Patterns of Electrocardiographic Abnormalities in Children with Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM), a common cardiomyopathy in children, is an important cause of morbidity and mortality. Early recognition and appropriate management are important. An electrocardiogram (ECG) is often used as a screening tool in children to detect heart disease. The ECG patterns in children with HCM are not well described.ECGs collected from an international cohort of children, and adolescents (≤ 21 years) with HCM were reviewed. 482 ECGs met inclusion criteria. Age ranged from 1 day to 21 years, median 13 years. Of the 482 ECGs, 57 (12%) were normal. The most common abnormalities noted were left ventricular hypertrophy (LVH) in 108/482 (22%) and biventricular hypertrophy (BVH) in 116/482 (24%) Of the patients with LVH/BVH (n = 224), 135 (60%) also had a strain pattern (LVH in 83, BVH in 52). Isolated strain pattern (in the absence of criteria for hypertrophy) was seen in 43/482 (9%). Isolated pathologic Q waves were seen in 71/482 (15%). Pediatric HCM, 88% have an abnormal ECG. The most common ECG abnormalities were LVH or BVH with or without strain. Strain pattern without hypertrophy and a pathologic Q wave were present in a significant proportion (24%) of patients. Thus, a significant number of children with HCM have ECG abnormalities that are not typical for "hypertrophy". The presence of the ECG abnormalities described above in a child should prompt further examination with an echocardiogram to rule out HCM.

Didactic education in paediatric cardiology during the COVID-19 pandemic: a national fellow survey.

The coronavirus disease 2019 (COVID-19) pandemic has had a profound impact on medical educational curricula. We aimed to examine the impact of these unprecedented changes on the formal education of paediatric cardiology fellows through a nationwide survey. A REDCap™-based voluntary anonymous survey was sent to all current paediatric cardiology fellows in the United States of America in May, 2020. Of 143 respondents, 121 were categorical fellows, representing over one-fourth of all categorical paediatric cardiology fellows in the United States of America. Nearly all (140/143, 97.9%) respondents utilised online learning during the pandemic, with 134 (93.7%) reporting an increase in use compared to pre-pandemic. The percentage of respondents reporting curriculum supplementation with outside lectures increased from 11.9 to 88.8% during the pandemic. Respondents considered online learning to be "equally or more effective" than in-person lectures in convenience (133/142, 93.7%), improving fellow attendance (132/142, 93.0%), improving non-fellow attendance (126/143, 88.1%), and meeting individual learning needs (101/143, 70.6%). The pandemic positively affected the lecture curriculum of 83 respondents (58.0%), with 35 (24.5%) reporting no change and 25 (17.5%) reporting a negative effect. A positive effect was most noted by those whose programmes utilised supplemental outside lectures (62.2 versus 25.0%, p = 0.004) and those whose lecture frequency did not decrease (65.1 versus 5.9%, p < 0.001). Restrictions imposed by the COVID-19 pandemic have greatly increased utilisation of online learning platforms by medical training programmes. This survey reveals that an online lecture curriculum, despite inherent obstacles, offers advantages that may mitigate some negative consequences of the pandemic on fellowship education.

Novel Assessment of Accessory Pathway Function in Patients with Wolff-Parkinson-White Syndrome.

Surrogates for the shortest pre-excited R-R interval in atrial fibrillation (SPERRI) such as the accessory pathway effective refractory period (APERP) and shortest pre-excited paced cycle length (SPPCL) are flawed assessments of accessory pathway function in patients with WPW. Multi-extrastimulus pacing may have the theoretical advantage of more accurately mimicking the clinical reality of atrial fibrillation and thus may serve to better assess accessory pathway function. This cross-sectional study included 25 consecutive patients, aged ≤ 18 years, undergoing electrophysiology study for WPW. The longest S1S2, S2S3, S3S4 coupling intervals at which the antegrade AP refractoriness occurred, SPERRI, and SPPCL were recorded. Induction of atrial fibrillation was attempted in all patients and induced in 8 (32%, 4 SPERRIbaseline (265 ms ± 61 ms), 4 SPERRIIsuprel (258 ms ± 41 ms)). At baseline, the lower value of the S3ERP or S4ERP (274 ms ± 52 ms) was lower than the SPPCL (296 ms ± 54 ms, p < 0.0001) and APERP (296 ms ± 41 ms, p < 0.0001). More patients had S3ERP or S4ERP ≤ 250 ms (12/25, 48%) compared to those with APERP ≤ 250 ms (2/25 8%), p = 0.0016), SPPCL 5/24, 20%), p = 0.008 or either (6/25, 24%), p = 0.0143). With Isuprel, the lower value of the S3ERP or S4ERP (221 ms ± 36 ms) trended to be lower than the APERP (252 ms ± 36 ms, p = 0.0001) and the SPPCL (266 ms ± 57 ms, p = 0.001). With Isuprel, there was no statistical difference in the proportion of patients with S3ERP or S4ERP < 250 ms (12/16, 75%) compared to those with APERP ≤ 250 ms ((9/16, 56%), p = 0.08), SPPCL ≤ 250 ms ((9/16, 56%), p = 0.08), or either ((10/16, 63%), p = 0.16). Multi-extrastimulus pacing protocols demonstrate that accessory pathways are less refractory than as defined by single extrastimulus pacing and straight decremental pacing.

