Limited Relationship Between Echocardiographic Measures and Electrocardiographic Markers of Left Ventricular Size in Healthy Children.

Pediatric ECG standards have been defined without echocardiographic confirmation of normal anatomy. The Pediatric Heart Network Normal Echocardiogram Z-score Project provides a racially diverse group of healthy children with normal echocardiograms. We hypothesized that ECG and echocardiographic measures of left ventricular (LV) dimensions are sufficiently correlated in healthy children to imply a clinically meaningful relationship. This was a secondary analysis of a previously described cohort including 2170 digital ECGs. The relationship between 6 ECG measures associated with LV size were analyzed with LV Mass (LVMass-z) and left ventricular end-diastolic volume (LVEDV-z) along with 11 additional parameters. Pearson or Spearman correlations were calculated for the 78 ECG-echocardiographic pairs with regression analyses assessing the variance in ECG measures explained by variation in LV dimensions and demographic variables. ECG/echocardiographic measurement correlations were significant and concordant in 41/78 (53%), though many were significant and discordant (13/78). Of the 6 ECG parameters, 5 correlated in the clinically predicted direction for LV Mass-z and LVEDV-z. Even when statistically significant, correlations were weak (0.05-0.24). R2 was higher for demographic variables than for echocardiographic measures or body surface area in all pairs, but remained weak (R2 ≤ 0.17). In a large cohort of healthy children, there was a positive association between echocardiographic measures of LV size and ECG measures of LVH. These correlations were weak and dependent on factors other than echocardiographic or patient derived variables. Thus, our data support deemphasizing the use of solitary, traditional measurement-based ECG markers traditionally thought to be characteristic of LVH as standalone indications for further cardiac evaluation of LVH in children and adolescents.

Multicenter retrospective evaluation of magnetic resonance imaging in pediatric and congenital heart disease patients with cardiac implantable electronic devices.

BACKGROUND: Guidelines addressing magnetic resonance imaging (MRI) in patients with cardiac implantable electronic devices (CIEDs) provide algorithms for imaging pediatric and congenital heart disease (CHD) patients. Guideline acceptance varies by institution. Guidelines also do not support routine MRI scans in patients with epicardial or abandoned leads, common in pediatric and CHD patients. OBJECTIVE: The purpose of this study was to determine the incidence of MRI-related complications in pediatric and CHD patients with CIEDs, including epicardial and/or abandoned leads. METHODS: A multicenter retrospective review included patients with CIEDs who underwent any MRI between 2007 and 2022 at congenital cardiac centers. The primary outcome was any patient adverse event or clinically significant CIED change after MRI, defined as pacing lead capture threshold increase >0.5 V with output change, P- or R- wave amplitude decrease >50% with sensitivity change, or impedance change >50%. RESULTS: Across 14 institutions, 314 patients (median age 18.8 [1.3; 31.4] years) underwent 389 MRIs. There were 288 pacemakers (74%) and 87 implantable cardioverter-defibrillators (22%); 52% contained epicardial leads, and 14 (4%) were abandoned leads only. Symptoms or CIED changes occurred in 4.9% of MRI scans (6.1% of patients). On 9 occasions (2%), warmth or pain occurred. Pacing capture threshold or lead impedance changes occurred in 1.4% and 2.0% of CIEDs post-MRI and at follow-up. CONCLUSION: Our data provide evidence that MRIs can be performed in pediatric and CHD patients with CIEDs, including non-MRI-conditional CIEDs and epicardial and/or abandoned leads, with rare minor symptoms or CIED changes but no other complications.

Evaluation of age at symptom onset, proband status, and sex as predictors of disease severity in pediatric catecholaminergic polymorphic ventricular tachycardia.

