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Clinically significant bradycardia is an uncommon problem in children, but one that can cause significant morbidity and sometimes necessitates implantation of a pacemaker. The most common causes of bradycardia are complete heart block (CHB), which can be congenital or acquired, and sinus node dysfunction, which is rare in children with structurally normal hearts. Pacemaker is indicated as therapy for the majority of children with CHB, and while early mortality is lower in postnatally diagnosed CHB than in fetal CHB, it is still up to 16%. In young children, less invasive transvenous pacemaker systems can be technically challenging to place and carry a high risk of complications, often necessitating surgical epicardial pacemaker placement, which usually entails a median sternotomy. We report three cases of pediatric patients referred for pacemaker implantation for different types of bradycardia, treated at our institution with oral albuterol with therapeutic results that avoided the need for surgical pacemaker implantation at that time., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Little is known about the outcomes of children with second-degree heart block. We aimed to determine whether children with structurally normal hearts and Mobitz 1, 2:1 block or Mobitz 2 are at increased risk for progressing to complete heart block (CHB) or requiring a pacemaker (PM) at long-term follow-up. We searched our institutional electrophysiology database for children with potentially concerning second-degree block on ambulatory rhythm monitoring between 2009 and 2021, defined as frequent episodes of Mobitz 1 or 2:1 block, episodes of Mobitz 1 or 2:1 block with additional evidence of conduction disease (i.e. first-degree heart block, bundle branch block), or episodes of Mobitz 2. Ambulatory rhythm monitor, ECG, and demographic data were reviewed. The primary composite outcome was CHB on follow-up rhythm monitor or PM placement. 20 patients were in the final analysis. Six (30%) patients either developed CHB but do not have a PM (4 = 20%) or have a PM (2 = 10%). Median follow-up was 5.8 years (IQR 4.4-7.0). Patients with CHB or PM were more likely to have second-degree block at maximum sinus rate (67% vs. 0%, p = 0.003), a below normal average heart rate (67% vs. 14%, p = 0.04), and 2:1 block on initial ECG (50% vs. 0%, p = 0.02). In this study of children with potentially concerning second-degree block, 30% of patients progressed to CHB or required a PM. Second-degree block at maximum sinus rate, a low average heart, and 2:1 block on initial ECG were associated with increased risk of disease progression., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The AliveCor KardiaMobile (ACKM) is a remote electrocardiogram (ECG) monitoring device. Little research has been conducted on its accuracy with pediatric patients. This prospective study aims to compare the ACKM six-lead device with a standard fifteen-lead ECG in measuring the QTc, QRS, and axis in pediatric patients. Pediatric patients ages 5 to 21 years were enrolled prospectively to have their ECG recorded using an ACKM six-lead device following a recording with the standard 15-lead ECG. A pediatric electrophysiologist measured the QTc, QRS interval, and QRS axis for both ECGs. Bland-Altman analysis was performed to assess agreement among measurements. The study included 141 patients. The mean age was 12.3 ± 4.4 years. Average heart rate was 79 ± 16 bpm. The mean difference in the QTc measurements for a paired standard ECG and ACKM was - 0.6 ms [95% confidence interval - 48 to 47 ms]. Of the ACKM QTc measurements, 117 (83%) were within 30 ms of the standard ECG. The mean difference in paired QRS measurements was - 1.3 ms [95% confidence interval - 23 to 21 ms]. Of the ACKM QRS measurements, 134 (95%) were within 20 ms of the standard ECG. The measured axis was the same for 84% of ACKM and standard ECGs. Over 80% of the ACKM six-lead ECGs produced QTc, QRS, and axis deviation measurements within a clinically useful range of the standard ECG. However, it is not accurate enough to be used consistently in place of a standard ECG for QTc and QRS measurement for pediatric patients., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Sudden cardiac arrest in pediatric patients is a rare occurrence. Supraventricular tachycardia without the presence of ventricular preexcitation in pediatric patients with a structurally normal heart is generally considered benign. Previous literature in adults reported a subset of patients in whom SVT was suspected to be the primary trigger of sudden cardiac arrest. We performed a single-center, retrospective cohort study of pediatric patients without known heart disease, 1-21 years of age, presenting with aborted SCA between 2009 and 2019. We collected diagnostic studies in all patients to identify the etiology of the aborted SCA. Thirty patients met the inclusion criteria. The median age at the time of SCA was 15.2 years. The etiology of SCA was identified in 23 (77%) patients. Of the seven patients with unknown diagnosis after initial diagnostic studies, three patients subsequently developed fast SVT that was presumed to be the etiology of the initial SCA. These three patients had varying diagnoses of atrioventricular nodal reentry tachycardia, ectopic atrial tachycardia, and a concealed accessory pathway with atrioventricular reentrant tachycardia. After ablation or medical treatment of the SVT substrate, no further tachyarrhythmias were observed. Pediatric patients presenting with an aborted SCA of unknown etiology ought to be considered for electrophysiology testing to elicit occult SVT substrates that may lead to a malignant ventricular tachyarrhythmia., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Block in accessory pathway (AP) conduction with adenosine has been previously described. However, conduction characteristics of these APs has not been well defined to date. All patients with APs 2 and Fisher's exact were used for analysis. Fourteen (7%) out of 207 patients had an adenosine sensitive AP. The median age of patients with adenosine sensitive APs was 11.8 (IQR 8.5-13.5) years vs. 14 (IQR 10.6-16.7) for the rest of the cohort (p = 0.04). Three of the 134 patients with preexcitation had adenosine sensitive APs (2%) vs. 11 of the 73 patients with concealed APs (15%) (p = 0.001). The median local AV/VA time at the site of successful ablation was longer in group 1 vs group 2 [78 ms, IQR 62-116 vs. 31 ms, IQR 30-38; p < 0.001]. Antegrade AP effective refractory period and total procedure time were longer in patients with adenosine sensitive APs (p = 0.03 & p = 0.04, respectively). Adenosine sensitive APs which occur in children are more often concealed. These APs have a longer conduction time at the site of successful ablation., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Definitive treatment of supraventricular tachycardia (SVT) substrate involves catheter ablation. While objective success rates have been well established, long-term subjective patient experiences have not been well described. We quantify a subjective cure rate and characterize long-term patient experience after acutely successful ablation. A cross-sectional survey of pediatric patients with accessory pathways or atrioventricular nodal reentrant tachycardia who underwent acutely successful ablation from 2008 to 2012 was performed. Data were obtained from medical records and patient surveys. Patients with congenital heart disease other than patent ductus arteriosus, patent foramen ovale, or coronary artery abnormalities were excluded. Statistical analyses included Student's t-test and χ 2 analysis for continuous and categorical variables, respectively. Surveys were sent to 153 patients of which 147 responded with median follow-up of 7.2 (IQR 6.1-8.5) years. Of the 147 responders, 124 (84%) patients reported cure with a male predominance. Symptoms were present in 130/147 (88%) patients pre-ablation and in 53/147 (36%) post-ablation. Among those with post-ablation symptoms, 50/53 (94%) reported symptomatic improvement. Recurrence occurred in 23/147 (16%) patients and was more prevalent following cryoablation. Ablation of SVT substrate can be curative with excellent long-term results and patient satisfaction. Long-term subjective cure rate is high and there is a substantial decrease in symptoms post-ablation. Many patients continue to have symptoms following ablation; however, the majority of these patients consider themselves cured and symptoms can be attributed to other etiologies. Recurrence is uncommon and occurs more frequently following cryoablation.

