Background Intracardiac echocardiography (ICE) is conventionally used as an endovascular imaging modality during electrophysiology procedures. Reports of transesophageal ICE are limited and have not included pediatric electrophysiology procedures. Case Summary We report the first case series of transesophageal ICE (NuVision NAV) in 6 infants and young children with congenital heart disease undergoing electrophysiology studies and catheter ablation. Indications included preoperative conduction mapping and clinical arrhythmias. Discussion Transesophageal placement preserves the imaging advantages of ICE while avoiding large-bore venous access in small children without compromising image quality. The technique facilitates electroanatomic mapping by providing accurate delineation of the atrioventricular annulus in patients with complex congenital heart disease. Take-Home Message Transesophageal ICE with four-dimensional multiplanar imaging provides high-quality real-time anatomical guidance for electrophysiology procedures in infants and young children with complex congenital heart disease and may offer a practical alternative to intravascular ICE when large-bore venous access is undesirable.

Purpose: Permanent pacing in the young pediatric population can be challenging, especially in small neonates. We describe our institutional experience with the surgical placement of dual-chamber permanent pacemaker (PPM) systems in neonates weighing <3 kg at the time of implantation. Methods: The Cincinnati Children's Hospital database was used to identify patients who had an epicardial dual-chamber PPM and weighed <3 kg at implantation from 2000 to 2022. Descriptive analyses focused on surgical techniques, postimplant complications, and survival. Results: Twenty patients underwent dual-chamber PPM implantation. Median age at implantation was 6.0 days [3.0-27.0], weight 2.6 kg [2.2-3.0], with the smallest being 1.9 kg. Eight of 20 patients (40%) were premature (<37 weeks), and 2/20 (10%) had Trisomy 21. Most implantations were via median sternotomy [17/20 (85%)]. Most had generator placement in the left upper quadrant [13/20 (65%)] above the posterior fascia and below the rectus muscle. Surgical indication for implantation was congenital heart block [18/20 (90%)], of which 4/18 (22%) were due to maternal lupus. Two patients had PPM secondary to postoperative heart block and 3/20 (15%) had emergent temporary epicardial wires placed before PPM. Pacemaker-related complications occurred in 1/20 (5%) patient on postoperative day 20 related to minor wound dehiscence, without infection, leading to a dual-chamber PPM exchange for a single-chamber device. Another patient (5%) developed a seroma requiring drainage on postoperative day 16. There were no PPM-related in-hospital mortalities or other complications, including late PPM infections. Conclusions: Dual-chamber epicardial PM implantation in neonates <3 kg is feasible with minimal complications and good outcomes based on our reported technique.

Tetralogy of Fallot is the most common cyanotic congenital heart disease, characterized by 4 defects: pulmonary outflow obstruction, ventricular septal defect, overriding aorta, and right ventricular hypertrophy. Advances in surgical repair have significantly improved survival, but patients remain at risk for long-term complications, especially arrhythmias. Immediate postoperative arrhythmias include junctional ectopic tachycardia, complete heart block, while long-term atrial tachycardias, and life-threatening ventricular tachycardias occur linked to scar-related reentry circuits. Modern management includes antiarrhythmic medications, catheter ablation, and implantable cardioverted defibrillators, with newer strategies focusing on identifying and ablating slow-conducting anatomical isthmuses for ventricular tachycardia.

ABSTRACT Background Catheter‐based ablation in the coronary venous sinus (CS) can be associated with inadvertent coronary artery (CA) injury. However, a significant gap remains in the literature with regard to safety of such ablation in pediatrics. Objectives The primary aim of this study was to describe the safety of catheter‐based ablation within the CS. Secondary aim was to describe the practice pattern of ablation energy source within the CS among pediatric centers. Methods This was a multi‐center, retrospective study over a period of 20 years (1999–2019) involving seven centers. Pediatric patients (≤ 21 years of age) undergoing ablation within the CS were included. Results A total of 211 patients were included (median age: 14 [IQR: 10.5, 16.0]). Accessory pathways were the target in almost 90% of the patients with cryoablation in 55%, nonirrigated RF in 40% and irrigated RF in 6%. Only 16% had coronary arteriogram done before RF. There was a single patient who had CA injury, in the form of a transient spasm of the left circumflex CA following RF in the proximal CS. There was transient high‐grade AV block in six patients (2.8%) who either had RF or cryoablation. There was no permanent AV block. Conclusion The use coronary arteriogram before RF in the CS is infrequent, although acute CA injury appears to be rare following such ablation. Transient heart block is not uncommon, and the operators need to be vigilant in monitoring AV nodal conduction.

Non-invasive assessment of myocardial work is a newly described technique to assess myocardial energetics. This has not been previously studied to assess the effects of right ventricular pacing at different sites or at different heart rates in children. We aimed to study the effects of right ventricular apical, septal, and His bundle pacing on myocardial work along with the effects of increasing heart rate. This was a prospective pilot study performed on six patients with structurally normal hearts and function following an electrophysiology study. Global work index and global work efficiency was highest during His pacing and lowest during right ventricular apical pacing. The global constructive work, index, and efficiency were progressively worse with increasing heart rates. In this prospective pilot study, we demonstrated that myocardial work indices differ depending on myocardial activation pattern and at different heart rates in pediatric patients. Myocardial performance as assessed by myocardial work efficiency is worse when pacing is performed at the right ventricular apex when compared to His and right ventricular septal pacing. Myocardial performance can be affected by higher heart rates, following a work–frequency relationship.