BACKGROUND: Children with catecholaminergic polymorphic ventricular tachycardia (CPVT) are at risk for sudden death, and a risk stratification tool does not exist. OBJECTIVE: The purpose of this study was to determine whether proband status, age at symptom onset, and/or sex are independent predictors of cardiac events. METHODS: A multicenter, ambispective, cohort of pediatric CPVT patients was categorized by sex, proband status, and age at symptom onset (D1: first decade of life [symptom onset <10 years] or D2: second decade of life [symptom onset 10-18 years, inclusive]). Demographics, therapy, genetics, and outcomes were compared between groups. RESULTS: A total of 133 patients were included and stratified into 58 D1 and 75 D2 patients (68 female and 65 male; 106 probands and 27 relatives). Localization of RYR2 variants to hotspots differed based on proband status and age at symptom onset. The cardiac event rate was 33% (n = 44/133), inclusive of a 3% (n = 4/133) mortality rate, over a median of 6 years (interquartile range 3-11) after time of symptom onset. Proband status, rather than age at of symptom onset or sex, was an independent predictor of time to first cardiac event (P = .008; hazard ratio = 4.4). The 5-, 10- and 15-year event-free survival rates for probands were 77%, 56%, and 46%, respectively, and for relatives were 96%, 91%, and 86%, respectively. Event risk after diagnosis was 48% (32/67) in patients on ß-blocker or flecainide alone vs 10% (5/48) in patients on ß-blocker plus flecainide and/or left cardiac sympathetic denervation (P <.001). CONCLUSION: Proband status, but not age at symptom onset or male sex, independently predicted an earlier onset of cardiac events. A larger sample size would enable a comprehensive investigation of other risk factors.

Impact of a paediatric cardiac rehabilitation programme upon patient quality of life.

INTRODUCTION: Cardiac rehabilitation programmes for paediatric patients with congenital heart disease (CHD) have been shown to promote emotional and physical health without any associated adverse events. While prior studies have demonstrated the effectiveness of these types of interventions, there has been limited research into how the inclusion of psychological interventions as part of the programme impacts parent-reported and patient-reported quality of life. MATERIALS AND METHODS: Patients between the ages of 7 and 24 years with CHD completed a cardiac rehabilitation programme that followed a flexible structure of four in person-visits with various multidisciplinary team members, including paediatric psychologists. Changes in scores from the earliest to the latest session were assessed regarding exercise capacity, patient functioning (social, emotional, school, psychosocial), patient general and cardiac-related quality of life, patient self-concept, and patient behavioural/emotional problems. RESULTS: From their baseline to final session, patients exhibited significant improvement in exercise capacity (p = 0.00009). Parents reported improvement in the patient's emotional functioning, social functioning, school functioning, psychosocial functioning, cognitive functioning, communication, and overall quality of life. While patients did not report improvement in these above areas, they did report perceived improvement in certain aspects of cardiac-related quality of life and self-concept. DISCUSSION: This paediatric cardiac rehabilitation programme, which included regular consultations with paediatric psychologists, was associated with divergent perceptions by parents and patients on improvement related to quality of life and other aspects of functioning despite improvement in exercise capacity. Further investigation is recommended to identify underlying factors associated with the differing perceptions of parents and patients.

Contact force ablation of accessory pathways in pediatric patients.

INTRODUCTION: Contact force (CF) catheters provide feedback confirming adequate tissue contact for optimal lesion size and minimal complications. CF ablation catheters have resulted in decreased procedure times and improved outcomes for ablation of atrial fibrillation in adults. There is limited data evaluating CF use for accessory pathway (AP) ablation or in pediatric patients. The aim of our study was to compare a cohort who underwent AP ablation with a CF catheter to historical controls, evaluating for differences in procedure times, number of lesions, and outcomes. METHODS: A retrospective chart review of CF ablation cases at Children's Wisconsin performed between June 2015 to April 2018 was compared to a historical control cohort of traditional radiofrequency (RF) ablations between June 2012 and June 2015. 43 patients with APs underwent 49 CF ablation procedures (18 males, 13.6 ± 3 years old) and a control cohort consisted of 77 procedures in 69 patients (38 males, 12.4 ± 4 years). RESULTS: The groups did not differ significantly on procedure time (CF 2.01 ± 0.48 h, control 1.53 ± 0.48 h, p = .37), or total lesions administered (CF and control 7 ± 6 lesions, p = .89). CF cases showed a trend toward improvement in acute success (98% CF, 90% controls, p = .15) though with increased recurrence compared to controls (13% CF, 4.3% controls, p = .16), neither being statistically significant. CONCLUSION: Our study suggests that ablation outcomes using CF are comparable to traditional RF ablation in pediatric patients with APs.

