Clinical characteristics and outcomes in childhood-onset hypertrophic cardiomyopathy

Epidemiology of Pediatric Cardiomyopathy in a Mediterranean Population

BACKGROUND

Our knowledge regarding the epidemiology of pediatric cardiomyopathy is based on large national population studies reporting an annual incidence of 1 case per 100,000 children, with a higher incidence observed in infancy and among selected populations. The aim here is to document the epidemiology of pediatric cardiomyopathy in a Mediterranean population.

METHODS

Children younger than 18 years of age living on the Mediterranean island of Crete, Greece, who have been evaluated since the establishment of tertiary pediatric cardiology services (2002-2022) were included in this retrospective study.

RESULTS

A total of 40 children were included, corresponding to an average annual incidence of pediatric cardiomyopathy of 1.59 cases (95% CI: 1.4-2.3) and a prevalence of 26 cases per 100,000 children. In decreasing order of frequency, most cases corresponded to dilated (50%), followed by hypertrophic (42.5%), arrhythmogenic (5%), and restrictive (2.5%) cardiomyopathy. An etiology was identified in 40%, including a genetic diagnosis in 22.5%.

CONCLUSIONS

The incidence of pediatric cardiomyopathy in the Mediterranean island of Crete is higher compared with that reported previously for other Caucasian populations. Further study is needed to investigate the exact prevalence and specific genetic factors associated with the epidemiology of pediatric cardiomyopathy in Mediterranean populations.

Evaluation of new predictive scores for sudden cardiac death in childhood hypertrophic cardiomyopathy in a French cohort

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is rare in children, and sudden cardiac death (SCD) is difficult to predict. Two prognostic scores - HCM Risk-Kids and Precision Medicine for Cardiomyopathy (PRIMaCY) - were developed to assess the risk of SCD in the next 5 years in children with HCM.

AIMS

To test the ability of these scores to predict SCD in children with HCM. Also, to identify factors associated with a severe cardiac rhythmic event (SCRE) (ventricular fibrillation, sustained ventricular tachycardia, heart transplant for rhythmic reasons or SCD).

METHODS

Retrospective, multicentre, observational study at 10 medical centres in the Nord-Pas-de-Calais region, France.

RESULTS

This study included 72 paediatric patients with HCM during 2009-2019 who were followed for a median (interquartile range [IQR]) of 8.5 (5.0-16.2) years. Eleven patients (15.3%) presented with SCRE. HCM Risk-Kids was high, with a median (IQR) score of 6.2% (2.1-12.8%; significant threshold≥6.0%) and the PRIMaCY median (IQR) score was 7.1% (2.6-15.0%; significant threshold≥8.3%). The positive predictive value was only 27.1% (95% confidence interval [CI] 21.5-32.5%) for HCM Risk-Kids (with a threshold of≥6.0%) and 33.2% (95% CI 27.1-38.9%) for the PRIMaCY score (with a threshold of≥8.3%). The negative predictive values were 95.4% (95% CI 92.3-97.7%) and 93.0% (95% CI 89.8-96.2%), respectively. Three of 28 patients with an implantable cardioverter defibrillator (ICD) experienced complications (including inappropriate shocks).

CONCLUSION

HCM Risk-Kids and the PRIMaCY score have low positive predictive values to predict SCD in paediatric patients. If used alone, they could increase the rate of ICD implantation and thus ICD complications. Therefore, the scores should be used in combination with other data (genetic and magnetic resonance imaging results).

Novel Multiplexed Plasma Biomarker Panel Has Diagnostic and Prognostic Potential in Children With Hypertrophic Cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is defined clinically by pathological left ventricular hypertrophy. We have previously developed a plasma proteomics biomarker panel that correlates with clinical markers of disease severity and sudden cardiac death risk in adult patients with HCM. The aim of this study was to investigate the utility of adult biomarkers and perform new discoveries in proteomics for childhood-onset HCM.

METHODS

Fifty-nine protein biomarkers were identified from an exploratory plasma proteomics screen in children with HCM and augmented into our existing multiplexed targeted liquid chromatography-tandem/mass spectrometry-based assay. The association of these biomarkers with clinical phenotypes and outcomes was prospectively tested in plasma collected from 148 children with HCM and 50 healthy controls. Machine learning techniques were used to develop novel pediatric plasma proteomic biomarker panels.

RESULTS

Four previously identified adult HCM markers (aldolase fructose-bisphosphate A, complement C3a, talin-1, and thrombospondin 1) and 3 new markers (glycogen phosphorylase B, lipoprotein a and profilin 1) were elevated in pediatric HCM. Using supervised machine learning applied to training (n=137) and validation cohorts (n=61), this 7-biomarker panel differentiated HCM from healthy controls with an area under the curve of 1.0 in the training data set (sensitivity 100% [95% CI, 95-100]; specificity 100% [95% CI, 96-100]) and 0.82 in the validation data set (sensitivity 75% [95% CI, 59-86]; specificity 88% [95% CI, 75-94]). Reduced circulating levels of 4 other peptides (apolipoprotein L1, complement 5b, immunoglobulin heavy constant epsilon, and serum amyloid A4) found in children with high sudden cardiac death risk provided complete separation from the low and intermediate risk groups and predicted mortality and adverse arrhythmic outcomes (hazard ratio, 2.04 [95% CI, 1.0-4.2]; P=0.044).

CONCLUSIONS

In children, a 7-biomarker proteomics panel can distinguish HCM from controls with high sensitivity and specificity, and another 4-biomarker panel identifies those at high risk of adverse arrhythmic outcomes, including sudden cardiac death.

Effect of beta-blockers and exercise restriction on the prevention of sudden cardiac death in pediatric hypertrophic cardiomyopathy

BACKGROUND

Risk assessment tools and effective prevention strategies for sudden cardiac death (SCD) in pediatric patients with hypertrophic cardiomyopathy (HCM) have not been established. This study aimed to evaluate the efficacy of beta-blockers and exercise restriction for SCD prevention in this population.

METHODS

We retrospectively reviewed the medical records of patients aged <18 years who were diagnosed with HCM at our center between January 1996 and December 2021. SCD and aborted SCD were defined as SCD equivalents. We divided patients based on whether they were prescribed beta-blockers or exercise restriction and compared the outcomes among the groups. The primary outcome was the overall survival (OS), and the secondary outcome was the cumulative SCD equivalent rate. Outcomes were analyzed using Kaplan-Meier curves and Cox proportional hazard analysis. We also compared patients according to the occurrence of SCD equivalents to identify SCD risk predictors.

RESULTS

Among the 43 included patients [mean age, 7.7 (1.6-12.1) years; 23 male individuals], SCD equivalents occurred in 13 patients over 11.2 (4.5-15.6) years of follow-up, among whom 12 were resuscitated and 1 died. The OS rate was significantly higher in the beta-blocker and exercise restriction groups than in the non-beta-blocker and non-exercise restriction groups (81.3 % vs. 19.1 %, p < 0.01 and 57.4 % vs. 12.7 %, p < 0.01, respectively). Among the 13 patients with SCD equivalents, 5 had 9 recurrent SCD equivalents. A significant difference was observed between the SCD equivalent and non-SCD equivalent groups in the history of suspected arrhythmogenic syncope (p < 0.01) in the univariable but not in the multivariable analysis.

CONCLUSIONS

Beta-blockers and exercise restriction may decrease the risk of SCD in pediatric patients with HCM and should be considered for SCD prevention in this population, particularly because predicting SCD in these patients remains challenging.

