Non-invasive pulse arrival time is associated with cardiac index in pediatric heart transplant patients with normal ejection fraction.

OBJECTIVE: Cardiac Index (CI) is a key physiologic parameter to ensure end organ perfusion in the pediatric intensive care unit (PICU). Determination of CI requires invasive cardiac measurements and is not routinely done at the PICU bedside. To date, there is no gold standard non-invasive means to determine CI. This study aims to use a novel non-invasive methodology, based on routine continuous physiologic data, called Pulse Arrival Time (PAT) as a surrogate for CI in patients with normal Ejection Fraction. Approach: Electrocardiogram (ECG) and photoplethysmogram (PPG) signals were collected from beside monitors at a sampling frequency of 250 samples per second. Continuous PAT, derived from the ECG and PPG waveforms was averaged per patient. Pearson's correlation coefficient was calculated between PAT and CI, PAT and heart rate (HR), and PAT and ejection fraction (EF). Main Results: Twenty patients underwent right heart cardiac catheterization. The mean age of patients was 11.7±5.4 years old, ranging from 11 months old to 19 years old, the median age was 13.4 years old. HR in this cohort was 93.8±17.0 beats per minute. The average EF was 54.4±9.6%. The average CI was 3.51±0.72 L/min/m2, with ranging from 2.6 to 4.77 L/min/m2. The average PAT was 0.31±0.12 seconds. Pearson correlation analysis showed a positive correlation between PAT and CI (0.57, p < 0.01). Pearson correlation between HR and CI, and correlation between EF and CI was 0.22 (p = 0.35) and 0.03 (p = 0.23) respectively. The correlation between PAT, when indexed by HR (i.e. PAT × HR), and CI minimally improved to 0.58 (p < 0.01). Significance: This pilot study demonstrates that PAT may serve as a valuable surrogate marker for CI at the bedside, as a non-invasive and continuous modality in the PICU. The use of PAT in clinical practice remains to be thoroughly investigated. .

Simultaneous stent implantation for pulmonary artery bifurcation stenosis in infants.

OBJECTIVES: Pulmonary artery (PA) bifurcation stenosis often requires simultaneous stent placement, which may be technically challenging. Limited data exist regarding this practice in infants. We aim to report the procedural outcomes and safety of bifurcation stent placement in infants. METHODS: We performed a single-center retrospective review of infants younger than 12 months who underwent simultaneous stent placement for PA bifurcation stenosis from January 1, 2001 through December 31, 2019. RESULTS: Seventeen infants underwent simultaneous PA bifurcation stent placement. The median age was 6.4 months (1.1-10.1 months), and weight was 5.8 kg (3-10.6 kg). Nine (52.9%) patients had had prior PA intervention. Most stents were placed in central PAs (28, 82.4%), followed by lobar branches (6, 17.6%). All patients received pre-mounted stents. The peak gradient across each branch decreased from 47.4 ± 16 to 18.7 ± 13 mm Hg (P less than .0001). The right ventricle to systemic systolic pressure ratio decreased from systemic (1.0 ± 0.3) to just over half systemic (0.58 ± 0.2) (P = .0001). The minimum vessel diameter increased from 3.6 ± 1.5 to 6.0 ± 1.9 mm (P less than .0001). There were 4 (23.5%) patients with high severity adverse events. There were no procedure-related deaths. The median follow-up period was 83.8 months (5.3 months-19.4 years). All patients had subsequent PA re-intervention at a median time of 8.1 months (2.9 months-8.8 years), and median time to re-operation was 19.1 months (2.9 months-7.5 years). CONCLUSIONS: Simultaneous PA stent placement is an effective strategy for relief of bifurcation stenosis in infants. Future transcatheter interventions are necessary to account for patient growth, but may delay the need for re-operation.

Catheterization for Congenital Heart Disease Adjustment for Risk Method II.