Methadone's Effect on Cardiac Repolarization: Safety in the PICU.

OBJECTIVES: Opioids are routinely used in the PICU. Methadone is an effective method of preventing and treating iatrogenic opioid withdrawal; however, it carries an Food and Drug Administration Boxed Warning due to the potential to prolong the corrected QT interval and potentially lead to life-threatening arrhythmias. Guidelines on the safe use of methadone have limited applicability to children since their cardiac intervals differ from those of adults. There is little data on the electrophysiologic effects in the pediatric population. We set out to describe the safety of methadone use in the PICU, hypothesizing that methadone does not cause a significant change in corrected QT interval from baseline. DESIGN: Retrospective cohort study. SETTING: Children's Hospital of Wisconsin, Milwaukee, WI. PATIENTS: Fifty-one patients, age less than or equal to 18 years old, initiated on methadone during PICU admission, over an 11-month period, for the prevention or treatment of opioid withdrawal. INTERVENTIONS: Retrospective data queried from the electronic health record and stored telemetry waveforms obtained from an automated real-time patient data acquisition software system (BedMasterEx; Anandic Medical Systems AG, Feuerthalen, Switzerland). MEASUREMENTS AND MAIN RESULTS: Corrected QT intervals were not significantly different at 12 hours, 96 hours, or PICU discharge (p values: 0.57, 0.54, and 0.34) when compared to baseline. The median change in corrected QT from baseline to 12 hours after the first dose of methadone was 5 ms (interquartile range, -12 to 11 ms), 0 ms to steady state (interquartile range, -18 to 18 ms), and 5 ms from baseline to 12 hours after the highest dose of methadone (interquartile range, -14 to 16 ms). The most common primary diagnosis was structural heart disease (29% of subjects) in our cohort and every subject that experienced an increase in corrected QT interval greater than or equal to 40 ms had some form of structural heart disease. CONCLUSIONS: Methadone did not significantly prolong the corrected QT interval in a population of critically ill children, suggesting that it can be safely used in this population, although patients with structural heart disease may warrant closer monitoring.

Cardiac Magnetic Resonance Imaging (MRI) in Children is Safe with Most Pacemaker Systems, Including Those with Epicardial Leads.

Magnetic resonance imaging (MRI) of patients with pacemakers remains concerning because of possible magnetic field effects on the device. Many pacemaker models are labeled as non-conditional, or contraindicated for MRI, or do not have any specific safety guidelines listed. This study describes our experience with pacemaker function and adverse events in pediatric and young adult patients after clinically indicated MRI scanning at 1.5 Tesla (T). We hypothesized that generator battery voltage, pacemaker lead threshold, and lead impedance would not be altered by MRI. This was a retrospective review of Children's Wisconsin clinical MRI data for all patients with pacemakers scanned between January 1, 2010 and March 31, 2018. Pacemakers were interrogated by the Electrophysiology Team before and immediately after MRI and at outpatient follow up. Twenty-one patients underwent forty-four MRI scans. No significant immediate changes were seen in any pacemaker parameter for any manufacturer/model/lead at the time of MRI. At first clinical follow up post MRI, (median 4.4 months, range 0.2-12.3), battery voltage was reduced (2.78 V pre-MRI versus 2.77 V at follow up, p = 0.02), but there were no other significant changes. No adverse events were noted. Pediatric patients with pacemakers, including those with epicardial leads, can be scanned at 1.5 T safely without alteration in pacemaker function. Using appropriate precautions, pediatric patients with pacemakers can be imaged with MRI.

Outcomes of catheter ablation of anteroseptal and midseptal accessory pathways in pediatric patients.

