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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., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

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., (© 2021 The Author(s).)

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., Competing Interests: POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose., (Copyright © 2021 by the American Academy of Pediatrics.)

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.

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., (Copyright © 2020 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

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., (Copyright © 2020 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

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 SPERRI baseline (265 ms ± 61 ms), 4 SPERRI Isuprel (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.

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)., (Copyright © 2019 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Predictors of risk of lethal arrhythmic events (LAE) is poorly understood and may differ from adults in children with hypertrophic cardiomyopathy (HCM)., Objective: The purpose of this study was to determine predictors of LAE in children with HCM., Methods: 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., Results: 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 wave > 3 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 gradient < 30 mm Hg (HR 2.0; P < .006). LV posterior wall thickness z score ≥ 5 was associated with LAE., Conclusion: 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., (Copyright © 2019 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

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.

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.

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., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

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 (

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., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Swallowing-induced tachycardia is a rare phenomenon, with only 50 cases documented worldwide. We present a unique case of an adolescent with hypertrophic cardiomyopathy (HCM) who presented with palpitations and a near syncopal episode. The patient was found to have a swallowing-induced atrial tachycardia. He underwent radiofrequency isolation of the right superior pulmonary vein and ablation of the right anterior ganglionated plexus, which led to a resolution of his symptoms. This case highlights the possible association between HCM and autonomic instability as potential aetiological mechanism for the tachycardia.

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 m 2 [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., (© 2017 Wiley Periodicals, Inc.)

Background: Permanent junctional reciprocating tachycardia (PJRT) is an uncommon form of supraventricular tachycardia in children. Treatment of this arrhythmia has been considered difficult because of a high medication failure rate and risk of cardiomyopathy. Outcomes in the current era of interventional treatment with catheter ablation have not been published., Objective: To describe the presentation and clinical course of PJRT in children., Methods: This is a retrospective review of 194 pediatric patients with PJRT managed at 11 institutions between January 2000 and December 2010., Results: The median age at diagnosis was 3.2 months, including 110 infants (57%; aged <1 year). PJRT was incessant in 47%. The ratio of RP interval to cycle length was higher with incessant than with nonincessant tachycardia. Tachycardia-induced cardiomyopathy was observed in 18%. Antiarrhythmic medications were used for initial management in 76%, while catheter ablation was used initially in only 10%. Medications achieved complete resolution in 23% with clinical benefit in an additional 47%. Overall, 140 patients underwent 175 catheter ablation procedures with a success rate of 90%. There were complications in 9% with no major complications reported. Patients were followed for a median of 45.1 months. Regardless of treatment modality, normal sinus rhythm was present in 90% at last follow-up. Spontaneous resolution occurred in 12% of the patients., Conclusion: PJRT in children is frequently incessant at the time of diagnosis and may be associated with tachycardia-induced cardiomyopathy. Antiarrhythmic medications result in complete control in few patients. Catheter ablation is effective, and serious complications are rare., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Robust risk-adjustment algorithms are often necessary if data from clinical registries is to be used to compare rates of important clinical outcomes between participating centers. Although such algorithms have been successfully developed for surgical and catheter-based cardiac interventions in children, outcomes of pediatric and congenital catheter ablation have not been modeled with respect to case mix., Methods: A working group was appointed by the Pediatric and Congenital Electrophysiology Society to develop a risk-adjustment algorithm for use in conjunction with a modernized, multicenter registry database. Expert consensus was used to develop relevant outcome measures, an inclusive list of possible predictors, and estimates of associated incremental risk. Historical data from the Pediatric Radiofrequency Ablation Registry was reanalyzed using multivariate regression to create statistical models of ablation outcomes., Results: Acute ablation failure and serious adverse event rates were modeled as outcomes. Statistical modeling was performed on 4486 cases performed in 19 centers. For ablation failure rate, a simple model including general category of arrhythmia mechanism and presence of structural congenital heart disease accounted for ∼71% of outcome variance. The model was useful for identification of between-center variability in the historical data set. Although expert consensus predicted the need for a more complex model, predicted univariate effects were similar to those generated by statistical modeling. Serious adverse events were too infrequent to permit statistical association with any predictive variable, but could be compared with the mean rate observed among all centers., Conclusion: A substantial component of the intercenter variability of acute ablation outcomes in a historical database of pediatric and congenital ablation patients may be accounted for by a simple statistical model, exposing variations in outcome specific to centers. This will be a useful initial model for use a modern registry for pediatric catheter ablation outcomes., (© 2013 Wiley Periodicals, Inc.)

