Subcutaneous cardioverter-defibrillator implantation in an adult with congenital heart disease and left infra-mammary pacemaker.

The approach/type of an implantable cardioverter defibrillator (ICD) is determined by the underlying cardiac anatomy, venous access, and pre-existing cardiac implantable electronic devices. We describe a case of subcutaneous ICD implantation in an adult with congenital heart disease (CHD) with a pre-existing inframammary transvenous pacemaker. This was preferred over adding a defibrillator coil to existing pacing leads, extraction/replacement of pacing system, or a sternotomy/epicardial ICD placement. The procedure was accomplished uneventfully with successful defibrillation threshold testing. Innovative approaches are required to manage arrhythmias in adults with CHD, with shared decision making playing a critical role.

Flecainide Is Associated With a Lower Incidence of Arrhythmic Events in a Large Cohort of Patients With Catecholaminergic Polymorphic Ventricular Tachycardia.

BACKGROUND: In severely affected patients with catecholaminergic polymorphic ventricular tachycardia, beta-blockers are often insufficiently protective. The purpose of this study was to evaluate whether flecainide is associated with a lower incidence of arrhythmic events (AEs) when added to beta-blockers in a large cohort of patients with catecholaminergic polymorphic ventricular tachycardia. METHODS: From 2 international registries, this multicenter case cross-over study included patients with a clinical or genetic diagnosis of catecholaminergic polymorphic ventricular tachycardia in whom flecainide was added to beta-blocker therapy. The study period was defined as the period in which background therapy (ie, beta-blocker type [beta1-selective or nonselective]), left cardiac sympathetic denervation, and implantable cardioverter defibrillator treatment status, remained unchanged within individual patients and was divided into pre-flecainide and on-flecainide periods. The primary end point was AEs, defined as sudden cardiac death, sudden cardiac arrest, appropriate implantable cardioverter defibrillator shock, and arrhythmic syncope. The association of flecainide with AE rates was assessed using a generalized linear mixed model assuming negative binomial distribution and random effects for patients. RESULTS: A total of 247 patients (123 [50%] females; median age at start of flecainide, 18 years [interquartile range, 14-29]; median flecainide dose, 2.2 mg/kg per day [interquartile range, 1.7-3.1]) were included. At baseline, all patients used a beta-blocker, 70 (28%) had an implantable cardioverter defibrillator, and 21 (9%) had a left cardiac sympathetic denervation. During a median pre-flecainide follow-up of 2.1 years (interquartile range, 0.4-7.2), 41 patients (17%) experienced 58 AEs (annual event rate, 5.6%). During a median on-flecainide follow-up of 2.9 years (interquartile range, 1.0-6.0), 23 patients (9%) experienced 38 AEs (annual event rate, 4.0%). There were significantly fewer AEs after initiation of flecainide (incidence rate ratio, 0.55 [95% CI, 0.38-0.83]; P=0.007). Among patients who were symptomatic before diagnosis or during the pre-flecainide period (n=167), flecainide was associated with significantly fewer AEs (incidence rate ratio, 0.49 [95% CI, 0.31-0.77]; P=0.002). Among patients with ≥1 AE on beta-blocker therapy (n=41), adding flecainide was also associated with significantly fewer AEs (incidence rate ratio, 0.25 [95% CI, 0.14-0.45]; P<0.001). CONCLUSIONS: For patients with catecholaminergic polymorphic ventricular tachycardia, adding flecainide to beta-blocker therapy was associated with a lower incidence of AEs in the overall cohort, in symptomatic patients, and particularly in patients with breakthrough AEs while on beta-blocker therapy.

Myocardial bridge in a child with cardiac arrest and ventricular fibrillation: a bridge over troubled water?

Resuscitated cardiac arrest in a child triggers a comprehensive workup to identify an aetiology and direct management. The presence of a myocardial bridge does not automatically imply causation. Careful determination of the haemodynamic significance of the myocardial bridge is critical to avoid an unnecessary sternotomy and to provide appropriate treatment.

Significance of electrocardiogram abnormalities in children presenting to the emergency department with acute COVID-19 infection.