Natural history and clinical outcomes of patients with hypertrophic cardiomyopathy from thin filament mutations

Hypertrophic cardiomyopathy (HCM) due to thick filament variants is more common; however, HCM due to thin filament variants (HCM-Thin) may be associated with a more malignant phenotype with an increased risk of sudden cardiac death. The aim of this study was to review all the published cases of HCM-Thin to better understand the natural history and clinical outcomes of this disease. A literature review of HCM-Thin identified 21 studies with a total of 177 patients that were suitable for analysis. There were three outcomes of interest, which included a heart failure composite, a ventricular arrhythmia composite and a heart failure and arrhythmia composite outcome. Kaplan-Meier (KM) survival analyses for freedom from each of the abovementioned composite outcomes were completed for the entire cohort and stratified by age of onset and sarcomeric variant. The heart failure composite occurred in 24 (13.6%) patients, the ventricular arrhythmia composite occurred in 30 patients (16.9%) and the combined heart failure and arrhythmia composite occurred in 50 patients (28.2%). In regard to left ventricular ejection fraction (LVEF), the majority of patients were preserved (LVEF > 50%) compared with mildly reduced (LVEF 41%-50%) and reduced (LVEF ≤ 40%) (respectively 26.6% vs. 0.6% vs. 3.4%). The median maximal left ventricular wall thickness (LVWT) was 19.0 mm [interquartile range (IQR) 5.3]. Only 10.7% of the cohort had evidence of left ventricular outflow tract (LVOT) obstruction. Those with paediatric-onset HCM had earlier onset and were at higher risk for each endpoint than their adult counterparts. When stratified by genetic variant, patients with TNNI3 and TPM1 were at a higher risk of the heart failure composite endpoint and the combined heart failure and arrhythmia composite endpoint in comparison with those with the other genetic variants. HCM-Thin is associated with significant morbidity and mortality, with a high arrhythmia burden despite low rates of cardiac obstruction and mild hypertrophy. The paediatric onset of disease and certain sarcomeric variants appear to be associated with a worse prognosis than their adult-onset and other sarcomeric variant counterparts. HCM-Thin seems to have a distinct phenotype, which may require a different management approach.

Cardiac MRI in diagnosis, prognosis, and follow-up of hypertrophic cardiomyopathy in children: current perspectives

Hypertrophic Cardiomyopathy (HCM) is an inherited myocardial disease characterised by left ventricular hypertrophy, which carries an increased risk of life-threatening arrhythmias and sudden cardiac death. The age of presentation and the underlying aetiology have a significant impact on the prognosis and quality of life of children with HCM, as childhood-onset HCM is associated with high mortality risk and poor long-term outcomes. Accurate cardiac assessment and identification of the HCM phenotype are therefore crucial to determine the diagnosis, prognostic stratification, and follow-up. Cardiac magnetic resonance (CMR) is a comprehensive evaluation tool capable of providing information on cardiac morphology and function, flow, perfusion, and tissue characterisation. CMR allows to detect subtle abnormalities in the myocardial composition and characterise the heterogeneous phenotypic expression of HCM. In particular, the detection of the degree and extent of myocardial fibrosis, using late-gadolinium enhanced sequences or parametric mapping, is unique for CMR and is of additional value in the clinical assessment and prognostic stratification of paediatric HCM patients. Additionally, childhood HCM can be progressive over time. The rate, timing, and degree of disease progression vary from one patient to the other, so close cardiac monitoring and serial follow-up throughout the life of the diagnosed patients is of paramount importance. In this review, an update of the use of CMR in childhood HCM is provided, focussing on its clinical role in diagnosis, prognosis, and serial follow-up.

A Review of Pediatric Cardiomyopathy

Though pediatric cardiomyopathy is rare in children, there is significant associated morbidity and mortality. Etiology varies from inborn errors of metabolism to familial genetic mutations and myocyte injury. Major classes include dilated, hypertrophic, restrictive, and non-compaction. Diagnosis generally involves a combination of clinical history and echocardiography. The use of cross-sectional imaging is gaining popularity. Management varies between subtype and may involve a combination of medical and surgical interventions depending on clinical status.

The Diagnostic and Therapeutic Implications of Phenocopies and Mimics of Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a common myocardial disease defined by increased left ventricular wall thickness unexplained by loading conditions. HCM frequently is caused by pathogenic variants in sarcomeric protein genes, but several other syndromic, metabolic, infiltrative, and neuromuscular diseases can result in HCM phenocopies. This review summarizes the current understanding of these HCM mimics, highlighting their importance across the life course. The central role of a comprehensive, multiparametric diagnostic approach and the potential of precision medicine in tailoring treatment strategies are emphasized.

Cardiomyopathies in children and adolescents: aetiology, management, and outcomes in the European Society of Cardiology EURObservational Research Programme Cardiomyopathy and Myocarditis Registry

BACKGROUND AND AIMS

Childhood-onset cardiomyopathies are rare and poorly characterized. This study examined the baseline characteristics and 1-year follow-up of children with cardiomyopathy in the first European Cardiomyopathy Registry.

METHODS

Prospective data were collected on individuals aged 1-<18 years enrolled in the European Society of Cardiology EURObservational Research Programme Cardiomyopathy and Myocarditis long-term registry (June 2014-December 2016).

RESULTS

A total of 633 individuals aged ≤18 years with hypertrophic [HCM; n = 388 (61.3%)], dilated [DCM; n = 206 (32.5%)], restrictive [RCM; n = 28 (4.4%)], and arrhythmogenic right ventricular cardiomyopathy [ARVC; n = 11 (1.7%)] were enrolled by 23 referral centres in 14 countries. Median age at diagnosis was 4.0 [interquartile range (IQR) 0-10] years, and there was a male predominance [n = 372 (58.8%)] across all subtypes, with the exception of DCM diagnosed <10 years of age; 621 (98.1%) patients were receiving cardiac medication and 80 (12.6%) had an implantable cardioverter-defibrillator. A total of 253 patients (253/535, 47.3%) had familial disease. Genetic testing was performed in 414 (67.8%) patients with a pathogenic or likely pathogenic variant reported in 250 (60.4%). Rare disease phenocopies were reported in 177 patients (28.0%) and were most frequent in patients under 10 years [142 (30.9%) vs. 35 (19.6%); P = .003]. Over a median follow-up of 12.5 months (IQR 11.3-15.3 months), 18 patients (3.3%) died [HCM n = 9 (2.6%), DCM n = 5 (3.0%), RCM n = 4 (16.0%)]. Heart failure events were most frequent in RCM patients (36.0%).

CONCLUSIONS

The findings confirm the heterogeneous aetiology of childhood cardiomyopathies and show a high frequency of familial disease. Outcomes differed by cardiomyopathy subtype, highlighting a need for disease-specific evaluation and treatment.

Childhood-onset hypertrophic cardiomyopathy caused by thin-filament sarcomeric variants

Up to 20% of children with sarcomeric hypertrophic cardiomyopathy (HCM) have disease-causing variants in genes coding for thin-filament proteins. However, data on genotype-phenotype correlations for thin-filament disease are limited. This study describes the natural history and outcomes of children with thin-filament-associated HCM and compares it to thick-filament-associated disease.Longitudinal data were collected from 40 children under 18 years with a disease-causing variant in a thin-filament protein from a single quaternary referral centre. Twenty-one (female n=6, 35.5%) were diagnosed with HCM at a median age of 13.0 years (IQR 8.3-14.0). Over a median follow-up of 5.0 years (IQR 4.0-8.5), three (14.3%) experienced one or more major adverse cardiac events (MACE) (two patients had an out-of-hospital arrest and eight appropriate implantable cardiac defibrillator (ICD) therapies in three patients). One gene carrier died suddenly at age 9 years. Compared with those with thick-filament disease, children with thin-filament variants more commonly experienced non-sustained ventricular tachycardia [NSVT; n=6 (28.6%) vs n=14 (10.8%), p=0.024] or underwent ICD insertion (thin, n=13 (61.9%) vs thick, n=50 (38.5%), p=0.040). However, there was no difference in the incidence of MACE (thin 2.47/100 pt years (95% CI 0.80 to 7.66) vs thick 3.63/100 pt years (95% CI 2.25 to 5.84)) or an arrhythmic event (thin 1.65/100 pt years (95% CI 0.41 to 6.58) vs thick 2.55/100 pt years (95% CI 1.45 to 4.48), p value 0.43).This study suggests that adverse events in thin-filament disease are predominantly arrhythmic and may occur in the absence of hypertrophy, but overall short-term outcomes do not differ significantly from thick-filament disease.

Characteristics and incidence of cardiac events across spectrum of age in cardiac sarcoidosis

Background

Clinical characteristics and the risk of cardiovascular events in patients with cardiac sarcoidosis (CS) according to the age of initial diagnosis are unclear.

Methods

This study is a sub-analysis of the ILLUMINATE-CS registry, which is a retrospective, multicenter registry that enrolled patients with CS between 2001 and 2017. Patients were divided into three groups according to the tertile of age at the time of initial diagnosis of CS. The study compared the clinical background at the time of CS diagnosis and the incidence rate of cardiac events across age categories.