BACKGROUND: Current metrics used to adjust for case mix complexity in congenital cardiac catheterization are becoming outdated due to the introduction of novel procedures, innovative technologies, and expanding patient subgroups. This study aims to develop a risk adjustment methodology introducing a novel, clinically meaningful adverse event outcome and incorporating a modern understanding of risk. METHODS: Data from diagnostic only and interventional cases with defined case types were collected for patients ≤18 years of age and ≥2.5 kg at all Congenital Cardiac Catheterization Project on Outcomes participating centers. The derivation data set consisted of cases performed from 2014 to 2017, and the validation data set consisted of cases performed from 2019 to 2020. Severity level 3 adverse events were stratified into 3 tiers by clinical impact (3a/b/c); the study outcome was clinically meaningful adverse events, severity level ≥3b (3bc/4/5). RESULTS: The derivation data set contained 15 224 cases, and the validation data set included 9462 cases. Clinically meaningful adverse event rates were 4.5% and 4.2% in the derivation and validation cohorts, respectively. The final risk adjustment model included age <30 days, Procedural Risk in Congenital Cardiac Catheterization risk category, and hemodynamic vulnerability score (C statistic, 0.70; Hosmer-Lemeshow P value, 0.83; Brier score, 0.042). CONCLUSIONS: CHARM II (Congenital Heart Disease Adjustment for Risk Method II) risk adjustment methodology allows for equitable comparison of clinically meaningful adverse events among institutions and operators with varying patient populations and case mix complexity performing pediatric cardiac catheterization.

Valved Sano conduit improves immediate outcomes following Norwood operation compared with nonvalved Sano conduit.

OBJECTIVE: Use of a valved Sano during the Norwood procedure has been reported previously, but its impact on clinical outcomes needs to be further elucidated. We assessed the impact of the valved Sano compared with the nonvalved Sano after the Norwood procedure in patients with hypoplastic left heart syndrome. METHODS: We retrospectively reviewed 25 consecutive neonates with hypoplastic left heart syndrome who underwent a Norwood procedure with a valved Sano conduit using a femoral venous homograft and 25 consecutive neonates with hypoplastic left heart syndrome who underwent a Norwood procedure with a nonvalved Sano conduit between 2013 and 2022. Primary outcomes were end-organ function postoperatively and ventricular function over time. Secondary outcomes were cardiac events, all-cause mortality, and Sano and pulmonary artery reinterventions at discharge, interstage, and pre-Glenn time points. RESULTS: Postoperatively, the valved Sano group had significantly lower peak and postoperative day 1 lactate levels (P = .033 and P = .025, respectively), shorter time to diuresis (P = .043), and shorter time to enteral feeds (P = .038). The valved Sano group had significantly fewer pulmonary artery reinterventions until the Glenn operation (n = 1 vs 8; P = .044). The valved Sano group showed significant improvement in ventricular function from the immediate postoperative period to discharge (P < .001). From preoperative to pre-Glenn time points, analysis of ventricular function showed sustained ventricular function within the valved Sano group, but a significant reduction of ventricular function in the nonvalved Sano group (P = .003). Pre-Glenn echocardiograms showed competent conduit valves in two-thirds of the valved Sano group (n = 16; 67%). CONCLUSIONS: The valved Sano is associated with improved multi-organ recovery postoperatively, better ventricular function recovery, and fewer pulmonary artery reinterventions until the Glenn procedure.

Outcomes and Risk Factors of Interventions for Pediatric Post-operative Pulmonary Vein Stenosis.