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., (Copyright © 2013 Mosby, Inc. All rights reserved.)

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., (©2013, The Authors. Journal compilation ©2013 Wiley Periodicals, Inc.)

Background: The RIFLE criteria (risk, injury, failure, loss, and end-stage kidney disease) have been used to assess acute kidney injury (AKI) in various populations of critically ill children. There are limited reports of AKI using RIFLE criteria in large pediatric populations undergoing congenital heart disease surgery., Methods: Records of patients 18 years and younger who underwent surgery for congenital heart disease between January 2006 and November 2009 were reviewed. The RIFLE score was determined for each patient postoperatively. Multivariate logistic regression analyses were performed to determine risk factors for AKI and the association with clinical outcomes, with subanalyses of patients 1 month of age or younger., Results: Data for 458 patients (median age, 7.6 months) were collected and analyzed. Evidence of AKI was demonstrated in 234 patients (51%), the vast majority of whom recovered within 48 hours. Younger age, higher RACHS-1 (risk-adjusted classification for congenital heart surgery) category, and longer cardiopulmonary bypass time were associated with development of AKI. Acute kidney injury was associated with longer duration of ventilation and lengths of intensive care unit and hospital stay. Incidence of AKI in patients 1 month of age or younger was 60.9%, of which more than half required greater than 72 hours to recover. In patients 1 month of age or younger, use of cardiopulmonary bypass, lower preoperative serum creatinine, and higher preoperative blood urea nitrogen were associated with AKI, and AKI was the only factor associated with longer intensive care unit and hospital lengths of stay., Conclusions: Incidence of AKI based on RIFLE criteria in patients undergoing congenital heart disease surgery is higher than previously reported. Risk factors include age 1 month or younger and use of cardiopulmonary bypass. Acute kidney injury is associated with longer lengths of stay., (Copyright © 2012 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)

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., (©2012, The Authors. Journal compilation ©2012 Wiley Periodicals, Inc.)

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.

Objectives: Our aim was to examine the prevalence of arrhythmias and identify independent associations of time to arrhythmia development., Background: Since introduction of the Fontan operation in 1971, long-term results have steadily improved with newer modifications. However, atrial arrhythmias are frequent and contribute to ongoing morbidity and mortality. Data are lacking regarding the prevalence of arrhythmias and risk factors for their development in the current era., Methods: The Pediatric Heart Network Fontan Cross-Sectional study evaluated data from 7 centers, with 520 patients age 6 to 18 years (mean 8.6 +/- 3.4 years after the Fontan operation), including echocardiograms, electrocardiograms, exercise testing, parent-reported Child Health Questionnaire (CHQ) results, and medical history., Results: Supraventricular tachycardias were present in 9.4% of patients. Intra-atrial re-entrant tachycardia (IART) was present in 7.3% (32 of 520). The hazard of IART decreased until 4 to 6 years post-Fontan, and then increased with age thereafter. Cardiac anatomy and resting heart rate (including marked bradycardia) were not associated with IART. We identified 3 independent associations of time to occurrence of IART: lower CHQ physical summary score (p < 0.001); predominant rhythm (p = 0.002; highest risk with paced rhythm), and type of Fontan operation (p = 0.037; highest risk with atriopulmonary connection). Time to IART did not differ between patients with lateral tunnel and extracardiac conduit types of Fontan repair. Ventricular tachycardia was noted in 3.5% of patients., Conclusions: Overall prevalence of IART was lower in this cohort (7.3%) than previously reported. Lower functional status, an atriopulmonary connection, and paced rhythm were determined to be independently associated with development of IART after Fontan. (Relationship Between Functional Health Status and Ventricular Performance After Fontan-Pediatric Heart Network; NCT00132782)., (Copyright © 2010 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: Our objective was to determine the relationship between functional outcome and abnormalities of heart rate and rhythm after the Fontan operation., Methods: The National Heart, Lung, and Blood Institute Pediatric Heart Network conducted a cross-sectional analysis of patients who had undergone a Fontan procedure at the 7 network centers. Analysis was based on 521 patients with an electrocardiogram (n = 509) and/or bicycle exercise test (n = 404). The Child Health Questionnaire parent report and the oxygen consumption at the anaerobic threshold were used as markers of functional outcome., Results: Various Fontan procedures had been performed: intracardiac lateral tunnel (59%), atriopulmonary connection (14%), extracardiac later tunnel (13%), and extracardiac conduit (11%). Prior volume unloading surgery was performed in 389 patients: bidirectional Glenn (70%) and hemi-Fontan (26%). A history of atrial tachycardia was noted in 9.6% of patients and 13.1% of patients had a pacemaker. Lower resting heart rate and higher peak heart rate were each weakly associated with better functional status, as defined by higher anaerobic threshold (R = -0.18, P = .004, and R = 0.16, P = .007, respectively) and higher Child Health scores for physical functioning (R = -0.18, P < .001, and R = 0.17, P = .002, respectively). Higher anaerobic threshold was also independently associated with younger age and an abnormal P-axis. Resting bradycardia was not associated with anaerobic threshold or Child Health scores., Conclusions: In pediatric patients (6-18 years) after the Fontan procedure, a lower resting heart rate and a higher peak heart rate are each independently associated with better physical function as measured by anaerobic threshold and Child Health scores. However, these correlations are weak, suggesting that other, nonrhythm and nonrate, factors may have a greater impact on the functional outcome of pediatric patients after the Fontan operation.

