Pediatric Cardiomyopathies

Genotype-phenotype insights of pediatric dilated cardiomyopathy

Dilated cardiomyopathy (DCM) in children is a severe myocardial disease characterized by enlargement of the left ventricle or both ventricles with impaired contractile function. DCM can cause adverse consequences such as heart failure, sudden death, thromboembolism, and arrhythmias. This article reviews the latest advances in genotype and phenotype research in pediatric DCM. With the development of gene sequencing technologies, considerable progress has been made in genetic research on DCM. Research has shown that DCM exhibits notable genetic heterogeneity, with over 100 DCM-related genes identified to date, primarily involving functions such as calcium handling, the cytoskeleton, and ion channels. As human genomic variations are linked to phenotypes, DCM phenotypes are influenced by numerous genetic variations across the entire genome. Children with DCM display high genetic heterogeneity and are characterized by early onset, rapid disease progression, and poor prognosis. The genetic architecture of pediatric DCM markedly differs from that of adult DCM, necessitating analyses through clinical phenotyping, familial cosegregation studies, and functional validation. Clarifying the genotype-phenotype relationship can improve diagnostic accuracy, enhance prognosis, and guide follow-up treatment for genotype-positive and phenotype-negative patients identified through genetic testing, providing new insights for precision medicine. Future research should further explore novel pathogenic genes and mutations and strengthen genotype-phenotype correlation analyses to facilitate precise diagnosis and treatment of DCM in children.

Pathogenetic mechanisms of muscle-specific ribosomes in dilated cardiomyopathy

The heart employs a specialized ribosome in its muscle cells to translate genetic information into proteins, a fundamental adaptation with an elusive physiological role1-3. Its significance is underscored by the discovery of neonatal patients suffering from often fatal heart failure caused by severe dilated cardiomyopathy when both copies of the gene RPL3L are mutated4-9. RPL3L is a muscle-specific paralog1-3 of the ubiquitous ribosomal protein L3 (RPL3), which makes the closest contact of any protein to the ribosome's RNA-based catalytic center10. RPL3L-linked heart failure represents the only known human disease associated with tissue-specific ribosomes, yet the underlying pathogenetic mechanisms remain poorly understood. Intriguingly, disease is linked to a large number of mostly missense variants in RPL3L, and RPL3L-knockout resulted in no severe heart defect in either human or mice3, 11-13, challenging the prevailing view that autosomal recessive diseases are caused by loss-of-function mutations. Here, we report three new cases of RPL3L-linked severe neonatal heart failure and present a unifying pathogenetic mechanism by which a large number of variants in the muscle-specific ribosome led to disease. Specifically, affected families often carry one of two recurrent toxic gain-of-function variants alongside a family-specific putative loss-of-function variant. While the non-recurrent variants often trigger partial compensation of RPL3 similar to Rpl3l-knockout mice, both recurrent variants exhibit increased affinity for the RPL3/RPL3L chaperone GRWD114-16 and 60S biogenesis factors, sequester 28S rRNA in the nucleus, disrupt ribosome biogenesis, and trigger severe cellular toxicity that extends beyond the loss of ribosomes. These findings provide critical insights for genetic screening and therapeutic development of neonatal heart failure. Our results suggest that gain-of-toxicity mechanisms may be more prevalent in autosomal recessive diseases, and a combination of gain-of-toxicity and loss-of-function mechanisms could underlie many diseases involving genes with paralogs.

Clinical impact of genetic testing in a large cohort of pediatric cardiomyopathies

BACKGROUND

There are limited data that can explain the earlier penetrance and the different expressivity of pediatric cardiomyopathy (pCM) compared to adult-onset cardiomyopathy (aCM). In addition, the relationship between genotype and pCM results is poorly described.

OBJECTIVE

We compared the genotypes between a cohort of aCM and a cohort of pCM to propose hypotheses on the earlier penetrance and expressivity of pCM. Finally, we report how genetic testing was used to guide genetic counseling in pCM.

METHODS

253 pCM (<18 years old) and 1466 aCM patients were sequenced on a panel of 67 cardiomyopathy genes. Risk factors for death and heart transplantation were analyzed.

RESULTS

In pCM, the variant of interest (VOI) yield was 53.7 % including 24.2 % carrying two VOI. De novo variants represented 11 % of VOI in pCM and 50 % in restrictive pCM. An age at diagnosis younger than 1 year (HR = 2.07, p = 0.029), restrictive phenotype (HR = 2.87, p = 0.03) and the presence of two VOI (HR = 2.97, p = 0.001) were independent risk factors for death or heart transplantation. In comparison with aCM, pCM patients harbored more frequently two VOI (p = 0.02), or de novo variants (p = 4.10-13). In addition, the distribution of VOI was different in aCM and pCM. Genotyping of pCM improved genetic counseling in families and led to ten prenatal-diagnosis.

CONCLUSIONS

Genetic testing provides clues for earlier penetrance of pCM. The presence of two VOI in children with CM is a risk factor for severe and early cardiac events.

Modeling the contribution of cardiac fibroblasts in dilated cardiomyopathy using induced pluripotent stem cells

Fibrosis is implicated in nearly all forms of cardiomyopathy and significantly influences disease severity and outcomes. The primary cell responsible for fibrosis is the cardiac fibroblast, which remains understudied relative to cardiomyocytes in the context of cardiomyopathy. The development of induced pluripotent stem cell-derived cardiac fibroblasts (iPSC-CFs) allows for the modeling of patient-specific disease characteristics and provides a scalable source of fibroblasts. iPSC-CFs are invaluable for understanding molecular pathways that affect disease progression and outcomes. This review explores various aspects of cardiomyopathy, with a focus on dilated cardiomyopathy, that can be modeled using iPSC-CFs and their application in drug discovery, given the current lack of approved therapies for cardiac fibrosis. We examine how iPSC-CFs can be utilized to study heart development, fibroblast heterogeneity, and activation, with the ultimate goal of developing better therapies for patients with cardiomyopathies. SIGNIFICANCE STATEMENT: We explore how induced pluripotent stem cell-derived cardiac fibroblasts (iPSC-CFs) are used to study the fibrotic component of dilated cardiomyopathy. Most research has focused on cardiomyocytes, but iPSC-CFs serve as a valuable tool to elucidate molecular pathways leading to fibrosis and paracrine interactions with cardiomyocytes. Gaining insights into these events could aid in the development of new therapies and enable the use of patient-derived iPSC-CFs for precision medicine, ultimately improving patient outcomes.

Pulmonary artery banding for cardiomyopathy in young children: First trial in China

AIMS

Heritable dilated cardiomyopathy (DCM) or DCM associated with congenital or acquired left ventricular diseases carries a significant mortality risk. Pulmonary artery banding (PAB) has been proposed as an alternative to heart transplantation. This study aimed to delineate the clinical development, ventricular reverse remodelling, and functional regeneration of the dilated left ventricle, presenting as a pioneering approach in China.

