were collected. High-risk APs were defined as APERP, SPERRI, or SPPCL ≤ 250 ms.Of 1589 patients, 244 (15%) had nonpersistent preexcitation and 1345 (85%) had persistent preexcitation. There were no differences in sex (58% vs 60% male; P=.49) or age (13.3±3.6 years vs 13.1±3.9 years; P=.43) between groups. Although APERP (344±76 ms vs 312±61 ms; P.001) and SPPCL (394±123 ms vs 317±82 ms; P.001) were longer in nonpersistent vs persistent preexcitation, there was no difference in SPERRI at EPS (331±71 ms vs 316±73 ms; P=.15). Nonpersistent preexcitation was associated with fewer high-risk APs (13% vs 23%; P.001) than persistent preexcitation. Of 61 patients with SCA or RC-AF, 6 (10%) had nonpersistent preexcitation (3 SCA, 3 RC-AF).Nonpersistent preexcitation was associated with fewer high-risk APs, though it did not exclude the risk of SCA or RC-AF in children with WPW.

Obesity is associated with additional left ventricular hypertrophy (LVH) in adults with hypertrophic cardiomyopathy (HCM). It is not known whether obesity can lead to further LVH in children with HCM. Echocardiographic LV dimensions were determined in 504 children with HCM. Measurements of interventricular septal thickness (IVST) and posterior wall thickness (PWT), and patients' weight and height were recorded. Obesity was defined as a body mass index (BMI) ≥ 99th percentile for age and sex. IVST data was available for 498 and PWT data for 484 patients. Patient age ranged from 2 to 20 years (mean ± SD, 12.5 ± 3.9) and 340 (68%) were males. Overall, patient BMI ranged from 7 to 50 (22.7 ± 6.1). Obesity (BMI 18-50, mean 29.1) was present in 140 children aged 2-19.6 (11.3 ± 4.1). The overall mean IVST was 20.5 ± 9.6 mm and the overall mean PWT was 11.0 ± 8.4 mm. The mean IVST in the obese patients was 21.6 ± 10.0 mm and mean PWT was 13.3 ± 14.7 mm. The mean IVST in the non-obese patients was 20.1 ± 9.5 mm and mean PWT was 10.4 ± 4.3 mm. Obesity was not significantly associated with IVST (p = 0.12), but was associated with increased PWT (0.0011). Obesity is associated with increased PWT but not IVST in children with HCM. Whether obesity and its impact on LVH influences clinical outcomes in children with HCM needs to be studied.

Predictors of risk of lethal arrhythmic events (LAE) is poorly understood and may differ from adults in children with hypertrophic cardiomyopathy (HCM).The purpose of this study was to determine predictors of LAE in children with HCM.A retrospective data collection was performed on 446 children and teenagers 20 years and younger (290 [65%] male; mean age 10.1 ± 5.7 years) with idiopathic HCM from 35 centers. Patients were classified as group 1 (HCM with LAE) if having a secondary prevention implantable cardioverter-defibrillator (ICD) or primary prevention ICD with appropriate interventions or group 2 (HCM without LAE) if having a primary prevention ICD without appropriate interventions.There were 152 children (34%) in group 1 and 294 (66%) in group 2. Risk factors for group 1 by univariate analysis were septal thickness, posterior left ventricular (LV) wall thickness, lower LV outflow gradient, and Q wave3 mm in inferior electrocardiographic leads. Factors not associated with LAE were family history of SCD, abnormal blood pressure response to exercise, and ventricular tachycardia on ambulatory electrocardiographic monitoring. Risk factors for SCD by multivariate analysis were age at ICD placement (hazard ratio [HR] 0.9; P = .0025), LV posterior wall thickness z score (HR 1.02; P.005), and LV outflow gradient30 mm Hg (HR 2.0; P.006). LV posterior wall thickness z score ≥ 5 was associated with LAE.Risk factors for LAE appear different in children compared to adults. Conventional adult risk factors were not significant in children. Further prospective studies are needed to improve risk stratification for LAE in children with HCM.

