Clinical and Mechanistic Insights Into the Genetics of Cardiomyopathy

Inpatient outcomes of mechanical circulatory support devices and heart transplantation in hypertrophic cardiomyopathy

INTRODUCTION

The pathophysiology of HCM presents unique challenges for the management of cardiogenic shock and the use of mechanical circulatory support devices (MCSD). However, outcomes investigations for MCSD and HT in HCM patients is limited to case reports. The present study investigated MCSD and HT outcomes in HCM patients in a large retrospective cohort.

METHODS

The National Inpatient Sample (2016-2019) was used for the retrospective analysis of patients hospitalized for MCSD and HT using ICD-10 codes. Patients with implantation of more than one device category were excluded. These patients were divided into two cohorts, with and without HCM, and compared in terms of in-hospital mortality, trends in mortality rates, hospitalization costs and mean length of stay.

RESULTS

Among 267,780 patients hospitalized for MCSD and HT, 1155 patients had underlying HCM. Underlying HCM was associated with increased odds of mortality in patients receiving left ventricular assist devices (LVAD) (OR 3.4, 95% CI 1.03-11.2, p = 0.04) and temporary MCSD (OR 2.5, CI 1.8-3.6, p < 0.001). HCM was not associated with increased mortality in patients hospitalized for HT (OR 0.67, CI 0.15-2.85, p = 0.6). Patients with HCM undergoing MCSD and HT had a longer mean length of stay (22.1 vs 13.2 days, p = 0.004), and higher mean hospitalization charges ($830,103 vs $460,383, p < 0.0001) as compared to non-HCM patients.

CONCLUSION

Underlying HCM is associated with increased in-hospital mortality in patients undergoing LVAD and temporary MCSD placement. Further prospective studies are required to expand our understanding of prognosis among HCM patients undergoing MCSD and establish management guidelines.

Multiscale mapping of transcriptomic signatures for cardiotoxic drugs

Drug-induced gene expression profiles can identify potential mechanisms of toxicity. We focus on obtaining signatures for cardiotoxicity of FDA-approved tyrosine kinase inhibitors (TKIs) in human induced-pluripotent-stem-cell-derived cardiomyocytes, using bulk transcriptomic profiles. We use singular value decomposition to identify drug-selective patterns across cell lines obtained from multiple healthy human subjects. Cellular pathways affected by cardiotoxic TKIs include energy metabolism, contractile, and extracellular matrix dynamics. Projecting these pathways to published single cell expression profiles indicates that TKI responses can be evoked in both cardiomyocytes and fibroblasts. Integration of transcriptomic outlier analysis with whole genomic sequencing of our six cell lines enables us to correctly reidentify a genomic variant causally linked to anthracycline-induced cardiotoxicity and predict genomic variants potentially associated with TKI-induced cardiotoxicity. We conclude that mRNA expression profiles when integrated with publicly available genomic, pathway, and single cell transcriptomic datasets, provide multiscale signatures for cardiotoxicity that could be used for drug development and patient stratification.

Hypertrophic Cardiomyopathy: From Medical Treatment to Advanced Heart Failure Therapies

PURPOSE OF REVIEW

There has been much debate surrounding novel medical therapies and heart transplantation listing challenges in patients with hypertrophic cardiomyopathy (HCM).

RECENT FINDINGS

Recent clinical trials led to FDA approval of mavacamten (a cardiac myosin inhibitor), offering symptom relief and potentially delaying/avoiding invasive septal reduction therapies for some patients with HCM and left ventricular outflow obstruction (LVOTO). For those with refractory symptoms and end-stage heart failure, heart transplantation remains the gold standard. However, the concern for the organ allocation system failing to prioritize those individuals persists. HCM is a heterogeneous genetic condition with variable penetration and clinical presentation. Even though a large portion of patients remain asymptomatic, an important minority develops debilitating symptoms refractory to medical therapy. Post-HT short- and long-term outcomes are favorable. However, HT waitlist mortality remains high. For highly selected patients with HCM, a left ventricular assist device is a viable option.

Echocardiographic Strain Abnormalities Precede Left Ventricular Hypertrophy Development in Hypertrophic Cardiomyopathy Mutation Carriers

Hypertrophic cardiomyopathy (HCM) is a genetic disease characterized by unexplained left ventricular hypertrophy (LVH), diastolic dysfunction, and increased sudden-death risk. Early detection of the phenotypic expression of the disease in genetic carriers without LVH (Gen+/Phen-) is crucial for emerging therapies. This clinical study aims to identify echocardiographic predictors of phenotypic development in Gen+/Phen-. Sixteen Gen+/Phen- (one subject with troponin T, six with myosin heavy chain-7, and nine with myosin-binding protein C3 mutations), represented the study population. At first and last visit we performed comprehensive 2D speckle-tracking strain echocardiography. During a follow-up of 8 ± 5 years, five carriers developed LVH (LVH+). At baseline, these patients were older than those who did not develop LVH (LVH-) (30 ± 8 vs. 15 ± 8 years, p = 0.005). LVH+ had reduced peak global strain rate during the isovolumic relaxation period (SRIVR) (0.28 ± 0.05 vs. 0.40 ± 0.11 1/s, p = 0.048) and lower global longitudinal strain (GLS) (-19.8 ± 0.4 vs. -22.3 ± 1.1%; p < 0.0001) than LVH- at baseline. SRIVR and GLS were not correlated with age (overall, p > 0.08). This is the first HCM study investigating subjects before they manifest clinically significant or relevant disease burden or symptomatology, comparing at baseline HCM Gen+/Phen- subjects who will develop LVH with those who will not. Furthermore, we identified highly sensitive, easily obtainable, age- and load-independent echocardiographic predictors of phenotype development in HCM gene carriers who may undergo early preventive treatment.

