Fontan Heart: Insight Into the Physiological Role of the Right Heart.

BACKGROUND: Cardiac output (CO) is almost normal in children born without a functional right ventricle (RV), and a Fontan repair, so why is RV dysfunction such a clinical problem? We tested the hypotheses that increased pulmonary vascular resistance (PVR) is the dominant factor and volume expansion by any means is of limited benefit. METHODS: We removed the RV from a previously used MATLAB model and altered vascular volume, venous compliance (Cv), PVR, and measures of left ventricular (LV) systolic and diastolic function. CO and regional vascular pressures were the primary outcome measures. RESULTS: RV removal decreased CO by 25%, and raised mean systemic filling pressure (MSFP). A 10 mL/kg increase in stressed volume only moderately increased CO with or without the RV. Decreasing systemic Cv increased CO but also markedly increased pulmonary venous pressure. With no RV, increasing PVR had the greatest effect on CO. Increasing LV function had little benefit. CONCLUSIONS: Model data indicate that increasing PVR dominates the decrease in CO in Fontan physiology. Increasing stressed volume by any means only moderately increased CO and increasing LV function had little effect. Decreasing systemic Cv unexpectedly markedly increased pulmonary venous pressures even with the RV intact.

SCN5A mutations in 442 neonates and children: genotype-phenotype correlation and identification of higher-risk subgroups.

Aims: To clarify the clinical characteristics and outcomes of children with SCN5A-mediated disease and to improve their risk stratification. Methods and results: A multicentre, international, retrospective cohort study was conducted in 25 tertiary hospitals in 13 countries between 1990 and 2015. All patients ≤16 years of age diagnosed with a genetically confirmed SCN5A mutation were included in the analysis. There was no restriction made based on their clinical diagnosis. A total of 442 children {55.7% boys, 40.3% probands, median age: 8.0 [interquartile range (IQR) 9.5] years} from 350 families were included; 67.9% were asymptomatic at diagnosis. Four main phenotypes were identified: isolated progressive cardiac conduction disorders (25.6%), overlap phenotype (15.6%), isolated long QT syndrome type 3 (10.6%), and isolated Brugada syndrome type 1 (1.8%); 44.3% had a negative electrocardiogram phenotype. During a median follow-up of 5.9 (IQR 5.9) years, 272 cardiac events (CEs) occurred in 139 (31.5%) patients. Patients whose mutation localized in the C-terminus had a lower risk. Compound genotype, both gain- and loss-of-function SCN5A mutation, age ≤1 year at diagnosis in probands and age ≤1 year at diagnosis in non-probands were independent predictors of CE. Conclusion: In this large paediatric cohort of SCN5A mutation-positive subjects, cardiac conduction disorders were the most prevalent phenotype; CEs occurred in about one-third of genotype-positive children, and several independent risk factors were identified, including age ≤1 year at diagnosis, compound mutation, and mutation with both gain- and loss-of-function.

Exposure to Low-Dose Ionizing Radiation From Cardiac Procedures in Patients With Congenital Heart Disease: 15-Year Data From a Population-Based Longitudinal Cohort.

BACKGROUND: The burden of low-dose ionizing radiation (LDIR) exposure from medical procedures among individuals with congenital heart disease (CHD) is unknown. In this longitudinal population-based study, we sought to determine exposure to LDIR-related cardiac imaging and therapeutic procedures in children and adults with CHD. METHODS AND RESULTS: In an analysis of the Quebec CHD database, exposure to the following LDIR-related cardiac procedures was recorded: catheter-based diagnostic procedures, structural heart interventions, coronary interventions, computed tomography scans of the chest, nuclear procedures, and pacemaker/implantable cardioverter-defibrillator insertion and repair. From 1990 to 2005, there were 16 253 LDIR-exposed patients with CHD with 317 988 patient-years of available follow-up. The total number of LDIR-related procedures increased from 18.5 to 51.9 per 1000 CHD patients per year (P<0.0001). This increase was attributable to increases in rates per 1000 CHD patients in diagnostic cardiac catheterizations (11.7 to 13.7 per 1000), structural heart interventions (1.0 to 5.2 per 1000), coronary interventions (1.0 to 2.4 per 1000), pacemaker/implantable cardioverter-defibrillator insertions (1.6 to 4.4 per 1000), nuclear procedures (4.2 to 13.8 per 1000), and computed tomography scans of the chest (2.5 to 12.3 per 1000). Over time, among children with CHD, the median age at first LDIR procedure decreased from 5.0 years to 9.6 months. Severity of CHD significantly predicted extent of exposure. CONCLUSIONS: From 1990 to 2005, patients with CHD were exposed to increasing numbers of LDIR-emitting cardiac procedures. This exposure occurred at progressively younger ages. These findings provide an important perspective on longitudinal LDIR exposure in this at-risk population.

Cancer Risk in Congenital Heart Disease-What Is the Evidence?