BACKGROUND: Outcomes for catheter ablation of accessory pathways in pediatric patients have steadily improved, with the exception of pathways located in the anteroseptal (AS) and midseptal (MS) regions, where success is limited by the close proximity of normal atrioventricular conduction. OBJECTIVE: The purpose of this study was to evaluate the efficacy of different catheter approaches and ablation energy modalities used for catheter ablation at these sites. METHODS: A retrospective review was performed of all electrophysiology studies conducted between July 2001 and July 2017. Acute success and recurrence rates were assessed by comparing catheter approaches and energy modalities used for ablation. RESULTS: A total of 255 electrophysiology procedures were performed in 223 patients (178 AS, 72 MS, 5 unspecified). Ablation was attempted in 241 procedures, with acute success in 87% (AS 89%, MS 83%). Recurrence was evident in 18% of successful ablation procedures (AS 18%, MS 19%). Success rates were higher with repeat procedures than with primary procedures (P = .006). Multiple approaches were more often used for AS pathways, though no single approach was superior. There was no difference in success when comparing energy modalities, though the overall recurrence rate was higher for cryoablation. Significant complications occurred in 1.2% of procedures, though no patient had complete heart block. CONCLUSION: Ablation of AS and MS pathways remains challenging. Multiple approaches are often necessary to successfully ablate AS pathways. While both ablation energy modalities were equally successful, cryoablation may be associated with a higher chance of recurrence. Recurrences and repeat procedures may be anticipated to minimize risk to normal atrioventricular conduction during ablation in these regions.

Genetic testing and cascade screening in pediatric long QT syndrome and hypertrophic cardiomyopathy.

BACKGROUND: The efficacy of cascade screening for the inherited heart conditions long QT syndrome (LQTS) and hypertrophic cardiomyopathy (HCM) is incompletely characterized. OBJECTIVE: The purpose of this study was to examine the use of genetic testing and yield of cascade screening across diverse regions in the United States and to evaluate obstacles to screening in multipayer systems. METHODS: An institutional review board-approved 6 United States pediatric center retrospective chart review of LQTS and HCM patients from 2008-2014 was conducted for (1) genetic test completion and results and (2) family cascade screening acceptance, methods, results, and barriers. RESULTS: The families of 315 index patients (mean age 9.0 ± 5.8 years) demonstrated a 75% (254) acceptance of cascade screening. The yield of relative screening was 39% (232/601), an average of 0.91 detected per family. Genetic testing was less utilized in HCM index patients and relatives. Screening participation was greater in families of gene-positive index patients (88%) (P <.001) compared to gene-negative patients (53%). Cascade method utilization: Cardiology-only 45%, combined genetic and cardiology 39%, and genetic only 16%. Screening yield by method: combined 57%, genetic-only 29%, and cardiology-only 20%. Family decisions were the leading barriers to cascade screening (26% lack of followthrough and 26% declined), whereas insurance (6%) was the least cited barrier. CONCLUSION: Family participation in cascade screening is high, but the greatest barriers are family mediated (declined, lack of followthrough). Positive proband genetic testing led to greater participation. Cardiology-only screening was the most utilized method, but combined cardiology and genetic screening had the highest detection.

Cardiac arrest in a healthy child due to paradoxical embolus across a previously unrecognised sinus venosus defect.

A previously healthy, preadolescent female suffered an unwitnessed cardiac arrest with prompt return of circulation following bystander initiated resuscitation. Workup demonstrated the cause of her cardiac arrest to be distal left anterior descending coronary artery occlusion with small apical left ventricular transmural myocardial infarction, from a paradoxical embolus traversing a previously undiagnosed large sinus venous defect. This case demonstrates the value of cardiac magnetic resonance imaging may bring to the diagnosis of the pathophysiology leading to cardiac arrest.

Chronotropic incompetence in paediatric heart transplant recipients with prior congenital heart disease.