OBJECTIVES: Acute COVID-19 infection may be associated with electrocardiogram (EKG) abnormalities in pediatric patients. We have anecdotally observed EKG abnormalities in patients without MIS-C or significant cardiac disease requiring intervention or further follow-up. Our aim was to determine the incidence of abnormal EKG findings and correlate with evidence of significant cardiac pathology in pediatric patients who present to the emergency department during an acute COVID-19 infection. METHODS: We conducted a retrospective chart review of 209 pediatric patients diagnosed in the emergency department with acute COVID-19 infection and had an EKG during the same encounter; patients with MIS-C were excluded. Primary objectives included determination of the incidence of EKG abnormalities in patients presenting to the emergency department (ED) with acute COVID-19 infection who did not require hospitalization. Secondary objectives included correlation of these findings with other concomitant testing of possible cardiac pathology (echocardiograms, biomarkers), and clinical outcomes. RESULTS: EKG abnormalities were identified in 84 (40%) patients. Echo was performed in 28 (13.4%) patients; only 1 was abnormal, and considered an incidental finding. The most common EKG abnormality involved nonspecific ST-T wave patterns, suggestive of but not diagnostic for underlying pericardial or myocardial disease. Serum troponin and BNP values were normal in all patients tested, either with a normal or abnormal EKG. A normal EKG had a 100% sensitivity and negative predictive value in predicting a normal echocardiogram. No patients were hospitalized and there was normalization of EKG abnormalities during short-term follow up. CONCLUSIONS: Despite a high incidence of abnormal EKG repolarization patterns in pediatric patients presenting with acute (non-MIS-C) COVID-19 infections, these patients generally do not have abnormal cardiac biomarkers or echocardiograms, and the risk for adverse cardiac events is low.

Combination Therapy of Ivabradine with Procainamide for the Management of Pediatric Postoperative Junctional Ectopic Tachycardia.

Pediatric postoperative junctional ectopic tachycardia (JET), although usually self-limited, may lead to significant morbidity and mortality. Anti-arrhythmic medications are often necessary to restore atrioventricular synchrony when non-pharmacological measures fail. Multiple drugs have been described for the management of postoperative JET, with enteral ivabradine being the latest addition. While safe administration of ivabradine has been described in combination with other anti-arrhythmics (amiodarone, flecainide), no study has described the use of ivabradine in conjunction with intravenous procainamide for the management of postoperative JET. Our case report describes the safe use of ivabradine and procainamide combination therapy in a young patient.

Left Main Coronary Artery Ostial Stenosis in a Pediatric Patient With Sudden Cardiac Arrest.

Pediatric resuscitated sudden cardiac arrest may result from diverse conditions and, therefore, warrants a comprehensive work-up. Although rare, coronary artery abnormalities must be ruled out in these patients. We describe a case with congenital left main coronary artery ostial stenosis diagnosed using advanced imaging techniques. (Level of Difficulty: Advanced.).

Palpitations, Dizziness, and Syncope in Teenage Girls: Practical Approach of a Pediatric Cardiologist.

Palpitations, dizziness, and syncope are common in seemingly healthy teenage girls. Unfortunately, these symptoms can raise significant concerns in the patient and family, present diagnostic challenges to health care providers, and result in unhelpful and expensive testing and unnecessary restrictions on the patient. The possibility of serious underlying pathology may prompt referral to pediatric subspecialists including cardiology. This article presents some relevant background principles and practical guidelines from the perspective of a pediatric cardiologist. Elements of initial personal and family medical history and physical examination often distinguish benign conditions from more nefarious ones, or direct limited additional testing that ultimately confirms the presence or absence of heart disease. In addition, whether these symptoms are due to a condition that is serious or benign, every patient can benefit from an intervention, sometimes simple education and reassurance, behavioral or dietary modifications, medications, invasive procedures, or referral to other health care providers. [Pediatr Ann. 2022;51(11):e440-e447.].

Non-fluoroscopic Techniques for Catheter Ablation of Typical Atrioventricular Nodal Re-entry Tachycardia in a Pediatric Patient with Atypical Venous Anatomy.