Flavonoids: Potential therapeutic agents for cardiovascular disease

Flavonoids are found in the roots, stems, leaves, and fruits of many plant taxa. They are related to plant growth and development, pigment formation, and protection against environmental stress. Flavonoids function as antioxidants and exert anti-inflammatory effects in the cardiovascular system by modulating classical inflammatory response pathways, such as the TLR4-NF-ĸB, PI3K-AKT, and Nrf2/HO-1 signalling pathways. There is increasing evidence for the therapeutic effects of flavonoids on hypertension, atherosclerosis, and other diseases. The potential clinical value of flavonoids for diseases of the cardiovascular system has been widely explored. For example, studies have evaluated the roles of flavonoids in the regulation of blood pressure via endothelium-dependent and non-endothelium-dependent pathways and in the regulation of myocardial systolic and diastolic functions by influencing calcium homeostasis and smooth muscle-related protein expression. Flavonoids also have hypoglycaemic, hypolipidemic, anti-platelet, autophagy, and antibacterial effects. In this paper, the role and mechanism of flavonoids in cardiovascular diseases were reviewed in order to provide reference for the clinical application of flavonoids in the future.

2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy" provides recommendations to guide clinicians in the management of patients with hypertrophic cardiomyopathy.

METHODS

A comprehensive literature search was conducted from September 14, 2022, to November 22, 2022, encompassing studies, reviews, and other evidence on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through May 23, 2023, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Hypertrophic cardiomyopathy remains a common genetic heart disease reported in populations globally. Recommendations from the "2020 AHA/ACC Guideline for the Diagnosis and Treatment of Patients With Hypertrophic Cardiomyopathy" have been updated with new evidence to guide clinicians.

2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy" provides recommendations to guide clinicians in the management of patients with hypertrophic cardiomyopathy.

METHODS

A comprehensive literature search was conducted from September 14, 2022, to November 22, 2022, encompassing studies, reviews, and other evidence on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through May 23, 2023, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Hypertrophic cardiomyopathy remains a common genetic heart disease reported in populations globally. Recommendations from the "2020 AHA/ACC Guideline for the Diagnosis and Treatment of Patients With Hypertrophic Cardiomyopathy" have been updated with new evidence to guide clinicians.

Obstruction in Hypertrophic Cardiomyopathy: Many Faces

Hypertrophic cardiomyopathy (HCM), the most common inherited cardiomyopathy, exhibits left ventricular hypertrophy not secondary to other causes, with varied phenotypic expression. Enhanced actin-myosin interaction underlies excessive myocardial contraction, frequently resulting in dynamic obstruction within the left ventricle. Left ventricular outflow tract obstruction, occurring at rest or with provocation in 75% of HCM patients, portends adverse prognosis, contributes to symptoms, and is frequently a therapeutic target. Transthoracic echocardiography plays a crucial role in the screening, initial diagnosis, management, and risk stratification of HCM. Herein, we explore echocardiographic evaluation of HCM, emphasizing Doppler assessment for obstruction. Echocardiography informs management strategies through noninvasive hemodynamic assessment, which is frequently obtained with various provocative maneuvers. Recognition of obstructive HCM phenotypes and associated anatomical abnormalities guides therapeutic decision-making. Doppler echocardiography allows monitoring of therapeutic responses, whether it be medical therapies (including cardiac myosin inhibitor therapy) or septal reduction therapies, including surgical myectomy and alcohol septal ablation. This article discusses the hemodynamics of obstruction and practical application of Doppler assessment in HCM. In addition, it provides a visual atlas of obstruction in HCM, including high-quality figures and complementary videos that illustrate the many facets of dynamic obstruction.

Structural dynamics of the intrinsically disordered linker region of cardiac troponin T

The cardiac troponin complex, composed of troponins I, T, and C, plays a central role in regulating the calcium-dependent interactions between myosin and the thin filament. Mutations in troponin can cause cardiomyopathies; however, it is still a major challenge for the field to connect how changes in sequence affect troponin's function. Recent high-resolution structures of the thin filament revealed critical insights into the structure-function relationship of the troponin complex, but there remain large, unresolved segments of troponin, including the troponin-T linker region that is a hotspot for several cardiomyopathy mutations. This unresolved yet functionally-significant linker region has been proposed to be intrinsically disordered, with behaviors that are not well described by traditional structural approaches; however, this proposal has not been experimentally verified. Here, we used a combination of single-molecule Förster resonance energy transfer (FRET), molecular dynamics simulations, and functional reconstitution assays to investigate the troponin-T linker region. We experimentally and computationally show that in the context of both isolated troponin and the fully regulated troponin complex, the linker behaves as a dynamic, intrinsically disordered region. This region undergoes polyampholyte expansion in the presence of high salt and distinct conformational changes during the assembly of the troponin complex. We also examine the ΔE160 hypertrophic cardiomyopathy mutation in the linker, and we demonstrate that this mutation does not affect the conformational dynamics of the linker, rather it allosterically affects interactions with other subunits of the troponin complex, leading to increased molecular contractility. Taken together, our data clearly demonstrate the importance of disorder within the troponin-T linker and provide new insights into the molecular mechanisms controlling the pathogenesis of cardiomyopathies.

Aficamten for Symptomatic Obstructive Hypertrophic Cardiomyopathy

BACKGROUND

One of the major determinants of exercise intolerance and limiting symptoms among patients with obstructive hypertrophic cardiomyopathy (HCM) is an elevated intracardiac pressure resulting from left ventricular outflow tract obstruction. Aficamten is an oral selective cardiac myosin inhibitor that reduces left ventricular outflow tract gradients by mitigating cardiac hypercontractility.