Results

A total of 511 patients were analyzed in this study. In baseline, older patients were more likely to be female. History of hypertension, heart failure admission, and atrioventricular block were more common in patients with older age. There was no significant difference in the history of ventricular arrhythmias and left ventricular ejection fraction among all age groups. During a median follow-up period of 3.2 [IQR: 1.7-4.2] years, 35 deaths, 56 heart failure hospitalization, and 98 fatal ventricular arrhythmias was observed. The incidence rate of all-cause death and heart failure hospitalization was significantly higher in patients with older age (p < 0.001), while there was no significant difference in the incidence rate of ventricular arrhythmia among age groups (p = 0.74).

Conclusions

In patients with CS, the risk of all-cause death and heart failure hospitalization was higher in older patients compared with other age groups; however, the risk of ventricular arrhythmia was comparable across all age groups.

Trends in prevalence of major etiologies leading to heart failure in young patients: An integrative review

The prevalence of Heart failure (HF) is increasing with the aging of the population but it is estimated that 10% of HF patients are younger than 50 years-old. HF development in this population is characterized with a fast-growing prevalence, and important disparities according to underlying etiologies or gender. These observations highlight the need to identify specific and preventable factors in these patients, a topic that is under-studied. Here we provide an overview of trends in prevalence of major etiologies leading to HF in young subjects, including genetic factors associated with cardiomyopathies, premature vascular dysfunction and related ischemia, metabolic stress, cardio-toxic responses to different agents, and myocarditis. We also highlight the increasing influence of major risk factors that are driving HF in younger patients, such as obesity, diabetes or arterial hypertension.

Meta-Analysis of Penetrance and Systematic Review on Transition to Disease in Genetic Hypertrophic Cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is characterized by unexplained left ventricular hypertrophy and is classically caused by pathogenic or likely pathogenic variants (P/LP) in genes encoding sarcomere proteins. Not all subclinical variant carriers will manifest clinically overt disease because penetrance (proportion of sarcomere or sarcomere-related P/LP variant carriers who develop disease) is variable, age dependent, and not reliably predicted.

METHODS

A systematic search of the literature was performed. We used random-effects generalized linear mixed model meta-analyses to contrast the cross-sectional prevalence and penetrance of sarcomere or sarcomere-related genes in 2 different contexts: clinically-based studies on patients and families with HCM versus population or community-based studies. Longitudinal family/clinical studies were additionally analyzed to investigate the rate of phenotypic conversion from subclinical to overt HCM during follow-up.

RESULTS

In total, 455 full-text manuscripts and articles were assessed. In family/clinical studies, the prevalence of sarcomere variants in patients diagnosed with HCM was 34%. The penetrance across all genes in nonproband relatives carrying P/LP variants identified during cascade screening was 57% (95% CI, 52%-63%), and the mean age at HCM diagnosis was 38 years (95% CI, 36%-40%). Penetrance varied from ≈32% for MYL3 (myosin light chain 3) to ≈55% for MYBPC3 (myosin-binding protein C3), ≈60% for TNNT2 (troponin T2) and TNNI3 (troponin I3), and ≈65% for MYH7 (myosin heavy chain 7). Population-based genetic studies demonstrate that P/LP sarcomere variants are present in the background population but at a low prevalence of <1%. The penetrance of HCM in incidentally identified P/LP variant carriers was also substantially lower at ≈11%, ranging from 0% in Atherosclerosis Risk in Communities to 18% in UK Biobank. In longitudinal family studies, the pooled phenotypic conversion across all genes was 15% over an average of ≈8 years of follow-up, starting from a mean of ≈16 years of age. However, short-term gene-specific phenotypic conversion varied between ≈12% for MYBPC3 and ≈23% for MYH7.

CONCLUSIONS

The penetrance of P/LP variants is highly variable and influenced by currently undefined and context-dependent genetic and environmental factors. Additional longitudinal studies are needed to improve our understanding of true lifetime penetrance in families and in the community and to identify drivers of the transition from subclinical to overt HCM.

Contemporary review on pediatric hypertrophic cardiomyopathy: insights into detection and management

Hypertrophic cardiomyopathy is the most common genetic cardiac disorder and is defined by the presence of left ventricular (LV) hypertrophy in the absence of a condition capable of producing such a magnitude of hypertrophy. Over the past decade, guidelines on the screening, diagnostic, and management protocols of pediatric primary (i.e., sarcomeric) HCM have undergone significant revisions. Important revisions include changes to the appropriate screening age, the role of cardiac MRI (CMR) in HCM diagnosis, and the introduction of individualized pediatric SCD risk assessment models like HCM Risk-kids and PRIMaCY. This review explores open uncertainties in pediatric HCM that merit further attention, such as the divergent American and European recommendations on CMR use in HCM screening and diagnosis, the need for incorporating key genetic and imaging parameters into HCM-Risk Kids and PRIMaCY, the best method of quantifying myocardial fibrosis and its prognostic utility in SCD prediction for pediatric HCM, devising appropriate genotype- and phenotype-based exercise recommendations, and use of heart failure medications that can reverse cardiac remodeling in pediatric HCM.

Inherited Arrhythmias in the Pediatric Population: An Updated Overview

Pediatric cardiomyopathies (CMs) and electrical diseases constitute a heterogeneous spectrum of disorders distinguished by structural and electrical abnormalities in the heart muscle, attributed to a genetic variant. They rank among the main causes of morbidity and mortality in the pediatric population, with an annual incidence of 1.1-1.5 per 100,000 in children under the age of 18. The most common conditions are dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). Despite great enthusiasm for research in this field, studies in this population are still limited, and the management and treatment often follow adult recommendations, which have significantly more data on treatment benefits. Although adult and pediatric cardiac diseases share similar morphological and clinical manifestations, their outcomes significantly differ. This review summarizes the latest evidence on genetics, clinical characteristics, management, and updated outcomes of primary pediatric CMs and electrical diseases, including DCM, HCM, arrhythmogenic right ventricular cardiomyopathy (ARVC), Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), long QT syndrome (LQTS), and short QT syndrome (SQTS).

Penetrance and Prognosis of MYH7 Variant-Associated Cardiomyopathies: Results From a Dutch Multicenter Cohort Study

BACKGROUND

MYH7 variants cause hypertrophic cardiomyopathy (HCM), noncompaction cardiomyopathy (NCCM), and dilated cardiomyopathy (DCM). Screening of relatives of patients with genetic cardiomyopathy is recommended from 10 to 12 years of age onward, irrespective of the affected gene.

OBJECTIVES

This study sought to study the penetrance and prognosis of MYH7 variant-associated cardiomyopathies.

METHODS

In this multicenter cohort study, penetrance and major cardiomyopathy-related events (MCEs) were assessed in carriers of (likely) pathogenic MYH7 variants by using Kaplan-Meier curves and log-rank tests. Prognostic factors were evaluated using Cox regression with time-dependent coefficients.

RESULTS

In total, 581 subjects (30.1% index patients, 48.4% male, median age 37.0 years [IQR: 19.5-50.2 years]) were included. HCM was diagnosed in 226 subjects, NCCM in 70, and DCM in 55. Early penetrance and MCEs (age <12 years) were common among NCCM-associated variant carriers (21.2% and 12.0%, respectively) and DCM-associated variant carriers (15.3% and 10.0%, respectively), compared with HCM-associated variant carriers (2.9% and 2.1%, respectively). Penetrance was significantly increased in carriers of converter region variants (adjusted HR: 1.87; 95% CI: 1.15-3.04; P = 0.012) and at age ≤1 year in NCCM-associated or DCM-associated variant carriers (adjusted HR: 21.17; 95% CI: 4.81-93.20; P < 0.001) and subjects with a family history of early MCEs (adjusted HR: 2.45; 95% CI: 1.09-5.50; P = 0.030). The risk of MCE was increased in subjects with a family history of early MCEs (adjusted HR: 1.82; 95% CI: 1.15-2.87; P = 0.010) and at age ≤5 years in NCCM-associated or DCM-associated variant carriers (adjusted HR: 38.82; 95% CI: 5.16-291.88; P < 0.001).

CONCLUSIONS

MYH7 variants can cause cardiomyopathies and MCEs at a young age. Screening at younger ages may be warranted, particularly in carriers of NCCM- or DCM-associated variants and/or with a family history of MCEs at <12 years.

