Overview of Cardiomyopathies in Childhood

A Reversible Etiology of Progressive Motor Decline in a Previously Healthy Child

We describe the clinical presentation and evaluation of a 10-year-old boy who presented to our medical center with years of progressive proximal muscle weakness, muscle atrophy, and weight loss. In addition to a myopathic phenotype, he was found to have tachycardia, tremor, and learning difficulties. Electromyography revealed chronic myopathic changes and laboratory screening was notable for undetectable thyroid stimulating hormone. Follow-up testing revealed elevated thyroid peroxidase antibodies and thyroid stimulating immunoglobulins. Ultrasound examination revealed an enlarged heterogeneous thyroid gland. Four weeks after treatment with atenolol and methimazole, his strength and cognition began to improve. This case highlights the importance of evaluating for potentially reversible toxic-metabolic etiologies in children presenting with any progressive neurologic symptoms.

Pediatric dilated cardiomyopathy: a review of current clinical approaches and pathogenesis

Pediatric dilated cardiomyopathy (DCM) is a rare, yet life-threatening cardiovascular condition characterized by systolic dysfunction with biventricular dilatation and reduced myocardial contractility. Therapeutic options are limited with nearly 40% of children undergoing heart transplant or death within 2 years of diagnosis. Pediatric patients are currently diagnosed based on correlating the clinical picture with echocardiographic findings. Patient age, etiology of disease, and parameters of cardiac function significantly impact prognosis. Treatments for pediatric DCM aim to ameliorate symptoms, reduce progression of disease, and prevent life-threatening arrhythmias. Many therapeutic agents with known efficacy in adults lack the same evidence in children. Unlike adult DCM, the pathogenesis of pediatric DCM is not well understood as approximately two thirds of cases are classified as idiopathic disease. Children experience unique gene expression changes and molecular pathway activation in response to DCM. Studies have pointed to a significant genetic component in pediatric DCM, with variants in genes related to sarcomere and cytoskeleton structure implicated. In this regard, pediatric DCM can be considered pediatric manifestations of inherited cardiomyopathy syndromes. Yet exciting recent studies in infantile DCM suggest that this subset has a distinct etiology involving defective postnatal cardiac maturation, such as the failure of programmed centrosome breakdown in cardiomyocytes. Improved knowledge of pathogenesis is central to developing child-specific treatment approaches. This review aims to discuss the established biological pathogenesis of pediatric DCM, current clinical guidelines, and promising therapeutic avenues, highlighting differences from adult disease. The overarching goal is to unravel the complexities surrounding this condition to facilitate the advancement of novel therapeutic interventions and improve prognosis and overall quality of life for pediatric patients affected by DCM.

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.

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.

Left Ventricular Non-Compaction in Children: Aetiology and Diagnostic Criteria

Left ventricular non-compaction (LVNC) is a heterogeneous myocardial disorder characterized by prominent trabeculae protruding into the left ventricular lumen and deep intertrabecular recesses. LVNC can manifest in isolation or alongside other heart muscle diseases. Its occurrence among children is rising due to advancements in imaging techniques. The origins of LVNC are diverse, involving both genetic and acquired forms. The clinical manifestation varies greatly, with some cases presenting no symptoms, while others typically manifesting with heart failure, systemic embolism, and arrhythmias. Diagnosis mainly relies on assessing heart structure using imaging tools like echocardiography and cardiac magnetic resonance. However, the absence of a universally agreed-upon standard and limitations in diagnostic criteria have led to ongoing debates in the scientific community regarding the most reliable methods. Further research is crucial to enhance the diagnosis of LVNC, particularly in early life stages.

Adolescent Onset of Acute Heart Failure

Heart failure in adolescents can manifest due to a multitude of causes. Presentation is often quite variable ranging from asymptomatic to decompensated heart failure or sudden cardiac death. Because of the diverse nature of this disease, a thoughtful and extensive evaluation is critical to establishing the diagnosis and treatment plan. Identifying and addressing reversible pathologies often leads to functional cardiac recovery. Some disease states are irreversible and progressive, requiring chronic heart failure management and potentially advanced therapies such as transplantation.

Pulmonary hemodynamics before and after pediatric heart transplantation

BACKGROUND

Pulmonary hypertension (PH) may limit the outcome of pediatric heart transplantation (pHTx). We evaluated pulmonary hemodynamics in children undergoing pHTx.

METHODS

Cross-sectional, single-center, observational study analyzing pulmonary hemodynamics in children undergoing pHTx.