Current estimates of the incidence of tachyarrhythmias in infants rely on clinical documentation and may not reflect the true rate in the general population. Our aim was to describe the epidemiology of tachyarrhythmia detected in a large cohort of infants using direct-to-consumer heart rate (HR) monitoring.Data were collected from Owlet Smart Sock devices used in infants in the US with birthdates between February 2017 and February 2019. We queried the HR data for episodes of tachyarrhythmia (HR of ≥240 bpm for60 seconds).The study included 100 949 infants (50.8% male) monitored for more than 200 million total hours. We identified 5070 episodes of tachyarrhythmia in 2508 infants. The cumulative incidence of tachyarrhythmia in our cohort was 2.5% over the first year of life. The median age at the time of the first episode of tachyarrhythmia was 36 days (range, 1-358 days). Tachyarrhythmia was more common in infants with congenital heart disease (4.0% vs 2.4%; P = .015) and in females (2.7% vs 2.0%; P .001). The median length of an episode was 7.3 minutes (range, 60 seconds to 5.4 hours) and the probability of an episode lasting longer than 45 minutes was 16.8% (95% CI, 15.4%-18.3%).We found the cumulative incidence of tachyarrhythmia among infants using direct-to-consumer HR monitors to be higher than previously reported in studies relying on clinical diagnosis. This finding may represent previously undetected subclinical disease in young infants, the significance of which remains uncertain. Clinicians should be prepared to discuss these events with parents.

Congenital Long QT Syndrome (LQTS) results in abnormal ventricular repolarization in patients with otherwise structurally normal hearts. Following the initial clinical descriptions of LQTS, there has been a great deal of investigation into the genetic etiology and pathophysiology of these entities, with the goal of improved screening tools and understanding of associated risks. Through this work, heart rhythm experts continue to revise their recommendations regarding sports eligibility. We review the evolution of sports participation recommendations for LQTS.

Background Radiation exposure related to medical procedures carries known medical risk. Electrophysiology (EP) and catheter ablation procedures are traditionally performed under fluoroscopic guidance. Three-dimensional (3D) electroanatomical navigation systems decrease or eliminate fluoroscopy use in EP procedures. Objective The aim of this study was to assess the efficacy and outcome of a minimal or no fluoroscopic electroanatomical mapping approach for catheter ablations for supraventricular tachycardia (SVT) in the pediatric population. Methods Patients were identified through our EP database. A retrospective chart review was performed at a single institution. Results Sixty-three pediatric patients underwent catheter ablations with a minimal fluoroscopic and 3D electroanatomical mapping using CARTO-3 system (Biosense Webster, Diamond Bar, CA, USA) between October 2012 and March 2015. We selected 20 age-matched patients who underwent ablations for SVT by the same operator prior to October 2012 with fluoroscopy use as our control group. The mean age in the study and control group was 13.9 years and 13.7 years, respectively. Mean procedure time was 208.7 minutes and 217.2 minutes in the study and control group (P = NS). Thirty-four (54%) in the study group had no fluoroscopy use. Mean fluoroscopy time was 4.1 minutes versus 35.4 minutes between the study and the control group (P < 0.001). Radiation dose was 6.7 mGy versus 209.3 mGy between the study and the control group (P < 0.001). Acute procedural success was achieved in 95% and 90% of patients in the study and control groups, respectively. On follow-up, the recurrence rate was 5.3% in the study group and 5.6% in the control group. Conclusion Catheter ablation for SVT in children can be successfully performed in patients with normal cardiac anatomy using minimal or no fluoroscopy with favorable outcomes.