BACKGROUND: Cardiopulmonary exercise testing has been used to measure functional capacity in children who have undergone a heart transplant. Cardiopulmonary exercise testing results have not been compared between children transplanted for a primary diagnosis of CHD and those with a primary diagnosis of cardiomyopathy despite differences in outcomes. This study is aimed to compare cardiopulmonary exercise testing performance between these two groups. METHODS: Patients who underwent heart transplant with subsequent cardiopulmonary exercise testing at least 6 months after transplant at our institution were identified. They were then divided into two groups based on primary cardiac diagnosis: CHD or cardiomyopathy. Patient characteristics, echocardiograms, cardiac catheterisations, outcomes, and cardiopulmonary exercise test results were compared between the two groups. RESULTS: From the total of 35 patients, 15 (43%) had CHD and 20 (57%) had cardiomyopathy. Age at transplant, kidney disease, lung disease, previous rejection, coronary vasculopathy, catheterisation, and echocardiographic data were similar between the groups. Mean time from transplant to cardiopulmonary exercise testing, exercise duration, and maximum oxygen consumption were similar in both groups. There was a difference in heart rate response with CHD heart rate response of 63 beats per minute compared to cardiomyopathy group of 78 (p = 0.028). Patients with CHD had more chronotropic incompetence than those with cardiomyopathy (p = 0.036). CONCLUSION: Primary diagnosis of CHD is associated with abnormal heart rate response and more chronotropic incompetence compared to those transplanted for cardiomyopathy.

Cardiopulmonary Exercise Testing for Surgical Risk Stratification in Adults with Congenital Heart Disease.

Adult congenital heart disease (ACHD) patients often require repeat cardiothoracic surgery, which may result in significant morbidity and mortality. Currently, there are few pre-operative risk assessment tools available. In the general adult population, pre-operative cardiopulmonary exercise testing (CPET) has a predictive value for post-operative morbidity and mortality following major non-cardiac surgery. The utility of CPET for risk assessment in ACHD patients requiring cardiothoracic surgery has not been evaluated. Retrospective chart review was conducted on 75 ACHD patients who underwent CPET less than 12 months prior to major cardiothoracic surgery at Children's Hospital of Wisconsin. Minimally invasive procedures, cardiomyopathy, acquired heart disease, single ventricle physiology, and heart transplant patients were excluded. Demographic information, CPET results, and peri-operative surgical data were collected. The study population was 56% male with a median age of 25 years (17-58). Prolonged post-operative length of stay correlated with increased ventilatory efficiency slope (VE/[Formula: see text] slope) (P = 0.007). Prolonged intubation time correlated with decreased peak HR (P = 0.008), decreased exercise time (P = 0.002), decreased heart rate response (P = 0.008) and decreased relative peak oxygen consumption (P = 0.034). Post-operative complications were documented in 59% of patients. While trends were noted between post-operative complications and some measurements of exercise capacity, none met statistical significance. Future studies may further define the relationship between exercise capacity and post-operative morbidity in ACHD patients.

Electrocardiograms in Healthy North American Children in the Digital Age.

BACKGROUND: Interpretation of pediatric ECGs is limited by lack of accurate sex- and race-specific normal reference values obtained with modern technology for all ages. We sought to obtain contemporary digital ECG measurements in healthy children from North America, to evaluate the effects of sex and race, and to compare our results to commonly used published datasets. METHODS: Digital ECGs (12-lead) were retrospectively collected for children ≤18 years old with normal echocardiograms at 19 centers in the Pediatric Heart Network. Patients were classified into 36 groups: 6 age, 2 sex, and 3 race (white, black, and other/mixed) categories. Standard intervals and amplitudes were measured; mean±SD and 2nd/98th percentiles were determined by age group, sex, and race. For each parameter, multivariable analysis, stratified by age, was conducted using sex and race as predictors. Parameters were compared with 2 large pediatric ECG data sets. RESULTS: Among ECGs from 2400 children, significant differences were found by sex and race categories. The corrected QT interval in lead II was greater for girls compared with boys for age groups ≥3 years (P≤0.03) and for whites compared with blacks for age groups ≥12 years (P<0.05). The R wave amplitude in V6 was greater for boys compared with girls for age groups ≥12 years (P<0.001), for blacks compared with white or other race categories for age groups ≥3 years (P≤0.006), and greater compared with a commonly used public data set for age groups ≥12 years (P<0.0001). CONCLUSIONS: In this large, diverse cohort of healthy children, most ECG intervals and amplitudes varied by sex and race. These differences have important implications for interpreting pediatric ECGs in the modern era when used for diagnosis or screening, including thresholds for left ventricular hypertrophy.