Objective: Electrocardiographic (ECG) rhythm analysis algorithms for cardiac rhythm analysis in automated external defibrillators (AEDs) have been tested against pediatric patient rhythms (patients < or = 8 years old) using adult ECG algorithm criteria. However these adult algorithms may fail to detect non-shockable pediatric tachycardias because they do not account for the difference in the rates of normal sinus rhythm and typical tachyarrhythmias in childhood., Methods: This study was designed to define shockable and non-shockable rhythm detection criteria specific to pediatric patients to create a pediatric rhythm database of annotated rhythms, to develop a pediatric-based AED rhythm analysis algorithm, and to test the algorithm's accuracy. Pediatric rhythm detection criteria were defined for coarse ventricular fibrillation, rapid ventricular tachycardia, and non-shockable rhythms, including pediatric supraventricular tachycardia. Pediatric rhythms were collected as sustained, classifiable, rhythms > or = 9 s in length, and were annotated by pediatric electrophysiologists as clinically shockable or non-shockable based on pediatric criteria. Rhythms were placed into a pediatric rhythm database; each rhythm was converted to digitally accessible, public-domain, MIT rhythm data format. The database was used to evaluate a pediatric-based AED rhythm analysis algorithm., Results: Electrocardiographic rhythms from 198 children were recorded. There were 120 shockable rhythms from 49 patients (sensitivity; coarse ventricular fibrillation: 42 rhythms, 100%; rapid ventricular tachycardia: 78 rhythms, 94%), for combined sensitivity of 96.0% (115/120). There were 585 non-shockable rhythms from 155 patients (specificity normal sinus: 208 rhythms, 100%; asystole: 29 rhythms, 100%; supraventricular tachycardia: 161 rhythms, 99%; other arrhythmias: 187 rhythms, 100%), for combined specificity of 99.7% (583/585). Overall accuracy for shockable and non-shockable rhythms was 99.0% (702/709)., Conclusions: New pediatric rhythm detection criteria were defined and analysis based on these criteria demonstrated both high sensitivity (coarse ventricular fibrillation, rapid ventricular tachycardia) and high specificity (non-shockable rhythms, including supraventricular tachycardia). A pediatric-based AED can detect shockable rhythms correctly, making it safe and exceptionally effective for children.