RESULTS

Twenty-three children (female 15) underwent pHTx at median (IQR) age of 3.9 (.9-8.2) years with a time interval between first clinical signs and pHTx of 1.1 (.4-3.2) years. Indications for pHTx included cardiomyopathy (CMP) (n = 17, 74%), congenital heart disease (CHD) (n = 5, 22%), and intracardiac tumor (n = 1, 4%). Before pHTx, pulmonary hemodynamics included elevated pulmonary artery pressure (PAP) 26 (18.5-30) mmHg, pulmonary capillary wedge pressure (PCWP) 19 (14-21) mmHg, left ventricular enddiastolic pressure (LVEDP) 17 (13-22) mmHg. Transpulmonary pressure gradient (TPG) was 6.5 (3.5-10) mmHg and pulmonary vascular resistance (Rp) 2.65 WU*m2 (1.87-3.19). After pHTx, at immediate evaluation 2 weeks after pHTx PAP decreased to 20.5 (17-24) mmHg, PCWP 14.5 (10.5-18) mmHg (p < .05), LVEDP 16 (12.5-18) mmHg, TPG 6.5 (4-12) mmHg, Rp 1.49 (1.08-2.74) WU*m2 resp.at last invasive follow up 4.0 (1.4-6) years after pHTx, to PAP 19.5 (17-21) mmHg (p < .05), PCWP 13 (10.5-14.5) mmHg (p < .05), LVEDP 13 (10.5-14) mmHg, TPG 7 (5-9.5) mmHg, Rp 1.58 (1.38-2.19) WU*m2 (p < .05). In CHD patients PAP increased (p < .05) after pHTx at immediate evaluation and decreased until last follow-up (p < .05), while in CMP patients there was a continuous decline of mean PAP values immediately after HTx (p < .05).

CONCLUSIONS

While PH before pHTx is frequent, after pHTx the normalization of PH starts immediately in CMP patients but is delayed in CHD patients.

Focus on Paediatric Restrictive Cardiomyopathy: Frequently Asked Questions

Restrictive cardiomyopathy (RCM) is characterized by restrictive ventricular pathophysiology determined by increased myocardial stiffness. While suspicion of RCM is initially raised by clinical evaluation and supported by electrocardiographic and echocardiographic findings, invasive hemodynamic evaluation is often required for diagnosis and management of patients during follow-up. RCM is commonly associated with a poor prognosis and a high incidence of heart failure, and PH is reported in paediatric patients with RCM. Currently, only a few therapies are available for specific RCM aetiologies. Early referral to centres for advanced heart failure treatment is often necessary. The aim of this review is to address questions frequently asked when facing paediatric patients with RCM, including issues related to aetiologies, clinical presentation, diagnostic process and prognosis.

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.

Biallelic variants in FLII cause pediatric cardiomyopathy by disrupting cardiomyocyte cell adhesion and myofibril organization

Pediatric cardiomyopathy (CM) represents a group of rare, severe disorders that affect the myocardium. To date, the etiology and mechanisms underlying pediatric CM are incompletely understood, hampering accurate diagnosis and individualized therapy development. Here, we identified biallelic variants in the highly conserved flightless-I (FLII) gene in 3 families with idiopathic, early-onset dilated CM. We demonstrated that patient-specific FLII variants, when brought into the zebrafish genome using CRISPR/Cas9 genome editing, resulted in the manifestation of key aspects of morphological and functional abnormalities of the heart, as observed in our patients. Importantly, using these genetic animal models, complemented with in-depth loss-of-function studies, we provided insights into the function of Flii during ventricular chamber morphogenesis in vivo, including myofibril organization and cardiomyocyte cell adhesion, as well as trabeculation. In addition, we identified Flii function to be important for the regulation of Notch and Hippo signaling, crucial pathways associated with cardiac morphogenesis and function. Taken together, our data provide experimental evidence for a role for FLII in the pathogenesis of pediatric CM and report biallelic variants as a genetic cause of pediatric CM.

Pediatric restrictive cardiomyopathy: a case report

Restrictive cardiomyopathy (RCM) is a rare childhood cardiomyopathy that is a challenging diagnostic problem for clinicians. We describe a case of an 8-year-old girl with a 2-year history of shortness of breath on exertion. Electrocardiogram and echocardiography showed biatrial enlargement, while cardiac magnetic resonance showed biatrial dilation and normal pericardial thickness. Left and right heart catheterization revealed a left ventricular (LV) end-diastolic pressure (EDP) of 20 mmHg, right ventricular (RV) EDP of 13 mmHg, and pulmonary arterial systolic pressure of 51 mmHg. LV and RV pressure traces showed that LV and RV pressures moved concordantly with respiration, and that the systolic area index was 0.98. Cardiac catheterization data were therefore supportive of RCM. Next-generation sequencing identified a heterozygous variant of the troponin I gene (TNNI3; c.574C>T). Combining these findings led to a diagnosis of RCM. The patient's parents chose conservative treatment, but at the 12-month follow-up she died of worsening heart failure and cerebral infarction. This case emphasizes the need for cardiac catheterization and genetic testing in RCM, and suggests that anticoagulants should be recommended to reduce the risk of thromboembolic events.