Sudden cardiac death in childhood RASopathy-associated hypertrophic cardiomyopathy: Validation of the HCM risk-kids model and predictors of events

BACKGROUND

RASopathies account for nearly 20% of cases of childhood hypertrophic cardiomyopathy (HCM). Sudden cardiac death (SCD) occurs in patients with RASopathy-associated HCM, but the risk factors for SCD have not been systematically evaluated.

AIM

To validate the HCM Risk-Kids SCD risk prediction model in children with RASopathy-associated HCM and investigate potential specific SCD predictors in this population.

METHODS

Validation of HCM Risk-Kids was performed in a retrospective cohort of 169 patients with a RASopathy-associated HCM from 15 international paediatric cardiology centres. Multiple imputation by chained equations was used for missing values related to the HCM Risk-Kids parameters.

RESULTS

Eleven patients (6.5%) experienced a SCD or equivalent event at a median age of 12.5 months (IQR 7.7-28.64). The calculated SCD/equivalent event incidence was 0.78 (95% CI 0.43-1.41) per 100 patient years. Six patients (54.54%) with an event were in the low-risk category according to the HCM Risk-Kids model. Harrell's C index was 0.60, with a sensitivity of 9.09%, specificity of 63.92%, positive predictive value of 1.72%, and negative predictive value of 91%; with a poor distinction between the different risk groups. Unexplained syncope (HR 42.17, 95% CI 10.49-169.56, p < 0.001) and non-sustained ventricular tachycardia (HR 5.48, 95% CI 1.58-19.03, p < 0.007) were predictors of SCD on univariate analysis.

CONCLUSION

Unexplained syncope and the presence of NSVT emerge as predictors for SCD in children with RASopathy-associated HCM. The HCM Risk-Kids model may not be appropriate to use in this population, but larger multicentre collaborative studies are required to investigate this further.

Age and Sex Differences in the Genetics of Cardiomyopathy

Cardiomyopathy has variable penetrance. We analyzed age and sex-related genetic differences in 1,397 cardiomyopathy patients (Ontario, UK) with whole genome sequencing. Pediatric cases (n = 471) harbored more deleterious protein-coding variants in Tier 1 cardiomyopathy genes compared to adults (n = 926) (34.6% vs 25.9% respectively, p = 0.0015), with variant enrichment in constrained coding regions. Pediatric patients had a higher burden of sarcomere and lower burden of channelopathy gene variants compared to adults. Specifically, pediatric patients had more MYH7 and MYL3 variants in hypertrophic cardiomyopathy, and fewer TTN truncating variants in dilated cardiomyopathy. MYH7 variants clustered in the myosin head and neck domains in children. OBSCN was a top mutated gene in adults, enriched for protein-truncating variants. In dilated cardiomyopathy, female patients had a higher burden of z-disc gene variants compared to males. Genetic differences may explain age and sex-related variability in cardiomyopathy penetrance. Genotype-guided predictions of age of onset can inform pre-test genetic counseling. Pediatric cardiomyopathy patients were more likely to be genotype-positive than adults with a higher burden of variants in MYH7, MYL3, TNNT2, VCL. Adults had a higher burden of OBSCN and TTN variants. Females with dilated cardiomyopathy (DCM) had a higher burden of z-disc gene variants compared to males.

Performance of the PRIMaCY sudden death risk prediction model for childhood hypertrophic cardiomyopathy: implications for implantable cardioverter-defibrillator decision-making

AIMS

The validated HCM Risk-Kids model provides accurate individualized estimates of sudden cardiac death risk in children with hypertrophic cardiomyopathy (HCM). A second validated model, PRIMaCY, also provides individualized estimates of risk, but its performance and clinical impact has not been independently investigated. The aim of this study was to investigate the clinical impact of using the PRIMaCY sudden cardiac death (SCD) risk model in childhood HCM.

METHODS AND RESULTS

The estimated 5-year SCD risk was calculated for children meeting diagnostic criteria for HCM in a large single-centre cohort using PRIMaCY (clinical and genetic) and HCM Risk-Kids model, and model performance was assessed. Three hundred one patients [median age 10 (interquartile range 4-14)] were followed up for an average of 4.9 (±3.8) years, during which 30 (10.0%) reached the SCD or equivalent event endpoint. Harrell's C-statistic for the clinical and genetic models was 0.66 [95% confidence interval (CI) 0.52-0.8] and 0.66 (95% CI 0.54-0.80) with a calibration slope of 0.19 (95% CI 0.04-0.54) and 0.26 (95% CI -0.03-0.62), respectively. The number needed to treat to potentially treat one life-threatening arrhythmia for the PRIMaCY clinical, PRIMaCY genetic, and HCM Risk-Kids models was 13.7, 14.5, and 9.4, respectively.

CONCLUSION

Although PRIMaCY has a similar discriminatory ability to that reported for HCM Risk-Kids, estimated risk estimates did not correlate well with observed risk. A higher proportion of patients met implantable cardioverter-defibrillator thresholds using PRIMaCY model compared with HCM Risk-Kids. This has important clinical implications as these patients will be exposed to a lifetime risk of complications and inappropriate therapies.

International Consensus on Differential Diagnosis and Management of Patients With Danon Disease: JACC State-of-the-Art Review

Danon disease is a rare X-linked autophagic vacuolar cardioskeletal myopathy associated with severe heart failure that can be accompanied with extracardiac neurologic, skeletal, and ophthalmologic manifestations. It is caused by loss of function variants in the LAMP2 gene and is among the most severe and penetrant of the genetic cardiomyopathies. Most patients with Danon disease will experience symptomatic heart failure. Male individuals generally present earlier than women and die of either heart failure or arrhythmia or receive a heart transplant by the third decade of life. Herein, the authors review the differential diagnosis of Danon disease, diagnostic criteria, natural history, management recommendations, and recent advances in treatment of this increasingly recognized and extremely morbid cardiomyopathy.

Genetic Contribution to End-Stage Cardiomyopathy Requiring Heart Transplantation

BACKGROUND

Many cardiovascular disorders propel the development of advanced heart failure that necessitates cardiac transplantation. When treatable causes are excluded, studies to define causes are often abandoned, resulting in a diagnosis of end-stage idiopathic cardiomyopathy. We studied whether DNA sequence analyses could identify unrecognized causes of end-stage nonischemic cardiomyopathy requiring heart transplantation and whether the prevalence of genetic causes differed from ambulatory cardiomyopathy cases.

METHODS

We performed whole exome and genome sequencing of 122 explanted hearts from 101 adult and 21 pediatric patients with idiopathic cardiomyopathy from a single center. Data were analyzed for pathogenic/likely pathogenic variants in nuclear and mitochondrial genomes and assessed for nonhuman microbial sequences. The frequency of damaging genetic variants was compared among cardiomyopathy cohorts with different clinical severity.

RESULTS

Fifty-four samples (44.3%) had pathogenic/likely pathogenic cardiomyopathy gene variants. The frequency of pathogenic variants was similar in pediatric (42.9%) and adult (43.6%) samples, but the distribution of mutated genes differed (P=8.30×10-4). The prevalence of causal genetic variants was significantly higher in end-stage than in previously reported ambulatory adult dilated cardiomyopathy cases (P<0.001). Among remaining samples with unexplained causes, no damaging mitochondrial variants were identified, but 28 samples contained parvovirus genome sequences, including 2 samples with 6- to 9-fold higher levels than the overall mean levels in other samples.

CONCLUSIONS

Pathogenic variants and viral myocarditis were identified in 45.9% of patients with unexplained end-stage cardiomyopathy. Damaging gene variants are significantly more frequent among transplant compared with patients with ambulatory cardiomyopathy. Genetic analyses can help define cause of end-stage cardiomyopathy to guide management and risk stratification of patients and family members.