Background: The fast pathway effective refractory period (ERP) has been reported to decrease after slow pathway modification with radiofrequency (RF) energy. How the fast pathway ERP changes during the ablation application has not been reported with either RF or cryoenergy., Objectives: Using the unique features of cryotherapy, this study assesses the short-term changes in fast pathway ERP during cryomodification of the slow pathway and examines whether these changes are a useful marker for successful slow pathway modification in children., Methods: Nineteen pediatric patients (median age 15.1 years, range 9.6-19.6 years; weight 60.7 kg, range 35.6-130.2 kg) with anterograde dual AV nodal physiology underwent slow pathway modification with catheter-based cryoablation. Programmed stimulation was performed during cryoapplications after reaching -25 degrees C to assess fast pathway and slow pathway conduction. Data were analyzed from 59 of 237 cryoapplications where the fast pathway ERP was measured more than once (n = 13 patients)., Results: For 23 of 59 applications where the slow pathway was modified, the fast pathway ERP significantly increased during cryotherapy (Delta = 33.5 ms, P <.0001). The magnitude of fast pathway ERP prolongation during cryotherapy was larger when the slow pathway was modified than when there was no effect on slow pathway conduction (33.5 +/- 30.5 vs 5.8 +/- 18.9 ms, P =.0005). Prolongation of fast pathway ERP by >/=20 ms had 70% sensitivity and 72% specificity for predicting slow pathway modification. Following termination of cryoapplications, which resulted in slow pathway modification, the fast pathway ERP had significantly decreased from baseline (difference 44.5 ms, P <.0001). The effect on fast pathway ERP was not related to changes in cycle length during (R(2) = 0.04, P = .045) or after ablation (R(2) = 0.13, P = .012)., Conclusion: The fast pathway ERP prolongs during cryoapplications that result in slow pathway modification and shortens after termination of cryoapplications. The magnitude of fast pathway ERP prolongation during cryoapplication may be useful as a marker for successful slow pathway modification.

Objectives: The aim of this study was to evaluate the efficacy and safety of catheter-based cryo-therapy for septal tachycardia substrates in pediatric patients., Background: Cryo-therapy may be particularly useful for ablation of septal tachycardias, including atrioventricular nodal re-entry tachycardia (AVNRT), atrioventricular reciprocating tachycardia (AVRT), and ventricular tachycardia (VT) originating high in the conduction system., Methods: Thirty-one pediatric patients (median = 13.7 years, range 5.3 to 19.6 years) with septal tachycardia substrates underwent cryo-ablation (CA). Twenty-two had AVNRT, 8 AVRT, and 1 VT. Applications were considered cryo-maps (CMs) if the temperature set-point was -35 degrees C or the application time was <120 s. Other lesions were considered CAs., Results: A total of 242 CMs (4 per patient, range 0 to 40 CMs) and 89 CAs (2 per patient, range 1 to 8 CMs) were performed, for a total cryo-therapy time of 689 s/patient (range 158 to 3,300 s). Procedural success with cryo-therapy was achieved in 27 of 31 patients (87.1%), including two procedures with a His potential at the CA location and three performed in tachycardia. The success rate for AVNRT was higher than for AVRT (95.5% vs. 62.5%, p < 0.05). For AVRT, a sustained effect on accessory pathway conduction occurred -3.3 +/- 4.9 s after reaching -25 degrees C, whereas for those sites at which the effect was transient, the effect took 24.8 +/- 25.5 s (p = 0.07). Transient atrioventricular (AV) block occurred during eight cryo-applications (1 CA, 7 CMs) with immediate return of normal AV conduction upon cessation of application. There were no other complications., Conclusions: Cryo-therapy was used to effectively and safely ablate septal tachycardias in this group of 31 pediatric patients. Cryo-therapy may be more effective for AVNRT than septal AVRT.

Little data exists to support the use of procedural modifications during radiofrequency catheter ablation (RFCA) in small children. A single institution database was reviewed for patients under 15 kg undergoing RFCA from January 1998 to August 2001. Of 268 RFCA procedures, 18 were done in 14 patients under 15 kg (median weight 5.7 kg, 3.5-13.7; age 5.8 months, 1.2-19.8). Six patients had normal hearts, 4 had congenital heart disease, and 4 patients had cardiomyopathy. Diagnoses were orthodromic reciprocating tachycardia (ORT) in nine patients/nine studies, chaotic atrial tachycardia (CAT) in one patient/two studies, and VT in four patients/seven studies. RFCA variables included maximum temperature (69 degrees C, 50-78), total applications (10, 2-21), applications > 20 seconds (5, 0-15), and total application time (331 s, 26-1,006 s). Complications were pericardial effusion in 1 patient, mild mitral regurgitation in 1, and myocardial infarction in 1 patient. When indexed for weight, the number of applications with a duration > 20 seconds in the ORT group was significantly greater in complicated versus uncomplicated procedures (0.7 applications/kg vs 0.16 applications/kg, P = 0.05). In addition, for the ORT subgroup, the indexed total application time trended higher in complicated versus uncomplicated procedures (40.6 s/kg, vs 6.6 s/kg, P = 0.1). RFCA success was 9/9 in ORT, 6/7 in VT, and 0/2 in CAT. RFCA can be successful in small children; however, complications appear to be related to RF dose indexed for body size. Thus, the decision to proceed with RFCA, and the application duration and number should be guided by patient size, balanced against the risks of the arrhythmia, and reserved for dire circumstances.