METHODS

In this phase 3, double-blind trial, we randomly assigned adults with symptomatic obstructive HCM to receive aficamten (starting dose, 5 mg; maximum dose, 20 mg) or placebo for 24 weeks, with dose adjustment based on echocardiography results. The primary end point was the change from baseline to week 24 in the peak oxygen uptake as assessed by cardiopulmonary exercise testing. The 10 prespecified secondary end points (tested hierarchically) were change in the Kansas City Cardiomyopathy Questionnaire clinical summary score (KCCQ-CSS), improvement in the New York Heart Association (NYHA) functional class, change in the pressure gradient after the Valsalva maneuver, occurrence of a gradient of less than 30 mm Hg after the Valsalva maneuver, and duration of eligibility for septal reduction therapy (all assessed at week 24); change in the KCCQ-CSS, improvement in the NYHA functional class, change in the pressure gradient after the Valsalva maneuver, and occurrence of a gradient of less than 30 mm Hg after the Valsalva maneuver (all assessed at week 12); and change in the total workload as assessed by cardiopulmonary exercise testing at week 24.

RESULTS

A total of 282 patients underwent randomization: 142 to the aficamten group and 140 to the placebo group. The mean age was 59.1 years, 59.2% were men, the baseline mean resting left ventricular outflow tract gradient was 55.1 mm Hg, and the baseline mean left ventricular ejection fraction was 74.8%. At 24 weeks, the mean change in the peak oxygen uptake was 1.8 ml per kilogram per minute (95% confidence interval [CI], 1.2 to 2.3) in the aficamten group and 0.0 ml per kilogram per minute (95% CI, -0.5 to 0.5) in the placebo group (least-squares mean between-group difference, 1.7 ml per kilogram per minute; 95% CI, 1.0 to 2.4; P<0.001). The results for all 10 secondary end points were significantly improved with aficamten as compared with placebo. The incidence of adverse events appeared to be similar in the two groups.

CONCLUSIONS

Among patients with symptomatic obstructive HCM, treatment with aficamten resulted in a significantly greater improvement in peak oxygen uptake than placebo. (Funded by Cytokinetics; SEQUOIA-HCM ClinicalTrials.gov number, NCT05186818.).

The Genetic Factors Influencing Cardiomyopathies and Heart Failure across the Allele Frequency Spectrum

Heart failure (HF) remains a major cause of mortality and morbidity worldwide. Understanding the genetic basis of HF allows for the development of disease-modifying therapies, more appropriate risk stratification, and personalised management of patients. The advent of next-generation sequencing has enabled genome-wide association studies; moving beyond rare variants identified in a Mendelian fashion and detecting common DNA variants associated with disease. We summarise the latest GWAS and rare variant data on mixed and refined HF aetiologies, and cardiomyopathies. We describe the recent understanding of the functional impact of titin variants and highlight FHOD3 as a novel cardiomyopathy-associated gene. We describe future directions of research in this field and how genetic data can be leveraged to improve the care of patients with HF.

Myosin-Catalyzed ATP Hydrolysis in the Presence of Disease-Causing Mutations: Mavacamten as a Way to Repair Mechanism

Hypertrophic cardiomyopathy is one of the most common forms of genetic cardiomyopathy. Mavacamten is a first-in-class myosin modulator that was identified via activity screening on the wild type, and it is FDA-approved for the treatment of obstructive hypertrophic cardiomyopathy (HCM). The drug selectively binds to the cardiac β-myosin, inhibiting myosin function to decrease cardiac contractility. Though the drug is thought to affect multiple steps of the myosin cross-bridge cycle, its detailed mechanism of action is still under investigation. Individual steps in the overall cross-bridge cycle must be queried to elucidate the full mechanism of action. In this study, we utilize the rare-event method of transition path sampling to generate reactive trajectories to gain insights into the action of the drug on the dynamics and rate of the ATP hydrolysis step for human cardiac β-myosin. We study three known HCM causative myosin mutations: R453C, P710R, and R712L to observe the effect of the drug on the alterations caused by these mutations in the chemical step. Since the crystal structure of the drug-bound myosin was not available at the time of this work, we created a model of the drug-bound system utilizing a molecular docking approach. We find a significant effect of the drug in one case, where the actual mechanism of the reaction is altered from the wild type by mutation. The drug restores both the rate of hydrolysis to the wildtype level and the mechanism of the reaction. This is a way to check the effect of the drug on untested mutations.

Genotype-Phenotype Insights of Inherited Cardiomyopathies-A Review

Background: Cardiomyopathies (CMs) represent a heterogeneous group of primary myocardial diseases characterized by structural and functional abnormalities. They represent one of the leading causes of cardiac transplantations and cardiac death in young individuals. Clinically they vary from asymptomatic to symptomatic heart failure, with a high risk of sudden cardiac death due to malignant arrhythmias. With the increasing availability of genetic testing, a significant number of affected people are found to have an underlying genetic etiology. However, the awareness of the benefits of incorporating genetic test results into the care of these patients is relatively low. Aim: The focus of this review is to summarize the current basis of genetic CMs, including the most encountered genes associated with the main types of cardiomyopathies: hypertrophic, dilated, restrictive arrhythmogenic, and non-compaction. Materials and Methods: For this narrative review, we performed a search of multiple electronic databases, to select and evaluate relevant manuscripts. Results: Advances in genetic diagnosis led to better diagnosis precision and prognosis prediction, especially with regard to the risk of developing arrhythmias in certain subtypes of cardiomyopathies. Conclusions: Implementing the genomic information to benefit future patient care, better risk stratification and management, promises a better future for genotype-based treatment.