Catheter ablation of the slow pathway to the atrioventricular node is generally a safe and effective treatment for atrioventricular nodal re-entry tachycardia (AVNRT). However, congenital anomalies of the inferior vena cava and superior draining veins can limit traditional catheter approaches to the right heart from femoral venous access and distort local anatomy within the triangle of Koch, necessitating alternative electrophysiology (EP) mapping and ablation strategies. Despite the widespread availability of non-fluoroscopic 3-dimensional imaging systems, many providers still rely on venography to describe unusual cardiovascular anatomy and fluoroscopy to position EP catheters when mapping and ablating the slow pathway. Herein, we report our experience with a pediatric patient with inducible AVNRT and atypical venous anatomy in whom slow pathway ablation was performed successfully without the use of fluoroscopy. In addition, we describe the modification of a novel mapping technique for targeting the slow pathway for ablation.

Medical Management of Infants With Supraventricular Tachycardia: Results From a Registry and Review of the Literature.

Background: Several medication choices are available for acute and prophylactic treatment of refractory supraventricular tachycardia (SVT) in infants. There are almost no controlled trials, and medication choices are not necessarily evidence based. Our objective was to report the effectiveness of management strategies for infant SVT. Methods: A registry of infants admitted to hospital with re-entrant SVT and no haemodynamically significant heart disease were prospectively followed at 11 international tertiary care centres. In addition, a systematic review of studies on infant re-entrant SVT in MEDLINE and EMBASE was conducted. Data on demographics, symptoms, acute and maintenance treatments, and outcomes were collected. Results: A total of 2534 infants were included: n = 108 from the registry (median age, 9 days [0-324 days], 70.8% male) and n = 2426 from the literature review (median age, 14 days; 62.3% male). Propranolol was the most prevalent acute (61.4%) and maintenance treatment (53.8%) in the Registry, whereas digoxin was used sparingly (4.0% and 3.8%, respectively). Propranolol and digoxin were used frequently in the literature acutely (31% and 33.2%) and for maintenance (17.8% and 10.1%) (P < 0.001). No differences in acute or prophylactic effectiveness between medications were observed. Recurrence was higher in the Registry (25.0%) vs literature (13.4%) (P < 0.001), and 22 (0.9%) deaths were reported in the literature vs none in the Registry. Conclusion: This was the largest cohort of infants with SVT analysed to date. Digoxin monotherapy use was rare amongst contemporary paediatric cardiologists. There was limited evidence to support one medication over another. Overall, recurrence and mortality rates on antiarrhythmic treatment were low.

Contexte: De nombreux choix de médicaments existent pour le traitement aigu et prophylactique de la tachycardie supraventriculaire (TSV) réfractaire chez les nourrissons. Or, il n'y a presque pas d'essais contrôlés à ce sujet, et les choix de médicaments ne sont pas nécessairement fondés sur des données probantes. Notre objectif était de faire état de l'efficacité des stratégies de prise en charge de la TSV chez les nourrissons. Méthodologie: Un registre des nourrissons admis à l'hôpital pour une TSV par réentrée, sans cardiopathie d'importance hémodynamique, a été tenu de façon prospective dans 11 centres de soins tertiaires à l'échelle mondiale. De plus, une revue systématique des études sur la TSV par réentrée chez le nourrisson a été effectuée dans MEDLINE et EMBASE. Des données sur les caractéristiques démographiques, les symptômes, les traitements aigus et d'entretien, et les résultats ont été recueillis. Résultats: Un total de 2 534 nourrissons ont été inclus : n = 108 du registre (âge médian de 9 jours [0-324 jours], 70,8 % de sexe masculin) et n = 2 426 de la revue de la littérature (âge médian de 14 jours; 62,3 % de sexe masculin). Le propranolol était le traitement de soins aigus (61,4 %) et d'entretien (53,8 %) le plus fréquent dans le registre, alors que la digoxine a été utilisée occasionnellement (respectivement dans 4,0 % et 3,8 % des cas). Dans la littérature, le propranolol et la digoxine étaient fréquemment utilisés en soins aigus (31 % et 33,2 %) et en traitement d'entretien (17,8 % et 10,1 %) (p < 0,001). Aucune différence n'a été observée entre les médicaments au chapitre de l'efficacité du traitement de soins aigus ou du traitement prophylactique. Le taux de récurrence était plus élevé dans le registre (25,0 %) que dans la littérature (13,4 %) (p < 0,001), et 22 (0,9 %) décès ont été signalés dans la littérature, mais aucun dans le registre. Conclusion: Il s'agit de la plus grande cohorte de nourrissons atteints de TSV analysée à ce jour. De nos jours, les cardiologues pédiatriques prescrivent rarement la digoxine en monothérapie. Peu de données probantes favorisent l'utilisation d'un médicament par rapport à l'autre. Dans l'ensemble, les taux de récurrence et de mortalité sous traitement antiarythmique étaient faibles.