Pulmonary vein stenosis (PVS) in children is a challenging condition with poor outcomes. Post-operative stenosis can occur after repair of anomalous pulmonary venous return (APVR) or stenosis within native veins. There is limited data on the outcomes of post-operative PVS. Our objective was to review our experience and assess surgical and transcatheter outcomes. Single-center retrospective study was performed including patients < 18 years who developed restenosis after baseline pulmonary vein surgery that required additional intervention(s) from 1/2005 to 1/2020. Non-invasive imaging, catheterization and surgical data were reviewed. We identified 46 patients with post-operative PVS with 11 (23.9%) patient deaths. Median age at index procedure was 7.2 months (range 1 month-10 years), and median follow-up was 10.8 months (range 1 day-13 years). Index procedure was surgical in 36 (78.3%) and transcatheter in 10 (21.7%). Twenty-three (50%) patients developed vein atresia. Mortality was not associated with number of affected veins, vein atresia, or procedure type. Single ventricle physiology, complex congenital heart disease (CCHD), and genetic disorders were associated with mortality. Survival rate was higher in APVR patients (p = 0.03). Patients with three or more interventions had a higher survival rate compared to patients with 1-2 interventions (p = 0.02). Male gender, necrotizing enterocolitis, and diffuse hypoplasia were associated with vein atresia. In post-operative PVS, mortality is associated with CCHD, single ventricle physiology, and genetic disorders. Vein atresia is associated with male gender, necrotizing enterocolitis, and diffuse hypoplasia. Multiple repeated interventions may offer a patient survival benefit; however, larger prospective studies are necessary to elucidate this relationship further.

Surgical and Medical Management of Purulent Bacterial Pericarditis With Pericardial Mass in a Young Child.

Purulent bacterial pericarditis is rare and associated with significant short- and long-term morbidity. We report a case of purulent bacterial pericarditis caused by Group A Streptococcus in an immunocompetent young child presenting with a pericardial mass. She was successfully treated with a combined medical and early surgical approach. (Level of Difficulty: Intermediate.).

Safety and Short-Term Outcomes for Infants < 2.5 kg Undergoing PDA Device Closure: A C3PO Registry Study.

To evaluate short-term procedural outcomes and safety for infants < 2.5 kg who underwent catheterization with intended patent ductus arteriosus (PDA) device closure in a multi-center registry, as performance of this procedure becomes widespread. A multi-center retrospective review was performed using data from the Congenital Cardiac Catheterization Project on Outcomes (C3PO) registry. Data were collected for all intended cases of PDA closure in infants < 2.5 kg from April 2019 to December 2020 at 13 participating sites. Successful device closure was defined as device placement at the conclusion of the catheterization. Procedural outcomes and adverse events (AE) were described, and associations between patient characteristics, procedural outcomes and AEs were analyzed. During the study period, 300 cases were performed with a median weight of 1.0 kg (range 0.7-2.4). Successful device closure was achieved in 98.7% of cases with a 1.7% incidence of level 4/5 AEs, including one periprocedural mortality. Neither failed device placement nor adverse events were significantly associated with patient age, weight or institutional volume. Higher incidence of adverse events associated with patients who had non-cardiac problems (p = 0.017) and cases with multiple devices attempted (p = 0.064). Transcatheter PDA closure in small infants can be performed with excellent short-term outcomes and safety across institutions with variable case volume.

COVID-19 international experience in paediatric patients with congenital heart disease.

OBJECTIVE: As COVID-19 continues to affect the global population, it is crucial to study the impact of the disease in vulnerable populations. This study of a diverse, international cohort aims to provide timely, experiential data on the course of disease in paediatric patients with congenital heart disease (CHD). METHODS: Data were collected by capitalising on two pre-existing CHD registries, the International Quality Improvement Collaborative for Congenital Heart Disease: Improving Care in Low- and Middle-Income Countries and the Congenital Cardiac Catheterization Project on Outcomes. 35 participating sites reported data for all patients under 18 years of age with diagnosed CHD and known COVID-19 illness during 2020 identified at their institution. Patients were classified as low, moderate or high risk for moderate or severe COVID-19 illness based on patient anatomy, physiology and genetic syndrome using current published guidelines. Association of risk factors with hospitalisation and intensive care unit (ICU) level care were assessed. RESULTS: The study included 339 COVID-19 cases in paediatric patients with CHD from 35 sites worldwide. Of these cases, 84 patients (25%) required hospitalisation, and 40 (12%) required ICU care. Age <1 year, recent cardiac intervention, anatomical complexity, clinical cardiac status and overall risk were all significantly associated with need for hospitalisation and ICU admission. A multivariable model for ICU admission including clinical cardiac status and recent cardiac intervention produced a c-statistic of 0.86. CONCLUSIONS: These observational data suggest risk factors for hospitalisation related to COVID-19 in paediatric CHD include age, lower functional cardiac status and recent cardiac interventions. There is a need for further data to identify factors relevant to the care of patients with CHD who contract COVID-19 illness.

