Long-Term Outcomes of Hypertrophic Cardiomyopathy Diagnosed During Childhood: Results From a National Population-Based Study

Unique Aspects of Hypertrophic Cardiomyopathy in Children

Hypertrophic cardiomyopathy (HCM) is a primary heart muscle disease characterized by left ventricular hypertrophy that can be asymptomatic or with presentations that vary from left ventricular outflow tract obstruction, heart failure from diastolic dysfunction, arrhythmias, and/or sudden cardiac death. Children younger than 1 year of age tend to have worse outcomes and often have HCM secondary to inborn errors of metabolism or syndromes such as RASopathies. For children who survive or are diagnosed after 1 year of age, HCM outcomes are often favourable and similar to those seen in adults. This is because of sudden cardiac death risk stratification and medical and surgical innovations. Genetic testing and timely cardiac screening are paving the way for disease-modifying treatment as gene-specific therapies are being developed.

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.

Innovation in surgical treatment of hypertrophic obstructive cardiomyopathy in children

Hypertrophic cardiomyopathy is the second most common cardiomyopathy affecting children and adolescents and is the main cause of sudden death of young athletes. The natural prognosis of children with severe hypertrophic obstructive cardiomyopathy is not optimistic, and it is not uncommon for children with hypertrophic obstructive cardiomyopathy who do not respond to medication. Surgical treatment is often the only solution. Conventional surgical methods in the past include classic or modified extended Morrow operation, classic or modified Konno operation, and Ross-Konno operation. In recent years, with the development of minimally invasive surgery, various minimally invasive surgical methods have emerged endlessly. Because the incision of minimally invasive cardiac surgery is significantly smaller than that of traditional surgery, it causes less trauma, recovers quickly after surgery, and has the advantage of no difference in surgical effect compared with traditional median sternotomy. Tally endoscopic transmitral myectomy, RTM, minimally right thoracotomy, and other surgical methods have achieved encouraging results in adults and some older children with hypertrophic obstructive cardiomyopathy. The appearance of transapical beating-heart septectomy has brought the treatment of hypertrophic obstructive cardiomyopathy from the era of cardiopulmonary bypass and cardiac arrest to a new era of minimally invasive beating-heart surgery. In the past, there were few articles about the treatment of children with hypertrophic obstructive cardiomyopathy. This article reviewed the new progress and prognosis of surgical treatment of children with hypertrophic obstructive cardiomyopathy at home and abroad.

Natural history and outcomes in paediatric RASopathy-associated hypertrophic cardiomyopathy

AIMS

This study aimed to describe the natural history and predictors of all-cause mortality and sudden cardiac death (SCD)/equivalent events in children with a RASopathy syndrome and hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

This is a retrospective cohort study from 14 paediatric cardiology centres in the United Kingdom and Ireland. We included children <18 years with HCM and a clinical and/or genetic diagnosis of a RASopathy syndrome [Noonan syndrome (NS), NS with multiple lentigines (NSML), Costello syndrome (CS), cardiofaciocutaneous syndrome (CFCS), and NS with loose anagen hair (NS-LAH)]. One hundred forty-nine patients were recruited [111 (74.5%) NS, 12 (8.05%) NSML, 6 (4.03%) CS, 6 (4.03%) CFCS, 11 (7.4%) Noonan-like syndrome, and 3 (2%) NS-LAH]. NSML patients had higher left ventricular outflow tract (LVOT) gradient values [60 (36-80) mmHg, P = 0.004]. Over a median follow-up of 197.5 [inter-quartile range (IQR) 93.58-370] months, 23 patients (15.43%) died at a median age of 24.1 (IQR 5.6-175.9) months. Survival was 96.45% [95% confidence interval (CI) 91.69-98.51], 90.42% (95% CI 84.04-94.33), and 84.12% (95% CI 75.42-89.94) at 1, 5, and 10 years, respectively, but this varied by RASopathy syndrome. RASopathy syndrome, symptoms at baseline, congestive cardiac failure (CCF), non-sustained ventricular tachycardia (NSVT), and maximal left ventricular wall thickness were identified as predictors of all-cause mortality on univariate analysis, and CCF, NSVT, and LVOT gradient were predictors for SCD or equivalent event.

CONCLUSIONS

These findings highlight a distinct category of patients with Noonan-like syndrome with a milder HCM phenotype but significantly worse survival and identify potential predictors of adverse outcome in patients with RASopathy-related HCM.

RAF1 mutation leading to hypertrophic cardiomyopathy in a Chinese family with a history of sudden cardiac death: A diagnostic insight into Noonan syndrome

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is predominantly caused by mutations in sarcomeric genes. However, a subset of cases is attributed to genetic disorders unrelated to sarcomeric genes, such as Noonan syndrome (NS) and other RASopathies. In this study, we present a family with a history of sudden cardiac death (SCD) and focus on two adults with syndromic left ventricular hypertrophy (LVH).

METHODS

Clinical evaluations, including echocardiography, were conducted to assess cardiac manifestations. Whole-exome sequencing was performed to identify potential genetic variants underlying syndromic LVH in the study participants.

RESULTS

Whole-exome sequencing revealed a missense variant in the RAF1 gene, c.782C>T (p.Pro261Leu). This variant confirmed the diagnosis of NS in the affected individuals.

CONCLUSION

The findings of this study underscore the importance of family history investigation and genetic testing in diagnosing syndromic LVH. By identifying the underlying genetic cause, clinicians can better understand the etiology of RAS-HCM and its association with SCD in young adults.

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.

Administrative Databases: Friend or Foe in Paediatric Cardiomyopathy

Background

Cardiomyopathy (CM) is a rare childhood disease associated with morbidity and mortality. Limited data exist on paediatric CM in Canada. Given the rare nature, single-centre studies are not sufficiently powered to address important questions. Therefore, administrative health data may serve as a resource for the study of childhood CM. The goal of this study was to validate the accuracy of International Classification of Diseases (ICD)-based algorithms to identify paediatric CM in health databases using a clinical registry as the gold standard.