Background: The clinical course of children with advanced heart block secondary to Lyme disease has not been well characterized., Objective: To review the presentation, management, and time to resolution of heart block due to Lyme disease in previously healthy children., Methods: An IRB approved single-center retrospective study was conducted of all patients < 21 years old with confirmed Lyme disease and advanced second or third degree heart block between 2007 and 2017., Results: Twelve patients (100% male) with a mean age of 15.9 years (range 13.2-18.1) were identified. Six patients (50%) had mild to moderate atrioventricular valve regurgitation and all had normal biventricular function. Five patients had advanced second degree heart block and 7 had complete heart block with an escape rate of 20-57 bpm. Isoproterenol was used in 4 patients for 3-4 days and one patient required transvenous pacing for 2 days. Patients were treated with 21 days (n = 6, 50%) or 28 days (n = 6, 50%) of antibiotics. Three patients received steroids for 3-4 days. Advanced heart block resolved in all patients within 2-5 days, and all had a normal PR interval within 3 days to 16 months from hospital discharge., Conclusion: Symptomatic children who present with new high-grade heart block from an endemic area should be tested for Lyme disease. Antibiotic therapy provides quick and complete resolution of advanced heart block within 5 days, while steroids did not appear to shorten the time course in this case series. Importantly, no patients required a permanent pacemaker.