Implantable cardioverter-defibrillators (ICDs) reduce the incidence of sudden cardiac death (SCD) in adults with end-stage heart failure; however, their efficacy in pediatric patients awaiting heart transplantation is not well established.This study sought to investigate the role of ICDs in preventing SCD and waiting list mortality as well as to determine risk factors for SCD in pediatric patients listed for heart transplantation.We queried the United Network for Organ Sharing database for all pediatric patients (age ≤18 years) listed for heart transplantation (2005-2014). The Cox proportional hazards model was used to identify risk factors for SCD and all-cause mortality.A total of 5072 mostly White (55%) male (55%) patients (mean age 6.2 ± 6.5 years) were identified, of whom 426 (8.3%) had ICD at listing. At 6 months, 65% underwent heart transplantation, 15% died (4% died of SCD), and 20% were alive. In a multivariable model, United Network for Organ Sharing status 1B (hazard ratio [HR] 0.52; 95% confidence interval [CI] 0.29-0.95; P = .03), myocarditis (HR 0.19; 95% CI 0.05-0.77; P = .02), restrictive cardiomyopathy (HR 0.19; 95% CI 0.05-0.76; P = .02), and dilated cardiomyopathy (HR 0.32; 95% CI 0.20-0.52; P.001) were associated with lower SCD risk, while younger age at listing (HR 0.94 per year; 95% CI 0.90-0.98; P = .003) was associated with higher SCD risk. ICD at listing was not associated with reduced SCD (P = .12), all-cause mortality, or delisting (P = .57).In pediatric patients listed for heart transplantation, the risk of SCD remains low and does not differ between patients with and without an ICD at listing.

Hypertrophic cardiomyopathy (HCM) is a complex cardiovascular disease with a wide spectrum of phenotypic variations. The symptomatology and severity of HCM is less well defined in children as age specific norms for most modalities are extrapolated from adult data. Furthermore, the role of left

The population of patients with congenital heart disease (CHD) is continuously increasing with more and more patients reaching adulthood. A significant portion of these young adults will suffer from arrhythmias due to the underlying congenital heart defect itself or as a sequela of interventional or surgical treatment. The medical community will encounter an increasing challenge as even most of the individuals with complex congenital heart defects nowadays become young adults. Within the past 20 years, management of patients with arrhythmias has gained remarkable progress including pharmacological treatment, catheter ablation, and device therapy. Catheter ablation in patients with CHD has paralleled the advances of this technology in pediatric and adult patients with structurally normal hearts. Growing experience and introduction of new techniques like the 3D mapping systems into clinical practice have been particularly beneficial for this growing population of patients with abnormal cardiac anatomy and physiology. Finally, device therapies allowing maintanence of chronotropic competence and AV conduction, improving haemodynamics by cardiac resynchronization, and preventing sudden death are increasingly used. For pharmacological therapy, ablation procedures, and device therapy decision making requires a deep understanding of the individual pathological anatomy and physiology as well as detailed knowledge on natural history and long-term prognosis of our patients. Composing expert opinions from cardiology and paediatric cardiology as well as from non-invasive and invasive electrophysiology this position paper was designed to state the art in management of young individuals with congenital heart defects and arrhythmias.

BACKGROUND: Little is known about the predictors of pre–emergency medical service (EMS) automated external defibrillator (AED) application in pediatric out-of-hospital cardiac arrests. We sought to determine patient- and neighborhood-level characteristics associated with pre-EMS AED application in the pediatric population. METHODS: We reviewed prospectively collected data from the Cardiac Arrest Registry to Enhance Survival on pediatric patients (age >1 to ≤18 years old) who had out-of-hospital nontraumatic arrest (2013–2015). RESULTS: A total of 1398 patients were included in this analysis (64% boys, 45% white, and median age of 11 years old). An AED was applied in 28% of the cases. Factors associated with pre-EMS AED application in univariable analyses were older age (odds ratio [OR]: 1.9; 12–18 years old vs 2–11 years old; P < .001), white versus African American race (OR: 1.4; P = .04), public location (OR: 1.9; P < .001), witnessed status (OR: 1.6; P < .001), arrests presumed to be cardiac versus respiratory etiology (OR: 1.5; P = .02) or drowning etiology (OR: 2.0; P < .001), white-populated neighborhoods (OR: 1.2 per 20% increase in white race; P = .01), neighborhood median household income (OR: 1.1 per $20 000 increase; P = .02), and neighborhood level of education (OR: 1.3 per 20% increase in high school graduates; P = .006). However, only age, witnessed status, arrest location, and arrests of presumed cardiac etiology versus drowning remained significant in the multivariable model. The overall cohort survival to hospital discharge was 19%. CONCLUSIONS: The overall pre-EMS AED application rate in pediatric patients remains low.