Methods

The clinical registry was compiled from outpatient and inpatient records at the Stollery Children's Hospital (January 1, 2013, to December 31, 2021). Patients were categorized as having CM or screened without CM. Data were linked to administrative health databases using the patient's Unique Lifetime Identifier. Algorithms based on the presence of ICD, 10th Revision, codes for CM were then evaluated, and cross-tabulations against the clinical registry were generated. Accuracy, positive predictive value, negative predictive value, sensitivity, and specificity were calculated.

Results

The clinical registry had 90 patients with CM and 249 screened without CM. The algorithms ruled out CM (high negative predictive value) but had variability in the ability to diagnose CM positive predictive value. The algorithm that performed the best was based on a diagnosis of CM in a hospitalization or 2 ambulatory visits.

Conclusions

A combination of inpatient and outpatient databases can be used, with acceptable accuracy, to identify paediatric patients with CM. This finding allows for the use of the identified algorithm for the comprehensive study of paediatric CM in Canada.

Sudden Death Risk Assessment in Hypertrophic Cardiomyopathy Across the Lifespan: Reconciling the American and European Approaches

Hypertrophic cardiomyopathy (HCM) is the most prevalent inherited cardiac disease. Since the modern description of HCM more than seven decades ago, great focus has been placed on preventing its most catastrophic complication: sudden cardiac death (SCD). Implantable cardioverter-defibrillators (ICD) have been recognized to provide effective prophylactic therapy. Over the years, two leading societies, the European Society of Cardiology (ESC) and the American Heart Association/American College of Cardiology (AHA/ACC), have proposed risk stratification models to assess SCD in adults. European guidelines rely on a risk calculator, the HCM Risk-SCD, while American guidelines propose a stand-alone risk factor approach. Recently, risk prediction models were also developed in the pediatric population. This article reviews the latest recommendations on the risk stratification of SCD in HCM and summarises current indications for ICD use.

Septal Myectomy Outcomes in Children and Adolescents With Obstructive Hypertrophic Cardiomyopathy

BACKGROUND

Little data exist regarding characteristics and outcomes of pediatric patients undergoing septal myectomy. We evaluated this in a large referral population.

METHODS

Septal myectomy was performed in 199 consecutive patients aged ≤18 years with obstructive hypertrophic cardiomyopathy from January 1, 1976, to June 30, 2021.

RESULTS

Median age was 13 years (interquartile range [IQR], 8-15 years). Left ventricular myectomy approaches included transaortic (163 of 198 [82%]), transapical (16 of 198 [8%]), and combined (19 of 198 [10%]). Right ventricular interventions included myectomy (13 of 199 [7%]) and patch reconstruction of the outflow tract (15 of 199 [8%]). Maximum left ventricular outflow tract gradients decreased after myectomy (prebypass: 50 mm Hg [IQR, 31-73 mm Hg] vs postbypass: 4 mm Hg [IQR, 0-9 mm Hg], P < .001), and this was sustained long-term (5 mm Hg [IQR, 5-10 mm Hg] at 10 years). Iatrogenic aortic and mitral valve injuries occurred in 13 of 199 (7%) and 1 of 199 (1%), respectively; however, all were successfully repaired. Operative mortality was 2 of 199 (1%). The cumulative incidence of redo myectomy was low, at 5.8% at 5 and 8.3% at 10 years. Redo myectomy patients had higher maximum left ventricular outflow tract gradients on echocardiography at predischarge and 1 year and were younger at the index operation (8 years [IQR, 2.5-10 years] vs 13 years [IQR, 9-16 years], P < .001). Overall survival at 10 years was 90%, relative to 47% in a previously reported pediatric nonoperative cohort.

CONCLUSIONS

Pediatric septal myectomy provides safe, effective, and durable relief of ventricular outflow tract obstruction. Iatrogenic valve injury remains a low but nonnegligible risk. Recurrent obstruction requiring redo myectomy is infrequent and can be identified early. Long-term survival in this pediatric septal myectomy cohort appears to fare better than pediatric hypertrophic cardiomyopathy cohorts managed nonoperatively.

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.

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.

Risk of Sudden Death in Patients With RASopathy Hypertrophic Cardiomyopathy

BACKGROUND

Genetic defects in the RAS/mitogen-activated protein kinase pathway are an important cause of hypertrophic cardiomyopathy (RAS-HCM). Unlike primary HCM (P-HCM), the risk of sudden cardiac death (SCD) and long-term survival in RAS-HCM are poorly understood.

OBJECTIVES

The study's objective was to compare transplant-free survival, incidence of SCD, and implantable cardioverter-defibrillator (ICD) use between RAS-HCM and P-HCM patients.

METHODS

In an international, 21-center cohort study, we analyzed phenotype-positive pediatric RAS-HCM (n = 188) and P-HCM (n = 567) patients. The between-group differences in cumulative incidence of all outcomes from first evaluation were compared using Gray's tests, and age-related hazard of all-cause mortality was determined.

RESULTS

RAS-HCM patients had a lower median age at diagnosis compared to P-HCM (0.9 years [IQR: 0.2-5.0 years] vs 9.8 years [IQR: 2.0-13.9 years], respectively) (P < 0.001). The 10-year cumulative incidence of SCD from first evaluation was not different between RAS-HCM and P-HCM (4.7% vs 4.2%, respectively; P = 0.59). The 10-year cumulative incidence of nonarrhythmic deaths or transplant was higher in RAS-HCM compared with P-HCM (11.0% vs 5.4%, respectively; P = 0.011). The 10-year cumulative incidence of ICD insertions, however, was 5-fold lower in RAS-HCM compared with P-HCM (6.9% vs 36.6%; P < 0.001). Nonarrhythmic deaths occurred primarily in infancy and SCD primarily in adolescence.

CONCLUSIONS

RAS-HCM was associated with a higher incidence of nonarrhythmic death or transplant but similar incidence of SCD as P-HCM. However, ICDs were used less frequently in RAS-HCM compared to P-HCM. In addition to monitoring for heart failure and timely consideration of advanced heart failure therapies, better risk stratification is needed to guide ICD practices in RAS-HCM.

