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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.

Catheter ablation of accessory pathways (APs) in Ebstein anomaly (EA) has been associated with a high recurrence risk.The purpose of this study was to compare outcomes of AP ablation in EA in an early (1990-2004) vs a recent (2005-2019) era and identify variables associated with recurrence.A retrospective review of all catheter ablations for supraventricular tachycardia in EA at our institution was performed.We identified 76 patients with median (25th-75th quartiles) age 9 (2.6-13.3) years. Of these patients, 52 had AP alone, 12 had atrial flutter, 3 had atrioventricular nodal reentrant tachycardia, and 9 had AP plus at least 1 additional arrhythmia. Of the 61 patients with APs, a total of 78 separate APs were identified: 40 right-sided, 37 septal, and 1 left-sided. Acute success for AP first procedure was 89% and did not differ between early and recent eras (89% vs 88%; P = .48). However, 19 patients (31%) required repeat procedures (average 1.4 per patient) due to AP recurrence or ablation failure at first attempt. In comparison to early era, recent era ablations had significantly lower recurrence rates at 1 year (62% vs 19%; P = .005). At median follow-up of 2.5 (0.2-7) years, ultimate AP elimination after all procedures was 93%. Younger age at time of electrophysiological study (2 vs 12-47 years: hazard ratio [HR] 7.3; P = .003) and ablation era (early era vs recent era: HR 3.65; P = .009) predicted recurrence.Outcomes for AP ablation in patients with EA have improved, but there is still a relatedly high recurrence risk requiring repeat procedures.

Background Transvenous permanent pacemaker (PPM) implantation is an available option for Fontan patients with sinus node dysfunction. However, the thrombogenic potential of leads within the Fontan baffle is unknown. Objective The purpose of this study was to compare the clot burden in Fontan patients with a transvenous atrial PPM to those without a PPM and those with an epicardial PPM. Methods This was a retrospective cohort study of all transvenous PPM implantations in Fontan patients followed at our institution (2000–2018). We performed frequency matching on Fontan type and age group. Primary outcome was identification of intracardiac clot, pulmonary embolus, or embolic stroke. Results Of 1920 Fontan patients, 58 patients (median age 23 years; interquartile range [25th–75th percentiles] 14–33) at the time of transvenous PPM implantation and 174 matched subjects formed our cohort. The type of Fontan performed in case subjects was right atrium–pulmonary artery or right atrium–right ventricle conduit (54%), lateral tunnel (43%), and extracardiac (3%). The cumulative incidence of clot was highest in patients with transvenous PPM, followed by patients with epicardial PPM and no PPM (1.2 vs 0.87 vs 0.67 per 100 person-years of follow-up, respectively). In multivariable analysis, anticoagulation and/or antiplatelet therapy were protective against clot and resulted in reduction of clot risk by 3-fold (incidence rate ratio 0.33; 95% confidence interval 0.21–0.53; P Conclusion In a large cohort of Fontan patients matched for age and Fontan type, patients with transvenous PPM had a higher but not statistically significant incidence of clot compared to those with no PPM and epicardial PPM. Patients treated with warfarin/aspirin had lower clot risk.

Ventricular fibromas frequently present with life-threatening ventricular tachycardia (VT) or ventricular fibrillation (VF) in children. The long-term risk of sustained ventricular arrhythmias after surgical resection is unknown.The aims of this study were to quantify the VT/VF risk after surgical resection and to examine the results of early (during index surgical hospitalization) and late (≥3 months after surgery) postoperative ventricular stimulation (V-stim) studies.We performed a retrospective cohort study of all patients with ventricular fibromas who underwent surgical resection at our institution (2000-2020). The primary outcome was defined as recurrent VT/VF ≥3 months after index surgical resection.Forty-six patients with a median age at surgery of 2 years (range 0.3-18.9 years) formed our study cohort. Indications for surgery included cardiac arrest in 11 (24%), sustained VT in 16 (35%), premature ventricular contractions/nonsustained VT in 10 (22%), and hemodynamic abnormalities in 9 (20%). Of the 11 patients who presented with cardiac arrest, 4 underwent pre-resection implantable cardioverter-defibrillator (ICD) implantation, all of which were explanted at the time of surgery. An early postoperative V-stim study was performed in 26 (57%) patients, and all were negative for inducible VT/VF. Of the 13 late postoperative V-stim studies, 3 were positive: 2 underwent ICD implantation and 1 was initiated on amiodarone and underwent loop recorder implantation. At the time of last follow-up (median 1.5 years; range 0.3-16.5 years), 45 (98%) were free of clinical VT/VF and no patient with an ICD has received an appropriate shock.Surgical resection of ventricular fibromas significantly reduces the risk of life-threatening arrhythmias in children; however, a small number of patients remain vulnerable.

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.

A young child presented with severe ventricular dysfunction and troponin leak in the setting of Coronavirus-19 disease (COVID-19). He developed intermittent, self-resolving, and hemodynamically insignificant episodes of complete heart block (CHB), which were diagnosed on telemetry and managed conservatively. This report is the first description of COVID-19 induced transient CHB in a child., Graphical abstract

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

Exercise stress echocardiography (ESE) is a versatile diagnostic tool that has been integrated into the standard clinical assessment of adult patients with coronary artery disease, hypertrophic cardiomyopathy (HCM), and pulmonary hypertension. Experience with ESE in children with these disorders is more limited. Given the potential value of this technology is significant, its role in the clinical diagnosis and management of pediatric patients continues to evolve. Since 2006, Boston Children’s Hospital has been performing stress echocardiography in children for both ischemia and assessment of hemodynamics of exercise.