OBJECTIVES:This study evaluates the short- and long-term outcomes of patients with single-ventricle morphology with arrhythmias prior to Fontan surgery, assessing the association between early arrhythmias and subsequent clinical outcomes. BACKGROUND:Staged surgical palliation for single-ventricle physiology involves complex operations with a high incidence of arrhythmias. The optimal duration of antiarrhythmic medication use and its impact on surgical outcomes and long-term prognosis remain unclear. METHODS:A single-center retrospective analysis was conducted on patients treated between August 2011 and January 2024. Patients with single-ventricle physiology undergoing staged surgical palliation with documented arrhythmias were selected for detailed analysis. Data on patient characteristics, arrhythmia type, antiarrhythmic medication use, and outcomes were collected and analyzed. RESULTS:The study included 109 patients, predominantly male, with hypoplastic left heart syndrome being the most common morphology. Arrhythmias were primarily encountered during Stage 1 admission (97%), with no initial arrhythmia occurrence during interstage times. Pre-Fontan electrophysiology studies showed inducible tachycardia in 33% of patients. The need for ablation was seen in conjunction with heterotaxy syndrome and patients with longer duration and complexity of tachycardia prior to Fontan. Overall survival to Fontan was poor, with significant mortality at each stage of palliation. Subsequent post-Fontan arrhythmia was rare and there was no recurrence of patients undergoing ablation. CONCLUSION:Early arrhythmias are common in single-ventricle patients undergoing staged palliation and this cohort is associated with significant morbidity and mortality. Pre-Fontan electrophysiology studies and ablation may improve outcomes, particularly in high-risk cohorts, highlighting the need for tailored arrhythmia monitoring and management strategies. CONDENSED ABSTRACT:This study evaluates the outcomes of patients with single-ventricle physiology and arrhythmias occurring before Fontan surgery, examining the relationship between early arrhythmias and clinical outcomes. Conducted as a single-center retrospective analysis from August 2011 to January 2024, it includes 109 patients with hypoplastic left heart syndrome. Arrhythmias were common during Stage 1 admission (97%). Pre-Fontan electrophysiology studies showed inducible tachycardia in 33% of patients, with ablation needed in those with heterotaxy syndrome and complex tachycardia. Survival to Fontan was poor, with significant mortality at each stage. Tailored arrhythmia monitoring and management strategies are essential.

BACKGROUND:Cardiac rehabilitation (CR) is underused in pediatric and congenital heart disease populations. Concern about arrhythmia risk may be an obstacle to CR referral. We sought to describe the frequency and risk factors for arrhythmia in patients who participated in a standardized CR program. METHODS:We conducted a retrospective chart review of all patients who completed at least 1 CR encounter from 2017 to 2022 at a pediatric cardiology center. We used descriptive statistics to determine the frequency of atrial and ventricular ectopy. Logistic regression was performed to identify predictors of frequent ventricular ectopy, nonsustained ventricular tachycardia, or ventricular tachycardia. RESULTS:There were 177 patients who participated in 4494 rehabilitation encounters over the 6-year study period (median age, 17 years [14-22]). Most patients had congenital heart disease (63%). Moderate or severe systolic dysfunction was noted in 14% of patients. Presence of an implantable cardioverter-defibrillator (9% of patients) and a ventricular assist device (5% of patients) was noted. Nonsustained ventricular tachycardia occurred in 7 patients (3.9%) across 18 sessions (0.4%). There was an episode of sustained ventricular tachycardia resulting in an appropriate implantable cardioverter-defibrillator shock. There were no deaths. Patients ≥18 years old (odds ratio, 2.7 [95% CI, 1.1 - 6.4]) were more likely to have frequent ventricular ectopy, nonsustained ventricular tachycardia, or ventricular tachycardia. CONCLUSIONS:Supervised CR in pediatric and congenital heart disease populations is associated with a low risk for clinically significant arrhythmias, and should not be an obstacle to referral for individuals who would otherwise benefit from CR.