The heart in RASopathies

The cardiovascular phenotype associated with RASopathies has expanded far beyond the original descriptions of pulmonary valve stenosis by Dr Jaqueline Noonan in 1968 and hypertrophic cardiomyopathy by Hirsch et al. in 1975. Because of the common underlying RAS/MAPK pathway dysregulation, RASopathy syndromes usually present with a typical spectrum of overlapping cardiovascular anomalies, although less common cardiac defects can occur. The identification of the causative genetic variants has enabled the recognition of specific correlations between genotype and cardiac phenotype. Characterization and understanding of genotype-phenotype associations is not only important for counseling a family of an infant with a new diagnosis of a RASopathy condition but is also critical for their clinical prognosis with respect to cardiac disease, neurodevelopment and other organ system involvement over the lifetime of the patient. This review will focus on the cardiac manifestations of the most common RASopathy syndromes, the relationship between cardiac defects and causal genetic variation, the contribution of cardiovascular abnormalities to morbidity and mortality and the most relevant follow-up issues for patients affected by RAS/MAPK pathway diseases, with respect to cardiac clinical outcomes and management, in children and in the adult population.

Secondary genomic findings in the 2020 China Neonatal Genomes Project participants

BACKGROUND

During next generation sequencing (NGS) data interpretation in critically ill newborns, there is a potential for recognizing and reporting secondary findings (SFs). Early awareness of SFs may provide clues for disease prevention. In this study, we assessed the frequency of SFs in the China Neonatal Genomes Project (CNGP) participants.

METHODS

A total of 2020 clinical exome sequencing (CES) datasets were screened for variants from a list of 59 genes recommended by the American College of Medical Genetics and Genomics (ACMG) for secondary findings reporting v2.0 (ACMG SF v2.0). Identified variants were classified according to the evidence-based guidelines reached by a joint consensus of the ACMG and the Association for Molecular Pathology (AMP).

RESULTS

Among the 2020 CES datasets, we identified 23 ACMG-reportable genes in 61 individuals, resulting in an overall frequency of SFs at 3.02%. A total of 53 unique variants were identified, including 35 pathogenic and 18 likely pathogenic variants. The common disease categories of SFs associated were cardiovascular and cancer disease. The SF results affected the medical management and follow-up strategy in 49 (80.3%) patients.

CONCLUSIONS

We presented the frequency of SFs and their impact on clinical management strategies in CNGP participants. Our study demonstrated that SFs have important practical value in disease prevention and intervention at an early stage.

Findings and Outcome of Transcatheter Right Ventricular Endomyocardial Biopsy and Hemodynamic Assessment in Children with Suspected Myocarditis or Cardiomyopathy

OBJECTIVE

The study objective is assessing findings and outcome in children with suspected cardiomyopathy (CMP) or myocarditis undergoing cardiac catheterization with transcatheter right ventricular endomyocardial biopsy (RV-EMB).

METHODS

All consecutive children undergoing cardiac catheterization with RV-EMB for suspected CMP/myocarditis between 2002-2021 were analysed regarding clinical presentation, cardiac biomarkers, periprocedural management, hemodynamic, histological/immunohistological findings, and outcome.

RESULTS

Eighty-five RV-EMBs were performed in 81 patients at a median age of 6.8 (IQR 9.9) years and a bodyweight of 20 (32.2) kg. Histological/immunohistological findings of RV-EMB revealed dilated CMP in 10 (12%), chronic myocarditis in 28 (33%), healing myocarditis in 5 (6%), acute myocarditis in 9 (11%), other heart muscle diseases in 23 (27%) (7 restrictive CMP, 5 hypertrophic CMP, 4 toxic/anthracycline-induced CMP, 4 endocardfibroelastosis, 1 arrhythmogenic right ventricular CMP, 1 laminin CMP, 1 haemangioma), no conclusive histology in 7 (8%), and normal histology in 3 (4%) patients. Median LVEDP was 17 mmHg (IQR 9), LAP 15 mmHg (10), and PVR 1.83 (1.87) Wood Units/m². There were 3 major complications (3%), all patients recovered without any sequelae. At follow-up (median 1153, IQR 1799 days) 47 (59%) patients were alive, 11 (13%) dead, 15 (18%) underwent cardiac transplantation, and 8 (9%) were lost to follow-up. Death/cardiac transplantation occurred within 3 years from RV-EMB. All patients with an acute myocarditis survived. NT-pro-BNP, echo parameters, and invasive hemodynamics correlate independently with death/cardiac transplant.

CONCLUSION

Hemodynamic invasive data and morphological findings in RV-EMB complete clinical diagnosis in children with suspected CMP/myocarditis and provide important information for further clinical management.

Thirty-year outcome in children with hypertrophic cardiomyopathy based on the type

BACKGROUND

We reviewed the long-term outcome of children with hypertrophic cardiomyopathy (HCM) based on the type.

METHODS

We reviewed the medical records of 100 patients (male 54 female 46) with HCM at our hospital between 1977 and 2015. The survival and cardiac event-free survival rates were calculated by the Kaplan-Meier method.

RESULTS

The age at the time of the diagnosis ranged from 0 to 15 years with a median of 8 years. The number of patients with Noonan syndrome and hypertrophic obstructive cardiomyopathy (HOCM), idiopathic HCM (i-HCM), and secondary HCM (s-HCM) was 13, 13, 65, and 9 respectively. A dilated phase of HCM occurred in 24 patients. Nineteen (79 %) of the 24 patients died of heart failure, and two underwent a heart transplantation. Eight (33 %) of the 24 patients had s-HCM. The median age when a dilated phase occurred was 15 years old, and the median interval from the initial diagnosis to the dilated phase was 8 years. The median time from the diagnosis of a dilated phase to death was 1.6 years. Sudden death and implantable cardioverter defibrillator implantations occurred in 6 and 11 patients at around 15 years old, respectively. The 20-year survival rates were as follows: Noonan syndrome 84 %; HOCM 82 %; i-HCM 71 %; and s-HCM 17 %. Overall, the survival rates at 10, 20, and 30 years were 83 % (95 % confidence interval 73-89), 69 % (58-78), and 63 % (50-74), respectively. The overall cardiac event-free survival rates at 10, 20, and 30 years were 57 % (47-67), 39 % (31-50), and 32 % (21-44), respectively.