Dilated cardiomyopathy-associated skeletal muscle actin (ACTA1) mutation R256H disrupts actin structure and function and causes cardiomyocyte hypocontractility

Skeletal muscle actin (ACTA1) mutations are a prevalent cause of skeletal myopathies consistent with ACTA1's high expression in skeletal muscle. Rare de novo mutations in ACTA1 associated with combined cardiac and skeletal myopathies have been reported, but ACTA1 represents only ~20% of the total actin pool in cardiomyocytes, making its role in cardiomyopathy controversial. Here we demonstrate how a mutation in an actin isoform expressed at low levels in cardiomyocytes can cause cardiomyopathy by focusing on a unique ACTA1 mutation, R256H. We previously identified this mutation in multiple family members with dilated cardiomyopathy (DCM), who had reduced systolic function without clinical skeletal myopathy. Using a battery of multiscale biophysical tools, we show that R256H has potent functional effects on ACTA1 function at the molecular scale and in human cardiomyocytes. Importantly, we demonstrate that R256H acts in a dominant manner, where the incorporation of small amounts of mutant protein into thin filaments is sufficient to disrupt molecular contractility, and that this effect is dependent on the presence of troponin and tropomyosin. To understand the structural basis of this change in regulation, we resolved a structure of R256H filaments using Cryo-EM, and we see alterations in actin's structure that have the potential to disrupt interactions with tropomyosin. Finally, we show that ACTA1R256H/+ human induced pluripotent stem cell cardiomyocytes demonstrate reduced contractility and sarcomeric disorganization. Taken together, we demonstrate that R256H has multiple effects on ACTA1 function that are sufficient to cause reduced contractility and establish a likely causative relationship between ACTA1 R256H and clinical cardiomyopathy.

Deletion of DWORF does not affect cardiac function in aging and in PLN-R14del cardiomyopathy

The phospholamban (PLN) pathogenic gene variant p.Arg14del causes cardiomyopathy, which is characterized by perinuclear PLN protein clustering and can lead to severe heart failure (HF). Elevated expression of dwarf open reading frame (DWORF), a protein counteracting the function of PLN in the sarcoplasmic reticulum (SR), can delay disease progression in a PLN-R14del mouse model. Here, we evaluated whether deletion of DWORF (DWORF-/-) would have an opposite effect and accelerate age-dependent disease progression in wild-type (WT) mice and mice with a pathogenic PLN-R14del allele (R14Δ/+). We show that DWORF-/- mice maintained a normal left ventricular ejection fraction (LVEF) during aging and no difference with WT control mice could be observed up to 20 mo of age. R14Δ/+ mice maintained a normal cardiac function until 12 mo of age, but at 18 mo of age, LVEF was significantly reduced as compared with WT mice. Absence of DWORF did neither accelerate the R14Δ/+-induced reduction in LVEF nor enhance the increases in gene expression of markers related to cardiac remodeling and fibrosis and did not exacerbate cardiac fibrosis caused by the R14Δ/+ mutation. Together, these results demonstrate that absence of DWORF does not accelerate or exacerbate PLN-R14del cardiomyopathy in mice harboring the pathogenic R14del allele. In addition, our data indicate that DWORF appears to be dispensable for cardiac function during aging.NEW & NOTEWORTHY Although DWORF overexpression significantly delayed heart failure development and strongly prolonged life span in PLN-R14del mice, the current study shows that deletion of DWORF does not accelerate or exacerbate PLN-R14del cardiomyopathy in mice harboring the pathogenic R14del allele. In addition, DWORF appears to be dispensable for cardiac function during aging. Changes in DWORF gene expression are therefore unlikely to contribute to the clinical heterogeneity observed in patients with PLN-R14del cardiomyopathy.

Assessing Cardiac Contractility From Single Molecules to Whole Hearts

Fundamentally, the heart needs to generate sufficient force and power output to dynamically meet the needs of the body. Cardiomyocytes contain specialized structures referred to as sarcomeres that power and regulate contraction. Disruption of sarcomeric function or regulation impairs contractility and leads to cardiomyopathies and heart failure. Basic, translational, and clinical studies have adapted numerous methods to assess cardiac contraction in a variety of pathophysiological contexts. These tools measure aspects of cardiac contraction at different scales ranging from single molecules to whole organisms. Moreover, these studies have revealed new pathogenic mechanisms of heart disease leading to the development of novel therapies targeting contractility. In this review, the authors explore the breadth of tools available for studying cardiac contractile function across scales, discuss their strengths and limitations, highlight new insights into cardiac physiology and pathophysiology, and describe how these insights can be harnessed for therapeutic candidate development and translational.

Prdm16 mutation determines sex-specific cardiac metabolism and identifies two novel cardiac metabolic regulators

AIMS

Mutation of the PRDM16 gene causes human dilated and non-compaction cardiomyopathy. The PRDM16 protein is a transcriptional regulator that affects cardiac development via Tbx5 and Hand1, thus regulating myocardial structure. The biallelic inactivation of Prdm16 induces severe cardiac dysfunction with post-natal lethality and hypertrophy in mice. The early pathological events that occur upon Prdm16 inactivation have not been explored.

METHODS AND RESULTS

This study performed in-depth pathophysiological and molecular analyses of male and female Prdm16csp1/wt mice that carry systemic, monoallelic Prdm16 gene inactivation. We systematically assessed early molecular changes through transcriptomics, proteomics, and metabolomics. Kinetic modelling of cardiac metabolism was performed in silico with CARDIOKIN. Prdm16csp1/wt mice are viable up to 8 months, develop hypoplastic hearts, and diminished systolic performance that is more pronounced in female mice. Prdm16csp1/wt cardiac tissue of both sexes showed reductions in metabolites associated with amino acid as well as glycerol metabolism, glycolysis, and the tricarboxylic acid cycle. Prdm16csp1/wt cardiac tissue revealed diminished glutathione (GSH) and increased inosine monophosphate (IMP) levels indicating oxidative stress and a dysregulated energetics, respectively. An accumulation of triacylglycerides exclusively in male Prdm16csp1/wt hearts suggests a sex-specific metabolic adaptation. Metabolic modelling using CARDIOKIN identified a reduction in fatty acid utilization in males as well as lower glucose utilization in female Prdm16csp1/wt cardiac tissue. On the level of transcripts and protein expression, Prdm16csp1/wt hearts demonstrate an up-regulation of pyridine nucleotide-disulphide oxidoreductase domain 2 (Pyroxd2) and the transcriptional regulator pre-B-cell leukaemia transcription factor interacting protein 1 (Pbxip1). The strongest concordant transcriptional up-regulation was detected for Prdm16 itself, probably through an autoregulatory mechanism.