Smartphone applications that record a single-lead ECG are increasingly available. We sought to determine the utility of a smartphone application (AliveCor) to record supraventricular tachycardia (SVT) and to distinguish atrioventricular reentrant tachycardia (AVRT) from atrioventricular nodal reentrant tachycardia (AVNRT) in pediatric patients. A prior study demonstrated that interpretation of standard event and Holter monitors accurately identifies the tachycardia mechanism in only 45 % of recordings. We performed an IRB-approved prospective study in pediatric patients undergoing an ablation for SVT. Tracings were obtained by placing the smartphone in three different positions on the chest (PI-horizontal, PII-rotated 60° clockwise, and PIII-rotated 120° clockwise). Two blinded pediatric electrophysiologists jointly analyzed a pair of sinus and tachycardia tracings in each position. Tracings with visible retrograde P waves were classified as AVRT. The three positions were compared by Chi-square test. Thirty-seven patients (age 13.7 ± 2.8 years) were enrolled in the study. Twenty-four had AVRT, and 13 had AVNRT. One hundred and eight pairs of tracings were obtained. The correct diagnosis was made in 27/37 (73 %) with position PI, 28/37 (76 %) with PII, and 20/34 (59 %) with PIII (p = 0.04 for PII vs. PIII and p = NS for other comparisons). A single-lead ECG obtained with a smartphone monitor can successfully record SVT in pediatric patients and can predict the SVT mechanism at least as well as previously published reports of Holter monitors, along with the added convenience of not requiring patients to carry a dedicated monitor.

Hypoplastic left heart syndrome (HLHS) is a severe form of congenital heart disease characterized by underdevelopment of the left heart. There has been no previously defined "classic" ECG pattern in a large homogenous population of patients with HLHS. We performed a retrospective review of ECGs from neonates with HLHS from 2001 to 2011 with electrocardiograms available prior to surgical intervention. Eighty-nine neonates met the inclusion criteria and were compared to a control population. HLHS patients had a longer PR interval 108 ± 18 versus 98 ± 11 ms (p < 0.05), a wider QRS complex 84 ± 17 versus 54 ± 5 ms (p < 0.05), lower voltage S waves in V1 2.0 ± 3.3 versus 5.8 ± 4.6 mm (p < 0.001) or absent S waves in V1 52 versus 4 % (p < 0.001) and lower voltage R waves in V6 7.8 ± 4.8 versus 9.3 ± 4.2 mm (p < 0.05). Patients with HLHS were more likely to have absent Q waves in the lateral precordial leads 78 versus 0 % (p < 0.001) and inferior leads 20 versus 1 % (p < 0.001) and an abnormal frontal plane QRS axis 26 versus 11 % (p < 0.05). HLHS patients were more likely to have a preexcited appearance 11 versus 0 % (p = 0.001). Despite these findings, 20 % of patients with HLHS had a normal ECG. Compared to age-matched controls, patients with HLHS were more likely to exhibit a longer PR interval, a wider QRS complex, decreased left-sided forces, an absence of septal Q waves in the inferior and lateral leads, an abnormal frontal plane QRS axis and a preexcited appearance.

Remifentanil is commonly used during anesthesia in pediatric electrophysiologic studies (EPS). The purpose of this study is to determine the effects of remifentanil on the cardiac electrophysiologic properties of children undergoing ablation of supraventricular tachycardia (SVT). A prospective study was performed in patients undergoing EPS before ablation of SVT. Each patient received two different anesthetic protocols: protocol 1 = propofol (200 mcg/kg/min) and protocol 2 = propofol (120 mcg/kg/min) plus remifentanil (0.3 mcg/kg/min). EPS data were measured during the steady state of each protocol. Paired Student t test was performed for analysis of continuous data. All p values <0.05 were considered statistically significant. Fifteen patients were enrolled between April 2005 and January 2006. The mean age was 13.3 ± 2.9 years (range 6.7 to 17.7). Seven patients had atrioventricular (AV) nodal re-entry tachycardia; 5 patients had Wolff-Parkinson-White syndrome; 2 patients had a concealed accessory pathway; and 1 patient was not inducible. Of the 14 patients who underwent ablation, 13 (93%) achieved successful. The baseline sinus cycle length extended from 884 ± 141 ms during protocol 1 to 980 ± 165 ms during protocol 2 (p = 0.01), and the Wenckebach cycle length lengthened from 377 ± 96 ms to 406 ± 109 ms (p = 0.01). No other variables measured (atrial-His (AH) and His-ventricular (HV) interval, atrioventricular node (AVN), and atrial, ventricular, and accessory pathway effective refractory periods) changed significantly between the two different protocols. In pediatric patients undergoing EPS before ablation of SVT, remifentanil appears to slow both sinus and AV nodal function. These effects should be taken into consideration when performing EPS.

A 16-year-old female patient with Wolff-Parkinson-White syndrome and supraventricular tachycardia underwent radiofrequency (RF) catheter ablation of an accessory pathway in the left lateral area. During RF ablation she developed reversible ST segment elevation secondary to coronary artery spasm. Coronary angiography demonstrated the ablation catheter in close proximity to the circumflex coronary artery, with no evidence of coronary artery injury. Subsequently, conduction by way of the accessory pathway was successfully eliminated with cryoablation with no further coronary spasm or injury.