CONCLUSION

The long-term outcome in children with HCM was poor, and the outcome of s-HCM was very poor. The occurrence of a dilated phase worsened the outcome in HCM patients. Sudden death and d-HCM often occurred at around 15 years old.

Cardiac myosin binding protein-C variants in paediatric-onset hypertrophic cardiomyopathy: natural history and clinical outcomes

BACKGROUND

Variants in the cardiac myosin-binding protein C gene (MYBPC3) are a common cause of hypertrophic cardiomyopathy (HCM) in adults and have been associated with late-onset disease, but there are limited data on their role in paediatric-onset HCM. The objective of this study was to describe natural history and clinical outcomes in a large cohort of children with HCM and pathogenic/likely pathogenic (P/LP) MYBPC3 variants.

METHODS AND RESULTS

Longitudinal data from 62 consecutive patients diagnosed with HCM under 18 years of age and carrying at least one P/LP MYBPC3 variant were collected from a single specialist referral centre. The primary patient outcome was a major adverse cardiac event (MACE). Median age at diagnosis was 10 (IQR: 2-14) years, with 12 patients (19.4%) diagnosed in infancy. Forty-seven (75%) were boy and 31 (50%) were probands. Median length of follow-up was 3.1 (IQR: 1.6-6.9) years. Nine patients (14.5%) experienced an MACE during follow-up and five (8%) died. Twenty patients (32.3%) had evidence of ventricular arrhythmia, including 6 patients (9.7%) presenting with out-of-hospital cardiac arrest. Five-year freedom from MACE for those with a single or two MYBPC3 variants was 95.2% (95% CI: 78.6% to 98.5%) and 68.4% (95% CI: 40.6% to 88.9%), respectively (HR 4.65, 95% CI: 1.16 to 18.66, p=0.03).

CONCLUSIONS

MYBPC3 variants can cause childhood-onset disease, which is frequently associated with life-threatening ventricular arrhythmia. Clinical outcomes in this cohort vary substantially from aetiologically and genetically mixed paediatric HCM cohorts described previously, highlighting the importance of identifying specific genetic subtypes for clinical management of childhood HCM.

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.

A Comprehensive Assessment of Cardiomyopathies through Cardiovascular Magnetic Resonance: Focus on the Pediatric Population

Cardiomyopathies (CMPs) are a heterogeneous group of diseases that involve the myocardium and result in systolic or diastolic impairment of the cardiac muscle, potentially leading to heart failure, malignant arrhythmias, or sudden cardiac death. Occurrence in pediatric age is rare but has been associated with worse outcomes. Non-invasive cardiac imaging techniques, integrated with clinical, genetic, and electrocardiographic data, have shown a pivotal role in the clinical work-up of such diseases by defining structural alterations and assessing potential complications. Above all modalities, cardiovascular magnetic resonance (CMR) has emerged as a powerful tool complementary to echocardiography to confirm diagnosis, provide prognostic information and guide therapeutic strategies secondary to its high spatial and temporal resolution, lack of ionizing radiation, and good reproducibility. Moreover, CMR can provide in vivo tissue characterization of the myocardial tissue aiding the identification of structural pathologic changes such as replacement or diffuse fibrosis, which are predictors of worse outcomes. Large prospective randomized studies are needed for further validation of CMR in the context of childhood CMPs. This review aims to highlight the role of advanced imaging with CMR in CMPs with particular reference to the dilated, hypertrophic and non-compacted phenotypes, which are more commonly seen in children.

External validation of the HCM Risk-Kids model for predicting sudden cardiac death in childhood hypertrophic cardiomyopathy

AIMS

Sudden cardiac death (SCD) is the most common mode of death in childhood hypertrophic cardiomyopathy (HCM). The newly developed HCM Risk-Kids model provides clinicians with individualized estimates of risk. The aim of this study was to externally validate the model in a large independent, multi-centre patient cohort.

METHODS AND RESULTS

A retrospective, longitudinal cohort of 421 patients diagnosed with HCM aged 1-16 years independent of the HCM Risk-Kids development and internal validation cohort was studied. Data on HCM Risk-Kids predictor variables (unexplained syncope, non-sustained ventricular tachycardia, maximal left ventricular wall thickness, left atrial diameter, and left ventricular outflow tract gradient) were collected from the time of baseline clinical evaluation. The performance of the HCM Risk-Kids model in predicting risk at 5 years was assessed. Twenty-three patients (5.4%) met the SCD end-point within 5 years, with an overall incidence rate of 2.03 per 100 patient-years [95% confidence interval (CI) 1.48-2.78]. Model validation showed a Harrell's C-index of 0.745 (95% CI 0.52-0.97) and Uno's C-index 0.714 (95% 0.58-0.85) with a calibration slope of 1.15 (95% 0.51-1.80). A 5-year predicted risk threshold of ≥6% identified 17 (73.9%) SCD events with a corresponding C-statistic of 0.702 (95% CI 0.60-0.81).

CONCLUSIONS

This study reports the first external validation of the HCM Risk-Kids model in a large and geographically diverse patient population. A 5-year predicted risk of ≥6% identified over 70% of events, confirming that HCM Risk-Kids provides a method for individualized risk predictions and shared decision-making in children with HCM.

MYH7 Genotype–Phenotype Correlation in a Cohort of Finnish Patients

Cardiomyopathies (CMPs) are a heterogeneous group of diseases, frequently genetic, affecting the heart muscle. The symptoms range from asymptomatic to dyspnea, arrhythmias, syncope, and sudden cardiac death. This study is focused on MYH7 (beta-myosin heavy chain), as this gene is commonly mutated in cardiomyopathy patients. Due to the high combined prevalence of MYH7 variants and severe health outcomes, it is one of the most frequently tested genes in clinical settings. We analyzed the clinical presentation and natural history of 48 patients with MYH7-related cardiomyopathy belonging to a cohort from a tertiary center at Helsinki University Hospital, Finland. We made special reference to three age subgroups (0–1, 1–12, and >12 years). Our results characterize a clinically significant MYH7 cohort, emphasizing the high variability of the CMP phenotype depending on age. We observed a subgroup of infants (0–1 years) with MYH7 associated severe DCM phenotype. We further demonstrate that patients under the age of 12 years have a similar symptom burden compared to older patients.