Electrocardiographic Findings in Genotype-Positive and Non-sarcomeric Children with Definite Hypertrophic Cardiomyopathy and Subclinical Variant Carriers

In children with hypertrophic cardiomyopathy (HCM), the genotype-phenotype association of abnormal electrocardiographic (ECG) features in the backdrop of gene positivity has not been well described. This study aimed to describe the abnormal ECG findings in children with HCM harboring who have genetic variants and determine the association with major adverse cardiac events (MACE). We retrospectively analyzed 81 variants-positive, phenotype-positive (V+P+), 66 variant-positive, phenotype-negative (V+P-), and 85 non-sarcomeric subjects. We analyzed ECG findings and clinical outcomes in the three groups of subjects. Repolarization abnormalities (ST and T wave changes) and pathologic Q waves were the most common abnormalities in variant and non-sarcomeric subjects. The V+P+ group showed higher occurrence of ST segment changes and T wave abnormalities compared to V+P- group. Independent predictors of MACE included ST segment changes (OR 3.54, CI 1.20-10.47, p = 0.022). T wave changes alone did not predict outcome (OR 2.13, CI 0.75-6.07, p = 0.157), but combined repolarization abnormalities (ST+T changes) were strong predictors of MACE (OR 5.84, CI 1.43-23.7, p = 0.014) than ST segment changes alone. Maximal wall z score by echocardiography was a predictor of MACE (OR 1.21, CI 1.07-1.37, p = 0.002). Despite the presence of significant myocardial hypertrophy (z score > 4.7), voltage criteria for LVH were much less predictive. In the non-sarcomeric group, RVH was significantly associated with MACE (OR 3.85, CI 1.08-13.73, p = 0.038). These abnormal ECG findings described on the platform of known genetic status and known myocardial hypertrophy may add incremental value to the diagnosis and surveillance of disease progression in children with HCM. Select ECG findings, particularly repolarization abnormalities, may serve as predictors of MACE in children.

The evolving paradigm and current perception of hypertrophic cardiomyopathy: Implications for management

Recent evidence from imaging and genetic screening studies has clearly shown that hypertrophic cardiomyopathy (HCM) is more common than initially perceived, emphasizing the need to reassess its associated clinical and social burden. While clinical and academic efforts have long been focused on stratification of arrhythmic risk and management of intraventricular obstruction, progression of cardiac dysfunction and heart failure-related complications have emerged as most relevant from the epidemiological standpoint, delineating a major unmet need. Furthermore, a broader perspective of our patients' needs has become central in the care of individuals with HCM, addressing issues that are not strictly clinical but equally important to their wellbeing, such as quality of life, athletic participation, lifestyle and reproductive choices and psychological adaptation to a chronic condition often detected at a young age. The appropriate evaluation and objective assessment of disease burden associated with HCM are increasingly relevant not only to management but also to trial design and evaluation of the efficacy of emerging, targeted treatments. In this review, we discuss the evolving perception of HCM prevalence and natural history, as well as recent acquisitions regarding its true, often under-appreciated socio-economic and clinical burden.

Waitlist and Posttransplant Outcomes of Children and Young Adults With Hypertrophic Cardiomyopathy

BACKGROUND

Heart transplantation (HT) is standard therapy for end-stage hypertrophic cardiomyopathy (HCM); however, few studies have described outcomes of older children and young adults with HCM listed for HT. Our objective was to compare waitlist and post-HT outcomes among pediatric and young adult patients with HCM and dilated cardiomyopathy (DCM).

METHODS

The Scientific Registry of Transplant Recipients was queried for patients with HCM and DCM listed at ≤25 years of age. Patient characteristics, waitlist and post-HT survival were compared between younger (≤5 years of age) and older (>5 to ≤25 years of age) HCM patients and between HCM and DCM patients.

RESULTS

Among 6252 patients listed for HT at ≤25 years of age with DCM and HCM, 3926 and 250 were in the older cohort and 1944 and 132 were in the younger cohort, respectively. Older HCM patients were less likely to be critically ill at listing compared with younger HCM patients (P = .0001). Waitlist mortality was similar between HCM and DCM patients in both age cohorts. Post-HT survival in HCM patients was similar between the age cohorts. In the younger cohort, early post-HT survival was worse in HCM compared with DCM (P = .009), with no difference in long-term survival. Survival was similar between the older cohorts.

CONCLUSIONS

Older children and young adults with HCM are less critically ill than the younger cohort and show waitlist and post-HT survival similar to DCM patients. The young children with HCM had worse early posttransplantation survival, though long-term survival was same as DCM.

Left Ventricular Systolic Dysfunction in Patients Diagnosed With Hypertrophic Cardiomyopathy During Childhood: Insights From the SHaRe Registry

BACKGROUND

The development of left ventricular systolic dysfunction (LVSD) in hypertrophic cardiomyopathy (HCM) is rare but serious and associated with poor outcomes in adults. Little is known about the prevalence, predictors, and prognosis of LVSD in patients diagnosed with HCM as children.

METHODS

Data from patients with HCM in the international, multicenter SHaRe (Sarcomeric Human Cardiomyopathy Registry) were analyzed. LVSD was defined as left ventricular ejection fraction <50% on echocardiographic reports. Prognosis was assessed by a composite of death, cardiac transplantation, and left ventricular assist device implantation. Predictors of developing incident LVSD and subsequent prognosis with LVSD were assessed using Cox proportional hazards models.

RESULTS

We studied 1010 patients diagnosed with HCM during childhood (<18 years of age) and compared them with 6741 patients with HCM diagnosed as adults. In the pediatric HCM cohort, median age at HCM diagnosis was 12.7 years (interquartile range, 8.0-15.3), and 393 (36%) patients were female. At initial SHaRe site evaluation, 56 (5.5%) patients with childhood-diagnosed HCM had prevalent LVSD, and 92 (9.1%) developed incident LVSD during a median follow-up of 5.5 years. Overall LVSD prevalence was 14.7% compared with 8.7% in patients with adult-diagnosed HCM. Median age at incident LVSD was 32.6 years (interquartile range, 21.3-41.6) for the pediatric cohort and 57.2 years (interquartile range, 47.3-66.5) for the adult cohort. Predictors of developing incident LVSD in childhood-diagnosed HCM included age <12 years at HCM diagnosis (hazard ratio [HR], 1.72 [CI, 1.13-2.62), male sex (HR, 3.1 [CI, 1.88-5.2), carrying a pathogenic sarcomere variant (HR, 2.19 [CI, 1.08-4.4]), previous septal reduction therapy (HR, 2.34 [CI, 1.42-3.9]), and lower initial left ventricular ejection fraction (HR, 1.53 [CI, 1.38-1.69] per 5% decrease). Forty percent of patients with LVSD and HCM diagnosed during childhood met the composite outcome, with higher rates in female participants (HR, 2.60 [CI, 1.41-4.78]) and patients with a left ventricular ejection fraction <35% (HR, 3.76 [2.16-6.52]).

CONCLUSIONS

Patients with childhood-diagnosed HCM have a significantly higher lifetime risk of developing LVSD, and LVSD emerges earlier than for patients with adult-diagnosed HCM. Regardless of age at diagnosis with HCM or LVSD, the prognosis with LVSD is poor, warranting careful surveillance for LVSD, especially as children with HCM transition to adult care.

Analysis of risk stratification and prevention of sudden death in pediatric patients with hypertrophic cardiomyopathy: Dilemmas and clarity

Hypertrophic cardiomyopathy (HCM) has been considered the most common cause of sudden death (SD) in the young. However, introduction of implantable cardioverter-defibrillators (ICDs) in HCM has proved highly effective and the mainstay of preventing SD in children, adolescents, and adults by terminating malignant ventricular tachyarrhythmias. Nevertheless, ICD decision making is generally regarded as more difficult in pediatrics, and the strategy for selecting ICD patients from this population remains without consensus. Prospective studies in HCM children and adolescents have shown the American Heart Association/American College of Cardiology traditional major risk marker strategy to be reliable with >90% sensitivity in selecting patients for SD prevention. International data in >2000 young HCM patients assembled over 20 years who were stratified by major risk markers showed ICDs effectively prevented SD in 20%. Alternatively, novel quantitative risk scoring initiatives provide 5-year risk estimates that are potentially useful as adjunctive tools to facilitate discussion of prophylactic ICD risks vs benefit but are as yet unsupported by prospective outcome studies. Risk scoring strategies are characterized by reasonable discriminatory statistical power (C-statistic 0.69-0.76) for identifying patients with SD events but with relatively low sensitivity, albeit with specificity comparable with the risk marker strategy. While some reticence for obligating healthy-appearing young patients to lifelong device implants is understandable, underutilization of the ICD in high-risk children and adolescents can represent a lost opportunity for fulfilling the long-standing aspiration of SD prevention. This review provides a critical assessment of the current strengths and weaknesses of SD risk stratification strategies in young HCM patients in an effort to clarify clinical decision making in this challenging subpopulation.

