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Aims: Current guidelines recommend initiating family screening for hypertrophic cardiomyopathy (HCM) after age 10 or 12 years unless early screening criteria are met. The aim was to evaluate if current screening guidelines miss early onset disease., Methods and Results: Children who underwent family screening for HCM before age 18 years were analysed. Major cardiac events (MaCEs) were defined as death, sudden cardiac death (SCD), or need for major cardiac interventions (myectomy, implantable cardioverter-defibrillator insertion, transplantation). Of 524 children screened, 331 were under 10 years of age, 9.9% had echocardiographic evidence of HCM, and 1.1% were symptomatic at first screening. The median (interquartile range) age at HCM onset was 8.9 (4.7-13.4) years, and at MaCE was 10.9 (8.5-14.3) years with a median time to MaCE from HCM onset of 1.5 (0.5-4.1) years. About 52.5% phenotype-positive children and 41% with MaCEs were <10 years old. Only 69% children with early HCM met early screening criteria. Cox regression identified male gender, family history of SCD, and pathogenic variants in MYH7/MYBPC3 as a predictor of early onset HCM and MaCEs., Conclusion: A third of children not eligible for early screening by current guidelines had phenotype-positive HCM. MYH7 and MYBC3 mutation-positive patients were at highest risk for developing early HCM and experiencing an event or requiring a major intervention. Our findings suggest that younger family members should be considered for early clinical and genetic screening to identify the subset in need of closer monitoring and interventions., (© The Author(s) 2019. Published by Oxford University Press on behalf of the European Society of Cardiology.)

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.

Aims: Atrial flutter causes late postoperative morbidity in congenital heart disease (CHD). Sinoatrial node dysfunction is associated with late postoperative atrial flutter, but pacing interventions driven by minimum heart rates (HR) have yielded mixed results., Methods and Results: A retrospective case-control study was used to test the hypothesis that late postoperative atrial flutter is associated with chronotropic incompetence in active young CHD patients. Control CHD patients aged < or =18 years without documented supraventricular ectopy (n = 42) were matched with 42 patients (cases) having atrial flutter onset > or =6 months postoperatively. Minimum, average, and maximum non-flutter HRs were obtained from outpatient ambulatory 24 h ECG (Holter) recordings and graded exercise tests. Chronotropic competence was assessed using percentage of age-specific predicted maximum HR achieved, and calculated chronotropic index. Effects of rate-adaptive programming and maximum atrial pacing rates were analysed in 19 permanently paced cases. Least square estimates of minimum HRs were similar in cases and controls (54+/-2 vs. 52+/-2 bpm). Average HRs were lower in cases (75+/-2 vs. 81+/-2 bpm, P=0.02). Cases and controls differed most significantly with respect to percentage of predicted maximum HR achieved (67+/-2 vs. 80+/-2%, P < 0.001). This difference remained highly significant when the data were adjusted for age, sex, permanent pacing, and negatively chronotropic medication usage at the time of testing. Among paced patients, atrial flutter was significantly less likely to be observed in the setting of rate-adaptive pacing [odds ratio (OR) = 0.36; P < 0.05], and the likelihood of detecting atrial flutter decreased relative to the maximum programmed atrial pacing rate (OR 0.87 for every 5% increment in maximum pacing rate relative to maximum predicted HR for age; P < 0.05)., Conclusion: Late postoperative atrial flutter is associated with chronotropic incompetence in paediatric CHD patients.