Background: Hypertrophic cardiomyopathy (HCM) is the leading cause of sudden cardiac death (SCD) in children and young adults. Our objective was to develop and validate a SCD risk prediction model in pediatric HCM to guide SCD prevention strategies. Methods: In an international multi-center observational cohort study, phenotype-positive patients with isolated HCM <18 years at diagnosis were eligible. The primary outcome variable was the time from diagnosis to a composite of SCD events at 5-year follow-up: SCD, resuscitated sudden cardiac arrest (SCA), and aborted SCD, i.e. appropriate shock following primary prevention ICD. Competing risk models with cause-specific hazard regression were used to identify and quantify clinical and genetic factors associated with SCD. The cause-specific regression model was implemented using boosting, and tuned with ten repeated four-fold cross-validations. The final model was fitted using all data with the tuned hyperparameter value that maximizes the c-statistic, and its performance was characterized using c-statistic for competing risk models. The final model was validated in an independent external cohort (SHaRe, n=285). Results: Overall, 572 patients met eligibility criteria with 2855 patient-years of follow-up. The 5-year cumulative proportion of SCD events was 9.1% (14 SCD, 25 resuscitated SCA, 14 aborted SCD). Risk predictors included age at diagnosis, documented non-sustained ventricular tachycardia, unexplained syncope, septal diameter z-score, LV posterior wall diameter z-score, LA diameter z-score, peak LV outflow tract (LVOT) gradient, and presence of a pathogenic variant. Unlike adults, LVOT gradient had an inverse association, and family history of SCD had no association with SCD. Clinical and clinical/genetic models were developed to predict 5-year freedom from SCD. Both models adequately discriminated patients with and without SCD events with a c-statistic of 0.75 and 0.76 respectively and demonstrated good agreement between predicted and observed events in the primary and validation cohorts (validation c-statistic 0.71 and 0.72 respectively). Conclusions: Our study provides a validated SCD risk prediction model with over 70% prediction accuracy and incorporates risk factors that are unique to pediatric HCM. An individualized risk prediction model has the potential to improve the application of clinical practice guidelines and shared decision-making for ICD insertion. Clinical Trial Registration: URL: https://clinicaltrials.gov Unique Identifier: NCT04036799

Background: Anomalous origin of the left coronary artery from the pulmonary artery causes severe myocardial ischemia, global left ventricular dysfunction, and annular dilatation producing varying degrees of mitral regurgitation. Mitral regurgitation secondary to the left ventricular or papillary muscle dysfunction in infants will usually improve in the absence of ongoing ischemia. The aim of this study is to determine the influence of the degree of preoperative mitral regurgitation on the early and late outcomes of patients with anomalous origin of the left coronary artery from the pulmonary artery who underwent coronary reimplantation.Methods: Twenty-five patients underwent coronary reimplantation and 1 early patient had ligation during a 30-year period (median age, 4 months; range, 1 month to 16 years), with a median follow-up of 7 years (range, 4 months to 25 years). Before repair, 7 infants (27%) presented in extremis requiring ventilatory and inotropic support, and 17 patients (65%) presented with heart failure. Mitral regurgitation was present in all patients: trivial in 6 patients, mild in 12 patients, moderate in 5 patients, and severe in 3 patients. No patient underwent mitral valve repair or replacement at the time of anomalous origin of the left coronary artery from the pulmonary artery repair.Results: Hospital survival was 92%. Three patients underwent mitral valve repair or replacement at the mean time of 3.5 years (all with severe preoperative mitral regurgitation). The degree of mitral regurgitation gradually improved in all remaining patients with preoperative mild and moderate mitral regurgitation. Echocardiographic studies demonstrated improvement in left ventricular function in all children. None of the patients showed any evidence of supravalvar pulmonary stenosis as a result of their pulmonary artery reconstruction.

We aimed to determine whether malignancy after pediatric HTx for ACM affects overall post-HTx survival. Patients <18y listed for HTx for ACM in the PHTS database between 1993 and 2014 were compared to those with DCM. A 2:1 matched DCM cohort was also compared. Wait-list and post-HTx survival, along with freedom from common HTx complications, were compared. Eighty subjects were listed due to ACM, whereas 1985 were listed for DCM. Although wait-list survival was higher in the ACM group, post-HTx survival was lower for the ACM cohort. Neither difference persisted in the matched cohort analysis. Primary cause of death in the ACM group was infection, which was higher than the DCM group. Malignancy rates were not different. All ACM malignancies were due to PTLD without primary cancer recurrence or SMN. Long-term graft survival after pediatric HTx for ACM is no different than for matched DCM peers, nor is there an increased risk of any malignancy. However, risk of infection and death from infection after HTx are higher in the ACM group. Further studies are needed to assess the effects of prior chemotherapy on susceptibility to infection in this group.

Left ventricular noncompaction is a rare type of cardiomyopathy, the genetics of which are poorly understood to date. Lamin A/C gene mutations have been associated with dilated cardiomyopathy and diseases of the conduction system, but rarely in left ventricular noncompaction cardiomyopathy. This report describes the cases of 4 family members with a lamin A/C gene mutation, 3 of whom had phenotypic expression of left ventricular noncompaction.

Pulmonary balloon valvuloplasty remains a safe and effective treatment for children with isolated pulmonary valve stenosis, with excellent long-term outcomes and no mortality. A few patients require further intervention. Long-term follow-up demonstrates decreased, residual stenosis. Patients have a small, acute increase in pulmonary regurgitation following valvuloplasty, but no long-term progression.