Cardiac Myosin Inhibitors for Managing Obstructive Hypertrophic Cardiomyopathy: JACC: Heart Failure State-of-the-Art Review

Hypertrophic cardiomyopathy (HCM) is frequently caused by pathogenic variants in genes encoding sarcomere proteins and is characterized by left ventricular (LV) hypertrophy, hypercontractility, and-in many cases-left ventricular outflow tract (LVOT) obstruction. Despite standard management, obstructive HCM (oHCM) can still cause substantial morbidity, highlighting the critical need for more effective disease-specific therapeutic approaches. Over the past decade, improved understanding of the molecular pathobiology of HCM has culminated in development of cardiac myosin inhibitors (CMIs), a novel drug class that in recent randomized clinical trials has been shown to decrease LVOT obstruction, improve exercise capacity, and ameliorate symptom burden in patients with oHCM. Although promising, areas of uncertainty remain, including the long-term safety and efficacy of CMIs and whether they have the potential to modify progression of disease. Herein, we review key milestones in the clinical development of CMIs, contextualize CMIs with established oHCM therapies, and discuss future challenges and opportunities for the use of CMIs across the HCM spectrum.

Cardiomyopathies in children: An overview

Paediatric cardiomyopathies form a heterogeneous group of disorders characterized by structural and electrical abnormalities of the heart muscle, commonly due to a gene variant of the myocardial cell structure. Mostly inherited as a dominant or occasionally recessive trait, they might be part of a syndromic disorder of underlying metabolic or neuromuscular defects or combine early developing extracardiac abnormalities (i.e., Naxos disease). The annual incidence of 1 per 100,000 children appears higher during the first two years of life. Dilated and hypertrophic cardiomyopathy phenotypes share an incidence of 60% and 25%, respectively. Arrhythmogenic right ventricular cardiomyopathy (ARVC), restrictive cardiomyopathy, and left ventricular noncompaction are less commonly diagnosed. Adverse events such as severe heart failure, heart transplantation, or death usually appear early after the initial presentation. In ARVC patients, high-intensity aerobic exercise has been associated with worse clinical outcomes and increased penetrance in at-risk genotype-positive relatives. Acute myocarditis in children has an incidence of 1.4-2.1 cases/per 100,000 children per year, with a 6-14% mortality rate during the acute phase. A genetic defect is considered responsible for the progression to dilated cardiomyopathy phenotype. Similarly, a dilated or arrhythmogenic cardiomyopathy phenotype might emerge with an episode of acute myocarditis in childhood or adolescence. This review provides an overview of childhood cardiomyopathies focusing on clinical presentation, outcome, and pathology.

Residual or recurrent obstruction after septal myectomy in young children and infants with hypertrophic cardiomyopathy: cohort study

BACKGROUND

The outcomes after septal myectomy in young children and infants with hypertrophic obstructive cardiomyopathy (HOCM) are not clear. The study sought to report the outcomes after septal myectomy in young children and infants and identify the mechanisms of residual or recurrent obstruction after surgery.

METHODS

The authors performed an observational cohort study of children and infants under the age of 14 who underwent septal myectomy for HCOM from January 2013 to December 2020. Mean follow-up among 94.3% ( n =50) of hospital survivors was 42.09±24.38 months.

RESULTS

In total, 56 children and infants [mean (SD) age, 5.38 (3.78) years; 29 (58.1%) were male] underwent septal myectomy for HOCM. Cumulative survival was 100, 96.6, 93.0, and 81.4% at 1, 3, 5, and 7 years, respectively, among hospital survivors. The incidence of residual and recurrent obstruction was 14.3% (8/56) and 13.0% (6/46), respectively. The mechanisms of residual obstruction were identified as subaortic obstruction caused by inadequacy of previous septal excision in two patients, midventricular obstruction caused by inadequacy of septal excision in five patients, and untreated abnormal papillary muscles in one patient. Recurrent obstruction was caused by isolated midventricular obstruction ( n =4) and newly emerged systolic anterior motion (SAM)-related subaortic obstruction combining abnormal mitral valve apparatus ( n =2). Residual or recurrent obstruction was associated with age less than 2 years at surgery (OR=6.157, 95% CI: 1.487-25.487, P =0.012) and biventricular outflow obstruction (OR=6.139, 95% CI: 1.292-29.172, P =0.022). Recurrent obstruction was associated with age less than 2 years at surgery (OR=6.976, 95% CI: 1.233-39.466, P =0.028).

CONCLUSIONS

Septal myectomy is still effective and safe in young children and infants. The rate of residual or recurrent obstruction with diverse causes is relatively high, which is more likely to occur in children aged less than 2 years at surgery and those with biventricular obstruction.

Genetic profile and genotype-phenotype correlations in childhood cardiomyopathy

BACKGROUND

Genetic cardiomyopathy is a rare disease in childhood.

AIMS

To analyse clinical and genetic aspects of a paediatric cardiomyopathy population, and to establish genotype-phenotype correlations.

METHODS

We performed a retrospective study of all patients with idiopathic cardiomyopathy aged<18years in Southeast France. Secondary causes of cardiomyopathy were excluded. All data (clinical, echocardiography, genetic testing) were collected retrospectively. Patients were classified into six groups: hypertrophic cardiomyopathy; dilated cardiomyopathy; restrictive cardiomyopathy; left ventricular non-compaction; arrhythmogenic right ventricular dysplasia; and mixed cardiomyopathy. Patients who did not have a complete genetic test according to current scientific developments had another deoxyribonucleic acid blood sample during the study time. Genetic tests were considered positive if the variant found was classified as pathogenic, likely pathogenic or a variant of uncertain significance.

RESULTS

Eighty-three patients were included between 2005 and 2019. Most patients had hypertrophic cardiomyopathy (39.8%) or dilated cardiomyopathy (27.7%). The median age at diagnosis was 1.28years (interquartile range: 0.27-10.48years). Heart transplantation was performed in 30.1% of patients, and 10.8% died during follow-up. Among 64 patients with a complete genetic analysis, 64.1% had genetic anomalies, mostly in MYH7 (34.2%) and MYBPC3 (12.2%) genes. There were no differences in the whole cohort between genotype-positive and genotype-negative patients. In the hypertrophic cardiomyopathy group, 63.6% had a positive genetic test. Patients with a positive genetic test more often had extracardiac impact (38.1% vs. 8.3%; P=0.009), and more often required an implantable cardiac defibrillator (23.8% vs. 0%; P=0.025) or a heart transplant (19.1% vs. 0%; P=0.047).

CONCLUSIONS

In our population, children with cardiomyopathy had a high positive genetic test rate. Hypertrophic cardiomyopathy with a positive genetic test is associated with a worse outcome.

Indications and management of implantable cardioverter-defibrillator therapy in childhood hypertrophic cardiomyopathy

Sudden cardiac death is the most common mode of death during childhood and adolescence in hypertrophic cardiomyopathy, and identifying those individuals at highest risk is a major aspect of clinical care. The mainstay of preventative therapy is the implantable cardioverter-defibrillator, which has been shown to be effective at terminating malignant ventricular arrhythmias in children with hypertrophic cardiomyopathy but can be associated with substantial morbidity. Accurate identification of those children at highest risk who would benefit most from implantable cardioverter-defibrillator implantation while minimising the risk of complications is, therefore, essential. This position statement, on behalf of the Association for European Paediatric and Congenital Cardiology (AEPC), reviews the currently available data on established and proposed risk factors for sudden cardiac death in childhood-onset hypertrophic cardiomyopathy and current approaches for risk stratification in this population. It also provides guidance on identification of individuals at risk of sudden cardiac death and optimal management of implantable cardioverter-defibrillators in children and adolescents with hypertrophic cardiomyopathy.