Changes in Practice/Outcomes of Pediatric/Congenital Catheterization in Response to the First Wave of COVID.

Background: The COVID-19 pandemic has posed tremendous stress on the health care system. Its effects on pediatric/congenital catheterization program practice and performance have not been described. Objectives: The purpose of this study was to evaluate how case volumes, risk-profile, and outcomes of pediatric/congenital catheterization procedures changed in response to the first wave of COVID-19 and after that wave. Methods: A multicenter retrospective observational study was performed using Congenital Cardiac Catheterization Project on Outcomes Registry (C3PO) data to study changes in volume, case mix, and outcomes (high-severity adverse events [HSAEs]) during the first wave of COVID (March 1, 2020, to May 31, 2020) in comparison to the period prior to (January 1, 2019, to February 28, 2020) and after (June 1, 2020, to December 31, 2020) the first wave. Multivariable analyses adjusting for case type, hemodynamic vulnerability, and age group were performed. Hospital responses to the first wave were captured with an electronic study instrument. Results: During the study period, 12,557 cases were performed at 14 C3PO hospitals (with 8% performed during the first wave of COVID and 32% in the postperiod). Center case volumes decreased from a median 32.1 cases/month (IQR: 20.7-49.0 cases/month) before COVID to 22 cases/month (IQR: 13-31 cases/month) during the first wave (P = 0.001). The proportion of cases with risk factors for HSAE increased during the first wave, specifically proportions of infants and neonates (P < 0.001) and subjects with renal insufficiency (P = 0.02), recent cardiac surgery (P < 0.001), and a higher hemodynamic vulnerability score (P = 0.02). The observed HSAE risk did not change significantly (P = 0.13). In multivariable analyses, odds of HSAE during the first wave of COVID (odds ratio: 0.75) appeared to be lower than that before COVID, but the difference was not significant (P = 0.09). Conclusions: Despite increased case-mix complexity, C3PO programs maintained, if not improved, their performance in terms of HSAE. Exploratory analyses of practice changes may inform future harm-reduction efforts.

Interventions for Congenital Atrioventricular Valve Dysfunction: JACC Focus Seminar.

Innovation and creativity have led to tremendous advancements in the care and management of patients with congenital heart disease (CHD) that have resulted in considerably increased survival. Catheter-based interventions have contributed significantly to these advancements. However, catheter-based interventions for congenital lesions of the atrioventricular (AV) valves have been limited in scope and effectiveness mainly because of patient size and anatomical challenges. Thus, surgical repair and replacement for congenital AV valve lesions have remained the preferred therapy. However, the ongoing transcatheter heart valve revolution has led to techniques and technologies that are changing the landscape, particularly for adult CHD patients. Many devices for AV valve repair and replacement are being studied in adult patients without CHD, and translation of select practices to CHD patients has begun, with many more to come. Transcatheter AV valve interventions represent exciting opportunities for the growing numbers of adult CHD patients.

Transcatheter Cardiac Interventions in the Newborn: JACC Focus Seminar.