Exercise Recommendations in Pediatric HCM: Variation and Influence of Provider Characteristics

Pediatric Hypertrophic Cardiomyopathy (HCM) is associated with sudden cardiac death (SCD) that can be related to physical activity. Without pediatric specific guidelines, recommendations for activity restriction may be varied. Therefore, our aim is to determine the current practice and variability surrounding exercise clearance recommendations (ER) in pediatric HCM referral centers as well as provider and patient characteristics that influence them. We designed a survey that was distributed to the Pediatric Heart Transplant Study (PHTS) providers and members of the Pediatric and Adult Congenital Electrophysiology Society (PACES) querying provider demographics and patient variables from 2 patient vignettes. The study is a multicenter survey of current practice of specialized providers caring for pediatric HCM patients. Survey of PHTS and PACES providers via email to the respective listservs with a response rate of 28% and 91 overall completing the entire survey after self-identifying as providers for pediatric HCM patients at their center. ER varies for pediatric HCM and is associated with provider training background as well as personal and professional history. Of the 91 providers who completed the survey, 42% (N = 38) trained in pediatric electrophysiology (EP), and 40% (N = 36) in pediatric heart failure (HF). Responses varied and only 53% of providers cleared for mild to moderate activity for the patient in Vignette 1, which is more in line with recent published adult guidelines. ER in both vignettes was significantly associated with type of training background. EP providers were more likely to recommend no restriction (27.8% vs 5.9%) than HF providers even when controlling for provider age and time out of training. Syncope with exercise was deemed "Most Important" by 81% of providers when making ER. ER for pediatric HCM are variable and the majority of providers make ER outside of previously published adult guidelines. Furthermore, ER are influenced by provider background and experience. Further study is needed for risks and benefits of physical activity in this population to inform the development of pediatric specific guidelines.

Clinical presentation and long-term outcomes of infantile hypertrophic cardiomyopathy: a European multicentre study

AIMS

Children presenting with hypertrophic cardiomyopathy (HCM) in infancy are reported to have a poor prognosis, but this heterogeneous group has not been systematically characterized. This study aimed to describe the aetiology, phenotype, and outcomes of infantile HCM in a well-characterized multicentre European cohort.

METHODS AND RESULTS

Of 301 children diagnosed with infantile HCM between 1987 and 2019 presenting to 17 European centres [male n = 187 (62.1%)], underlying aetiology was non-syndromic (n = 138, 45.6%), RASopathy (n = 101, 33.6%), or inborn error of metabolism (IEM) (n = 49, 16.3%). The most common reasons for presentation were symptoms (n = 77, 29.3%), which were more prevalent in those with syndromic disease (n = 62, 61.4%, P < 0.001), and an isolated murmur (n = 75, 28.5%). One hundred and sixty-one (53.5%) had one or more co-morbidities. Genetic testing was performed in 163 (54.2%) patients, with a disease-causing variant identified in 115 (70.6%). Over median follow-up of 4.1 years, 50 (16.6%) underwent one or more surgical interventions; 15 (5.0%) had an arrhythmic event (6 in the first year of life); and 48 (15.9%) died, with an overall 5 year survival of 85%. Predictors of all-cause mortality were an underlying diagnosis of IEM [hazard ratio (HR) 4.4, P = 0.070], cardiac symptoms (HR 3.2, P = 0.005), and impaired left ventricular systolic function (HR 3.0, P = 0.028).

CONCLUSIONS

This large, multicentre study of infantile HCM describes a complex cohort of patients with a diverse phenotypic spectrum and clinical course. Although overall outcomes were poor, this was largely related to underlying aetiology emphasizing the importance of comprehensive aetiological investigations, including genetic testing, in infantile HCM.

Outcomes of hypertrophic cardiomyopathy in Japanese children: a retrospective cohort study

There has been no multicenter study on the prognosis of pediatric hypertrophic cardiomyopathy (HCM) in Japan. Therefore, we conducted a retrospective multicenter observational study on the long-term survival rate in patients diagnosed with HCM under the age of 18 between 1990 and 2014. Twenty institutions participated. A total of 180 patients were identified. The median age at diagnosis was 5.8 years old and median duration of observation was 8.3 years. Although six patients (3%) deteriorated into the dilated phase of HCM, no patient received heart transplantation. Freedom from death at 1, 5, 10, and 20 years were 97%, 92%, 84%, and 80%, respectively. There were 26 deaths. Among them, 11 patients died suddenly, presumably due to arrhythmia, and 15 patients died of heart failure. The presence of heart failure symptoms and a greater cardiothoracic ratio were significant risk factors for heart failure-related death. There were no significant risk factors identified for arrhythmia-related death. In conclusion, the prognosis of pediatric HCM in Japan is good and similar to those reported in population-based studies in the United States and Australia. Significant risk factors for heart failure-related death were identified in pediatric patients with HCM in Japan.

The Risk of Sudden Death in Children with Hypertrophic Cardiomyopathy

Sudden cardiac death (SCD) is the most common cause of death in childhood hypertrophic cardiomyopathy (HCM) and occurs more frequently than in adult patients. Risk stratification strategies have traditionally been extrapolated from adult practice, but newer evidence has highlighted important differences between childhood and adult cohorts, with the implication that pediatric-specific risk stratification strategies are required. Current guidelines use cumulative risk factor thresholds to recommend implantable cardioverter defibrillator (ICD) implantation but have been shown to have limited discriminatory ability. Newer pediatric models that allow clinicians to calculate individualized estimates of 5-year risk allowing, for the first time, personalization of ICD implantation decision-making have been developed. This article describes the pathophysiology, risk factors, and approach to risk stratification for SCD in childhood HCM and highlights unanswered questions.

Hypertrophic cardiomyopathy in children

Hypertrophic cardiomyopathy (HCM) characterized by asymmetric ventricular septal hypertrophy, is the commonest cause of sudden cardiac death (SCD) in the young. The underlying etiology of HCM in the childhood and adolescent patients is diverse. Moreover, the prognosis of pediatric HCM depends on the age of presentation and etiology. Despite the complexity of children with obstructive HCM, surgical treatment results in a favorable outcome for carefully selected patients in experienced tertiary referral center in contemporary era. Implantable cardioverter-defibrillator (ICD) remains the most effective and reliable treatment to prevent SCD. New pediatric SCD risk prediction model, which has good discrimination and calibration and can distinguish patients who are most benefit from an ICD implantation, is expected to be further refined in the future.