Clinical and Genetic Screening for Hypertrophic Cardiomyopathy in Paediatric Relatives: Changing Paradigms in Clinical Practice

Hypertrophic cardiomyopathy (HCM) is an important cause of morbidity and mortality in children. While the aetiology is heterogeneous, most cases are caused by variants in the genes encoding components of the cardiac sarcomere, which are inherited as an autosomal dominant trait. In recent years, there has been a paradigm shift in the role of clinical screening and predictive genetic testing in children with a first-degree relative with HCM, with the recognition that phenotypic expression can, and often does, manifest in young children and that familial disease in the paediatric age group may not be benign. The care of the child and family affected by HCM relies on a multidisciplinary team, with a key role for genomics. This review article summarises current evidence in clinical and genetic screening for hypertrophic cardiomyopathy in paediatric relatives and highlights aspects that remain to be resolved.

Genetic Basis of Childhood Cardiomyopathy

BACKGROUND

The causes of cardiomyopathy in children are less well described than in adults. We evaluated the clinical diagnoses and genetic causes of childhood cardiomyopathy and outcomes of cascade genetic testing in family members.

METHODS

We recruited children from a pediatric cardiology service or genetic heart diseases clinic. We performed Sanger, gene panel, exome or genome sequencing and classified variants for pathogenicity using American College of Molecular Genetics and Genomics guidelines.

RESULTS

Cardiomyopathy was diagnosed in 221 unrelated children aged ≤18 years. Children mostly had hypertrophic cardiomyopathy (n=98, 44%) or dilated cardiomyopathy (n=89, 40%). The highest genetic testing diagnostic yields were in restrictive cardiomyopathy (n=16, 80%) and hypertrophic cardiomyopathy (n=65, 66%), and lowest in dilated cardiomyopathy (n=26, 29%) and left ventricular noncompaction (n=3, 25%). Pathogenic variants were primarily found in genes encoding sarcomere proteins, with TNNT2 and TNNI3 variants associated with more severe clinical outcomes. Ten children (4.5%) had multiple pathogenic variants. Genetic test results prompted review of clinical diagnosis in 14 families with syndromic, mitochondrial or metabolic gene variants. Cascade genetic testing in 127 families confirmed 24 de novo variants, recessive inheritance in 8 families, and supported reclassification of 12 variants.

CONCLUSIONS

Genetic testing of children with cardiomyopathy supports a precise clinical diagnosis, which may inform prognosis.

Family screening of hypertrophic cardiomyopathy in children: a case report

Background

Paediatric hypertrophic cardiomyopathy (HCM) caused by sarcomere protein gene mutations is more common than previously thought. We present the case of a 9-year-old boy that was diagnosed with HCM during family screening.

Case summary

We present a case of a 9-year-old boy with a family history of sarcomeric HCM who was diagnosed with hypertrophic obstructive cardiomyopathy (HOCM) during clinical screening. Echocardiography and cardiovascular magnetic resonance imaging revealed asymmetric left ventricular hypertrophy with a maximum wall thickness of 18–19 mm. Cardiovascular magnetic resonance late gadolinium enhancement imaging showed patchy fibrosis within the area of maximum wall thickness. Genetic testing confirmed the presence of the familial mutation in the MYL2 gene. The patient was started on bisoprolol. Furthermore, risk stratification was performed and a recommendation for implantable cardioverter-defibrillator implantation was made.

Discussion

This case demonstrates that significant HCM can already start in childhood and discusses the recommendations for family screening on the basis of recently published studies and the present European Society of Cardiology guideline.

Clinical characteristics and survival of children with hypertrophic cardiomyopathy in China: A multicentre retrospective cohort study

BACKGROUND

Few data on paediatric hypertrophic cardiomyopathy (HCM) are available in developing countries. A multicentre, retrospective, cohort study was conducted to profile the clinical characteristics and survival of children with HCM in China.

METHODS

We collected longitudinal data on children with HCM aged 0-18 years at three participating institutions between January 1, 2010 and December 31, 2019. Patients were identified by searching for the diagnosis using ICD-10 codes from the electronic medical records database. HCM was diagnosed morphologically with echocardiography or cardiovascular magnetic resonance imaging. The exclusion criteria were secondary aetiologies of myocardial hypertrophy. The primary outcomes were all-cause death or heart transplantation. The Kaplan-Meier method was used to estimate the survival rate of different groups.

FINDINGS

A total of 564 children were recruited, with a median age at diagnosis of 1.0 year (interquartile range, IQR: 0.4-8.0 years), followed for a median of 2.6 years (1977 patient-years, IQR:0.5, 5.9 years). The underlying aetiology was sarcomeric (382, 67.7%), inborn errors of metabolism (IEMs) (108, 19.2%), and RASopathies (74, 13.1%). A total of 149 patients (26.4%) died and no patients underwent heart transplantation during follow-up. The survival probability was 71.1% (95% confidence interval [CI], 66.3%-75.3%) at 5 years. Patients with IEMs or those diagnosed during infancy had the poorest outcomes, with an estimated 5-year survival rate of 16.9% (95% CI, 7.7%-29.1%) and 56.0% (95% CI, 48.8%-62.5%), respectively. Heart failure was the leading cause of death in the cohort (90/149, 60.4%), while sudden cardiac death was the leading cause in patients with sarcomeric HCM (32/66, 48.5%).

INTERPRETATION

There is a high proportion of patients with IEM and a low proportion of patients with neuromuscular disease in children with HCM in China. Overall, mortality remains high in China, especially in patients with IEMs and those diagnosed during infancy.

FUNDING

National Natural Science Fund of China (81770380, 81974029), China Project of Shanghai Municipal Science and Technology Commission (20MC1920400, 21Y31900301).

Prognostic factors in hypertrophic cardiomyopathy in children: An MRI based study

BACKGROUND

Clinical and prognostic role of cardiac magnetic resonance (CMR) in adult population with hypertrophic cardiomyopathy (HCM) have been largely assessed. We sought to investigate the role of CMR for predicting cardiovascular events in children with HCM.

METHODS

CMR was performed in 116 patients with HCM (37 sarcomeric mutations, 31 other mutations, mean age 10.4 ± 4.3 yrs). CMR protocol included cine imaging for evaluation of morphology and function and late gadolinium enhancement (LGE). Hard cardiac events (sustained VT, resuscitated cardiac arrest, sudden cardiac death, end-stage heart failure, heart transplant and appropriate ICD intervention) were recorded through a median follow-up of 4 (1-7) years.

RESULTS

During follow-up 21 heart cardiac events occurred. At maximal-rank statistic the optimal cut-point for LGE extent for predicting events was ≥2%. Syncope, non-sustained ventricular tachycardia (NSVT) and LGE extent ≥2% were independent predictors of events. At Harrel's C statistic combination of LGE extent ≥2% and syncope was the strongest model for predicting events. HR of patients with LGE extent ≥2% and no history of syncope was 3.6 (1.1-12.2) that increased to 37.6 (5.4-161) in those with LGE extent ≥2% and syncope. The median time dependent AUC of LGE extent (0.88, 95% CI 0.86-0.89) was significantly higher than that of syncope (0.63, 95% CI 0.61-0.66, p < 0.0001) and NSVT (0.52, 95% CI 0.50-0.53, p < 0.0001).

CONCLUSIONS

In children with HCM, LGE and syncope were independent predictors of hard cardiac events at follow-up.

Clinical Features and Natural History of Preadolescent Nonsyndromic Hypertrophic Cardiomyopathy

BACKGROUND

Up to one-half of childhood sarcomeric hypertrophic cardiomyopathy (HCM) presents before the age of 12 years, but this patient group has not been systematically characterized.

OBJECTIVES

The aim of this study was to describe the clinical presentation and natural history of patients presenting with nonsyndromic HCM before the age of 12 years.

METHODS

Data from the International Paediatric Hypertrophic Cardiomyopathy Consortium on 639 children diagnosed with HCM younger than 12 years were collected and compared with those from 568 children diagnosed between 12 and 16 years.

RESULTS

At baseline, 339 patients (53.6%) had family histories of HCM, 132 (20.9%) had heart failure symptoms, and 250 (39.2%) were prescribed cardiac medications. The median maximal left ventricular wall thickness z-score was 8.7 (IQR: 5.3-14.4), and 145 patients (27.2%) had left ventricular outflow tract obstruction. Over a median follow-up period of 5.6 years (IQR: 2.3-10.0 years), 42 patients (6.6%) died, 21 (3.3%) underwent cardiac transplantation, and 69 (10.8%) had life-threatening arrhythmic events. Compared with those presenting after 12 years, a higher proportion of younger patients underwent myectomy (10.5% vs 7.2%; P = 0.045), but fewer received primary prevention implantable cardioverter-defibrillators (18.9% vs 30.1%; P = 0.041). The incidence of mortality or life-threatening arrhythmic events did not differ, but events occurred at a younger age.