METHODS AND RESULTS

This prospective study was initiated in November 2021, involving paediatric patients with a significant dilated left ventricle and preserved right ventricle who underwent surgical PAB. The baseline characteristics and clinical information during follow-up were collected. Seven patients (five boys) with a median age of 240 (148, 1028) days have been included thus far. No procedural or follow-up mortality was observed. The modified Ross functional class improved from treatment to follow-up of 348 (200, 629) days, and the median left ventricular ejection fraction increased from 27.0 (15.0, 34.0) % before surgery to 61.0 (52.0, 68.0) % (P < 0.05); the median left ventricular end-diastolic diameter and corresponding Z-scores decreased from 43.0 (40.0, 55.0) mm [+9.4 (+7.7, +11.7)] to 33.0 (29.0, 39.0) mm [+1.8 (+1.3, +3.8)] (P < 0.05). Functional regeneration of the left ventricle was observed in five patients. Three of them underwent balloon dilation of the PAB to relieve excessively elevated right ventricular pressures.

CONCLUSIONS

The application of PAB should adhere to strict criteria. Initial results are promising for infants and even toddlers with a dilated left ventricle and limited probability of spontaneous recovery. PAB can be an alternative when there is a shortage of donor transplants and assist devices, especially for low- and middle-income countries.

Troponin C gene mutations on cardiac muscle cell and skeletal Regulation: A comprehensive review

BACKGROUND

The troponin complex plays a crucial role in regulating skeletal and cardiac contraction. Congenital myopathies can occur due to several mutations in genes that encode skeletal troponin. Moreover, there is limited information regarding the composition of skeletal troponin. This review specifically examines a comprehensive review of the TNNC gene mutations on cardiac and skeletal regulations.

MAIN BODY

Troponin C (TNNC) has been linked to a newly discovered inherited muscle disorder. Genetic variations in genes that encode skeletal troponin can impair the function of sarcomeres. Various treatment approaches have been employed to mitigate the impact of variations, including the use of troponin activators, the injection of wild-type protein via AAV gene therapy, and myosin modification to enhance muscle contraction. The processes responsible for the pathophysiological implications of the variations in genes that encode skeletal troponin are not fully understood.

CONCLUSION

This comprehensive review will contribute to the understanding of the relationship between human cardiomyopathy and TNNC mutations and will guide the development of therapy approaches.

Arrhythmias May Hide a Genetic Cardiomyopathy in Left Ventricular Hypertrabeculation in Children: A Single-Center Experience

BACKGROUND

Left ventricular hypertrabeculation (LVHT) is a myocardial disorder with different clinical manifestations, from total absence of symptoms to heart failure, arrhythmias, sudden cardiac death (SCD), and thromboembolic events. It is challenging to distinguish between the benign and pathological forms of LVHT. The aim of this study was to describe the arrhythmic manifestations of LVHT in a large group of pediatric patients and to correlate them with genetic results or other clinical markers.

METHODS

We retrospectively enrolled 140 pediatric patients with diagnosis of LVHT followed at our Institution from 2013 to 2023. Data regarding family history, instrumental exams, cardiac magnetic resonance, genetic testing and outcomes were collected. Most of them had isolated LVHT (80.7%); in other patients, mixed phenotypes (hypertrophic or dilated cardiomyopathy or congenital heart disease) were present.

RESULTS

Arrhythmias were found in 33 children (23.6%): 13 (9.3%) supraventricular tachyarrhythmias; 14 (10%) ventricular arrhythmias (five frequent PVCs (premature ventricular contractions), eight patients with ventricular tachycardia (VT), one ventricular fibrillation (VF)); two (1.4%) sinus node disfunctions; two (1.4%) complete atrio-ventricular blocks (AVB), three (2.1%) paroxysmal complete AVB, one (0.7%) severe I degree AVB. Three patients received an ICD (implantable cardioverter defibrillator). Comparison between LVHT patients with (33 pts) and without (107 pts) arrhythmias as regards genetic testing showed a statistical significance for the presence of class 4 or 5 genetic variants and arrhythmic manifestation (p = 0.037).

CONCLUSIONS

In our pediatric cohort with LVHT, good outcomes were observed, but arrhythmias were not so rare (23.6%); no SCD occurred.

Brazilian Guideline for Exercise Testing in Children and Adolescents - 2024

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Cardiomyopathy in Children and Adolescents in the Era of Precision Medicine

In childhood and adolescence, cardiomyopathies have their own characteristics and are an important cause of heart failure, arrhythmias, sudden death, and indication for heart transplantation. Diagnosis is a challenge in daily practice due to its varied clinical presentation, heterogeneous etiologies, and limited knowledge of tools related to clinical and molecular genetics. However, it is essential to recognize the different phenotypes and prioritize the search for the etiology. Recent advances in precision medicine have made molecular diagnosis accessible, which makes it possible to individualize therapeutic approaches, stratify the prognosis, and identify individuals in the family who are at risk of developing the disease. The objective of this review is to emphasize the particularities of cardiomyopathies in pediatrics and how the individualized approach impacts the therapy and prognosis of the patient. Through a systematized approach, the five-stage protocol used in our service is presented. These stages bring together clinical evaluation for determining the morphofunctional phenotype, identification of etiology, classification, establishment of prognosis, and the search for personalized therapies.

Ventricular assist device support in paediatric patients with restrictive cardiomyopathy-clinical outcomes and haemodynamics

OBJECTIVES

Restrictive cardiomyopathy is rare and is generally associated with worse clinical outcomes compared to other cardiomyopathies. Ventricular assist device (VAD) support for these children is seldom applied and often hampered by the surgical difficulties.

METHODS

All paediatric (<19 years) patients with a restricted cardiomyopathy supported by a VAD from the EUROMACS database were included and compared to patients with a dilated cardiomyopathy (retrospective database analyses). Participating centres were retrospectively contacted to provide additional detailed echo and Swan Ganz measurements to analyse the effect of VAD support on pulmonary artery pressure and right ventricular function.

RESULTS

Forty-four paediatric VAD-supported patients diagnosed with restricted cardiomyopathy were included, with a median age at implantation of 5.0 years. Twenty-six of the 44 patient with a restricted cardiomyopathy survived to transplantation (59.1%), 16 died (36.4%) and 2 are still on ongoing VAD support (4.5%) after a median duration of support of 95.5 days (interquartile range 33.3-217.8). Transplantation probability after 1 and 2 years of VAD support in patients with a restricted cardiomyopathy were comparable to patients with a dilated cardiomyopathy (52.3% vs 51.4% and 59.5% vs 60.1%, P = 0.868). However, mortality probability was higher in the restricted cardiomyopathy cohort (35.8% vs 17.0% and 35.8% vs 19.0%, P = 0.005). Adverse event rates were high (cerebrovascular accident in 31.8%, pump thrombosis in 29.5%, major bleeding 25.0%, eventual biventricular support in 59.1%). In the atrially cannulated group, cerebrovascular accident and pump thrombosis occurred in twice as much patients (21.1% vs 40.0%, P = 0.595 and 15.8% vs 40.0%, P = 0.464; probably non-significant due to the small numbers). Pulmonary arterial pressures improved after implantation of a VAD, and 6 patients who were initially labelled as ineligible due to pulmonary hypertension could eventually be transplanted.