Intrauterine growth restriction is not associated with decreased exercise capacity in adolescents with congenital heart disease.

OBJECTIVE: Multiple studies demonstrate the association of intrauterine growth restriction (IUGR) with impaired aerobic fitness in adolescents and adults. To our knowledge, there are no studies including individuals with the history of both IUGR and congenital heart disease (CHD). Thus, we sought to evaluate the impact of IUGR on exercise capacity in adolescents with CHD. STUDY DESIGN: We conducted a retrospective chart review of patients <18 years of age who underwent cardiopulmonary exercise testing (CPET) between August 1, 2003 and July 1, 2016. Individuals with birth weight <10th percentile for gestational age were defined as IUGR. Patients with IUGR were matched with non-IUGR patients by cardiac diagnosis and age at CPET. We excluded patients >18 years of age at time of CPET, those without a documented birth weight, gestational age, or Race. RESULTS: A total of 282 patients were included with CHD present in 86 IUGR cases and 86 controls. There was no difference in percent predicted exercise duration (IUGR: 65.2% ± 31.2, non-IUGR: 67.4% ± 27.2; P = .67). Resting heart rate, chronotropic index, percent-predicted peak oxygen consumption, and pulmonary function were similar between groups. Regression analyses confirmed that IUGR was not independently associated with difference in percent-predicted exercise duration. CONCLUSIONS: Intrauterine growth restriction is not associated with the differences in the measurements of exercise capacity in adolescents with CHD. These findings contrast earlier studies, showing decreased fitness in individuals with low birth weight but without CHD. To our knowledge, this is the first study to examine the impact of IUGR on exercise capacity in patients with CHD.

Transplacental treatment of fetal tachycardia: A systematic review and meta-analysis.

OBJECTIVE: Multiple transplacental medications can be used to treat fetal tachycardia. We sought to perform a systematic review and meta-analysis to determine whether digoxin, flecainide, or sotalol was the most efficacious therapy for converting fetal tachycardia to sinus rhythm. METHOD: We performed a systematic review and meta-analysis to compare digoxin, flecainide, or sotalol as first-line therapy for fetal tachycardia. Studies were identified by a search of PubMed (Medline), Web of Science, and Scopus. RESULTS: There were 21 studies included. Flecainide (OR: 1.4, 95% CI: 1.1-2.0, I2  = 60%, P = 0.03) and sotalol (OR:1.4, 95% CI:1.1-2.0, I2  = 30%, P = 0.02) were superior to digoxin for conversion of fetal tachycardia to sinus rhythm. In those with hydrops, the benefit over digoxin was more notable for both flecainide (OR: 5.0, 95% CI: 2.5-10.0, I2  = 0%, P < 0.001) and sotalol (OR: 2.5, 95% CI: 1.7-5.0, I2  = 0%, P < 0.001). When limited to atrioventricular reentrant tachycardia, flecainide was superior to digoxin (OR:1.7, 95% CI:1.1-3.3, I2  = 62%, P = 0.03) and sotalol (OR:1.3, 95% CI:1.1-1.7, I2  = 0%, P = 0.01). CONCLUSION: Digoxin should not be first-line therapy for fetal tachycardia, particularly in the presence of hydrops fetalis. Flecainide should be the first-line therapy of choice in atrioventricular reentrant tachycardia. Further study may identify further sub-populations responding differently.

Cardiopulmonary Exercise Testing in Fontan Patients With and Without Isomerism (Heterotaxy) as Compared to Patients With Primary Ciliary Dyskinesia and Subjects With Structurally Normal Hearts.