Examining the Utility of Coronary Artery Lack of Tapering and Perivascular Brightness in Incomplete Kawasaki Disease.

BACKGROUND: In 2017, the AHA published revised guidelines for the diagnosis of Kawasaki disease (KD). In the absence of compelling data supporting or refuting the utility of lack of tapering (LT) and perivascular brightness (PB), expert panel consensus removed LT and PB from consideration. We hypothesize that LT and PB are unreliable, subjective findings, non-specific to KD, which can be seen in systemic febrile illnesses without KD and in normal controls. METHODS: We performed a single-center retrospective study from 1/2008 to 12/2016. De-identified coronary artery (CA) echocardiographic clips from patients 0-10 years old were interpreted blindly by six pediatric cardiologists. Subjects were grouped as follows: (1) healthy: afebrile with benign murmur, (2) KD: IVIG treatment, 4-5 clinical criteria at presentation, (3) incomplete KD (iKD): IVIG, 1-3 clinical criteria, (4) Febrile: ≥3 days of fever, no IVIG, KD not suspected. The presence or absence of LT and PB was recorded. Inter-rater and intra-rater reliabilities were analyzed using intra-class correlation coefficient, Fleiss' Kappa and Cohen's Kappa coefficients. RESULTS: We interpreted 117 echocardiograms from healthy (27), KD (30), iKD (32), and febrile (28) subjects. Analysis showed moderate agreement in CA z score measurements. LT and PB were observed by most readers in control groups. LT exhibited fair inter-reader agreement (reliability coefficient 0.36) and PB slight inter-reader agreement (reliability coefficient 0.13). Intra-rater reliability was inconsistent for both parameters. CONCLUSIONS: LT and PB are subjective, poorly reproducible features that can be seen in febrile patients without KD and in healthy children.

Impact of Obesity on Left Ventricular Thickness in Children with Hypertrophic Cardiomyopathy.

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.

Usefulness of Routine Transtelephonic Monitoring for Supraventricular Tachycardia in Infants.

OBJECTIVE: We hypothesize that routine daily transtelephonic monitoring (TTM) transmissions can accurately detect supraventricular tachycardia (SVT) in asymptomatic infants and/or assuage parental concerns rather than being used solely to diagnose arrhythmias. STUDY DESIGN: Single center, retrospective chart review of 60 patients with fetal or infant SVT prescribed TTM for at least 30 days, January 2010-September 2016. Patients were excluded if initial SVT was not documented, was perioperative, was atrial flutter/fibrillation, or chaotic atrial tachycardia. Categorical variables expressed as mean ± SD. Mann-Whitney, Spearman correlation, and Fisher exact tests were used for continuous and categorical variables respectively. RESULTS: Sixty patients were included. There were 2688 TTM transmissions received from 55 of 60 patients over 61.1 ± 66.7 days (0.73 ± 0.65 TTM/patient/days). Routine asymptomatic TTM transmissions revealed actionable findings in 5 of 2801 TTM transmissions sent by 5 patients (8.3%). No patient presented in shock or died. Forty-five of 2688 TTM transmissions were sent for parental concerns/symptoms in 16 patients (25.8%) with findings of normal sinus rhythm in 37 of 45 TTM transmissions and SVT in 8 of 45 TTM transmissions. Symptomatic actionable findings were more likely sent by patients discharged on class I or III antiarrhythmics (95% CI = 11.5%-68.3%, P = .004) and patients with prolonged initial hospitalizations (95% CI = 6.98%-59.7%, P = .01). Flecainide was discontinued in 1 patient after widened QRS was noted on routine TTM. CONCLUSIONS: TTM accurately diagnose asymptomatic recurrent SVT in neonates and infants before they develop signs of congestive heart failure or shock and is helpful for recurrent SVT management.