BACKGROUND:Junctional ectopic tachycardia (JET) complicates congenital heart surgery in 2% to 8.3% of cases. JET is associated with postoperative morbidity in single-center studies. We used the Pediatric Cardiac Critical Care Consortium data registry to provide a multicenter epidemiologic description of treated JET. METHODS:This is a retrospective study (February 2019-August 2022) of patients with treated JET. Inclusion criteria were (1) <12 months old at the index operation, and (2) treated for JET <72 hours after surgery. Diagnosis was defined by receiving treatment (pacing, cooling, and medications). A multilevel logistic regression analysis with hospital random effect identified JET risk factors. Impact of JET on outcomes was estimated by margins/attributable risk analysis using previous risk-adjustment models. RESULTS:Among 24,073 patients from 63 centers, 1436 (6.0%) were treated for JET with significant center variability (0% to 17.9%). Median time to onset was 3.4 hours, with 34% present on admission. Median duration was 2 days (interquartile range, 1-4 days). Tetralogy of Fallot, atrioventricular canal, and ventricular septal defect repair represented >50% of JET. Patient characteristics independently associated with JET included neonatal age, Asian race, cardiopulmonary bypass time, open sternum, and early postoperative inotropic agents. JET was associated with increased risk-adjusted durations of mechanical ventilation (incidence rate ratio, 1.6; 95% CI, 1.5-1.7) and intensive care unit length of stay (incidence rate ratio, 1.3; 95% CI, 1.2-1.3), but not mortality. CONCLUSIONS:JET is treated in 6% of patients with substantial center variability. JET contributes to increased use of postoperative resources. High center variability warrants further study to identify potential modifiable factors that could serve as targets for improvement efforts to ameliorate deleterious outcomes.

BACKGROUND:Infants with complete heart block (CHB) require epicardial pacemaker (PM) insertion. Prior studies described epicardial pacing outcomes in infants and children, although they were limited by small or heterogeneous populations. OBJECTIVE:This study aimed to explore patient- and procedure-level associations with device complications in infants with CHB who received a permanent PM. METHODS:This was a multicenter, retrospective cohort study including infants receiving an epicardial PM between 2000 and 2021 for CHB. The primary outcome was time to device-related adverse event: lead failure requiring revision; pocket infection; exit block requiring increased pacing output; or lead-related coronary artery compression. Time-to-event analysis was performed by the Kaplan-Meier method with a multivariable Cox proportional hazards model. RESULTS:There were 174 infants who received an epicardial PM (282 bipolar, 39 unipolar leads) for CHB. Median age and weight at PM were 93.5 days and 4.5 kg, respectively. Pacing indication was postoperative CHB in 63% and congenital CHB in 37%. The median follow-up was 2.1 years. The primary outcome occurred in 26 infants at a median time to event of 0.6 year. Age ≤90 days at PM implantation was the most significant risk factor for a device-related adverse event (hazard ratio, 7.02; P < .001), primarily driven by pocket infections. Lead failure occurred in 3% of leads with a 5- and 10-year freedom from failure of 93% and 83%, respectively. CONCLUSION:Device complications affect 15% of infants receiving a permanent PM for heart block. Age ≤90 days at PM implantation is especially associated with infectious complications. Epicardial lead durability appears similar to previously reported pediatric experiences.

Background Selection of radiofrequency ablation (RF) or cryoablation (Cryo) for atrioventricular nodal re-entrant tachycardia (AVNRT) in children remains controversial due to a lack of contemporary comparison studies in this population. Objectives This study sought to compare outcomes of RF and Cryo for AVNRT in the pediatric population. Methods AVNRT ablation outcomes were retrospectively analyzed utilizing the National Cardiovascular Data Registry IMPACT (Improving Pediatric and Adult Congenital Treatment) Registry from April 2016 to March 2019. Data from subjects 1 to 21 years of age undergoing elective first-time slow pathway (SP) modification for AVNRT were included. Exclusion criteria included <1 year of age, congenital heart disease, and >1 ablation target. Cases were analyzed by ablation energy: 1) RF only; 2) Cryo only; 3) radiofrequency ablation switching to cryoablation (RF→Cryo); and 4) cryoablation switching to radiofrequency ablation (Cryo→RF). The primary outcome was acute ablation failure. Secondary outcomes included in-hospital adverse events. Results Among 2,448 patients (mean age 13.6 ± 3.4 years, 60% female), RF only was employed in 43% (n = 1,046), Cryo only in 49% (n = 1,201), RF→Cryo in 6% (n = 135), and Cryo→RF in 66 (3%). Acute ablation failure occurred in 1.3% (n = 33), with no difference by energy source (1% in RF only, 1.5% in Cryo only, 1.5% in RF→Cryo, 3% in Cryo→RF; P = 0.5). Atrioventricular (AV) block requiring permanent pacemaker did not occur in any group; transient AV block occurred in 0.4% of the cohort, with no difference by group. Conclusions In this largest pediatric study of AVNRT ablation, RF and Cryo demonstrated comparable high acute success and rare documentation of AV block that did not result in temporary or permanent pacing. Longitudinal data are important for further comparison of these modalities with regard to recurrence risk and late complications.

Double ventricular response (DVR), where a single P wave results in two QRS complexes, is a rare presentation of dual AV node physiology. It has been associated with ventricular dysfunction in the setting of incessant tachycardia. We present the case of an otherwise healthy adolescent who had frequent DVR without tachycardia leading to left ventricular dysfunction. Slow pathway modification led to a significant reduction in ectopy and normalization of ventricular function. This highlights that DVR without tachycardia might lead to ventricular dysfunction in pediatric patients. Slow pathway modification with reduction of ectopy may be sufficient to restore ventricular function.