Isomerism, also known as heterotaxy, is a clinical entity that impacts multiple organ systems both anatomically and functionally. The airways and lungs are involved in a great number of these patients, leading to increased sinopulmonary symptoms, increased need for oxygenation, and increased postoperative ventilatory support. Additionally, these patients often have congenital heart disease requiring Fontan palliation. What has not been previously described, and is the focus of this study, is the results of cardiopulmonary exercise testing in those who have undergone Fontan palliation with and without isomerism. We have now compared these finding with those from patients with primary ciliary dyskinesia, as many patients with isomerism have ciliary dyskinesia. We identified patients having the Fontan circulation with and without isomerism who had undergone cardiopulmonary exercise testing, comparing the findings from healthy individuals undergoing exercise, and a comparable number of individuals with primary ciliary dyskinesia but no congenital heart disease. We were able to include a total of 68 patients in our study, with 17 in each of the four groups. Cardiopulmonary exercise testing yielded the best results in healthy patients. All patients with the Fontan circulation demonstrated mixed pulmonary disease, although those with isomerism had greater FVC and FEV1. Exercise times did not differ, although peak consumption of oxygen was greater in those with isomerism. Those with ciliary dyskinesia had only obstructive pulmonary disease and had the lowest FEF25-75 between all groups. Those with isomerism had a lesser degree of obstructive pulmonary disease when compared to those with primary ciliary dyskinesia. Patients with the Fontan circulation with and without isomerism have relatively subtle differences in their cardiopulmonary exercise testing, with both groups demonstrating restrictive lung disease. In regard to obstructive lung disease, those with isomerism tend to be more similar to the patients with primary ciliary dyskinesia than those with the Fontan circulation but without isomerism. The results are likely limited by selection bias and highlight the need for multicentric efforts to characterize cardiopulmonary exercise testing in those patients with pulmonary isomerism.

Arrhythmias in Adults with Congenital Heart Disease: What Are Risk Factors for Specific Arrhythmias?

INTRODUCTION: An increasing number of patients with congenital heart disease are now surviving into adulthood. This has also led to the emergence of complications from the underlying congenital heart disease, related surgical interventions, and associated combordities. While the prevalence of particular arrhythmias with specific congenital heart disease has been previously described, a detailed analysis of all lesions and a large number of comorbidities has not been previously published. METHODS: Admissions with congenital heart disease were identified in the National Inpatient Sample. Associated comorbidities were also identified for these patients. Univariate analysis was done to compare those risk factors associated with specific arrhythmias in the setting of congenital heart disease. Next, regression analysis was done to identify what patient characteristics and comorbidities were associated with increased risk of specific arrhythmias. RESULTS: A total of 52,725,227 admissions were included in the analysis. Of these, 109,168 (0.21%) had congenital heart disease. Of those with congenital heart disease, 27,088 (25%) had an arrhythmia at some point. The most common arrhythmia in those with congenital heart disease was atrial fibrillation, which was noted in 86% of those with arrhythmia followed by atrial flutter which was noted in 20% of those with congenital heart disease. The largest burden of arrhythmia was found to be in those with tricuspid atresia with a 51% prevalence of arrhythmia in this group followed by Ebstein anomaly which had an arrhythmia prevalence of 39%. Increasing age, male gender, double outlet right ventricle, atrioventricular septal defect, heart failure, obstructive sleep apnea, transposition of the great arteries, congenitally corrected transposition, and tetralogy of Fallot were frequently noted to be independent risk factors of specific arrhythmias. CONCLUSION: Approximately, 25% of adult admissions with congenital heart disease are associated with arrhythmia. The burden of arrhythmia varies by the specific lesion and other risk factors as well. Understanding of these can help in risk stratification and can help devise strategies to lower this risk.

Clinical Presentation of Pediatric Patients at Risk for Sudden Cardiac Arrest.

OBJECTIVES: To identify the clinical presentation of children and adolescents affected by 1 of 4 cardiac conditions predisposing to sudden cardiac arrest: hypertrophic cardiomyopathy, long QT syndrome (LQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT), and anomalous origin of the left coronary artery from the right sinus of Valsalva (ALCA-R). STUDY DESIGN: This was a retrospective review of newly diagnosed pediatric patients with hypertrophic cardiomyopathy, LQTS, CPVT, and ALCA-R referred for cardiac evaluation at 6 US centers from 2008 to 2014. RESULTS: A total of 450 patients (257 male/193 female; median age 10.1 years [3.6-13.8 years, 25th-75th percentiles]) were enrolled. Patient age was ≤13 years for 70.4% of the cohort (n = 317). Sudden cardiac arrest was the initial presentation in 7%; others were referred on the basis of abnormal or suspicious family history, personal symptoms, or physical findings. Patients with LQTS and hypertrophic cardiomyopathy were referred most commonly because of family history concerns. ALCA-R was most likely to have abnormal signs or symptoms (eg, exercise chest pain, syncope, or sudden cardiac arrest). Patients with CPVT had a high incidence of syncope and the greatest incidence of sudden cardiac arrest (45%); 77% exhibited exercise syncope or sudden cardiac arrest. This study demonstrated that suspicious or known family history plays a role in identification of many patients ultimately affected by 1 of the 3 genetic disorders (hypertrophic cardiomyopathy, LQTS, CPVT). CONCLUSION: Important patient and family history and physical examination findings may allow medical providers to identify many pediatric patients affected by 4 cardiac disorders predisposing to sudden cardiac arrest.