Coronary injury during radiofrequency ablation is a rare but n. potentially life-threatening complication that has been reported for attempted elimination of accessory pathways. This is the first report of coronary artery injury during slow pathway ablation for AV nodal reentrant tachycardia. Manifest signs of injury may be transient or nonexistent and easily missed. Controlled studies are needed to determine the true risk of coronary artery injury during radiofrequency ablation for supraventricular tachycardia, particularly in small children.

Radiofrequency catheter ablation of a left lateral accessory atrioventricular pathway was performed in a 5-week-old infant with drug-refractory supraventricular tachycardia. Energy application via a 5-French mapping and ablation catheter in the temperature-controlled mode (60 degrees C, 30 W) at the atrial aspect of the mitral valve annulus repeatedly resulted in termination of the tachycardia by conduction block within the pathway. Tachycardia remained inducible subsequently. After a safety energy application during sinus rhythm, significant ST-segment elevation in the inferior, mid precordial, and left lateral leads was noted. Selective left coronary angiography revealed complete occlusion of the circumflex coronary artery. Moderate-to-severe mitral valve regurgitation developed, finally requiring mitral valve replacement.

Experience concerning radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) in pediatric patients is limited. In adults, success rates vary widely based on the etiology of the VT. Highest success rates have been achieved in patients without structural heart disease. Between March 1998 and December 1999, five young patients (age, 5 months to 15 years; body weight, 5.5-61.6 kg) underwent RFCA for VT at our institution [structurally normal heart (n = 4), preoperative tetralogy of Fallot (n = 1)]. Monomorphic VT was present in four children, and an infant with MIDAS syndrome had polymorphic VT. Clinical presentation varied: palpitations, n = 2, congestive heart failure, n = 3. All patients had been proven to be unresponsive to one to six (median, three) antiarrhythmic drugs. In all five patients, VT could be successfully eliminated by RFCA after a total of nine (range, 1-4) procedures. Activation mapping and pace mapping were used to identify the anatomical substrate, which was located in the right ventricle/right ventricular outflow tract in all four patients with monomorphic VT and in the left ventricular septum/left ventricular free wall in the infant with polymorphic VT. There were no significant complications in any patient. During follow-up (20-42 months), all patients are in normal sinus rhythm. Left ventricular function recovered in all three patients who had initially presented with congestive heart failure. RFCA can be effective, safe, and life saving in children with medically resistant VT who have not been operated on for congenital heart disease, even when the VT is polymorphic. Although the number of patients is small, RFCA may be the treatment of choice for symptomatic VT in pediatric patients.

Background: Idiopathic repetitive monomorphic ventricular tachycardia with an inferior axis and left bundle branch block pattern typically originates from the superior right ventricular outflow tract. When indicated, radiofrequency catheter ablation is usually safe and effective. However, a left ventricular origin has been described recently in adult patients in whom ablation attempts in the right ventricular outflow tract were unsuccessful. Experience in pediatric patients is limited., Patients and Methods: Since 1998, 13 young patients suffering from symptomatic ventricular tachycardia episodes with an inferior axis and left bundle branch block pattern underwent an electrophysiological study and radiofrequency catheter ablation. In 2 patients, age 13 and 15 years, no endocardial local electrograms preceding the surface ECG QRS complex could be recorded within the right ventricular outflow tract during ventricular ectopy. Detailed mapping within the left ventricular outflow tract and in the aortic root revealed local electrograms 25 and 53 ms earlier than the QRS complex and a 11/12 and 12/12 lead match during pacing inferior and anterior to the ostium of the left main coronary artery in the left aortic sinus cusp. Earliest activation was recorded 10 and 12 mm away from the coronary artery ostium identified angiographically. In each of the patients, one single radiofrequency current application (60 degrees C, 30 W, duration 30 and 60 s, respectively) resulted in complete cessation of ventricular ectopy. Subsequent selective injection into the left coronary artery did not reveal any abnormalities. During follow-up (2 and 34 months) off any antiarrhythmic drugs, both of the patients are in continuous normal sinus rhythm., Conclusion: In young patients with symptomatic idiopathic ventricular tachycardia originating from the left aortic sinus cusp, radiofrequency catheter ablation was safe and effective.