For neonates with critical congenital heart disease requiring intervention, transcatheter approaches for many conditions have been established over the past decades. These interventions may serve to stabilize or palliate to surgical next steps or effectively primarily treat the condition. Many transcatheter interventions have evidence-based records of effectiveness and safety, which have led to widespread acceptance as first-line therapies. Other techniques continue to innovatively push the envelope and challenge the optimal strategies for high-risk neonates with right ventricular outflow tract obstruction or ductal-dependent pulmonary blood flow. In this review, the most commonly performed neonatal transcatheter interventions will be described to illustrate the current state of the field and highlight areas of future opportunity.

Procedural Risk in Congenital Cardiac Catheterization (PREDIC3T).

Background Advancements in the field, including novel procedures and multiple interventions, require an updated approach to accurately assess patient risk. This study aims to modernize patient hemodynamic and procedural risk classification through the creation of risk assessment tools to be used in congenital cardiac catheterization. Methods and Results Data were collected for all cases performed at sites participating in the C3PO (Congenital Cardiac Catheterization Project on Outcomes) multicenter registry. Between January 2014 and December 2017, 23 119 cases were recorded in 13 participating institutions, of which 88% of patients were <18 years of age and 25% <1 year of age; a high-severity adverse event occurred in 1193 (5.2%). Case types were defined by procedure(s) performed and grouped on the basis of association with the outcome, high-severity adverse event. Thirty-four unique case types were determined and stratified into 6 risk categories. Six hemodynamic indicator variables were empirically assessed, and a novel hemodynamic vulnerability score was determined by the frequency of high-severity adverse events. In a multivariable model, case-type risk category (odds ratios for category: 0=0.46, 1=1.00, 2=1.40, 3=2.68, 4=3.64, and 5=5.25; all P≤0.005) and hemodynamic vulnerability score (odds ratio for score: 0=1.00, 1=1.27, 2=1.89, and ≥3=2.03; all P≤0.006) remained independent predictors of patient risk. Conclusions These case-type risk categories and the weighted hemodynamic vulnerability score both serve as independent predictors of patient risk for high-severity adverse events. This contemporary procedure-type risk metric and weighted hemodynamic vulnerability score will improve our understanding of patient and procedural outcomes.

Pilot phase experience of the International Quality Improvement Collaborative catheterization registry.

OBJECTIVES: To describe the development of a quality collaborative for congenital cardiac catheterization centers in low and middle-income countries (LMICs) including pilot study data and a novel procedural efficacy measure. BACKGROUND: Absence of congenital cardiac catheterization registries in LMICs led to the development of the International Quality Improvement Collaborative Congenital Heart Disease Catheterization Registry (IQIC-CHDCR). As a foundation for this initiative, the IQIC is a collaboration of pediatric cardiac surgical programs from LMICs. Participation in IQIC has been associated with improved patient outcomes. METHODS: A web-based registry was designed through a collaborative process. A pilot study was conducted from October through December 2017 at seven existing IQIC sites. Demographic, hemodynamic, and adverse event data were obtained and a novel tool to assess procedural efficacy was applied to five specific procedures. Procedural efficacy was categorized using ideal, adequate, and inadequate. RESULTS: A total of 429 cases were entered. Twenty-five adverse events were reported. The five procedures for which procedural efficacy was measured represented 48% of cases (n = 208) and 71% had complete data for analysis (n = 146). Procedure efficacy was ideal most frequently in patent ductus arteriosus (95%) and atrial septal defect (90%) device closure, and inadequate most frequently in coarctation procedures (100%), and aortic and pulmonary valvuloplasties (50%). CONCLUSIONS: The IQIC-CHDCR has designed a feasible collaborative to capture catheterization data in LMICs. The novel tool for procedural efficacy will provide valuable means to identify areas for quality improvement. This pilot study and lessons learned culminated in the full launch of the IQIC-CHDCR.

Neonates With Complex Cardiac Malformation and Congenital Diaphragmatic Hernia Born to SARS-CoV-2 Positive Women-A Single Center Experience.