Sarcomeric gene variants among Indians with hypertrophic cardiomyopathy: A scoping review

Hypertrophic cardiomyopathy (HCM) is a genetic heart muscle disease that frequently causes sudden cardiac death (SCD) among young adults. Several pathogenic mutations in genes encoding the cardiac sarcomere have been identified as diagnostic factors for HCM and proposed as prognostic markers for SCD. The objective of this review was to determine the scope of available literature on the variants encoding sarcomere proteins associated with SCD reported among Indian patients with HCM. The eligibility criteria for the scoping review included full text articles that reported the results of genetic screening for sarcomeric gene mutations in HCM patients of Indian south Asian ancestry. We systematically reviewed studies from the databases of Medline, Scopus, Web of Science core collection and Google Scholar. The electronic search strategy included a combination of generic terms related to genetics, disease and population. The protocol of the study was registered with Open Science Framework (https://osf.io/53gde/). A total of 19 articles were identified that reported pathogenic or likely pathogenic (P/LP) variants within MYH7, MYBPC3, TNNT2, TNNI3 and TPM1 genes, that included 16 singletons, one de novo and one digenic mutation (MYH7/ TPM1) associated with SCD among Indian patients. Evidence from functional studies and familial segregation implied a plausible mechanistic role of these P/LP variants in HCM pathology. This scoping review has compiled all the P/LP variants reported to-date among Indian patients and summarized their association with SCD. Single homozygous, de novo and digenic mutations were observed to be associated with severe phenotypes compared to single heterozygous mutations. The abstracted genetic information was updated with reference sequence ID (rsIDs) and compiled into freely accessible HCMvar database, available at https://hcmvar.heartfailure.org.in/. This can be used as a population specific genetic database for reference by clinicians and researchers involved in the identification of diagnostic and prognostic markers for HCM.

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.

Spectrum and Outcome of Prenatally Diagnosed Fetal Primary Cardiomyopathies-A Twenty-Year Overview

OBJECTIVE

to assess the course and outcome of fetuses affected by primary cardiomyopathy (CM).

METHODS

Retrospective study of 21 cases with prenatal diagnosis of a primary CM in one tertiary center over a period of 20 years. Charts were reviewed for echocardiographic findings, pregnancy outcome, and postnatal course. The utility of prenatal evaluation was discussed.

RESULTS

The mean gestational age (GA) at diagnosis was 26.7 (±5.1) weeks. A total of 33.3% (7/21) had associated anomalies. Genetic etiology was confirmed in 50.0% (10/20, with one case lost to follow up). The overall survival rate of the entire study population was 40% (8/20) including termination of pregnancy in 20% (4/20) and an intrauterine mortality rate of 5% (1/20). Of the initial survivors (n = 15), a neonatal and early infant mortality rate of 46.7% (7/15) was calculated. Prenatal isolated right ventricular involvement was the only identified significant parameter for survival (p = 0.035). Four phenotypical groups were identified: 42.9% (9/21) hypertrophic (HCM), 38.1% (8/21) dilated (DCM), 14.3% (3/21) isolated noncompaction (NCCM), and 4.8% (1/21) restrictive CM (RCM). Fetuses assigned to isolated NCCM revealed a 100% survival rate.

CONCLUSION

Prenatal detection is feasible but needs to a introduce classification method for better consulting and management practices. A poor outcome is still observed in many cases, but an increase in examiners' awareness may influence optimal multispecialized care.

Exosomes mediated fibrogenesis in dilated cardiomyopathy through a MicroRNA pathway

Cardiac fibrosis is a hallmark in late-stage familial dilated cardiomyopathy (DCM) patients, although the underlying mechanism remains elusive. Cardiac exosomes (Exos) have been reported relating to fibrosis in ischemic cardiomyopathy. Thus, we investigated whether Exos secreted from the familial DCM cardiomyocytes could promote fibrogenesis. Using human iPSCs differentiated cardiomyocytes we isolated Exos of angiotensin II stimulation conditioned media from either DCM or control (CTL) cardiomyocytes. Of interest, cultured cardiac fibroblasts had increased fibrogenesis following exposure to DCM-Exos rather than CTL-Exos. Meanwhile, injecting DCM-Exos into mouse hearts enhanced cardiac fibrosis and impaired cardiac function. Mechanistically, we identified the upregulation of miRNA-218-5p in the DCM-Exos as a critical contributor to fibrogenesis. MiRNA-218-5p activated TGF-β signaling via suppression of TNFAIP3, a master inflammation inhibitor. In conclusion, our results illustrate a profibrotic effect of cardiomyocytes-derived Exos that highlights an additional pathogenesis pathway for cardiac fibrosis in DCM.