CONCLUSIONS

VAD support in children with a restricted cardiomyopathy is rarely performed. Mortality and adverse event rates are high. On the other hand, survival to cardiac transplantation was 59.1% with all patients surviving the 1st 30 days after cardiac transplantation. Pulmonary arterial pressures improved while on support, potentially making cardiac transplantation a viable option for previously ineligible children.

Allele-Specific Suppression of Variant MHC With High-Precision RNA Nuclease CRISPR-Cas13d Prevents Hypertrophic Cardiomyopathy

BACKGROUND

Familial hypertrophic cardiomyopathy has severe clinical complications of heart failure, arrhythmia, and sudden cardiac death. Heterozygous single nucleotide variants (SNVs) of sarcomere genes such as MYH7 are the leading cause of this type of disease. CRISPR-Cas13 (clustered regularly interspaced short palindromic repeats and their associated protein 13) is an emerging gene therapy approach for treating genetic disorders, but its therapeutic potential in genetic cardiomyopathy remains unexplored.

METHODS

We developed a sensitive allelic point mutation reporter system to screen the mutagenic variants of Cas13d. On the basis of Cas13d homology structure, we rationally designed a series of Cas13d variants and obtained a high-precision Cas13d variant (hpCas13d) that specifically cleaves the MYH7 variant RNAs containing 1 allelic SNV. We validated the high precision and low collateral cleavage activity of hpCas13d through various in vitro assays. We generated 2 HCM mouse models bearing distinct MYH7 SNVs and used adenovirus-associated virus serotype 9 to deliver hpCas13d specifically to the cardiomyocytes. We performed a large-scale library screening to assess the potency of hpCas13d in resolving 45 human MYH7 allelic pathogenic SNVs.

RESULTS

Wild-type Cas13d cannot distinguish and specifically cleave the heterozygous MYH7 allele with SNV. hpCas13d, with 3 amino acid substitutions, had minimized collateral RNase activity and was able to resolve various human MYH7 pathological sequence variations that cause hypertrophic cardiomyopathy. In vivo application of hpCas13d to 2 hypertrophic cardiomyopathy models caused by distinct human MYH7 analogous sequence variations specifically suppressed the altered allele and prevented cardiac hypertrophy.

CONCLUSIONS

Our study unveils the great potential of CRISPR-Cas nucleases with high precision in treating inheritable cardiomyopathy and opens a new avenue for therapeutic management of inherited cardiac diseases.

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.

Biventricular noncompaction induced heart failure in premature newborn

Deep intertrabecular recesses and overly pronounced trabeculations in one ventricle are the hallmarks of noncompaction cardiomyopathy (NCCM), a rare congenital cardiomyopathy but very rarely right ventricle (RV), or both ventricles may be involved. We reported a 5-day-old preterm newborn with signs of congestive heart failure that the transthoracic echocardiography (TTE) revealed deep intertrabecular recesses perfused from the left ventricle (LV) and RV cavity, as well as significantly increased wall thickness of the right ventricles and hypertrabeculations in the apical and midventricular segments.

Cardiomyopathy in children: a single-centre, retrospective study of genetic and clinical characteristics

OBJECTIVES

This study aimed to describe the genetic and clinical characteristics of paediatric cardiomyopathy in a cohort of Chinese patients.

METHODS

We retrospectively reviewed the clinical history and mutation spectrum of 75 unrelated Chinese paediatric patients who were diagnosed with cardiomyopathy and referred to our hospital between January 2016 and December 2022.

RESULTS

Seventy-five children with cardiomyopathy were enrolled, including 32 (42.7%) boys and 43 (57.3%) girls. Dilated cardiomyopathy was the most prevalent cardiomyopathy (61.3%) in the patients, followed by hypertrophic cardiomyopathy (17.3%), ventricular non-compaction (14.7%), restrictive cardiomyopathy (5.3%) and arrhythmogenic right ventricular cardiomyopathy (1.3%). Whole-exome sequencing and targeted next-generation sequencing identified 34 pathogenic/likely pathogenic variants and 1 copy number variant in 14 genes related to cardiomyopathy in 30 children, accounting for 40% of all patients. TNNC1 p.Asp65Asn and MYH7 p.Glu500Lys have not been reported previously. The follow-up time ranged from 2 months to 6 years. Twenty-two children died (mortality rate 29%).

CONCLUSIONS

Comprehensive genetic testing was associated with a 40% yield of causal genetic mutations in Chinese cardiomyopathy cases. We found diversity in the mutation profile in different patients, which suggests that the mutational background of cardiomyopathy in China is heterogeneous, and the findings may be helpful to those counselling patients and families.

Paediatric Restrictive Cardiomyopathy - Diagnosis and Challenges: A report of two cases

Restrictive cardiomyopathy is one of the rarest forms of cardiomyopathies in paediatric patients characterised by impaired myocardial relaxation or compliance with restricted ventricular filling, leading to a reduced diastolic volume with a preserved systolic function. We report 2 cases-a 5-year-old boy who presented with abdominal distension and palpitation with family history of similar complaints but no definite genetic diagnosis as yet and a 5-year-old girl who presented with chronic cough and shortness of breath. Both cases were diagnosed in a tertiary care hospital in Muscat, Oman, in 2019 and are managed supportively with regular outpatient follow-up. This is the first series of reported cases of paediatric restrictive cardiomyopathy from Oman.

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.

Impaired Relaxation in Induced Pluripotent Stem Cell-Derived Cardiomyocytes with Pathogenic TNNI3 Mutation of Pediatric Restrictive Cardiomyopathy

BACKGROUND

Restrictive cardiomyopathy (RCM) is characterized by impaired diastolic function with preserved ventricular contraction. Several pathogenic variants in sarcomere genes, including TNNI3, are reported to cause Ca2+ hypersensitivity in cardiomyocytes in overexpression models; however, the pathophysiology of induced pluripotent stem cell (iPSC)-derived cardiomyocytes specific to a patient with RCM remains unknown.

METHODS AND RESULTS

We established an iPSC line from a pediatric patient with RCM and a heterozygous TNNI3 missense variant, c.508C>T (p.Arg170Trp; R170W). We conducted genome editing via CRISPR/Cas9 technology to establish an isogenic correction line harboring wild type TNNI3 as well as a homozygous TNNI3-R170W. iPSCs were then differentiated to cardiomyocytes to compare their cellular physiological, structural, and transcriptomic features. Cardiomyocytes differentiated from heterozygous and homozygous TNNI3-R170W iPSC lines demonstrated impaired diastolic function in cell motion analyses as compared with that in cardiomyocytes derived from isogenic-corrected iPSCs and 3 independent healthy iPSC lines. The intracellular Ca2+ oscillation and immunocytochemistry of troponin I were not significantly affected in RCM-cardiomyocytes with either heterozygous or homozygous TNNI3-R170W. Electron microscopy showed that the myofibril and mitochondrial structures appeared to be unaffected. RNA sequencing revealed that pathways associated with cardiac muscle development and contraction, extracellular matrix-receptor interaction, and transforming growth factor-β were altered in RCM-iPSC-derived cardiomyocytes.