The "hidden" concealed left-sided accessory pathway: An uncommon cause of SVT in young people.

BACKGROUND: Concealed left-sided accessory pathways (CLAP) are a cause of supraventricular tachycardia (SVT) in the young. Most are mapped with right ventricular (RV) apical/outflow pacing. Rarely, alternative means of mapping are required. We review our experience from three pediatric electrophysiology (EP) centers with a rare form of "hidden" CLAP. METHODS: All patients <21 years undergoing EP study from 2008 to 2014 with a "hidden" CLAP (defined as an accessory pathway [AP] for which RV pacing at cycle lengths [CL] stable for mapping did not demonstrate eccentric retrograde conduction) were included. EXCLUSION CRITERIA: preexcitation. Demographic, procedural, and follow-up data were collected. RESULTS: A total of 23 patients met the criteria (median age, 14.3 years [range 7-21], weight, 51 kg [31-99]). 21 (96%) had SVT and one AFIB (4%). APs were adenosine sensitive in 7/20 patients (35%) and VA conduction was decremental in six (26%). CLAP conduction was demonstrable with orthodromic reentrant tachycardia in all patients, with RV extrastimulus testing in seven (30%) and with rapid RV pacing (

A multicenter review of ablation in the aortic cusps in young people.

BACKGROUND: Ablation within the aortic cusp is safe and effective in adults. There are little data on aortic cusp ablation in the pediatric literature. We investigated the safety and efficacy of aortic cusp ablation in young patients. METHODS: A retrospective, descriptive study of aortic cusp ablation in five pediatric electrophysiology centers from 2008 to 2014 was performed. All patients <21 years of age who underwent ablation in the aortic cusps were included. Factors analyzed included patient demographics, procedural details, outcomes, and complications. RESULTS: Thirteen patients met inclusion criteria (median age 16 years [range 10-20.5] and median body surface area 1.58 m2 [range 1.12-2.33]). Substrates for ablation included: nine premature ventricular contractions or sustained ventricular tachycardia (69%), two concealed anteroseptal accessory pathways (APs) (15%), one Wolff-Parkinson-White with an anteroseptal AP (8%), and one ectopic atrial tachycardia (8%). Three-dimensional electroanatomic mapping in combination with fluoroscopy was used in 12/13 (92%) patients. Standard 4-mm-tip radiofrequency (RF) current was used in 11/13 (85%) and low-power irrigated-tip RF in 2/13 (15%). Angiography was used in 13/13 and intracardiac echocardiography was additionally utilized in 3/13 (23%). Ablation locations included: eight noncoronary (62%), three left (23%), and two right (15%) cusps. Ablation was acutely successful in all patients. At median follow-up of 20 months, there was one recurrence of PVCs (8%). There were no ablation-related complications and no valvular injuries observed. CONCLUSION: Arrhythmias originating from the coronary cusps in this series were successfully and safely ablated in young people without injury to the coronary arteries or the aortic valve.

KCNJ2 mutation in short QT syndrome 3 results in atrial fibrillation and ventricular proarrhythmia.

We describe a mutation (E299V) in KCNJ2, the gene that encodes the strong inward rectifier K(+) channel protein (Kir2.1), in an 11-y-old boy. The unique short QT syndrome type-3 phenotype is associated with an extremely abbreviated QT interval (200 ms) on ECG and paroxysmal atrial fibrillation. Genetic screening identified an A896T substitution in a highly conserved region of KCNJ2 that resulted in a de novo mutation E299V. Whole-cell patch-clamp experiments showed that E299V presents an abnormally large outward IK1 at potentials above -55 mV (P < 0.001 versus wild type) due to a lack of inward rectification. Coexpression of wild-type and mutant channels to mimic the heterozygous condition still resulted in a large outward current. Coimmunoprecipitation and kinetic analysis showed that E299V and wild-type isoforms may heteromerize and that their interaction impairs function. The homomeric assembly of E299V mutant proteins actually results in gain of function. Computer simulations of ventricular excitation and propagation using both the homozygous and heterozygous conditions at three different levels of integration (single cell, 2D, and 3D) accurately reproduced the electrocardiographic phenotype of the proband, including an exceedingly short QT interval with merging of the QRS and the T wave, absence of ST segment, and peaked T waves. Numerical experiments predict that, in addition to the short QT interval, absence of inward rectification in the E299V mutation should result in atrial fibrillation. In addition, as predicted by simulations using a geometrically accurate three-dimensional ventricular model that included the His-Purkinje network, a slight reduction in ventricular excitability via 20% reduction of the sodium current should increase vulnerability to life-threatening ventricular tachyarrhythmia.