CONCLUSIONS

Early-onset childhood HCM is associated with a comparable symptom burden and cardiac phenotype as in patients presenting later in childhood. Long-term outcomes including mortality did not differ by age of presentation, but patients presenting at younger than 12 years experienced adverse events at younger ages.

Relationship Between Maximal Left Ventricular Wall Thickness and Sudden Cardiac Death in Childhood Onset Hypertrophic Cardiomyopathy

BACKGROUND

Maximal left ventricular wall thickness (MLVWT) is a risk factor for sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM). In adults, the severity of left ventricular hypertrophy has a nonlinear relationship with SCD, but it is not known whether the same complex relationship is seen in childhood. The aim of this study was to describe the relationship between left ventricular hypertrophy and SCD risk in a large international pediatric HCM cohort.

METHODS

The study cohort comprised 1075 children (mean age, 10.2 years [±4.4]) diagnosed with HCM (1-16 years) from the International Paediatric Hypertrophic Cardiomyopathy Consortium. Anonymized, noninvasive clinical data were collected from baseline evaluation and follow-up, and 5-year estimated SCD risk was calculated (HCM Risk-Kids).

RESULTS

MLVWT Z score was <10 in 598 (58.1%), ≥10 to <20 in 334 (31.1%), and ≥20 in 143 (13.3%). Higher MLVWT Z scores were associated with heart failure symptoms, unexplained syncope, left ventricular outflow tract obstruction, left atrial dilatation, and nonsustained ventricular tachycardia. One hundred twenty-two patients (71.3%) with MLVWT Z score ≥20 had coexisting risk factors for SCD. Over a median follow-up of 4.9 years (interquartile range, 2.3-9.3), 115 (10.7%) had an SCD event. Freedom from SCD event at 5 years for those with MLVWT Z scores <10, ≥10 to <20, and ≥20 was 95.6%, 87.4%, and 86.0, respectively. The estimated SCD risk at 5 years had a nonlinear, inverted U-shaped relationship with MLVWT Z score, peaking at Z score +23. The presence of coexisting risk factors had a summative effect on risk.

CONCLUSIONS

In children with HCM, an inverted U-shaped relationship exists between left ventricular hypertrophy and estimated SCD risk. The presence of additional risk factors has a summative effect on risk. While MLVWT is important for risk stratification, it should not be used either as a binary variable or in isolation to guide implantable cardioverter defibrillator implantation decisions in children with HCM.

What Aspects of Phenotype Determine Risk for Sudden Cardiac Death in Pediatric Hypertrophic Cardiomyopathy?

Sudden cardiac death due to hypertrophic cardiomyopathy (HCM), is the most common autopsy-proven cause of unexpected medical death in children after infancy. This mode of death is preventable by implantation of an internal cardiac defibrillator (ICD), a procedure that has considerable morbidity in childhood patients, and even mortality. Since HCM is an inheritable disease (usually autosomal dominant, occasionally recessive), family screening may identify subjects at risk. This review summarizes published studies carried out to identify which phenotypic markers are important risk factors in childhood patients with HCM and reviews the performance of existing risk-stratification algorithms (HCM Risk-Kids, PRIMaCY) against those of single phenotypic markers. A significant proportion of HCM-patients diagnosed in childhood are associated with RASopathies such as Noonan syndrome, but a knowledge gap exists over risk stratification in this patient group. In conclusion, pediatric risk-stratification algorithms for sudden cardiac death perform better in children than adult HCM risk-stratification strategies. However, current multivariable algorithms overestimate risk substantially without having high sensitivity, and remain ‘a work in progress’. To include additional phenotypic parameters that can be reproducibly measured such as ECG-markers, e.g., ECG risk score (which has high sensitivity and negative predictive value), tissue Doppler diastolic function measurements, and quantification of myocardial scarring on cardiac magnetic resonance imaging, has the potential to improve risk-stratification algorithms. Until that work has been achieved, these are three factors that the clinician can combine with the current algorithm-calculated per cent risk, in order better to assess risk.

Pediatric Hypertrophic Cardiomyopathy: Exploring the Genotype-Phenotype Association

Pediatric hypertrophic cardiomyopathy (HCM) is the most common form of cardiomyopathy in children and a leading cause of sudden cardiac death. Yet, the association between genotype variation, phenotype expression, and adverse events in pediatric HCM has not been fully elucidated. Although the literature on this topic is evolving in adult HCM, the evidence in children is lacking. Solidifying our understanding of this relationship could improve risk stratification as well as improve our comprehension of the underlying pathophysiological characteristics of pediatric HCM. In this state‐of‐the‐art review, we examine the current literature on genetic variations in HCM and their association with outcomes in children, discuss the current approaches to identifying cardiovascular phenotypes in pediatric HCM, and explore possible avenues that could improve sudden cardiac death risk assessment.

The year in cardiovascular medicine 2021: heart failure and cardiomyopathies

In the year 2021, the universal definition and classification of heart failure (HF) was published that defines HF as a clinical syndrome with symptoms and/or signs caused by a cardiac abnormality and corroborated by elevated natriuretic peptide levels or objective evidence of cardiogenic congestion. This definition and the classification of HF with reduced ejection fraction (HFrEF), mildly reduced, and HF with preserved ejection fraction (HFpEF) is consistent with the 2021 ESC Guidelines on HF. Among several other new recommendations, these guidelines give a Class I indication for the use of the sodium–glucose co-transporter 2 (SGLT2) inhibitors dapagliflozin and empagliflozin in HFrEF patients. As the first evidence-based treatment for HFpEF, in the EMPEROR-Preserved trial, empagliflozin reduced the composite endpoint of cardiovascular death and HF hospitalizations. Several reports in 2021 have provided novel and detailed analyses of device and medical therapy in HF, especially regarding sacubitril/valsartan, SGLT2 inhibitors, mineralocorticoid receptor antagonists, ferric carboxymaltose, soluble guanylate cyclase activators, and cardiac myosin activators. In patients hospitalized with COVID-19, acute HF and myocardial injury is quite frequent, whereas myocarditis and long-term damage to the heart are rather uncommon.

Case report: Removal of a subcutaneous implantable cardiac defibrillator in a pediatric patient with hypertrophic cardiomyopathy after a septal myectomy. Insights on current indications of type of ICD in children with hypertrophic cardiomyopathy and left ventricular tract obstruction

Hypertrophic cardiomyopathy is a heart muscle disease with an annual incidence between 0.24 and 0.47/100000 in childhood. Sudden cardiac death is the most common cause of death in this population. Although some medical treatment can decrease the risk of sudden cardiac death, implantable cardioverter defibrillator continues to be the most reliable treatment. Different types of devices and programming strategies can be used in patients with hypertrophic cardiomyopathy depending on each center and specific patient condition. We report a pediatric patient affected with hypertrophic cardiomyopathy who had and ICD implantation in primary prevention. Four years later he developed symptomatic left ventricular outflow tract obstruction and a surgical septal myectomy was performed. After the myectomy the patient developed complete left bundle branch block on his 12 lead ECG, and unfortunately none of the S-ICD vectors were suitable after the myectomy and it had to be explanted and replaced for a new transvenous ICD.

A complex unit for a complex disease: the HCM-Family Unit

Hypertrophic cardiomyopathy (HCM) is a group of heterogeneous disorders that are most commonly passed on in a heritable manner. It is a relatively rare disease around the globe, but due to increased rates of consanguinity within the Kingdom of Saudi Arabia, we speculate a high incidence of undiagnosed cases. The aim of this paper is to elucidate a systematic approach in dealing with HCM patients and since HCM has variable presentation, we have summarized differentials for diagnosis and how different subtypes and genes can have an impact on the clinical picture, management and prognosis. Moreover, we propose a referral multi-disciplinary team HCM-Family Unit in Saudi Arabia and an integrated role in a network between King Faisal Hospital and Inherited and Rare Cardiovascular Disease Unit-Monaldi Hospital, Italy (among the 24 excellence centers of the European Reference Network (ERN) GUARD-Heart).   Graphical Abstract.