Chronic Arrhythmias in the Setting of Heterotaxy: Differences between Right and Left Isomerism.

So-called heterotaxy affects lateralization of the thoracic and abdominal organs. Congenital malformations may be present in one of several organ systems. Cardiac involvement includes both structural and conduction abnormalities. Data regarding arrhythmias in heterotaxy come from case reports and small case series. We pooled available data to further characterize arrhythmias in heterotaxy. A systematic review of the literature for manuscripts describing arrhythmias in heterotaxy patients was conducted. Databases including PubMed, EMBASE, and Ovid were searched. Studies describing arrhythmias in patients with heterotaxy were included if they were in English and presented characteristics of the arrhythmias. Arrhythmia characteristics were abstracted and are presented as pooled data. Freedom from arrhythmia by age was then analyzed using Kaplan-Meier analysis. A total of 19 studies with 121 patients were included in the pooled analysis. Those with right isomerism were found to be more likely to have atrial flutter, atrial tachycardia, junctional tachycardia, and ventricular tachycardia. Those with left isomerism were more likely to have atrioventricular block, intraventricular conduction delay, sick sinus syndrome, and atrioventricular nodal reentry tachycardia. Median age of onset for all arrhythmias was 4 years with no difference by specific arrhythmia or isomerism. Those with right and left isomerism are at risk for different arrhythmias but are likely to develop arrhythmias at the same age. Those with left isomerism are more likely to require pacemaker placement due to atrioventricular block. Understanding these differences allows for focused surveillance of development of these arrhythmias.

Mechanism and ablation of arrhythmia following total cavopulmonary connection.

BACKGROUND: The ability to identify and ablate different arrhythmia mechanisms after the total cavopulmonary connection has not been studied in detail. METHODS AND RESULTS: After obtaining Institutional Review Board approval according to institutional guidelines, consecutive patients after a total cavopulmonary connection undergoing electrophysiology study over a 6-year period were included (2006-2012). Arrhythmia mechanism was determined, and the procedural outcome was defined as complete, partial success, or failure. A 12-point arrhythmia severity score was calculated for each patient at baseline and on follow-up. Fifty-seven procedures were performed on 52 patients (18.4 ± 11.8 years; 53.0 ± 27.2 kg). Access to the pulmonary venous atrium was necessary in 33 procedures, via fenestration (16) or transbaffle puncture (17), and in 2 cases, an additional retrograde approach was used. In total, 80 arrhythmias were identified in 47 cases: macroreentrant (n = 25) or focal atrial tachycardia (n = 8), atrioventricular nodal reentry tachycardia (n = 13), reentry via an accessory pathway (n = 4) or via twin atrioventricular nodes (n = 4), ventricular tachycardia (n = 5), and undefined atrial tachycardia (n = 21). Procedural outcome in 32 patients who underwent ablation was complete success (n = 25), partial success (n = 3), failure (n = 3), or empirical ablation (n = 1). After successful ablation, there was a significant decrease in arrhythmia score over 18.2 (4-32) months follow-up, with a sustained trend even in the face of arrhythmia recurrence (50%). CONCLUSIONS: Arrhythmia mechanism post total cavopulmonary connection is highly varied, encompassing simple and more complex substrates, documentation of which facilitates a strategic approach to invasive arrhythmia management. Despite the anatomic limitations, successful and clinically meaningful ablation is possible.