Introduction: Cooling the catheter tip either passively with increased tip size or actively during radiofrequency catheter ablation (RFCA) has been shown in canine thigh preparations to create larger lesions than standard catheter tips, yielding a theoretical advantage for improving the outcome of RFCA for intra-atrial reentrant tachycardia (IART)., Methods and Results: The pediatric RFCA database at the Medical University of South Carolina was reviewed for RFCA of IART in patients with structural heart disease. From a total of 31 patients who underwent procedures during the study period, 8 patients in whom ablation with conventional ablation techniques failed and who went on to passive cooling with an 8-mm tip catheter or active cooling with an internally cooled-tip catheter were studied. Power delivery was greater but temperature and impedance were lower during cooled ablation than during conventional ablation. Passive cooling was associated with higher power than active cooling. These changes in RF biophysical characteristics were associated with successful elimination of 11 of 13 IART circuits in 7 of 8 patients., Conclusion: Cooling during RF ablation of atrial tachycardia clearly yielded greater power delivery in vivo and was associated with success.

Background: The objective of this study was to determine the indications, the safety, and the efficacy of pediatric radiofrequency catheter ablation (RFCA) in infants., Methods and Results: Data from the pediatric RFCA registry were reviewed. Between August 1989 and January 1999, 137 infants, defined by age 0 to 1.5 years (median 0.7 years; weight 1.9 to 14.8 kg, median 10 kg), underwent 152 procedures in 27 of 49 registry centers (55%), compared with 5960 noninfants undergoing 6610 procedures during a comparable period. Structural heart disease was present in 36% of infants, compared with 11.2% of noninfants (P<0.0001). RFCA in infants was performed more commonly for drug resistance or life-threatening arrhythmias than in noninfants. No differences were found between infants and noninfants in success for all tachycardia substrates (87.6% versus 90.6%, P=0.11), for single accessory pathways (94.5% versus 91.5%, P=0.4), or for total (7.8% versus 7.4%, P=1) and major (4.6% versus 2.9%, P=0.17) complications. Neither success for infants with a single accessory pathway nor complications for the entire infant group were related to weight, age, center size, or the presence of structural heart disease. Centers that performed infant procedures, however, enrolled more patients overall in the registry than those that did not perform infant procedures, and successful procedures in infants were performed by more experienced physicians than failed procedures., Conclusions: Compared with noninfants, RFCA in infants is usually performed for drug resistance or life-threatening arrhythmias, often in the presence of structural heart disease. The data support the use of RFCA by experienced physicians in selected infants.

Right free-wall and septal accessory pathways encompass the full spectrum of accessory pathway electrophysiology and are situated in complex anatomical arrangements. Understanding this diversity of physiology is necessary for the successful and safe elimination of these connections with transcatheter radiofrequency ablation. When radiofrequency catheter ablation of these pathways is attempted in children, anatomical relationships often become more complex, and spatial constraints require more adaptive techniques than in adults. It is clear that considerable progress has been made with radiofrequency catheter ablation, such that it is now first-line therapy for most children who have been diagnosed with one of the broad spectrum of clinical manifestations that result from the presence of these accessory connections. This review will discuss how accessory pathway electrophysiology and anatomy impact the clinical syndromes observed in children, and how these factors, as well as others particular to children, determine the approach, results and potential long-term consequences of radiofrequency catheter ablation of right-sided accessory pathways in the pediatric population.

The overall risk of pediatric cardiac catheterization remains low despite the enormous new complexity and potential for complications brought on by the growth of interventional catheterization techniques. For all patients aged < 21 years, balloon interventions carry the highest risk, diagnostic procedures carry more risk than non-balloon interventions, and although weight < or = 5 kg is a significant risk factor for complications, irrespective of the type of procedure performed, weight < or = 2.5 kg did not alter that risk.