As life expectancy in patients with congenital heart disease (CHD) has improved, the risk for developing noncardiac morbidities is increasing in adult patients with CHD (ACHD). Among these noncardiac complications, malignancies significantly contribute to the disease burden of ACHD patients. Epidemiologic studies of cancer risk in CHD patients are challenging because they require large numbers of patients, extended follow-up, detailed and validated clinical data, and appropriate reference populations. However, several observational studies suggest that cancer risks are significantly elevated in patients with CHD compared with the general population. CHD and cancer share genetic and environmental risk factors. An association with exposure to low-dose ionizing radiation secondary to medical therapeutic or diagnostic procedures has been reported. Patients with Down syndrome, as well as, to a lesser extent, deletion of 22q11.2 and renin-angiotensin system pathologies, may manifest both CHD and a predisposition to cancer. Such observations suggest that carcinogenesis and CHD may share a common basis in some cases. Finally, specific conditions, such as Fontan circulation and cyanotic CHD, may lead to multisystem consequences and subsequently to cancer. Nonetheless, there is currently no clear consensus regarding appropriate screening for cancer and surveillance modalities in CHD patients. Physicians caring for patients with CHD should be aware of this potential predisposition and meet screening recommendations for the general population fastidiously. An interdisciplinary and global approach is required to bridge the knowledge gap in this field.

Phenotypic Manifestations of Arrhythmogenic Cardiomyopathy in Children and Adolescents.

BACKGROUND: Arrhythmogenic cardiomyopathy (ACM) is a variably penetrant disease increasingly identified in young patients. OBJECTIVES: This study sought to describe the diverse phenotype, genotype, and outcomes in pediatric and adolescent patients. METHODS: Records from 1999 to 2016 were reviewed for individuals age <21 years with a consistent personal or family history. Patients were categorized by right ventricular (RV), left dominant (LD), or biventricular subtypes using 2010 Task Force Criteria or proposed features of LD disease, encompassing electrocardiographic, structural, histological, and arrhythmic characteristics. Genetic variants classified as pathogenic and/or likely pathogenic by 2015 American College of Medical Genetics and Genomics criteria in recognized disease-associated genes were included. RESULTS: Manifest disease was evident in 32 patients (age 15.1 ± 3.8 years), of whom 22 were probands, including 16 RV, 7 LD, and 9 biventricular ACM. Nondiagnostic features were seen in 5 of 15 family members. RV disease was associated with cardiac arrest and ventricular tachycardia (p = 0.02) and prevalence of PKP2 variants (p < 0.01), whereas biventricular disease was associated with a younger age of onset (p = 0.02). LD ACM was associated with variants in DSP and LMNA, and biventricular ACM with more a diverse etiology in desmosomal genes. Cardiac arrest was observed in 5 probands (age 15.3 ± 1.9 years) and ventricular tachycardia in 10 (age 16.6 ± 2.7 years), 6 probands, and 4 family members. Features suggestive of myocardial inflammation were seen in 6 patients, with ventricular tachycardia and/or cardiac arrest in 3 patients. Cardiac transplantation was performed in 10 patients. There were no deaths. In RV and biventricular disease, electrocardiographic preceded imaging features, whereas the reverse was seen in LD disease. CONCLUSIONS: ACM in the young has highly varied phenotypic expression incorporating life-threatening arrhythmia, heart failure, and myocardial inflammation. Increased awareness of early onset, aggressive disease has important implications for patient management and familial screening.

Cardiac Events During Competitive, Recreational, and Daily Activities in Children and Adolescents With Long QT Syndrome.

BACKGROUND: The 2005 Bethesda Conference Guidelines advise patients with long QT syndrome against competitive sports. We assessed cardiac event rates during competitive and recreational sports, and daily activities among treated long QT syndrome patients. METHODS AND RESULTS: Long QT syndrome patients aged ≥4 years treated with anti-adrenergic therapy were included. Demographics included mechanism of presentation, corrected QT interval pretreatment, symptom history, medication compliance, and administration of QT-prolonging medications. Corrected QT interval ≥550 ms or prior cardiac arrest defined high risk. Sports were categorized by cardiovascular demand per the 2005 Bethesda Conference Guidelines. Each was classified as recreational or competitive. One hundred seventy-two patients (90; 52% female) with median age 15.2 years (interquartile range 11.4, 19.4) were included. Evaluation was performed for family history (102; 59%), incidental finding (34; 20%), and symptoms (36; 21%). Median corrected QT interval was 474 ms (interquartile range 446, 496) and 14 patients (8%) were deemed high risk. Treatment included ß-blockers (171; 99%), implantable cardioverter-defibrillator (27; 16%), left cardiac sympathetic denervation (7; 4%), and pacemaker (3; 2%). Sports participation was recreational (66; 38%) or competitive (106; 62%), with 92 (53%) exercising against the Bethesda Conference Guidelines. There were no cardiac events in competitive athletes and no deaths. There were 13 cardiac events in 9 previously symptomatic patients during either recreational exercise or activities of daily life. CONCLUSIONS: In this cohort of appropriately managed children with long QT syndrome, cardiac event rates were low and occurred during recreational but not competitive activities. This study further supports the need for increased assessment of arrhythmia risk during exercise in this patient population.