Clinical outcomes and programming strategies of implantable cardioverter-defibrillator devices in paediatric hypertrophic cardiomyopathy: a UK National Cohort Study

AIMS

Sudden cardiac death (SCD) is the most common mode of death in paediatric hypertrophic cardiomyopathy (HCM). This study describes the implant and programming strategies with clinical outcomes following implantable cardioverter-defibrillator (ICD) insertion in a well-characterized national paediatric HCM cohort.

METHODS AND RESULTS

Data from 90 patients undergoing ICD insertion at a median age 13 (±3.5) for primary (n = 67, 74%) or secondary prevention (n = 23, 26%) were collected from a retrospective, longitudinal multi-centre cohort of children (<16 years) with HCM from the UK. Seventy-six (84%) had an endovascular system [14 (18%) dual coil], 3 (3%) epicardial, and 11 (12%) subcutaneous system. Defibrillation threshold (DFT) testing was performed at implant in 68 (76%). Inadequate DFT in four led to implant adjustment in three patients. Over a median follow-up of 54 months (interquartile range 28-111), 25 (28%) patients had 53 appropriate therapies [ICD shock n = 45, anti-tachycardia pacing (ATP) n = 8], incidence rate 4.7 per 100 patient years (95% CI 2.9-7.6). Eight inappropriate therapies occurred in 7 (8%) patients (ICD shock n = 4, ATP n = 4), incidence rate 1.1/100 patient years (95% CI 0.4-2.5). Three patients (3%) died following arrhythmic events, despite a functioning device. Other device complications were seen in 28 patients (31%), including lead-related complications (n = 15) and infection (n = 10). No clinical, device, or programming characteristics predicted time to inappropriate therapy or lead complication.

CONCLUSION

In a large national cohort of paediatric HCM patients with an ICD, device and programming strategies varied widely. No particular strategy was associated with inappropriate therapies, missed/delayed therapies, or lead complications.

Early Outcomes of Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy in Children With Noonan Syndrome

Noonan syndrome (NS) is a genetic syndrome causing obstructive hypertrophic cardiomyopathy (HCM) in infants. Studies of cardiac surgery in pediatric HCM patients with NS (NS-HCM) are lacking. We aim to characterize the early disease course of young NS-HCM patients before adolescence and assess their complications and survival condition after septal myectomy. Pediatric obstructive HCM patients who underwent septal myectomy at age 10 years or under were enrolled consecutively between 2009 and 2019. Ten patients with NS and 43 non-NS patients were enrolled in our study. NS-HCM patients were diagnosed at a younger age (5.00 ± 7.48 months vs. 18.73 ± 26.96 months) and more often had biventricular outflow tract obstruction (90.00% vs 30.23%). The surgical treatment can significantly reduce the pressure gradient of the outflow tract. More NS-HCM patients had biventricular reconstruction (70.00% vs 25.58%). The overall survival rates in all patients were 98.04% during 5-year follow-up, respectively. Complete heart block (CHB) was the most prevalent complication in patients with NS and tended to be more common than in non-NS patients (20% vs 7.32%). No sudden cardiac death (SCD) occurred in CHB patients who had pacemaker implantation. Biventricular reconstruction was the risk factor for CHB. Septal myectomy is safe and effective surgery to relieve obstruction in young age pediatric obstructive NS-HCM patients. Postoperative CHB is a common complication, especially in patients who underwent biventricular reconstruction. The implantation of pacemaker can protect CHB patients from SCD and improve their prognosis.

Patients who do not fulfill criteria for hypertrophic cardiomyopathy but have unexplained giant T-wave inversion: a cardiovascular magnetic resonance mid-term follow-up study

BACKGROUND

Patients who have unexplained giant T-wave inversions but do not meet criteria for hypertrophic cardiomyopathy (HCM) (left ventricular (LV) wall thickness < 1.5 cm) demonstrate LV apical morphological features that differ from healthy subjects. Currently, it remains unknown how the abnormal LV apical morphology in this patient population changes over time. The purpose of this study was to investigate LV morphological and functional changes in these patients using a mid-term cardiovascular magnetic resonance (CMR) exam.

METHODS

Seventy-one patients with unexplained giant T-wave inversion who did not fulfill HCM criteria were studied. The mean interval time of the follow-up CMR was 24.4 ± 8.3 months. The LV wall thickness was measured in each LV segment according to the American Heart Association 17-segmented model. The apical angle (ApA) was also measured. A receiver operating curve (ROC) was used to identify the predictive values of the CMR variables.

RESULTS

Of 71 patients, 16 (22.5%) progressed to typical apical HCM, while 55 (77.5%) did not progress to HCM criteria. The mean apical wall thickness was significantly different between the two groups at both baseline and follow-up, with the apical HCM group having greater wall thickness at both time points (all p < 0.001). There was a significant difference between the two groups in the change of ApA (- 1.5 ± 2.7°/yr vs. - 0.7 ± 2.0°/yr, p < 0.001) over time. The combination of mean apical wall thickness and ApA proved to be the best predictor for fulfilling criteria for apical HCM with a threshold value of 8.1 mm and 90° (sensitivity 93.8%, specificity 85.5%).

CONCLUSIONS

CMR metrics identify predictors for progression to HCM in patients with unexplained giant T-wave inversion.

Clinical characteristics and outcomes in childhood-onset hypertrophic cardiomyopathy

AIMS

Childhood-onset hypertrophic cardiomyopathy (HCM) is far less common than adult-onset disease, thus natural history is not well characterized. We aim to describe the characteristics and outcomes of childhood-onset HCM.