CONCLUSIONS

Monoallelic, global Prdm16 mutation diminishes cardiac performance in Prdm16csp1/wt mice. Metabolic alterations and transcriptional dysregulation in Prdm16csp1/wt affect cardiac tissue. Female Prdm16csp1/wt mice develop a more pronounced phenotype, indicating sexual dimorphism at this early pathological window. This study suggests that metabolic dysregulation is an early event in the PRDM16 associated cardiac pathology.

Anthracycline Toxicity: Light at the End of the Tunnel?

Anthracycline-induced cardiotoxicity (AIC) is a serious and common side effect of anthracycline therapy. Identification of genes and genetic variants associated with AIC risk has clinical potential as a cardiotoxicity predictive tool and to allow the development of personalized therapies. In this review, we provide an overview of the function of known AIC genes identified by association studies and categorize them based on their mechanistic implication in AIC. We also discuss the importance of functional validation of AIC-associated variants in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to advance the implementation of genetic predictive biomarkers. Finally, we review how patient-specific hiPSC-CMs can be used to identify novel patient-relevant functional targets and for the discovery of cardioprotectant drugs to prevent AIC. Implementation of functional validation and use of hiPSC-CMs for drug discovery will identify the next generation of highly effective and personalized cardioprotectants and accelerate the inclusion of approved AIC biomarkers into clinical practice.

Research Gaps in Pediatric Heart Failure: Defining the Gaps and Then Closing Them Over the Next Decade

Given the numerous opportunities and the wide knowledge gaps in pediatric heart failure, an international group of pediatric heart failure experts with diverse backgrounds were invited and tasked with identifying research gaps in each pediatric heart failure domain that scientists and funding agencies need to focus on over the next decade.

Human Genetics of Cardiomyopathies

The identification of a disease-causing variant in a patient diagnosed with cardiomyopathy allows for presymptomatic testing in at risk relatives. Carriers of a pathogenic variant can subsequently be screened at intervals by a cardiologist to assess the risk for potentially life-threatening arrhythmias which can be life-saving. In addition, gene-specific recommendations for risk stratification and disease specific pharmacological options for therapy are beginning to emerge. The large variability in disease penetrance, symptoms, and prognosis, and in some families even in cardiomyopathy subtype, makes genetic counseling both of great importance and complicated.

Exploring Health Care Disparities in Genetic Testing and Research for Hereditary Cardiomyopathy: Current State and Future Perspectives

Background  Hereditary cardiomyopathies are commonly occurring myocardial conditions affecting heart structure and function with a genetic or familial association, but the etiology is often unknown. Cardiomyopathies are linked to significant mortality, requiring robust risk stratification with genetic testing and early diagnosis. Hypothesis  We hypothesized that health care disparities exist in genetic testing for hereditary cardiomyopathies within clinical practice and research studies. Methods  In a narrative fashion, we conducted a literature search with online databases such as PubMed/MEDLINE, Google Scholar, EMBASE, and Science Direct on papers related to hereditary cardiomyopathies. A comprehensive analysis of findings from articles in English on disparities in diagnostics and treatment was grouped into four categories. Results  Racial and ethnic disparities in research study enrollment and health care delivery favor White populations and higher socioeconomic status, resulting in differences in the development and implementation of effective genetic screening. Such disparities have shown to be detrimental, as minorities often suffer from disease progression to heart failure and sudden cardiac death. Barriers related to clinical genetic testing included insurance-related issues and health illiteracy. The underrepresentation of minority populations extends to research methodologies, as testing in ethnic minorities resulted in a significantly lower detection rate and diagnostic yield, as well as a higher likelihood of misclassification of variants. Conclusions  Prioritizing minority-based participatory research programs and screening protocols can address systemic disparities. Diversifying research studies can improve risk stratification strategies and impact clinical practice.

RNA binding protein IGF2BP2 expression is induced by stress in the heart and mediates dilated cardiomyopathy

The IGF2BP family of RNA binding proteins consists of three paralogs that regulate intracellular RNA localization, RNA stability, and translational control. Although IGF2BP1 and 3 are oncofetal proteins, IGF2BP2 expression is maintained in many tissues, including the heart, into adulthood. IGF2BP2 is upregulated in cardiomyocytes during cardiac stress and remodeling and returns to normal levels in recovering hearts. We wondered whether IGF2BP2 might play an adaptive role during cardiac stress and recovery. Enhanced expression of an IGF2BP2 transgene in a conditional, inducible mouse line leads to dilated cardiomyopathy (DCM) and death within 3-4 weeks in newborn or adult hearts. Downregulation of the transgene after 2 weeks, however, rescues these mice, with complete recovery by 12 weeks. Hearts overexpressing IGF2BP2 downregulate sarcomeric and mitochondrial proteins and have fragmented mitochondria and elongated, thinner sarcomeres. IGF2BP2 is also upregulated in DCM or myocardial infarction patients. These results suggest that IGF2BP2 may be an attractive target for therapeutic intervention in cardiomyopathies.

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.

Genetic heterogeneity of cardiomyopathy and its correlation with patient care

BACKGROUND

Cardiomyopathy, which is a genetically and phenotypically heterogeneous pathological condition, is associated with increased morbidity and mortality. Genetic diagnosis of cardiomyopathy enables accurate phenotypic classification and optimum patient management and counseling. This study investigated the genetic spectrum of cardiomyopathy and its correlation with the clinical course of the disease.