What are we missing? Arrhythmia detection in the pediatric intensive care unit.

OBJECTIVES: To test the hypothesis that instituting a process of routine daily review of rhythm alarms in non-cardiac patients in the pediatric intensive care unit would yield clinically important disturbances that would otherwise go undetected. STUDY DESIGN: A prospective observational study was performed over a consecutive 28-day period. Total bedside monitor alarms, rhythm alarms, and heart rate (HR) trends were recorded. Rhythm alarm recordings were reviewed independently by two study team members. Medical records for patients with critical arrhythmias were reviewed to evaluate for prior knowledge of the event and to correlate with clinical data. RESULTS: We evaluated 86 patients (343 patient-days). There were 54,656 total monitor alarms (159.3 alarms/patient-day), of which 19,970 (37%) were rhythm alarms, including 4032 (20%) critical arrhythmias. Fifty-six percent of the critical alarms were artifactual. Seventeen of the 1786 ventricular tachycardia alarms represented true episodes that occurred in 5 patients. Two patients' care were altered as a result of detection of the arrhythmia in the review process. Eight hundred sixty-five (98%) of the 883 true critical alarms reviewed were for extreme HR. Eighty-three percent (5172) of the 6239 true non-critical alarms reviewed were HR alarms. CONCLUSIONS: Daily review of rhythm alarms improves detection of clinically relevant arrhythmias in non-cardiac pediatric intensive care unit patients.

Fascicular and nonfascicular left ventricular tachycardias in the young: an international multicenter study.

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

Cryoablation of AVNRT when sustained tachycardia cannot be induced.

BACKGROUND: Inducibility of sustained tachycardia is preferred prior to cryoablation for atrioventricular nodal reentrant tachycardia (AVNRT). METHOD: The Pediatric Electrophysiology Database of a single institution was retrospectively reviewed for patients with clinical sustained (≥ 30 seconds of symptoms) AVNRT documented by noninvasive means who underwent cryoablation for AVNRT to determine if intermediate-term success with cryoablation for AVNRT can be achieved without inducibility of sustained AVNRT during electrophysiology study (EPS). RESULTS: There were no differences between patients with sustained (≥ 30 seconds of tachycardia) AVNRT (N = 67) and patients with nonsustained (ns, ≥ 3 beats and <30 seconds of tachycardia) AVNRT at EPS (N = 16). Acute success was achieved without PR prolongation in all patients. Although duration of follow-up was shorter for the sustained group than the nonsustained group (2.7 ± 1.6 years vs 3.8 ± 1.4 years, P = 0.008), recurrence rate was similar (6% vs 6.3%, P = 0.6). In patients with only nonsustained AVNRT at EPS, supportive findings for procedural effectiveness seen: (1) Dual atrioventricular node physiology (DAVNP) was eliminated in 14/14, (2) the fast pathway effective refractory period (FPERP) decreased after ablation in 10/11, (3) sustained slow pathway conduction was eliminated in 8/8 including both patients without discrete DAVNP prior to ablation, and (4) FPERP increased during lesion formation in 10/10. CONCLUSION: Intermediate-term success can be achieved with cryoablation of ns AVNRT. Attention should be paid to supportive indicators of damage to slow pathway.

Transesophageal evaluation of asymptomatic Wolff-Parkinson-White syndrome.