A novel likely pathogenic variant in the FBXO32 gene associated with dilated cardiomyopathy according to whole‑exome sequencing

Background

Familial dilated cardiomyopathy (DCM) is a genetic heart disorder characterized by progressive heart failure and sudden cardiac death. Over 250 genes have been reported in association with DCM; nonetheless, the genetic cause of most DCM patients has been unknown. The goal of the present study was to determine the genetic etiology of familial DCM in an Iranian family.

Methods

Whole-exome sequencing was performed to identify the underlying variants in an Iranian consanguineous family with DCM. The presence of the candidate variant was confirmed and screened in available relatives by PCR and Sanger sequencing. The pathogenic effect of the candidate variant was assessed by bioinformatics analysis, homology modeling, and docking.

Results

One novel likely pathogenic deletion, c.884_886del: p.Lys295del, in F-box only protein 32 (muscle-specific ubiquitin-E3 ligase protein; FBXO32) was identified. Based on bioinformatics and modeling analysis, c.884_886del was the most probable cause of DCM in the studied family.

Conclusions

Our findings indicate that variants in FBXO32 play a role in recessive DCM. Variants in FBXO32 may disturb the degradation of target proteins in the ubiquitin–proteasome system and lead to severe DCM. We suggest considering this gene variants in patients with recessively inherited DCM.

Cardiac Muscle Training-A New Way of Recognizing and Supporting Recovery for LVAD Patients in the Pediatric Population

Patients with refractory heart failure due to chronic progressive cardiac myopathy (CM) may require mechanical circulatory support as a bridge to transplantation. A few patients can be weaned from support devices if recovery can be achieved. The identification of these patients is of great importance as recovery may be missed if the heart is unloaded by the ventricular assist device (VAD). Testing the load-bearing capacity of the supported left ventricle (LV) by temporarily and gradually reducing mechanical support during cardiac exercise can help identify responders and potentially aid the recovery process. An exercise training protocol was used in 3 patients (8 months, 18 months and 8 years old) with histological CM findings and myocarditis. They were monitored regularly using clinical information and functional imaging with VAD support. Echocardiographic examination included both conventional real-time 3D echocardiography (RT3DE) and speckle tracking (ST). A daily temporary reduction in pump rate (phase A) was followed by a permanent reduction in rate (phase B). Finally, pump stops of up to 30 min were performed once a week (phase C). The final decision on explantation was based on at least three pump stops. Two patients were weaned and successfully removed from the VAD. One of them was diagnosed with acute viral myocarditis. The other had chronic myocarditis with dilated myopathy and mild interstitial fibrosis. The noninvasive assessment of cardiac output and strain under different loading conditions during VAD therapy is feasible and helps identify candidates for weaning despite severe histological findings. The presented protocol, which incorporates new echocardiographic techniques for determining volume and deformation, can be of great help in positively guiding the process of individual recovery, which may be essential for selecting and increasing the number of patients to be weaned from VAD.

Pediatric Heart Failure Inpatient Mortality: A Cross-Sectional Analysis

Background

Heart failure constitutes significant morbidity and mortality among the pediatric population. Few data exist on the prevalence and mortality rate of pediatric heart failure (pHF) in the United States.

Objectives

This study aimed to determine the in-hospital mortality and the principal diagnoses in pediatric patients with heart failure who died while being hospitalized in the United States.

Methods

This is a retrospective cross-sectional study using data from the 2019 Kid Inpatient Database (KID). The KID contained data on hospitalized children below 21 years of age. Using Stata 17 software (StataCorp LLC, College Station, Texas), the data were searched for heart failure diagnoses using International Classification of Diseases 10th revision Clinical Modification (ICD-10-CM) codes. By using the “rank” command in Stata, the most common principal diagnoses were placed in descending order of frequency, and these were further divided into different ICD-10 code categories.

Results

There were 16,206 pHF admissions in 2019. Of these admissions, 1,023 (6.31%) patients died. The top five principal ICD 10 code categories among all pHF deaths in descending order were circulatory system (17.95%), congenital/chromosomal abnormalities (17.43%), respiratory system (10.28%), infectious diseases (9.24%, and perinatal diseases (7.90%). Among all pHF deaths, sepsis of unspecified organisms (5.14%), hypoplastic left heart syndrome (HLHS) (3.19%), and acute respiratory failure with hypoxia (3.14%) were the most common primary diagnoses.

Conclusion and significance

Pediatric heart failure in-hospital overall mortality is 6.31%, and sepsis of unspecified organisms, HLHS, and acute respiratory failure are the most common principal diagnoses among these children. Preventive measures and prompt treatment of infections are paramount to reducing pHF mortality.