METHODS

The samples of 72 Korean patients with cardiomyopathy (43 males and 29 females) were subjected to whole-exome sequencing (WES). The familial information and clinical characteristics of the patients were reviewed and analyzed according to their genotypes.

RESULTS

Dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), left ventricular non-compaction cardiomyopathy, and restrictive cardiomyopathy was detected in 41 (56.9%), 25 (34.7%), 4 (5.6%), and 2 (2.8%) patients, respectively. WES analysis revealed positive results in 37 (51.4%) patients. Subsequent familial testing identified ten additional familial cases. Among DCM cases, 19 (46.3%) patients exhibited positive results, with TTN variants being the most common alteration, followed by LMNA and MYH7 variants. Meanwhile, among HCM cases, 15 (60%) patients exhibited positive results with MYH7 variants being the most common alteration. In six patients with positive results, extracardiac surveillance was warranted based on disease information. The incidence of worse outcomes, such as mortality and life-threatening arrhythmic events, in patients with DCM harboring LMNA variants, was higher than that in patients with DCM harboring TTN or MYH7 variants.

CONCLUSIONS

Diverse genotypes were identified in a substantial proportion of patients with cardiomyopathy. Genetic diagnosis enables personalized disease surveillance and management.

Searching for Intrinsic Causality between Colonic Dysbiosis and Non-Ischemic Cardiomyopathy: A Mendelian Randomization-Based Analysis

Objective: Little is known about gut microbiota (GM) and cardiomyopathy. Their causal relationship was explored using two-sample Mendelian randomization (TSMR) performed by R software. Methods: The single nucleotide polymorphisms (SNPs) were further screened based on the genome-wide association studies (GWAS) of gut microbiota and cardiomyopathy obtained from an open database. TSMR was performed using an MR-Egger regression, simple estimator based on mode, weighted median method, inverse variance weighted (IVW), weighted estimator and CML-MA-BIC to explore the causal association. And the sensitivity analysis was carried out using an MR-Egger regression and the leave-one-out sensitivity test. Results: As for 211 GM taxa, IVW results confirmed that the class Actinobacteria (OR = 0.81, p = 0.021) and genus Coprobacter (OR = 0.85, p = 0.033) were protective factors for cardiomyopathy. The phylum Firmicutes (OR = 0.87, p < 0.01), family Acidaminococcaceae (OR = 0.89, p < 0.01), genus Desulfovibrio (OR = 0.92, p = 0.030) and genus Prevotella9 (OR = 0.93, p = 0.029) were protective factors for ischemic cardiomyopathy. The family Rhodospirillaceae (OR = 1.06, p = 0.036) and genus Turicibacter (OR = 1.09, p = 0.019) were risk factors for ischemic cardiomyopathy. The genus Olsenella (OR = 0.91, p = 0.032) was a protective factor for non-ischemic cardiomyopathy. The order Rhodospirillales (OR = 1.14, p = 0.024), family Rikenellaceae (OR = 1.21, p = 0.012) and genus Gordonibacter (OR = 1.12, p = 0.019) were risk factors for non-ischemic cardiomyopathy. The robustness of MR results was reflected in the heterogeneity (p > 0.05) and pleiotropy (p > 0.05) analyses. Conclusions: A potential causal relationship of cardiomyopathy with some GM taxa has been confirmed in the current study.

Loss of Sec-1 Family Domain-Containing 1 (scfd1) Causes Severe Cardiac Defects and Endoplasmic Reticulum Stress in Zebrafish

Dilated cardiomyopathy (DCM) is a common heart muscle disorder that frequently leads to heart failure, arrhythmias, and death. While DCM is often heritable, disease-causing mutations are identified in only ~30% of cases. In a forward genetic mutagenesis screen, we identified a novel zebrafish mutant, heart and head (hahvcc43), characterized by early-onset cardiomyopathy and craniofacial defects. Linkage analysis and next-generation sequencing identified a nonsense variant in the highly conserved scfd1 gene, also known as sly1, that encodes sec1 family domain-containing 1. Sec1/Munc18 proteins, such as Scfd1, are involved in membrane fusion regulating endoplasmic reticulum (ER)/Golgi transport. CRISPR/Cas9-engineered scfd1vcc44 null mutants showed severe cardiac and craniofacial defects and embryonic lethality that recapitulated the phenotype of hahvcc43 mutants. Electron micrographs of scfd1-depleted cardiomyocytes showed reduced myofibril width and sarcomere density, as well as reticular network disorganization and fragmentation of Golgi stacks. Furthermore, quantitative PCR analysis showed upregulation of ER stress response and apoptosis markers. Both heterozygous hahvcc43 mutants and scfd1vcc44 mutants survived to adulthood, showing chamber dilation and reduced ventricular contraction. Collectively, our data implicate scfd1 loss-of-function as the genetic defect at the hahvcc43 locus and provide new insights into the role of scfd1 in cardiac development and function.