Dual atrioventricular nodal (DAVN) physiology has been reported in up to 63% of pediatric patients with anatomically normal hearts, yet atrioventricular nodal reentrant tachycardia (AVNRT) accounts for only 13%-16% of supraventicular tachycardia (SVT) in childhood. The incidence of AVNRT increases with age and becomes the most common form of SVT by adolescence. We investigated the age related electrophysiological responses to programmed atrial and ventricular stimulation in 14 pediatric patients who underwent intracardiac electrophysiological study prior to radiofrequency catheter ablation for AVNRT and who exhibited DAVN physiology. Single atrial and ventricular extrastimuli were placed following drive trains with cycle lengths of 400-700 ms and 350-500 ms, respectively. Six children (mean age 8.2 years, range 5.2-11.5 years) were compared to eight adolescents (mean age 16.6 years, range 13.3-20.7 years). Adolescents were found to have a significantly longer fast pathway effective refractory period (ERP) (median 375 vs 270 ms, P = 0.03), slow pathway ERP (median 270 vs 218 ms, P = 0.04), atrio-Hisian (AH) during AVNRT (median 300 vs 225 ms, P = 0.007), and AVNRT cycle length (median 350 vs 290 ms, P = 0.03). There was a strong trend for the AH measured at the fast pathway ERP to be longer in adolescents than in children (median 258 vs 198 ms, P = 0.055). The AH at the fast pathway ERP was more strongly correlated with baseline cycle length than with age (r = 0.7, P = 0.01 vs r = 0.5, P = 0.7). There was no significant difference in the retrograde VA conduction between adolescents and children. These results demonstrate an age related difference in AV nodal response to programmed atrial stimuli in pediatric patients with DAVN physiology and AVNRT. These differences are consistent with mechanisms that may explain the increased incidence of AVNRT in adolescents compared to children.

Background: The survival rate to discharge after a cardiac arrest in a patient in the pediatric intensive care unit is reported to be as low as 7%. The survival rates and markers for survival strictly regarding infants with cardiac arrest after congenital heart surgery are unknown., Methods and Results: Infants in our pediatric cardiac intensive care unit database were identified who had a postoperative cardiac arrest between January 1994 and June 1998. Parameters from the perioperative, prearrest, and resuscitation periods were analyzed for these patients. Comparisons were made between survivors and nonsurvivors. Of 575 infants who underwent congenital heart surgery, 34 (6%) sustained a documented cardiac arrest; of these, 14 (41%) survived to discharge. Perioperative parameters, ventricular physiology, and primary rhythm at the time of arrest did not influence outcome. Prearrest blood pressure was lower in nonsurvivors than in survivors (P<0.001). A high level of inotropic support prearrest was associated with death (P=0.06). Survivors had a shorter duration of resuscitation (P<0.001) and higher minimal arterial pH (P<0.02) and received a smaller total dose of medication during the resuscitation. Although survivors had an overall shorter duration of resuscitation, 5 of 22 patients (23%) survived to discharge despite resuscitation of >30 minutes., Conclusions: The outcome of cardiac arrest in infants after congenital heart surgery was better than that for pediatric intensive care unit populations as a whole. Univentricular physiology did not increase the risk of death after cardiac arrest. Infants with more hemodynamic compromise before the arrest as demonstrated with lower mean arterial blood pressure and higher inotropic support were less likely to survive. The use of predetermined resuscitation end points in this subpopulation may not be justified.

Patients with left ventricular hypoplasia and left-sided heart obstructive lesions other than critical aortic stenosis may be inappropriately subjected to single ventricular repair because their assessment is based on faulty qualitative evaluations or on quantitative methods developed for critical aortic stenosis. Patients with left ventricular hypoplasia and left-sided heart obstructions other than critical aortic stenosis successfully underwent biventricular repair despite "failing" to pass established criteria for critical aortic stenosis.

Focal Tc-99m MDP uptake on bone scanning in regions of deep venous thrombosis (DVT) is reported in two patients with documented DVT. It is speculated that this uptake may be related to localized calcification or ossification, which is occasionally observed on radiographs of patients with chronic DVT.