CONCLUSIONS

Patient-specific iPSC-derived cardiomyocytes could effectively represent the diastolic dysfunction of RCM. Myofibril structures including troponin I remained unaffected in the monolayer culture system, although gene expression profiles associated with cardiac muscle functions were altered.

A fetal rat model of ventricular noncompaction caused by intrauterine hyperglycemia

BACKGROUND

This study aims to develop a fetal rat model of ventricular noncompaction (NVM) using streptozotocin (STZ)-induced gestational hyperglycemia and compare it with a retinoic acid (RA) model.

METHODS

Female SD rats were categorized into STZ, RA, and normal control (NC) groups. The STZ group was given a high-fat diet pre-pregnancy and 35 mg/kg of 2% STZ postpregnancy. The RA group received a 90 mg/kg dose of RA on day 13 postpregnancy. Embryonic myocardial morphology was analyzed through HE staining, and embryonic cardiomyocyte ultrastructures were studied using electron microscopy. Diagnoses of NVM were based on a ratio of noncompact myocardium (N) to compact myocardium (C) >1.4, accompanied by thick myocardial trabeculae and a thin myocardial compaction layer. Kruskal-Wallis test determined N/C ratio differences among groups.

RESULTS

Both STZ and RA groups displayed significant NVM characteristics. The left ventricular (LV) N/C in the STZ, RA, and NC groups were 1.983 (1.423-3.527), 1.640 (1.197-2.895), and 0.927 (0.806-1.087), respectively, with a statistically significant difference (P<0.001). The right ventricular (RV) N/C in the STZ, RA, and NC groups were 2.097 (1.364-3.081), 1.897 (1.337-2.662), and 0.869 (0.732-1.022), respectively, with a significant difference (P<0.001). Electron microscopy highlighted marked endoplasmic reticulum swelling in embryonic cardiomyocytes from both STZ and RA groups.

CONCLUSION

Our model underscores the pivotal role of an adverse intrauterine developmental environment in the onset of NVM. This insight holds significant implications for future studies exploring the pathogenesis of NVM.

Multidisciplinary approach in cardiomyopathies: From genetics to advanced imaging

Cardiomyopathies are myocardial diseases characterized by mechanical and electrical dysfunction of the heart muscle which could lead to heart failure and life-threatening arrhythmias. Certainly, an accurate anamnesis, a meticulous physical examination, and an ECG are cornerstones in raising the diagnostic suspicion. However, cardiovascular imaging techniques are indispensable to diagnose a specific cardiomyopathy, to stratify the risk related to the disease and even to track the response to the therapy. Echocardiography is often the first exam that the patient undergoes, because of its non-invasiveness, wide availability, and cost-effectiveness. Cardiac magnetic resonance imaging allows to integrate and implement the information obtained with the echography. Furthermore, cardiomyopathies' genetic basis has been investigated over the years and the list of genetic mutations deemed potentially pathogenic is expected to grow further. The aim of this review is to show echocardiographic, cardiac magnetic resonance imaging, and genetic features of several cardiomyopathies: dilated cardiomyopathy (DMC), hypertrophic cardiomyopathy (HCM), arrhythmogenic cardiomyopathy (ACM), left ventricular noncompaction cardiomyopathy (LVNC), myocarditis, and takotsubo cardiomyopathy.

Gene correction and overexpression of TNNI3 improve impaired relaxation in engineered heart tissue model of pediatric restrictive cardiomyopathy

Research on cardiomyopathy models using engineered heart tissue (EHT) created from disease-specific induced pluripotent stem cells (iPSCs) is advancing rapidly. However, the study of restrictive cardiomyopathy (RCM), a rare and intractable cardiomyopathy, remains at the experimental stage because there is currently no established method to replicate the hallmark phenotype of RCM, particularly diastolic dysfunction, in vitro. In this study, we generated iPSCs from a patient with early childhood-onset RCM harboring the TNNI3 R170W mutation (R170W-iPSCs). The properties of R170W-iPSC-derived cardiomyocytes (CMs) and EHTs were evaluated and compared with an isogenic iPSC line in which the mutation was corrected. Our results indicated altered calcium kinetics in R170W-iPSC-CMs, including prolonged tau, and an increased ratio of relaxation force to contractile force in R170W-EHTs. These properties were reversed in the isogenic line, suggesting that our model recapitulates impaired relaxation of RCM, i.e., diastolic dysfunction in clinical practice. Furthermore, overexpression of wild-type TNNI3 in R170W-iPSC-CMs and -EHTs effectively rescued impaired relaxation. These results highlight the potential efficacy of EHT, a modality that can accurately recapitulate diastolic dysfunction in vitro, to elucidate the pathophysiology of RCM, as well as the possible benefits of gene therapies for patients with RCM.

RETRACTED: 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.

Inherited Arrhythmias in the Pediatric Population: An Updated Overview

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

Recessive TMOD1 mutation causes childhood cardiomyopathy

Familial cardiomyopathy in pediatric stages is a poorly understood presentation of heart disease in children that is attributed to pathogenic mutations. Through exome sequencing, we report a homozygous variant in tropomodulin 1 (TMOD1; c.565C>T, p.R189W) in three individuals from two unrelated families with childhood-onset dilated and restrictive cardiomyopathy. To decipher the mechanism of pathogenicity of the R189W mutation in TMOD1, we utilized a wide array of methods, including protein analyses, biochemistry and cultured cardiomyocytes. Structural modeling revealed potential defects in the local folding of TMOD1R189W and its affinity for actin. Cardiomyocytes expressing GFP-TMOD1R189W demonstrated longer thin filaments than GFP-TMOD1wt-expressing cells, resulting in compromised filament length regulation. Furthermore, TMOD1R189W showed weakened activity in capping actin filament pointed ends, providing direct evidence for the variant's effect on actin filament length regulation. Our data indicate that the p.R189W variant in TMOD1 has altered biochemical properties and reveals a unique mechanism for childhood-onset cardiomyopathy.

Exploring the Regulation and Function of Rpl3l in the Development of Early-Onset Dilated Cardiomyopathy and Congestive Heart Failure Using Systems Genetics Approach

BACKGROUND

Cardiomyopathies, diseases affecting the myocardium, are common causes of congestive heart failure (CHF) and sudden cardiac death. Recently, biallelic variants in ribosomal protein L3-like (RPL3L) have been reported to be associated with severe neonatal dilated cardiomyopathy (DCM) and CHF. This study employs a systems genetics approach to gain understanding of the regulatory mechanisms underlying the role of RPL3L in DCM.

METHODS

Genetic correlation, expression quantitative trait loci (eQTL) mapping, differential expression analysis and comparative functional analysis were performed using cardiac gene expression data from the patients and murine genetic reference populations (GRPs) of BXD mice (recombinant inbred strains from a cross of C57BL/6J and DBA/2J mice). Additionally, immune infiltration analysis was performed to understand the relationship between DCM, immune cells and RPL3L expression.