Adverse Outcomes in Hospitalizations for Amyloid-Related Heart Failure

Transthyretin amyloid cardiomyopathy is being increasingly recognized as an important cause of heart failure (HF). In this study, we looked at adverse outcomes in hospitalizations with amyloid-related HF. This study was a retrospective analysis of the National Inpatient Sample data, collected from 2016 to 2019. Patients ≥41 years of age and admitted for HF were included in the study. In these hospitalizations, amyloid-related HF was identified through the International Classification of Diseases, Tenth Revision, Clinical Modification codes for amyloidosis. The primary outcome of the study was in-hospital mortality, whereas secondary outcomes were prolonged length of stay, mechanical ventilation, mechanical circulatory support, vasopressors use, and dispositions other than home. From 2016 to 2019, there were 4,705,274 HF hospitalizations, of which 16,955 (0.4%) had amyloid cardiomyopathy. In all HF hospitalizations, amyloid-related increased from 0.26% in 2016 to 0.46% in 2019 (relative increase, 76.9%, P for trend <0.001). Amyloid-related HF hospitalizations were more common in older, male, and Black patients. The odds of in-hospital mortality (odds ratio [OR], 1.29; 95% confidence interval [CI]: 1.11 to 1.38), prolonged hospital length (OR, 1.61; 95% CI: 1.49 to 1.73) and vasopressors use (OR, 1.59; 95% CI: 1.23 to 2.05) were significantly higher for amyloid-related hospitalizations. Amyloid-related HF hospitalizations are increasing substantially and are associated with adverse hospital outcomes. These hospitalizations were disproportionately higher for older, male, and Black patients. Amyloid-related HF is rare and underdiagnosed yet has several adverse outcomes. Hence, healthcare providers should be watchful of this condition for early identification and prompt management.

Nucleus Mechanosensing in Cardiomyocytes

Cardiac muscle contraction is distinct from the contraction of other muscle types. The heart continuously undergoes contraction-relaxation cycles throughout an animal's lifespan. It must respond to constantly varying physical and energetic burdens over the short term on a beat-to-beat basis and relies on different mechanisms over the long term. Muscle contractility is based on actin and myosin interactions that are regulated by cytoplasmic calcium ions. Genetic variants of sarcomeric proteins can lead to the pathophysiological development of cardiac dysfunction. The sarcomere is physically connected to other cytoskeletal components. Actin filaments, microtubules and desmin proteins are responsible for these interactions. Therefore, mechanical as well as biochemical signals from sarcomeric contractions are transmitted to and sensed by other parts of the cardiomyocyte, particularly the nucleus which can respond to these stimuli. Proteins anchored to the nuclear envelope display a broad response which remodels the structure of the nucleus. In this review, we examine the central aspects of mechanotransduction in the cardiomyocyte where the transmission of mechanical signals to the nucleus can result in changes in gene expression and nucleus morphology. The correlation of nucleus sensing and dysfunction of sarcomeric proteins may assist the understanding of a wide range of functional responses in the progress of cardiomyopathic diseases.

Biomechanical Impact of Pathogenic MYBPC3 Truncation Variant Revealed by Dynamically Tuning In Vitro Afterload

Engineered cardiac microtissues were fabricated using pluripotent stem cells with a hypertrophic cardiomyopathy associated c. 2827 C>T; p.R943x truncation variant in myosin binding protein C (MYBPC3+/-). Microtissues were mounted on iron-incorporated cantilevers, allowing manipulations of cantilever stiffness using magnets, enabling examination of how in vitro afterload affects contractility. MYPBC3+/- microtissues developed augmented force, work, and power when cultured with increased in vitro afterload when compared with isogenic controls in which the MYBPC3 mutation had been corrected (MYPBC3+/+(ed)), but weaker contractility when cultured with lower in vitro afterload. After initial tissue maturation, MYPBC3+/- CMTs exhibited increased force, work, and power in response to both acute and sustained increases of in vitro afterload. Together, these studies demonstrate that extrinsic biomechanical challenges potentiate genetically-driven intrinsic increases in contractility that may contribute to clinical disease progression in patients with HCM due to hypercontractile MYBPC3 variants.

Functional analysis of a common BAG3 allele associated with protection from heart failure

Multiple genetic association studies have correlated a common allelic block linked to the BAG3 gene with a decreased incidence of heart failure, but the molecular mechanism remains elusive. In this study, we used induced pluripotent stem cells to test if the only coding variant in this allele block, BAG3C151R, alters protein and cellular function in human cardiomyocytes. Quantitative protein interaction analysis identified changes in BAG3C151R protein partners specific to cardiomyocytes. Knockdown of genes encoding for BAG3-interacting factors in cardiomyocytes followed by myofibrillar analysis revealed that BAG3C151R associates more strongly with proteins involved in the maintenance of myofibrillar integrity. Finally, we demonstrate that cardiomyocytes expressing the BAG3C151R variant have improved response to proteotoxic stress in a dose-dependent manner. This study suggests that BAG3C151R could be responsible for the cardioprotective effect of the haplotype block, by increasing cardiomyocyte protection from stress. Preferential binding partners of BAG3C151R may reveal potential targets for cardioprotective therapies.

Differential expression profiles of plasma exosomal microRNAs in dilated cardiomyopathy with chronic heart failure

As one of the most prevalent heritable cardiovascular diseases, dilated cardiomyopathy (DCM) induces cardiac insufficiency and dysfunction. Although genetic mutation has been identified one of the causes of DCM, the usage of genetic biomarkers such as RNAs for DCM early diagnosis is still being overlooked. In addition, the alternation of RNAs could reflect the progression of the diseases, as an indicator for the prognosis of patients. Therefore, it is beneficial to develop genetic based diagnostic tool for DCM. RNAs are often unstable within circulatory system, leading to the infeasibility for clinical application. Recently discovered exosomal miRNAs have the stability that is then need for diagnostic purpose. Hence, fully understanding of the exosomal miRNA within DCM patients is vital for clinical translation. In this study, we employed the next generation sequencing based on the plasma exosomal miRNAs to comprehensively characterize the miRNAs expression in plasma exosomes from DCM patients exhibiting chronic heart failure (CHF) compared to healthy individuals. A complex landscape of differential miRNAs and target genes in DCM with CHF patients were identified. More importantly, we discovered that 92 differentially expressed miRNAs in DCM patients undergoing CHF were correlated with several enriched pathways, including oxytocin signalling pathway, circadian entrainment, hippo signalling pathway-multiple species, ras signalling pathway and morphine addiction. This study reveals the miRNA expression profiles in plasma exosomes in DCM patients with CHF, and further reveal their potential roles in the pathogenesis of it, presenting a new direction for clinical diagnosis and management of DCM patients with CHF.