BACKGROUND: Risk stratification for Wolff-Parkinson-White (WPW) by intracardiac electrophysiology study (ICEPS) carries risks related to catheterization. We describe an alternative approach by using transesophageal electrophysiology study (TEEPS). METHODS: The pediatric electrophysiology database was reviewed for patients with WPW and no documented clinical supraventricular tachycardia (SVT) who underwent risk stratification by TEEPS from October 2005 to November 2010. Of those who underwent subsequent ICEPS, only those with data available to compare accessory pathway (AP) conduction during ICEPS and TEEPS were included. RESULTS: Of 65 patients who underwent TEEPS, 42 were found to have an indication for ablation. The most common indication for ICEPS was inducible SVT, which was induced in 67% of patients. Of 42 patients who underwent subsequent ICEPS, 23 had sufficient data for comparison of AP conduction between ICEPS and TEEPS. There was no difference between the baseline minimum 1:1 antegrade conduction through the accessory pathway found at TEEPS versus ICEPS (312 ± 51 ms vs 316 ± 66 ms, P = 0.5). There was no significant difference between the baseline antegrade AP-effective refractory period found at TEEPS versus ICEPS (308 ± 34 ms vs 297 ± 37 ms, P = 0.07). There were no complications related to TEEPS or ICEPS. CONCLUSION: TEEPS is a safe and feasible alternative to ICEPS for risk stratification in patients with asymptomatic WPW and should be considered before ICEPS and 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.

Transesophageal electrophysiological evaluation of children with a history of supraventricular tachycardia in infancy.

Supraventricular tachycardia (SVT) presenting in the neonatal period may resolve by 1 year of age. Predicting which patients require therapy beyond 1 year of age is desirable. Pediatric electrophysiology databases from two institutions were reviewed for patients with a history of infant SVT who underwent transesophageal electrophysiology study (TEEPS) after initial SVT and before 2 years of age. All patients were tested off medications and followed for clinical recurrence. Forty-two patients presented with SVT at median age of 4 days (0-300 days). Initial control was achieved with one drug in 31 patients and multiple drugs in 11 patients. Prior to TEEPS, nine patients had clinical recurrence in the first year of life after initial control had been previously achieved. For all patients, TEEPS was performed, without complications, at median 13 months (9-22 months) of age and at median of 13 months (6-22 months) following the initial SVT episode. SVT was inducible in 27/42: 8 atrio-ventricular nodal reentry tachycardia (AVNRT) and 19 atrio-ventricular reciprocating tachycardia (AVRT). Inducibility was not associated with age at presentation, age at TEEPS, ventricular dysfunction at presentation, presence of structural congenital heart disease, number of drugs required to initially control SVT, or SVT recurrence after initial control. Of 15 not inducible at TEEPS, none had known SVT recurrence off medications at median follow-up of 27 months (6-37 months). In conclusion, among patients having SVT in early infancy, (1) TEEPS results are not associated with clinical variables, (2) non-inducibility is a good indicator of lack of clinical recurrence at intermediate follow-up, and (3) AVNRT may be more prevalent in infancy than previously reported.

Six Month Follow-up of Patients With Multi-System Inflammatory Syndrome in Children.

BACKGROUND AND OBJECTIVES: Myocardial dysfunction and coronary abnormalities are prominent features of multisystem inflammatory syndrome in children (MIS-C). In this study we aim to evaluate the early and midterm outcomes of MIS-C. METHODS: This is a longitudinal 6-month cohort study of all children admitted and treated for MIS-C from April 17 to June 20, 2020. Patients were followed ∼2 weeks, 8 weeks, and 6 months postadmission, with those with coronary aneurysms evaluated more frequently. RESULTS: Acutely, 31 (62%) patients required intensive care with vasoactive support, 26 (52%) had left ventricular (LV) systolic dysfunction, 16 (32%) had LV diastolic dysfunction, 8 (16%) had coronary aneurysms (z score ≥2.5), and 4 (8%) had coronary dilation (z score <2.5). A total of 48 patients (96%) received immunomodulatory treatment. At 2 weeks, there was persistent mild LV systolic dysfunction in 1 patient, coronary aneurysms in 2, and dilated coronary artery in 1. By 8 weeks through 6 months, all patients returned to functional baseline with normal LV systolic function and resolution of coronary abnormalities. Cardiac MRI performed during recovery in select patients revealed no myocardial edema or fibrosis. Some patients demonstrated persistent diastolic dysfunction at 2 weeks (5, 11%), 8 weeks (4, 9%), and 6 months (1, 4%). CONCLUSIONS: Children with MIS-C treated with immunomodulators have favorable early outcomes with no mortality, normalization of LV systolic function, recovery of coronary abnormalities, and no inflammation or scarring on cardiac MRI. Persistence of diastolic dysfunction is of uncertain significance and indicates need for larger studies to improve understanding of MIS-C. These findings may help guide clinical management, outpatient monitoring, and considerations for sports clearance.