BACKGROUND: Our understanding of the impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on pregnancies and perinatal outcomes is limited. The clinical course of neonates born to women who acquired coronavirus disease 2019 (COVID-19) during their pregnancy has been previously described. However, the course of neonates born with complex congenital malformations during the COVID-19 pandemic is not known. METHODS: We report a case series of seven neonates with congenital heart and lung malformations born to women who tested positive for SARS-CoV-2 during their pregnancy at a single academic medical center in New York City. RESULTS: Six infants had congenital heart disease and one was diagnosed with congenital diaphragmatic hernia. In all seven infants, the clinical course was as expected for the congenital lesion. None of the seven exhibited symptoms generally associated with COVID-19. None of the infants in our case series tested positive by nasopharyngeal test for SARS-CoV-2 at 24 hours of life and at multiple points during their hospital course. CONCLUSIONS: In this case series, maternal infection with SARS-CoV-2 during pregnancy did not result in adverse outcomes in neonates with complex heart or lung malformations. Neither vertical nor horizontal transmission of SARS-CoV-2 was noted.

Non-Elective Pediatric Cardiac Catheterization During COVID-19 Pandemic: A New York Center Experience.

BACKGROUND: COVID-19 has led to major changes in hospital systems across the world. In an effort to reduce viral transmission, conserve resources, and in accordance with institutional and state mandates, all elective procedures and surgeries were postponed during the initial outbreak. Guidelines for case selection are limited and management for pediatric catheterization laboratories during this crisis is unprecedented. OBJECTIVES: To report the protocols and case selection of a high-volume pediatric cardiac catheterization laboratory in the epicenter of the novel coronavirus (COVID-19) pandemic. METHODS: All pediatric cardiac catheterization procedures from March 16, 2020 through May 10, 2020 were reviewed. Changes to case selection and periprocedural workflow are described. Data were collected on COVID-19 testing status and primary procedure type, and all procedures were classified by urgency. RESULTS: There were 52 catheterizations performed on 50 patients. Endomyocardial biopsies were the most common procedure (n = 27; 52%). Interventional and diagnostic procedures represented 27% (n = 14) and 21% (n = 11) of cases, respectively. Two emergent procedures (3.8%) were performed on patients with positive COVID-19 testing. Most cases were performed on patients with negative COVID-19 testing (n = 33; 94%). CONCLUSIONS: Adjusting to the COVID-19 pandemic in a high-volume pediatric cardiac catheterization laboratory can be safely and effectively managed by prioritizing emergent and urgent cases and modifying workflow operations. The experience of this center may assist other pediatric cardiac catheterization laboratories in adapting to similar practice changes as the pandemic continues to evolve.

Cardiac workup and monitoring in hospitalised children with COVID- 19.

Approximately, 1.7 million individuals in the United States have been infected with SARS-CoV-2, the virus responsible for the novel coronavirus disease-2019 (COVID-19). This has disproportionately impacted adults, but many children have been infected and hospitalised as well. To date, there is not much information published addressing the cardiac workup and monitoring of children with COVID-19. Here, we share the approach to the cardiac workup and monitoring utilised at a large congenital heart centre in New York City, the epicentre of the COVID-19 pandemic in the United States.

The patient encounter index: a novel method of measuring clinical workload in a paediatric cardiology service.

Technological advances have led to better patient outcomes and the expansion of clinical services in paediatric cardiology. This expansion creates an ever-growing workload for clinicians, which has led to workflow and staffing issues that need to be addressed. The objective of this study was the development of a novel tool to measure the clinical workload of a paediatric cardiology service in Cape Town, South Africa: The patient encounter index is a tool designed to quantify clinical workload. It is defined as a ratio of the measured duration of clinical work to the total time available for such work. This index was implemented as part of a prospective cross-sectional study design. Clinical workload data were collected over a 10-day period using time-and-motion sampling. Clinicians were contractually expected to spend 50% of their daily workload on patient care. The median patient encounter index for the Western Cape Paediatric Cardiac Service was 0.81 (range 0.19-1.09), reflecting that 81% of total contractual working time was spent on clinical activities. This study describes the development and implementation of a novel tool for clinical workload quantification and describes its application to a busy paediatric cardiology service in Cape Town, South Africa. This tool prospectively quantifies clinical workload which may directly influence patient outcomes. Implementation of this novel tool in the described setting clearly demonstrated the excessive workload of the clinical service and facilitated effective motivation for improved allocation of resources.