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.

Exercise stress echocardiography (ESE) is a valuable diagnostic and prognostic tool in adults with hypertrophic cardiomyopathy (HCM). Inducible and resting left ventricular outflow tract gradients are important predictors of heart failure. However, there are minimal data on the utility of this modality in children.Retrospective review of all pediatric HCM patients who underwent ESE at Boston Children's Hospital (January 2007-June 2018) was carried out. Patients were assigned to one of three categories based on left ventricular outflow tract gradients: group 1:30 mm Hg at rest and exercise; group 2:30 mm Hg at rest and ≥30 mm Hg with exercise; and group 3: ≥ 30 mm Hg at rest and exercise. Records were reviewed for earliest occurrence of composite endpoint of any one of the following: cardiac syncope, chest pain, nonsustained and sustained ventricular tachycardia, aborted cardiac arrest, heart failure class ≥ II, or HCM-related death/transplantation.A total of 91 children (67% males) with median age 12 years (6-24 years) at first ESE and median left ventricle wall thickness of 20 mm formed the cohort. Median follow-up duration was 3 years. During ESE, only one child experienced an event and was resuscitated. Of the 91 children, 25 were classified as group 1, 40 as group 2, and 26 as group 3. Twenty-six patients met the composite endpoint, including two heart transplant, one aborted cardiac arrest, and one sudden cardiac death. Group 3 patients had a 5 times higher risk of developing symptoms and/or serious clinical outcome at any age (hazard ratio = 5.18; 95% CI, [1.39-19.2]; P = .014). During our short follow-up time, group 2 patients had a higher risk of outcome, but this did not achieve statistical significance (hazard ratio = 1.95; 95% CI, [0.5-7.6]; P = .33).In this large series of pediatric patients with HCM, ESE can be performed safely and served as an effective tool to identify the lowest risk patients for cardiac outcome.

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.

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.

Background Arrhythmia management has become the major treatment challenge in adult patients with congenital heart disease (ACHD). Objective We sought to investigate the utility and safety profile of dofetilide for atrial arrhythmias in ACHD. Methods A retrospective chart review was performed. We included patients (age ≥18 years) with congenital heart disease who had atrial fibrillation (AF) or intra-atrial reentrant tachycardia treated with dofetilide. Results We identified 64 patients with a mean age at initiation of 42 ± 14 years. ACHD type included single ventricle (n = 19, 30%), transposition of the great arteries (n = 14, 22%), atrial septal defect (n = 9, 14%), tetralogy of Fallot (n = 8, 12%), atrioventricular canal defect (n = 5, 8%), mitral/aortic stenosis (n = 7, 11%), and other (n = 2, 3%). Thirty-five (55%) had atrial fibrillation, and 29 (45%) had intra-atrial reentrant tachycardia. A total of 3 (4.7%) patients had major inpatient adverse events: torsades de pointes (n = 1, 1.5%), ventricular tachycardia (n = 1, 1.5%), and corrected QT prolongation requiring discontinuation (n = 1, 1.5%). Dofetilide was discontinued in 1 patient because of sinus node dysfunction, and another patient discontinued therapy before discharge because of persistent arrhythmia. Of the patients who were discharged on dofetilide (n = 59, 92%), 40 (68%) had adequate rhythm control and 19 (32%) had partial rhythm control. After a median follow-up of 3 years, 29 (49%) patients remained on dofetilide and 2 (3%) patients died. Reasons for discontinuation included waning effect (n = 16, 57%), side effects (n = 5, 18%), noncompliance (n = 2, 7%), successful ablation (n = 3, 11%), high cost (n = 1, 3.5%), and unknown (n = 1, 3.5%). Conclusion Dofetilide remains a viable antiarrhythmic drug option in this challenging population. At 3 years, 49% remained on dofetilide. Close monitoring of renal function, concomitant medications, and corrected QT interval is required.

Equine motor neuron disease (EMND) is a neurodegenerative disorder of unknown etiology affecting horses worldwide. Trans-Active Response DNA Binding Protein of 43 kDa (TDP-43) has been reported in the central nervous system (CNS) of several neurodegenerative conditions in humans including Amyotrophic Lateral Sclerosis (ALS) and assumed to play role in the disease. We examined whether horses afflicted with EMND express the TDP-43 in CNS. Ten horses with EMND and 6 controls of different ages and breed we enrolled. Detection of presence of TDP-43 protein in the CNS was analyzed by immunohistochemical staining using rabbit anti-human TARDBP (TDP-43) polyclonal antibody. Formalin fixed neuronal tissues from medulla, cervical, and lumbar spinal cord were harvested from EMND and from control horses. Sections were assigned randomly to TDP-43 treated or rabbit anti-IgG as control. Nuclear staining of TDP-43 was detected in one of the neural tissues of 75 % of EMND-positive and 0 of 0 % of control horses in the central nervous system (medulla, and/or cervical spinal cord and/or lumbar spinal cord). TDP-43 antibody was detected in the nucleus of EMND horses and no cytoplasmic staining was noted. As in ALS, there was no pattern of age clustering associated with the detection of TDP-43. This is the first report on the staining of TDP-43 in neuronal tissues of horses and suggests that TDP-43 may play a role in the pathogenesis of EMND. Further studies are needed to elucidate the etiologic role of this protein in the diseases.