METHODS AND RESULTS

We performed an observational cohort study of 7677 HCM patients from the Sarcomeric Human Cardiomyopathy Registry (SHaRe). Hypertrophic cardiomyopathy patients were stratified by age at diagnosis [<1 year (infancy), 1-18 years (childhood), >18 years (adulthood)] and assessed for composite endpoints reflecting heart failure (HF), life-threatening ventricular arrhythmias, atrial fibrillation (AF), and an overall composite that also included stroke and death. Stratifying by age of diagnosis, 184 (2.4%) patients were diagnosed in infancy; 1128 (14.7%) in childhood; and 6365 (82.9%) in adulthood. Childhood-onset HCM patients had an ∼2%/year event rate for the overall composite endpoint, with ventricular arrhythmias representing the most common event in the 1st decade following baseline visit, but HF and AF becoming more common by the end of the 2nd decade. Sarcomeric variants were more common in childhood-onset HCM (63%) and carried a worse prognosis than non-sarcomeric disease, including a greater than two-fold increased risk of HF [HRadj 2.39 (1.36-4.20), P = 0.003] and 67% increased risk of the overall composite outcome [HRadj 1.67 (1.16-2.41), P = 0.006]. When compared with adult-onset HCM, childhood-onset was 36% more likely to develop life-threatening ventricular arrhythmias [HRadj 1.36 (1.03-1.80)] and twice as likely to require transplant or ventricular assist device [HRadj 1.99 (1.23-3.23)].

CONCLUSION

Patients with childhood-onset HCM are more likely to have sarcomeric disease, carry a higher risk of life-threatening ventricular arrythmias, and have greater need for advanced HF therapies. These findings provide insight into the natural history of disease and can help inform clinical risk stratification.

Newer risk assessment strategies in hypertrophic cardiomyopathy

PURPOSE OF REVIEW

The present article serves to review current risk assessment guidelines for sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM) and to discuss how these guidelines can be applied to patients with childhood HCM. New diagnostic techniques that could lead to more accurate risk assessment tools are also discussed.

RECENT FINDINGS

Current guidelines for risk assessment in childhood HCM are extrapolated from adult guidelines and lack background research to validate their use. Continuous variables, such as wall thickness, are converted to binary variables, which is particularly concerning in pediatric patients' where weight gain and linear growth is likely to lead to more significant hemodynamic changes in shorter periods of time. Some studies have even shown that risk factors concerning in adults may actually be protective in pediatric patients. Additionally, large gaps still remain between genotype and phenotype expression in HCM.

SUMMARY

A better understanding of the relationship between cause, phenotype, and outcomes is needed to truly be able to determine risk for SCD in childhood HCM. Larger studies, including newer technologies and quantitative models, similar to the European HCM Risk-SCD model, which allows for a quantitative risk diagnosis, are needed as well.

Association Between Depression and Clinical Outcomes in Patients With Hypertrophic Cardiomyopathy

Background

Hypertrophic cardiomyopathy (HCM) is considered to be the most common cause of sudden death in young people and is associated with an elevated risk of mood disorders. Depression has emerged as a critical risk factor for development and progression of coronary artery disease; however, the association between depression and HCM outcomes is less clear. We sought to examine the impact of depression on clinical outcomes in patients with HCM.

Methods and Results

Between January 2014 and December 2017, 820 patients with HCM were recruited and followed for an average of 4.2 years. End points were defined as sudden cardiac death (SCD) events and HCM‐related heart failure events. A Chinese version of the Structured Clinical Interview followed the Diagnostic and Statistical Manual of Mental Disorders,Fifth Edition and was used to diagnose depression. During the follow‐up period, SCD events occurred in 75 individuals (21.8 per 1000 person‐years), and HCM‐related heart failure events developed in 149 individuals (43.3 per 1000 person‐years). Kaplan–Meier cumulative incidence curves showed a significant association of depression disorders with SCD events (log‐rank P=0.001) and HCM‐related heart failure events (log‐rank P=0.005). A multivariate Cox regression analysis indicated that depression was an independent predictor of SCD events and HCM‐related heart failure events (41.9 versus 21.7 per 1000 person‐years; adjusted hazard ratio [HR], 1.9; 95% CI, 1.6–2.3; P<0.001; and 69.9 versus 38.6 per 1000 person‐years; HR, 1.8; 95% CI, 1.6–2.1; P<0.001, respectively).

Conclusions

Depression is common among patients with HCM. The diagnosis of depression is significantly and independently associated with an increased risk of SCD events and heart failure events in patients with HCM.

The role of the electrocardiographic phenotype in risk stratification for sudden cardiac death in childhood hypertrophic cardiomyopathy

AIMS

The 12-lead electrocardiogram (ECG) is routinely performed in children with hypertrophic cardiomyopathy (HCM). An ECG risk score has been suggested as a useful tool for risk stratification, but this has not been independently validated. This aim of this study was to describe the ECG phenotype of childhood HCM in a large, international, multi-centre cohort and investigate its role in risk prediction for arrhythmic events.

METHODS AND RESULTS

Data from 356 childhood HCM patients with a mean age of 10.1 years (±4.5) were collected from a retrospective, multi-centre international cohort. Three hundred and forty-seven (97.5%) patients had ECG abnormalities at baseline, most commonly repolarization abnormalities (n = 277, 77.8%); left ventricular hypertrophy (n = 240, 67.7%); abnormal QRS axis (n = 126, 35.4%); or QT prolongation (n = 131, 36.8%). Over a median follow-up of 3.9 years (interquartile range 2.0-7.7), 25 (7%) had an arrhythmic event, with an overall annual event rate of 1.38 (95% CI 0.93-2.04). No ECG variables were associated with 5-year arrhythmic event on univariable or multivariable analysis. The ECG risk score threshold of >5 had modest discriminatory ability [C-index 0.60 (95% CI 0.484-0.715)], with corresponding negative and positive predictive values of 96.7% and 6.7.

CONCLUSION

In a large, international, multi-centre cohort of childhood HCM, ECG abnormalities were common and varied. No ECG characteristic, either in isolation or combined in the previously described ECG risk score, was associated with 5-year sudden cardiac death risk. This suggests that the role of baseline ECG phenotype in improving risk stratification in childhood HCM is limited.

Management and outcomes of hypertrophic cardiomyopathy in young adults

BACKGROUND

Management of young adults with hypertrophic cardiomyopathy (HCM) is challenging.

AIMS

To evaluate the profile of young adults (16-25 years) with HCM included in the French prospective HCM registry.