This review aims to summarize and provide an update of evidence for cardiac resynchronization therapy (CRT) in pediatric and adult congenital heart disease (CHD). CRT is a valuable tool in the treatment of heart failure in the setting of CHD. Current evidence points toward the ability of this therapy to increase hemodynamic parameters and reduce heart failure-related symptoms. Within the CHD population, patients with systemic left ventricles appear to benefit the most from CRT. Utilization of CRT in CHD has been technically difficult due to the complexity and variety of anatomic substrates. However, lateral thoracotomies and other advances have made implantation more feasible. The most up-to-date evidence continues to support the use of CRT in the heterogeneous population of CHD with careful and individualized patient selection. Further studies are needed to evaluate the utility of CRT for specific anatomic substrates within this population.

BACKGROUND AND OBJECTIVES: Previous estimates of sudden cardiac death in children and young adults vary significantly, and population-based studies in the United States are lacking. We sought to estimate the incidence, causes, and mortality trends of sudden cardiac death in children and young adults (1–34 years). METHODS: Demographic and mortality data based on death certificates for US residents (1–34 years) were obtained (1999–2015). Cases of sudden death and sudden cardiac death were retrieved by using the International Classification of Diseases, 10th Revision codes. RESULTS: A total of 1 452 808 subjects aged 1 to 34 years died in the United States, of which 31 492 (2%) were due to sudden cardiac death. The estimated incidence of sudden cardiac death is 1.32 per 100 000 individuals and increased with age from 0.49 (1–10 years) to 2.76 (26–34 years). During the study period, incidence of sudden cardiac death declined from 1.48 to 1.13 per 100 000 (P < .001). Mortality reduction was observed across all racial and ethnic groups with a varying magnitude and was highest in children aged 11 to 18 years. Significant disparities were found, with non-Hispanic African American individuals and individuals aged 26 to 34 years having the highest mortality rates. The majority of young children (1–10 years) died of congenital heart disease (n = 1525, 46%), whereas young adults died most commonly from ischemic heart disease (n = 5075, 29%). CONCLUSIONS: Out-of-hospital sudden cardiac death rates declined 24% from 1999 to 2015. Disparities in mortality exist across age groups and racial and ethnic groups, with non-Hispanic African American individuals having the highest mortality rates.

Little is known about the incidence of permanent pacemaker (PPM) implantation after heart transplantation (HTx) in the pediatric population.The purpose of this study was to investigate the incidence, predictors, and outcomes of acute need for PPM implantation in pediatric HTx recipients.We queried the United Network for Organ Sharing (UNOS) database for all pediatric (age18 years) patients who received HTx (1994-2014). Regression models are reported for prediction of PPM implantation.A total of 6156 patients were analyzed, of whom 69 (1.1%) required posttransplant PPM implantation acutely. PPM use decreased over the study period (hazard ratio [HR] 0.95, P = .01). Compared with the non-PPM group, PPM group was more likely to be older (10 vs 5.0 years, P.001), used antiarrhythmics (35.6% vs 18.3%, P = .006), required intraaortic balloon pump (2.9% vs 0.5%, P = .049), and had undergone biatrial anastomosis (68.1% vs 48.2%, P = .007). In a multivariable model, PPM implantation was predicted by higher donor age (HR 1.05, P = .002), biatrial anastomosis (HR 2.53, P = .04) and antiarrhythmic use (HR 2.12, P = .02). After adjusting for baseline characteristics, PPM recipients were at increased risk for posttransplant infection (47.8% vs 26.4%, P = .001) and dialysis (15.9% vs 6.6%, P = .003). Adjusted graft survival did not differ between the 2 groups (P = .78).Acute postoperative PPM implantation in pediatric HTx recipients is rare and has decreased over time. Acute PPM use is associated with biatrial anastomosis, antiarrhythmic use, and older donor age. Although PPM recipients had higher incidences of infections and dialysis, PPM implantation did not adversely impact survival.