Outcomes of Magnetic Resonance Imaging Detected Occult Neck of Femur Fractures: Do They Represent a Less Severe Injury with Improved Outcomes? / 대한고관절학회지

PURPOSE: Occult hip fractures in the elderly can be missed on standard radiographs and are a known cause of morbidity. These are generally diagnosed on either magnetic resonance imaging (MRI) or computed tomography scan, depending upon local hospital policy. While there is an abundance of literature on hip fractures in general, little is known about the clinical outcome of patients with occult hip fractures. The aim of this study was to review the demographics, injury characteristics, management and clinical outcome of patients diagnosed with occult femoral neck fractures on MRI. MATERIALS AND METHODS: Using an existing hospital database, a retrospective analysis of all patients with occult hip fractures diagnosed by MRI scan from 2005 to 2014 was conducted. RESULTS: Sixty-four patients (23 males and 41 females) were included. The mean duration of hospitalisation was 16 days. A significantly higher percentage of patients were discharged to their pre-existing residence compared to National Institute for Health and Care Excellence (NICE) commissioning guidelines (66% vs. 45%). The 30- and 60-day mortalities were 3% and 10%, respectively. Mortality was lower in patients who underwent internal fixation (n=3/31) compared with those undergoing replacement (hemi/total hip arthroplasty) (n=5/12) (P=0.056). CONCLUSION: Patients with occult hip fractures diagnosed on an MRI scan are more likely to be discharged to their pre-existing residence and have lower mortality rates compared to NICE guidelines and National Hip Fracture Database (NHFD).

Incidence and Predictors of Clinically Important and Dangerous Arrhythmias During Exercise Tests in Pediatric and Congenital Heart Disease Patients.

OBJECTIVES: This study quantified the incidence of arrhythmias during pediatric exercise stress tests (ESTs) and evaluated criteria to identify patients at risk of clinically important arrhythmias. BACKGROUND: The incidence of clinically important arrhythmias during pediatric ESTs and criteria for identifying high-risk patients are poorly characterized. METHODS: A retrospective review of ESTs performed from 2013 to 2015 was studied. Arrhythmias were categorized into 4 classes based on need for test termination and intervention. Risk factors evaluated included having an implantable cardioverter-defibrillator (ICD), cardiomyopathy, severe ventricular dysfunction, complex arrhythmia history, coronary disease with concern for ischemia, pulmonary hypertension, select poorly palliated congenital heart disease (CHD), and concerning symptoms. Negative predictive values (NPVs) were calculated. RESULTS: During the study period, 5307 ESTs were performed. Median age of the subjects was 16 years (interquartile range: 13 to 24 years); 20% had complex CHD. At least 1 high-risk criterion was present in 507 tests (10%); having an ICD (37%) and cardiomyopathy (36%) were the most common criteria. Some arrhythmias were seen in 46% of tests, but only 33 events (0.6%) required test termination. Three events (0.06%) required cardiopulmonary resuscitation, all with high-risk criteria. Absence of a high-risk criterion had a 99.7% (95% confidence interval [CI]: 99.5% to 99.8%) NPV for an arrhythmia that required test termination and a 99.96% (95% CI: 99.85% to 99.99%) NPV for an arrhythmia that required intervention beyond test termination. CONCLUSIONS: Although self-terminating arrhythmias are common, dangerous arrhythmias are rare during ESTs in a high-volume pediatric cardiology program. Pre-defined high-risk criteria identified all patients with the most serious events. The absence of any criteria predicted a low risk for arrhythmias that required test termination. These data permitted informed choices regarding supervision of ESTs.