METHODS

Patients were compared according to occurrence of major adverse cardiac events (MACE), comprising sudden cardiac death (SCD) events (implantable cardioverter defibrillator [ICD] discharge, SCD, sustained ventricular tachycardia), atrial fibrillation/embolic stroke, heart failure hospitalisation and unexplained syncope, at a mean follow-up of 4.4±2.2 years.

RESULTS

At baseline, among 61 patients (20.5±3.0 years; 16 women, 26.2%), 13 (21.3%) had a prophylactic ICD, 24.6% a family history of SCD, 29.5% obstruction, 86.0% magnetic resonance imaging myocardial fibrosis, 11.8% abnormal exercise blood pressure and 52.8% a European Society of Cardiology (ESC) 5-year SCD score<4% (24.5%≥6%). At follow-up, 15 patients (24.6%; seven women; all with fibrosis) presented 17 MACE, comprising: SCD events (n=7, 41.2%; including three patients with an ICD, five with at least one SCD major classical risk factor and an ESC score≥5% and two with no risk factors and an ESC score<4%); atrial fibrillation/stroke (n=6, 35.3%); heart failure (n=1, 5.9%); syncope (n=3, 17.6%). An ICD was implanted in 11 patients (four for secondary prevention), but in only 61.5% of patients with a score≥6%. Only obstruction significantly increased MACE risk (odds ratio 3.96; P=0.035), with a non-significant trend towards a lower risk in men (OR 0.29; P=0.065).

CONCLUSIONS

In young adults with HCM, MACE are common in the short term, especially in obstructive HCM and women, mostly arrhythmic in origin. Prophylactic ICD implantation is frequent and does not strictly follow the guidelines, while the use of European/USA guidelines is helpful but imperfect in identifying SCD risk.

Insights from Cardiopulmonary Exercise Testing in Pediatric Patients with Hypertrophic Cardiomyopathy

The usefulness of cardiopulmonary exercise test (CPET) in adult hypertrophic cardiomyopathy (HCM) patients is well-known, whereas its role in pediatric HCM patients has not yet been explored. The present study investigates possible insights from a CPET assessment in a cohort of pediatric HCM outpatients in terms of functional and prognostic assessment. Sixty consecutive pediatric HCM outpatients aged <18 years old were enrolled, each of them undergoing a full clinical assessment including a CPET; a group of 60 healthy subjects served as controls. A unique composite end-point of heart failure (HF) related and sudden cardiac death (SCD) or SCD-equivalent events was also explored. During a median follow-up of 53 months (25th–75th: 13–84 months), a total of 13 HF- and 7 SCD-related first events were collected. Compared to controls, HCM patients showed an impaired functional capacity with most of them showing peak oxygen uptake (pVO₂) values of <80% of the predicted, clearly discrepant with functional New York Heart Association class assessment. The composite end-point occurred more frequently in patients with the worst CPETs’ profiles. At the univariate analysis, pVO₂% was the variable with the strongest association with adverse events at follow-up (C-index = 0.72, p = 0.025) and a cut-off value equal to 60% was the most accurate in identifying those patients at the highest risk. In a pediatric HCM subset, the CPET assessment allows a true functional capacity estimation and it might be helpful in identifying early those patients at high risk of events.

Single Nuclei Sequencing Reveals Novel Insights Into the Regulation of Cellular Signatures in Children With Dilated Cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is a leading cause of death in children with heart failure. The outcome of pediatric heart failure treatment is inconsistent, and large cohort studies are lacking. Progress may be achieved through personalized therapy that takes age- and disease-related pathophysiology, pathology, and molecular fingerprints into account. We present single nuclei RNA sequencing from pediatric patients with DCM as the next step in identifying cellular signatures.

METHODS

We performed single nuclei RNA sequencing with heart tissues from 6 children with DCM with an age of 0.5, 0.75, 5, 6, 12, and 13 years. Unsupervised clustering of 18 211 nuclei led to the identification of 14 distinct clusters with 6 major cell types.

RESULTS

The number of nuclei in fibroblast clusters increased with age in patients with DCM, a finding that was confirmed by histological analysis and was consistent with an age-related increase in cardiac fibrosis quantified by cardiac magnetic resonance imaging. Fibroblasts of patients with DCM >6 years of age showed a profoundly altered gene expression pattern with enrichment of genes encoding fibrillary collagens, modulation of proteoglycans, switch in thrombospondin isoforms, and signatures of fibroblast activation. In addition, a population of cardiomyocytes with a high proregenerative profile was identified in infant patients with DCM but was absent in children >6 years of age. This cluster showed high expression of cell cycle activators such as cyclin D family members, increased glycolytic metabolism and antioxidative genes, and alterations in ß-adrenergic signaling genes.

CONCLUSIONS

Novel insights into the cellular transcriptomes of hearts from pediatric patients with DCM provide remarkable age-dependent changes in the expression patterns of fibroblast and cardiomyocyte genes with less fibrotic but enriched proregenerative signatures in infants.

Overview of Cardiomyopathies in Childhood

Paediatric cardiomyopathies are a heterogenous group of rare disorders, characterised by mechanical and electrical abnormalities of the heart muscle. The overall annual incidence of childhood cardiomyopathies is estimated at about 1 per 100,000 children and is significantly higher during the first 2 years of life. Dilated cardiomyopathies account for approximately half of the cases. Hypertrophic cardiomyopathies form the second largest group, followed by the less common left ventricular non-compaction and restrictive phenotypes. Infectious, metabolic, genetic, and syndromic conditions account for the majority of cases. Congestive heart failure is the typical manifestation in children with dilated cardiomyopathy, whereas presenting symptoms are more variable in other phenotypes. The natural history is largely influenced by the type of cardiomyopathy and its underlying aetiology. Results from a national population-based study revealed 10-year transplant-free survival rates of 80, 62, and 48% for hypertrophic, dilated and left ventricular non-compaction cardiomyopathies, respectively. Long-term survival rates of children with a restrictive phenotype have largely been obscured by early listing for heart transplantation. In general, the majority of adverse events, including death and heart transplantation, occur during the first 2 years after the initial presentation. This review provides an overview of childhood cardiomyopathies with a focus on epidemiology, natural history, and outcomes.