RESULTS

Systems genetics analysis identified high expression of Rpl3l mRNA, which ranged from 11.31 to 12.16 across murine GRPs of BXD mice, with an ~1.8-fold difference. Pathways such as "diabetic cardiomyopathy", "focal adhesion", "oxidative phosphorylation" and "DCM" were significantly associated with Rpl3l. eQTL mapping suggested Myl4 (Chr 11) and Sdha (Chr 13) as the upstream regulators of Rpl3l. The mRNA expression of Rpl3l, Myl4 and Sdha was significantly correlated with multiple echocardiography traits in BXD mice. Immune infiltration analysis revealed a significant association of RPL3L and SDHA with seven immune cells (CD4, CD8-naive T cell, CD8 T cell, macrophages, cytotoxic T cell, gamma delta T cell and exhausted T cell) that were also differentially infiltrated between heart samples obtained from DCM patients and normal individuals.

CONCLUSIONS

RPL3L is highly expressed in the heart tissue of humans and mice. Expression of Rpl3l and its upstream regulators, Myl4 and Sdha, correlate with multiple cardiac function traits in murine GRPs of BXD mice, while RPL3L and SDHA correlate with immune cell infiltration in DCM patient hearts, suggesting important roles for RPL3L in DCM and CHF pathogenesis via immune inflammation, necessitating experimental validations of Myl4 and Sdha in Rpl3l regulation.

Cardiac Involvement in Classical Organic Acidurias: Clinical Profile and Outcome in a Pediatric Cohort

BACKGROUND

Cardiac involvement is reported in a significant proportion of patients with classical organic acidurias (OAs), contributing to disability and premature death. Different cardiac phenotypes have been described, among which dilated cardiomyopathy (DCM) is predominant. Despite recent progress in diagnosis and treatment, the natural history of patients with OAs remains unresolved, specifically with regard to the impact of cardiac complications. We therefore performed a retrospective study to address this issue at our Referral Center for Pediatric Inherited Errors of Metabolism.

METHODS

Sixty patients with OAs (propionic (PA), methylmalonic (MMA) and isovaleric acidemias and maple syrup urine disease) diagnosed from 2000 to 2022 were systematically assessed at baseline and at follow-up.

RESULTS

Cardiac anomalies were found in 23/60 OA patients, all with PA or MMA, represented by DCM (17/23 patients) and/or acquired long QT syndrome (3/23 patients). The presence of DCM was associated with the worst prognosis. The rate of occurrence of major adverse cardiac events (MACEs) at 5 years was 55% in PA with cardiomyopathy; 35% in MMA with cardiomyopathy; and 23% in MMA without cardiomyopathy. Liver transplantation was performed in seven patients (12%), all with PA or MMA, due to worsening cardiac impairment, and led to the stabilization of metabolic status and cardiac function.

CONCLUSIONS

Cardiac involvement was documented in about one third of children diagnosed with classical OAs, confined to PA and MMA, and was often associated with poor outcome in over 50%. Etiological diagnosis of OAs is essential in guiding management and risk stratification.

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.

The risk of pediatric cardiovascular diseases in offspring born to mothers with systemic lupus erythematosus: a nationwide study

Background

Systemic lupus erythematosus (SLE), a common autoimmune disease predominantly affecting women, has been linked to various complications during pregnancy. The transfer of anti-Ro/SSA antibodies from SLE-affected mothers to their offspring can lead to neonatal lupus and cardiac issues. This study investigated the association between maternal SLE and the risk of pediatric cardiovascular disorders.

Methods

The study utilized South Korea's National Health Insurance Service (NHIS) database, covering 3,505,737 children born between 2007 and 2017 and tracked until 2020. Maternal SLE cases were identified using the World Health Organization's International Classification of Diseases Tenth revision (ICD-10) codes and linked with delivery records. Cardiologic disorders were categorized into congenital heart disease (CHD), arrhythmic disorders, and acquired heart disease. Propensity score matching with 1:4 ratios was applied to the set control group.

Results

Among 3,505,737 children, 0.7% (n = 23,330) were born to mothers with SLE. The incidence of preterm birth was significantly higher in the maternal SLE group (5.9% vs. 3.0%). Compared with the control group, children born to mothers with SLE exhibited a significantly elevated risk of overall CHDs (5.5%, adjusted odds ratio [aOR] 1.21; 95% confidence interval [CI] 1.14-1.29), including atrial septal defect (1.18; 1.09-1.28) and patent ductus arteriosus (1.15; 1.03-1.30). In addition, a notably higher risk was observed in arrhythmic disorders (complete atrioventricular block 7.20; 2.41-21.49) and acquired cardiac disorders, including cardiomyopathy (1.40; 1.17-1.68) and mucocutaneous lymph node syndrome (MCLS) (1.27; 1.15-1.43).

Conclusions

Maternal SLE is associated with congenital and acquired cardiac disorders in offspring, including structural, arrhythmic, and MCLS. This study highlights the need for continuous cardiovascular monitoring from the prenatal stage to preadolescence in these children due to multifactorial influences involving maternal autoantibodies, genetic predisposition, and environmental factors.

Survivors of Pediatric Hematopoietic Stem Cell Transplantation Exhibit Progressive Diastolic Dysfunction Over Years of Follow-Up

Patients who have undergone hematopoietic stem cell transplantation (HSCT) in childhood have a higher risk of diastolic heart failure (HF). The rate of progression of diastolic dysfunction in aging pediatric patients is unknown and is more difficult to assess in young patients secondary to changes in diastolic indices as they grow. HSCT recipients at our center were previously found to have decline in diastolic function indices at 1 year after HSCT. This study provides follow-up of this cohort, using age-normalized z-scores to assess whether the decline in diastolic function noted at 1-year post-HSCT persists, worsens, or improves over time. Patients age <21 years who underwent HSCT at Boston Children's Hospital/Dana-Farber Cancer Center between 2005 and 2008 with ≥3 surveillance echocardiograms, including 1 performed pre-HSCT, were included. Diastolic measures included mitral inflow (E/A ratio) and Doppler tissue imaging of left ventricular lateral wall (LV lateral e'), LV septal wall (septal e') and right ventricular free wall (RV e'). Systolic function was measured by LV ejection fraction (LVEF). Normalization by age was done using z-scores, and >±2 SD was defined as abnormal in linear modeling of diastolic dysfunction and systolic dysfunction over time. In a subset of patients with adequate post-HSCT images of the entire left atrium (LA), LA volume and LA strain analyses also were performed. The study cohort comprised 61 patients (41% female; median age at HSCT, 10.7 years; median follow-up, 7.4 years). Diastolic index z-scores declined by -.045/year for LV lateral e', -.06/year for LV septal e', and -.14/year for RV e' (P < .01). The E/A ratio z-score increased by .034/year (P = .028). Linear modeling demonstrated that LV lateral e' and LV septal e' would become abnormal at 25 and 20 years post-HSCT, respectively, whereas RV e' would become abnormal sooner, at 12.6 years. LVEF z-score declined by -.04/year (P < .01) and was estimated to become abnormal at 40 years post-HSCT. Exposure to total body irradiation (TBI) was associated with worsening diastolic indices, lower LVEF (P ≤ .002), and decreased LA reservoir strain (42.0% versus 45.0%; P = .016) and conduit strain (-31.5% versus -35.1%; P = .029), although there was significant overlap between TBI and anthracycline exposure. Treatment with anthracyclines even at low doses (median, 150 mg/m2) was associated with declining LVEF but not with changes in diastolic indices. Long-term survivors of childhood HSCT exhibit declines in both LV and RV diastolic function indices. These results inform the rate of progression of LV and RV diastolic dysfunction indices over time in long-term survivors of pediatric HSCT. A significant association was observed between TBI and diastolic dysfunction and a decline in LVEF. Treatment with anthracyclines even at low doses was associated with a mild decline in LVEF. Our results can inform a lifespan perspective on disease management in this population, encourage clinicians and patients to be vigilant in following guideline-directed surveillance echocardiography, and inform anticipatory responses by clinicians as patients transition from pediatric care to adult care.