Evaluation of age at symptom onset, proband status, and sex as predictors of disease severity in pediatric catecholaminergic polymorphic ventricular tachycardia.

BACKGROUND: Children with catecholaminergic polymorphic ventricular tachycardia (CPVT) are at risk for sudden death, and a risk stratification tool does not exist. OBJECTIVE: The purpose of this study was to determine whether proband status, age at symptom onset, and/or sex are independent predictors of cardiac events. METHODS: A multicenter, ambispective, cohort of pediatric CPVT patients was categorized by sex, proband status, and age at symptom onset (D1: first decade of life [symptom onset <10 years] or D2: second decade of life [symptom onset 10-18 years, inclusive]). Demographics, therapy, genetics, and outcomes were compared between groups. RESULTS: A total of 133 patients were included and stratified into 58 D1 and 75 D2 patients (68 female and 65 male; 106 probands and 27 relatives). Localization of RYR2 variants to hotspots differed based on proband status and age at symptom onset. The cardiac event rate was 33% (n = 44/133), inclusive of a 3% (n = 4/133) mortality rate, over a median of 6 years (interquartile range 3-11) after time of symptom onset. Proband status, rather than age at of symptom onset or sex, was an independent predictor of time to first cardiac event (P = .008; hazard ratio = 4.4). The 5-, 10- and 15-year event-free survival rates for probands were 77%, 56%, and 46%, respectively, and for relatives were 96%, 91%, and 86%, respectively. Event risk after diagnosis was 48% (32/67) in patients on ß-blocker or flecainide alone vs 10% (5/48) in patients on ß-blocker plus flecainide and/or left cardiac sympathetic denervation (P <.001). CONCLUSION: Proband status, but not age at symptom onset or male sex, independently predicted an earlier onset of cardiac events. A larger sample size would enable a comprehensive investigation of other risk factors.

Management and outcomes of atrial fibrillation in 241 healthy children and young adults: Revisiting "lone" atrial fibrillation-A multi-institutional PACES collaborative study.

BACKGROUND: Atrial fibrillation (AF) in healthy children and young adults is rare. Risk of recurrence and treatment efficacy are not well defined. OBJECTIVE: The purpose of this study was to assess recurrence patterns and treatment efficacy in AF. METHODS: A retrospective multicenter cohort study including 13 congenital heart centers was facilitated by the Pediatric & 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, electrophysiological 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 first-degree relative <50 years of age (odds ratio [OR] 1.9; P = .047) and longer PR interval in sinus rhythm (OR 1.1 per 10 ms; P = .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 = .39). Ablating non-AF substrate with supraventricular tachycardia improved freedom from AF recurrence (P = .013). CONCLUSION: 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 reentrant targets was the only intervention that decreased AF recurrence in children and young adults.

Outcomes of Pediatric Patients With Defibrillators Following Initial Presentation With Sudden Cardiac Arrest.