Incidence of arrhythmias and electrocardiographic abnormalities in symptomatic pediatric patients with PCR-positive SARS-CoV-2 infection, including drug-induced changes in the corrected QT interval.

BACKGROUND: There is limited data regarding the electrophysiological abnormalities and arrhythmias in children with COVID-19, including those associated with treatment using potentially proarrhythmic hydroxychloroquine (HCQ) and azithromycin (AZN). OBJECTIVES: To describe the electrophysiologic findings and arrhythmias associated with pediatric COVID-19 and its treatment. METHODS: A single-center retrospective chart review was undertaken and included all patients with (1) symptoms of COVID-19 and (2) PCR-positive nasopharyngeal swabs for SARS-CoV-2 who were placed on continuous telemetry for the duration of their hospitalization during March through May, 2020. RESULTS: Thirty-six patients were included in the study. Significant arrhythmias were found in 6 (nonsustained ventricular tachycardia in 5 and sustained atrial tachycardia in 1). All were self-resolving and half prompted prophylactic antiarrhythmic therapy. Patients with significant arrhythmias were likely to have noncardiac comorbidities (4/6), but these were not more common than in patients without arrhythmias (20/30, P = 1). The use of HCQ was associated with statistically significant QTc prolongation (413 ± 19 ms vs 425 ± 16 ms, P =.005). QTc was not statistically different in patients with and without arrhythmias (425 ± 15 ms vs 425 ± 15 ms, P = 1). CONCLUSIONS: In pediatric patients with PCR-positive active COVID-19 infection, significant arrhythmias are infrequent, but are more common than expected in a general pediatric population. Comorbidities are not more common in patients with arrhythmias than in patients without arrhythmias. COVID-19 treatment using HCQ is associated with QTc prolongation but was not associated with arrhythmias in pediatric patients.

Difficulties with invasive risk stratification performed under anesthesia in pediatric Wolff-Parkinson-White Syndrome.

BACKGROUND: Children with Wolff-Parkinson-White Syndrome (WPW) are at risk for sudden death. The gold standard for risk stratification in this population is the shortest pre-excited RR interval during atrial fibrillation (SPERRI). OBJECTIVE: The purpose of this study was to determine how closely measurements made in the electrophysiology laboratory in patients with WPW compared to SPERRI obtained during an episode of clinical pre-excited atrial fibrillation (Clinical-SPERRI). METHODS: This was a subgroup analysis of a multicenter study of children with WPW. Subjects in our study (N = 49) were included if they had Clinical-SPERRI measured in addition to 1 or more of 3 surrogate measurements: SPERRI obtained during electrophysiological study (EP-SPERRI), accessory pathway effective refractory period (APERP), or shortest pre-excited paced cycle length with 1:1 conduction (SPPCL). RESULTS: Seventy percent of electrophysiological measurements were made with patients under general anesthesia. Clinical-SPERRI moderately correlated with EP-SPERRI (r = 0.495; P = .012). However, 24% of our patients with Clinical-SPERRI ≤250 ms would have been misclassified as having a low-risk pathway based on EP-SPERRI >250 ms. Clinical-SPERRI did not correlate with APERP or SPPCL (r < 0.3; P >.1). Mean EP-SPERRI, APERP, and SPPCL all were greater than Clinical-SPERRI. CONCLUSION: Electrophysiology laboratory measurements of pathway characteristics made with patients under general anesthesia do not correlate well with Clinical-SPERRI. Of APERP, SPPCL, and EP-SPERRI, only EP-SPERRI had moderate correlation with Clinical-SPERRI. This study questions the predictive ability of invasive risk stratification with patients under general anesthesia, given that 24% of patients with high-risk Clinical-SPERRI (≤250 ms) had EP-SPERRI that may be considered low risk (>250 ms).

Loss of ventricular preexcitation during noninvasive testing does not exclude high-risk accessory pathways: A multicenter study of WPW in children.

BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.