Association Between Race/Ethnicity and Severity of Illness in Pediatric Cardiomyopathy and Myocarditis

INTRODUCTION

Previous reports demonstrate racial/ethnic differences in survival for children hospitalized with cardiomyopathy and myocarditis. The impact of illness severity, a potential mechanism for disparities, has not been explored.

METHODS

Using the Virtual Pediatric Systems (VPS, LLC), we identified patients ≤ 18 years old admitted to the intensive care unit (ICU) for cardiomyopathy/myocarditis. Multivariate regression models were used to evaluate the association between race/ethnicity and Pediatric Risk of Mortality (PRISM 3). Multivariate logistic and competing risk regression was used to examine the relationship between race/ethnicity and mortality, CPR, and ECMO.

RESULTS

Black patients had higher PRISM 3 scores on first admission (𝛽 = 2.02, 95% CI: 0.15, 3.90). There was no difference in survival across race/ethnicity over multiple hospitalizations. Black patients were less likely to receive a heart transplant (SHR = 0.65, 95% CI: 0.45-0.92). Black and unreported race/ethnicity had higher odds of CPR on first admission (OR = 1.64, 95% CI: 1.01-2.45; OR = 2.12, 95% CI: 1.11-4.08, respectively).

CONCLUSION

Black patients have higher severity of illness on first admission to the ICU, which may reflect differences in access to care. Black patients are less likely to receive a heart transplant. Additionally, Black patients and those with unreported race/ethnicity had higher odds of CPR, which was not mediated by severity of illness, suggesting variations in care may persist after admission.

Age and Sex Differences in the Genetics of Cardiomyopathy

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

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.

Compound Heterozygosity for Late-Onset Cardiomyopathy-Causative ALPK3 Coding Variant and Novel Intronic Variant Cause Infantile Hypertrophic Cardiomyopathy

Hypertrophic and dilated cardiomyopathy (HCM, DCM) are leading causes of cardiovascular morbidity and mortality in children. The pseudokinase alpha-protein kinase 3 (ALPK3) plays an essential role in sarcomere organization and cardiomyocyte differentiation. ALPK3 coding mutations are causative of recessively inherited pediatric-onset DCM and HCM with variable expression of facial dysmorphism and skeletal abnormalities and implicated in dominantly inherited adult-onset cardiomyopathy. We now report two variants in ALPK3-a coding variant and a novel intronic variant affecting splicing. We demonstrate that compound heterozygosity for both variants is highly suggestive to be causative of infantile-onset HCM with webbed neck, and heterozygosity for the coding variant presents with adult-onset HCM. Our data validate partial penetrance of heterozygous loss-of-function ALPK3 mutations in late-onset hypertrophic cardiomyopathy and expand the genotypic spectrum of autosomal recessive ALPK3-related cardiac disease with Noonan-like features.

[Phenotype and genotype characteristics of children with cardiomyopathy associated with MYH7 gene mutation: a retrospective analysis]

OBJECTIVES

To investigate the clinical phenotype and genotype characteristics of children withcardiomyopathy (CM) associated with MYH7 gene mutation.

METHODS

A retrospective analysis was conducted on the medical data of five children with CM caused by MYH7 gene mutation who were diagnosed and treated in the Department of Cardiology, Hebei Children's Hospital.

RESULTS

Among the five children with CM, there were three girls and two boys, all of whom carried MYH7 gene mutation. Seven mutation sites were identified, among which five were not reported before. Among the five children, there were three children with hypertrophic cardiomyopathy, one child with dilated cardiomyopathy, and one child with noncompaction cardiomyopathy. The age ranged from 6 to 156 months at the initial diagnosis. At the initial diagnosis, two children had the manifestations of heart failure such as cough, shortness of breath, poor feeding, and cyanosis of lips, as well as delayed development; one child had palpitation, blackness, and syncope; one child had fever, runny nose, and abnormal liver function; all five children had a reduction in activity endurance. All five children received pharmacotherapy for improving cardiac function and survived after follow-up for 7-24 months.

CONCLUSIONS

The age of onset varies in children with CM caused by MYH7 gene mutation, and most children lack specific clinical manifestations at the initial diagnosis and may have the phenotype of hypertrophic cardiomyopathy, dilated cardiomyopathy or noncompaction cardiomyopathy. The children receiving early genetic diagnosis and pharmacological intervention result in a favorable short-term prognosis.

Clinical profile and outcomes of pediatric hypertrophic cardiomyopathy in a South Indian tertiary care cardiac center: a three decade experience

INTRODUCTION

Although much research has been done on adult hypertrophic cardiomyopathy, data on pediatric hypertrophic cardiomyopathy is still limited.

METHODS AND RESULTS

The study enrolled all patients with cardiomyopathy who presented to us between 1990 to 2020 and were younger than 18 yrs. During the thirty-year study period, we identified 233 cases of pediatric cardiomyopathy. Sixty-three cases (27%) had hypertrophic cardiomyopathy. Out of the 63 HCM cases, 12% presented in the neonatal period and 37% presented in the first year of life. The median age of presentation was 7 yrs (Range 0.1-18 yrs). Sixteen patients had proven syndromic, metabolic, or genetic disease (25%). LV outflow obstruction was present in 30 patients (47%). Noonan syndrome was present in 9 of the 63 patients (14%). Dyspnea on exertion was the most common mode of presentation. Cardiac MRI was done in 28 patients, out of which 17 had late gadolinium enhancement (LGE). Mid myocardial enhancement was the most common pattern. Four patients had LGE of more than 15%. Over a mean follow-up period of 5.6 years (0.1-30 years), twenty-one were lost to follow-up (33%). Among the patients whose outcome was known, eleven died (26%), and thirty-one (73%) were alive. The 5-year survival rate of HCM patients was 82%, and the 10-year survival rate was 78%. Seven died of sudden cardiac death, three from heart failure, and one from ventricular arrhythmias. Sustained ventricular arrhythmias were seen in three patients and atrial arrhythmias in two. First-degree AV block was seen in 10 patients (15%) and bundle branch blocks (BBB) in five (8%). Eight patients required ICD or transplant (12.7%). Two patients underwent ICD for primary prevention, and one underwent PPI for distal AV conduction disease. Among the various clinical, echocardiographic, and radiological risk factors studied, only consanguinity showed a trend towards higher events of death or ventricular arrhythmias (P-value 0.08).