BACKGROUND: Implantable cardioverter defibrillators (ICD) are recommended for secondary prevention after sudden cardiac arrest (SCA). The outcomes of pediatric patients receiving an ICD after SCA remain unclear. The objective of this study is to evaluate outcomes, future risk for appropriate shocks, and identify characteristics associated with appropriate ICD therapy during follow-up. METHODS: Multicenter retrospective analysis of patients (age ≤21 years) without prior cardiac disease who received an ICD following SCA. Patient/device characteristics, cardiac function, and underlying diagnoses were collected, along with SCA event characteristics. Patient outcomes including complications and device therapies were analyzed. RESULTS: In total, 106 patients were included, median age 14.7 years. Twenty (19%) received appropriate shocks and 16 (15%) received inappropriate shocks (median follow-up 3 years). First-degree relative with SCA was associated with appropriate shocks (P<0.05). In total, 40% patients were considered idiopathic. Channelopathy was the most frequent late diagnosis not made at time of presentation. Neither underlying diagnosis nor idiopathic status was associated with increased incidence of appropriate shock. Monomorphic ventricular tachycardia (hazard ratio, 4.6 [1.2-17.3]) and family history of sudden death (hazard ratio, 6.5 [1.4-29.8]) were associated with freedom from appropriate shock in a multivariable model (area under the receiver operating characteristic curve, 0.8). Time from diagnoses to evaluation demonstrated a nonlinear association with freedom from appropriate shock (P=0.015). In patients >2 years from implantation, younger age (P=0.02) and positive exercise test (P=0.04) were associated with appropriate shock. CONCLUSIONS: The risk of future device therapy is high in pediatric patients receiving an ICD after SCA, irrelevant of underlying disease. Lack of a definitive diagnosis after SCA was not associated with lower risk of subsequent events and does not obviate the need for secondary prophylaxis.

An International Multicenter Evaluation of Type 5 Long QT Syndrome: A Low Penetrant Primary Arrhythmic Condition.

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<0.001). ECG penetrance for heterozygous genotype positive family members was 20.7% (29/140). A definite arrhythmic event was experienced in 16.9% (15/89) of heterozygous probands in comparison with 1.4% (2/140) of family members (adjusted hazard ratio [HR] 11.6 [95% CI, 2.6-52.2]; 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.

Identification of a Novel Homozygous Multi-Exon Duplication in RYR2 Among Children With Exertion-Related Unexplained Sudden Deaths in the Amish Community.

Importance: The exome molecular autopsy may elucidate a pathogenic substrate for sudden unexplained death. Objective: To investigate the underlying cause of multiple sudden deaths in young individuals and sudden cardiac arrests that occurred in 2 large Amish families. Design, Setting, and Participants: Two large extended Amish families with multiple sudden deaths in young individuals and sudden cardiac arrests were included in the study. A recessive inheritance pattern was suggested based on an extended family history of sudden deaths in young individuals and sudden cardiac arrests, despite unaffected parents. A family with exercise-associated sudden deaths in young individuals occurring in 4 siblings was referred for postmortem genetic testing using an exome molecular autopsy. Copy number variant (CNV) analysis was performed on exome data using PatternCNV. Chromosomal microarray validated the CNV identified. The nucleotide break points of the CNV were determined by mate-pair sequencing. Samples were collected for this study between November 2004 and June 2019. Main Outcomes and Measures: The identification of an underlying genetic cause for sudden deaths in young individuals and sudden cardiac arrests consistent with the recessive inheritance pattern observed in the families. Results: A homozygous duplication, involving approximately 26 000 base pairs of intergenic sequence, RYR2's 5'UTR/promoter region, and exons 1 through 4 of RYR2, was identified in all 4 siblings of a family. Multiple distantly related relatives experiencing exertion-related sudden cardiac arrest also had the identical RYR2 homozygous duplication. A second, unrelated family with multiple exertion-related sudden deaths and sudden cardiac arrests in young individuals, with the same homozygous duplication, was identified. Several living, homozygous duplication-positive symptomatic patients from both families had nondiagnostic cardiologic testing, with only occasional ventricular ectopy occurring during exercise stress tests. Conclusions and Relevance: In this analysis, we identified a novel, highly penetrant, homozygous multiexon duplication in RYR2 among Amish youths with exertion-related sudden death and sudden cardiac arrest but without an overt phenotype that is distinct from RYR2-mediated catecholaminergic polymorphic ventricular tachycardia. Considering that no cardiac tests reliably identify at-risk individuals and given the high rate of consanguinity in Amish families, identification of unaffected heterozygous carriers may provide potentially lifesaving premarital counseling and reproductive planning.