CONCLUSION

More than one-third of our HCM cohort presented in infancy. LV outflow tract obstruction is common (47%). Mid myocardial enhancement was the most common pattern of late gadolinium enhancement. SCD was the most common cause of death. The outcome in our HCM cohort is good and similar to other population cohorts. Only Consanguinity showed a trend towards higher events of death or ventricular arrhythmias.

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.

DiscoVari: A Web-Based Precision Medicine Tool for Predicting Variant Pathogenicity in Cardiomyopathy- and Channelopathy-Associated Genes

BACKGROUND

With genetic testing advancements, the burden of incidentally identified cardiac disease-associated gene variants is rising. These variants may carry a risk of sudden cardiac death, highlighting the need for accurate diagnostic interpretation. We sought to identify pathogenic hotspots in sudden cardiac death-associated genes using amino acid-level signal-to-noise (S:N) analysis and develop a web-based precision medicine tool, DiscoVari, to improve variant evaluation.

METHODS

The minor allele frequency of putatively pathogenic variants was derived from cohort-based cardiomyopathy and channelopathy studies in the literature. We normalized disease-associated minor allele frequencies to rare variants in an ostensibly healthy population (Genome Aggregation Database) to calculate amino acid-level S:N. Amino acids with S:N above the gene-specific threshold were defined as hotspots. DiscoVari was built using JavaScript ES6 and using open-source JavaScript library ReactJS, web development framework Next.js, and JavaScript runtime NodeJS. We validated the ability of DiscoVari to identify pathogenic variants using variants from ClinVar and individuals clinically evaluated at the Duke University Hospitals with cardiac genetic testing.

RESULTS

We developed DiscoVari as an internet-based tool for S:N-based variant hotspots. Upon validation, a higher proportion of ClinVar likely pathogenic/pathogenic variants localized to DiscoVari hotspots (43.1%) than likely benign/benign variants (17.8%; P<0.0001). Further, 75.3% of ClinVar variants reclassified to likely pathogenic/pathogenic were in hotspots, compared with 41.3% of those reclassified as variants of uncertain significance (P<0.0001) and 23.4% of those reclassified as likely benign/benign (P<0.0001). Of the clinical cohort variants, 73.1% of likely pathogenic/pathogenic were in hotspots, compared with 0.0% of likely benign/benign (P<0.01).

CONCLUSIONS

DiscoVari reliably identifies disease-susceptible amino acid residues to evaluate variants by searching amino acid-specific S:N ratios.

The Role of Multimodality Imaging in Pediatric Cardiomyopathies

Cardiomyopathies are a heterogeneous group of myocardial diseases representing the first cause of heart transplantation in children. Diagnosing and classifying the different phenotypes can be challenging, particularly in this age group, where cardiomyopathies are often overlooked until the onset of severe symptoms. Cardiovascular imaging is crucial in the diagnostic pathway, from screening to classification and follow-up assessment. Several imaging modalities have been proven to be helpful in this field, with echocardiography undoubtedly representing the first imaging approach due to its low cost, lack of radiation, and wide availability. However, particularly in this clinical context, echocardiography may not be able to differentiate from cardiomyopathies with similar phenotypes and is often complemented with cardiovascular magnetic resonance. The latter allows a radiation-free differentiation between different phenotypes with unique myocardial tissue characterization, thus identifying the presence and extent of myocardial fibrosis. Nuclear imaging and computed tomography have a complementary role, although they are less used in daily clinical practice due to the concern related to the use of radiation in pediatric patients. However, these modalities may have some advantages in evaluating children with cardiomyopathies. This paper aims to review the strengths and limitations of each imaging modality in evaluating pediatric patients with suspected or known cardiomyopathies.

Pathogenic Roles of Cardiac Fibroblasts in Pediatric Dilated Cardiomyopathy

Background Dilated cardiomyopathy (DCM) is a major cause of heart failure in children. Despite intensive genetic analyses, pathogenic gene variants have not been identified in most patients with DCM, which suggests that cardiomyocytes are not solely responsible for DCM. Cardiac fibroblasts (CFs) are the most abundant cell type in the heart. They have several roles in maintaining cardiac function; however, the pathological role of CFs in DCM remains unknown. Methods and Results Four primary cultured CF cell lines were established from pediatric patients with DCM and compared with 3 CF lines from healthy controls. There were no significant differences in cellular proliferation, adhesion, migration, apoptosis, or myofibroblast activation between DCM CFs compared with healthy CFs. Atomic force microscopy revealed that cellular stiffness, fluidity, and viscosity were not significantly changed in DCM CFs. However, when DCM CFs were cocultured with healthy cardiomyocytes, they deteriorated the contractile and diastolic functions of cardiomyocytes. RNA sequencing revealed markedly different comprehensive gene expression profiles in DCM CFs compared with healthy CFs. Several humoral factors and the extracellular matrix were significantly upregulated or downregulated in DCM CFs. The pathway analysis revealed that extracellular matrix receptor interactions, focal adhesion signaling, Hippo signaling, and transforming growth factor-β signaling pathways were significantly affected in DCM CFs. In contrast, single-cell RNA sequencing revealed that there was no specific subpopulation in the DCM CFs that contributed to the alterations in gene expression. Conclusions Although cellular physiological behavior was not altered in DCM CFs, they deteriorated the contractile and diastolic functions of healthy cardiomyocytes through humoral factors and direct cell-cell contact.

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.

Elevated Copeptin Levels Are Associated with Heart Failure Severity and Adverse Outcomes in Children with Cardiomyopathy

In children with cardiomyopathy, the severity of heart failure (HF) varies. However, copeptin, which is a biomarker of neurohormonal adaptation in heart failure, has not been studied in these patients. In this study, we evaluated the correlation of copeptin level with functional HF grading, B-type natriuretic peptide (BNP), and echocardiography variables in children with cardiomyopathy. Furthermore, we determined if copeptin levels are associated with adverse outcomes, including cardiac arrest, mechanical circulatory support, heart transplant, or death. In forty-two children with cardiomyopathy with a median (IQR) age of 13.1 years (2.5-17.2) and a median follow-up of 2.5 years (2.2-2.7), seven (16.7%) children had at least one adverse outcome. Copeptin levels were highest in the patients with adverse outcomes, followed by the patients without adverse outcomes, and then the healthy children. The copeptin levels in patients showed a strong correlation with their functional HF grading, BNP level, and left ventricular ejection fraction (LVEF). Patients with copeptin levels higher than the median value of 25 pg/mL had a higher likelihood of experiencing adverse outcomes, as revealed by Kaplan-Meier survival analysis (p = 0.024). Copeptin level was an excellent predictor of outcomes, with an area under the curve of 0.861 (95% CI, 0.634-1.089), a sensitivity of 86%, and a specificity of 60% for copeptin level of 25 pg/mL. This predictive value was superior in patients with dilated and restrictive cardiomyopathies (0.97 (CI 0.927-1.036), p < 0.0001, n = 21) than in those with hypertrophic and LV non-compaction cardiomyopathies (0.60 (CI 0.04-1.16), p = 0.7, n = 21).

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.

Juvenile-onset multifocal atrial arrhythmias, atrial standstill and compound heterozygosity of genetic variants in TAF1A: sentinel event for evolving dilated cardiomyopathy-a case report

Background

Juvenile onset of extensive atrial electromechanical failure, including atrial standstill, is a rare disease entity that may precede ventricular cardiomyopathy. Genetic variants associated with early-onset atrioventricular (AV) cardiomyopathy are increasingly recognized.

Case summary

A 16-year-old patient presented with atrial brady- and tachyarrhythmias and concomitant impaired atrial electromechanical function (atrial standstill). The atrial phenotype preceded the development of a predominantly right-sided AV dilated cardiomyopathy with pronounced myocardial fibrosis. A His-bundle pacemaker was installed for high-degree AV conduction block and sinus arrest. Using familial-based whole-exome sequencing, a missense mutation and a copy number variant deletion (compound heterozygosity) of the TAF1A gene (involved in ribosomal RNA synthesis) were identified.

Discussion

Juvenile onset of severe atrial electromechanical failure with atrial arrhythmias should prompt deep pheno- and genotyping and calls for vigilance for downstream cardiomyopathic deterioration.

Whole-Exome Sequencing Identifies Homozygote Nonsense Variants in LMOD2 Gene Causing Infantile Dilated Cardiomyopathy

As an essential component of the sarcomere, actin thin filament stems from the Z-disk extend toward the middle of the sarcomere and overlaps with myosin thick filaments. Elongation of the cardiac thin filament is essential for normal sarcomere maturation and heart function. This process is regulated by the actin-binding proteins Leiomodins (LMODs), among which LMOD2 has recently been identified as a key regulator of thin filament elongation to reach a mature length. Few reports have implicated homozygous loss of function variants of LMOD2 in neonatal dilated cardiomyopathy (DCM) associated with thin filament shortening. We present the fifth case of DCM due to biallelic variants in the LMOD2 gene and the second case with the c.1193G>A (p.W398*) nonsense variant identified by whole-exome sequencing. The proband is a 4-month male infant of Hispanic descent with advanced heart failure. Consistent with previous reports, a myocardial biopsy exhibited remarkably short thin filaments. However, compared to other cases of identical or similar biallelic variants, the patient presented here has an unusually late onset of cardiomyopathy during infancy. Herein, we present the phenotypic and histological features of this variant, confirm the pathogenic impact on protein expression and sarcomere structure, and discuss the current knowledge of LMOD2-related cardiomyopathy.

Clinical profile and outcomes of childhood dilated cardiomyopathy - A single-center three-decade experience

Introduction and Aims

Dilated cardiomyopathy (DCM) is an important cause of heart failure (HF) among children. Research on pediatric DCM remains surprisingly scarce. The primary objective of the study was to evaluate the clinical profile and outcomes of pediatric DCM and the secondary objective was to study the predictors of outcome.

Methods and Results

We enrolled all patients with cardiomyopathy who presented to us between 1990 and 2020 and were younger than 18 years. During the 30-year study period, we identified 233 cases of pediatric cardiomyopathy. One hundred and nineteen (51%) cases had DCM. This retrospective cohort was analyzed to study their outcome and the possible predictors of outcome. Nearly, 8% presented in the neonatal period, and 37% in infancy. The most common mode of presentation was dyspnea on exertion (71%). Ninety-three patients presented in heart failure (78%). The median left ventricular dimension z-score in diastole was 4.3 (range 2.5-9.06). The median left ventricle (LV) ejection fraction was 31%. Seventy-two percent of this cohort were on angiotensin-converting-enzyme inhibitors, 40% on aldosterone antagonists, and 47% on beta-blockers. One-third had syndromic, metabolic, genetic, or any secondary cause identified. Twenty-seven patients satisfied the three-tiered clinical classification for the diagnosis of probable acute myocarditis. Over a mean follow-up of 3.29 years, 27% were lost to follow-up. Among the remaining patients who were on follow-up (n = 86), 39 (45%) died, 31 (36%) recovered, and 16 (18%) had persistent LV dysfunction. Heart Failure was the most common cause of death. Eight patients in this cohort (4.2%) had thromboembolic phenomena. Nine had sustained ventricular arrhythmias and six had atrial/junctional arrhythmias. Among the various risk factors studied, only infantile onset had a significant relationship with death or ventricular arrhythmias (P value- 0.05). The 5-year survival rate of DCM patients was 59%.

Conclusion

A reasonably good percentage of our population showed recovery of the left ventricular function (36%). Only infantile onset had a significant relationship with death or ventricular arrhythmias. The outcome in our DCM cohort is similar to other population cohorts.

Impaired Reorganization of Centrosome Structure Underlies Human Infantile Dilated Cardiomyopathy

BACKGROUND

During cardiomyocyte maturation, the centrosome, which functions as a microtubule organizing center in cardiomyocytes, undergoes dramatic structural reorganization where its components reorganize from being localized at the centriole to the nuclear envelope. This developmentally programmed process, referred to as centrosome reduction, has been previously associated with cell cycle exit. However, understanding of how this process influences cardiomyocyte cell biology, and whether its disruption results in human cardiac disease, remains unknown. We studied this phenomenon in an infant with a rare case of infantile dilated cardiomyopathy (iDCM) who presented with left ventricular ejection fraction of 18% and disrupted sarcomere and mitochondria structure.

METHODS

We performed an analysis beginning with an infant who presented with a rare case of iDCM. We derived induced pluripotent stem cells from the patient to model iDCM in vitro. We performed whole exome sequencing on the patient and his parents for causal gene analysis. CRISPR/Cas9-mediated gene knockout and correction in vitro were used to confirm whole exome sequencing results. Zebrafish and Drosophila models were used for in vivo validation of the causal gene. Matrigel mattress technology and single-cell RNA sequencing were used to characterize iDCM cardiomyocytes further.

RESULTS

Whole exome sequencing and CRISPR/Cas9 gene knockout/correction identified RTTN, the gene encoding the centrosomal protein RTTN (rotatin), as the causal gene underlying the patient's condition, representing the first time a centrosome defect has been implicated in a nonsyndromic dilated cardiomyopathy. Genetic knockdowns in zebrafish and Drosophila confirmed an evolutionarily conserved requirement of RTTN for cardiac structure and function. Single-cell RNA sequencing of iDCM cardiomyocytes showed impaired maturation of iDCM cardiomyocytes, which underlie the observed cardiomyocyte structural and functional deficits. We also observed persistent localization of the centrosome at the centriole, contrasting with expected programmed perinuclear reorganization, which led to subsequent global microtubule network defects. In addition, we identified a small molecule that restored centrosome reorganization and improved the structure and contractility of iDCM cardiomyocytes.

CONCLUSIONS

This study is the first to demonstrate a case of human disease caused by a defect in centrosome reduction. We also uncovered a novel role for RTTN in perinatal cardiac development and identified a potential therapeutic strategy for centrosome-related iDCM. Future study aimed at identifying variants in centrosome components may uncover additional contributors to human cardiac disease.