Genetic Testing for Cardiomyopathy in Japan 2022: Current Status and Issues of Precision Medicine

Although many causative genes for primary cardiomyopathy have been identified, the use of genetic testing in routine practice is limited in Japan presently. Genetic diagnosis has been reported to be useful for early diagnosis through cascade genetic screening in the family, differentiating secondary cardiomyopathies, and predicting prognosis in some patients; nonetheless, the acquisition of genetic information for cardiomyopathy is stagnating in actual clinical practice. There seem to be a number of reasons for this phenomenon, and although the use of next-generation sequencers has resolved some of the past issues, the importance of pathogenicity studies of variants that are identified is growing. To ensure that patients with cardiomyopathy and their relatives can receive precision medicine, the results of genetic analysis linked to clinical information need to be collected, and a database of variants in Japanese people needs to be established.

Indirect epigenetic testing identifies a diagnostic signature of cardiomyocyte DNA methylation in heart failure

Precision-based molecular phenotyping of heart failure must overcome limited access to cardiac tissue. Although epigenetic alterations have been found to underlie pathological cardiac gene dysregulation, the clinical utility of myocardial epigenomics remains narrow owing to limited clinical access to tissue. Therefore, the current study determined whether patient plasma confers indirect phenotypic, transcriptional, and/or epigenetic alterations to ex vivo cardiomyocytes to mirror the failing human myocardium. Neonatal rat ventricular myocytes (NRVMs) and single-origin human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and were treated with blood plasma samples from patients with dilated cardiomyopathy (DCM) and donor subjects lacking history of cardiovascular disease. Following plasma treatments, NRVMs and hiPSC-CMs underwent significant hypertrophy relative to non-failing controls, as determined via automated high-content screening. Array-based DNA methylation analysis of plasma-treated hiPSC-CMs and cardiac biopsies uncovered robust, and conserved, alterations in cardiac DNA methylation, from which 100 sites were validated using an independent cohort. Among the CpG sites identified, hypo-methylation of the ATG promoter was identified as a diagnostic marker of HF, wherein cg03800765 methylation (AUC = 0.986, P < 0.0001) was found to out-perform circulating NT-proBNP levels in differentiating heart failure. Taken together, these findings support a novel approach of indirect epigenetic testing in human HF.

Brugada ECG phenocopy in hypertrophic cardiomyopathy: The time matter

An Implantable Cardioverter-Defibrillator was implanted in an asymptomatic 56-year-old man, with type 2 Brugada pattern on ECG, inducible ventricular fibrillation at elective electrophysiological study, and a family history of sudden cardiac death. Seventeen years later, the patient was admitted to the hospital due to palpitations related to a typical atrial flutter. A transthoracic echocardiogram unexpectedly revealed a clinically manifest hypertrophic cardiomyopathy.

Genetics of BAG3: A Paradigm for Developing Precision Therapies for Dilated Cardiomyopathies

Nonischemic dilated cardiomyopathy is a common form of heart muscle disease in which genetic factors play a critical etiological role. In this regard, both rare disease-causing mutations and common disease-susceptible variants, in the Bcl-2-associated athanogene 3 (BAG3) gene have been reported, highlighting the critical role of BAG3 in cardiomyocytes and in the development of dilated cardiomyopathy. The phenotypic effects of the BAG3 mutations help investigators understand the structure and function of the BAG3 gene. Indeed, we report herein that all of the known pathogenic/likely pathogenic variants affect at least 1 of 3 protein functional domains, ie, the WW domain, the second IPV (Ile-Pro-Val) domain, or the BAG domain, whereas none of the missense nontruncating pathogenic/likely pathogenic variants affect the proline-rich repeat (PXXP) domain. A common variant, p.Cys151Arg, associated with reduced susceptibility to dilated cardiomyopathy demonstrated a significant difference in allele frequencies among diverse human populations, suggesting evolutionary selective pressure. As BAG3-related therapies for heart failure move from the laboratory to the clinic, the ability to provide precision medicine will depend in large part on having a thorough understanding of the potential effects of both common and uncommon genetic variants on these target proteins. The current review article provides a roadmap that investigators can utilize to determine the potential interactions between a patient's genotype, their phenotype, and their response to therapeutic interventions with both gene delivery and small molecules.

Cardio-Oncology in Childhood: State of the Art

PURPOSE OF REVIEW

Cardio-oncology is an increasingly important field of cardiology that focuses on the detection, monitoring, and treatment of cardiovascular disease (CVD) occurring during and after oncological treatments. The survival rate for childhood cancer patients has dramatically increased thanks to new treatment protocols and cardiovascular (CV) sequelae represent the third most frequent cause of mortality in surviving patients. This study aims to provide a complete and updated review of all the main aspects of cardio-oncology in childhood and to highlight the critical issues.

RECENT FINDINGS

The problem of CV complications in childhood cancer survivors raises the need to make an early diagnosis of cardiotoxicity by the new imaging and laboratory techniques in order to intervene promptly and to implement pharmacological strategies and lifestyle changes to reduce or even to prevent cardiac injury. Furthermore, a stratification of CV risk, also including new predisposing factors such as the presence of some genetic mutations, is of paramount importance before undertaking oncological treatments. Besides, a systematic and personalized planning of long-term follow-up is fundamental to ensure a transition from pediatric to adult hospital and to avoid missed or late diagnosis of cardiomyopathy. We reviewed the main risk factors for cardiotoxicity in children, both traditional and emerging ones: the mechanisms of toxicity of both old and new antineoplastic therapies, the techniques for detecting cardiac damage, and the current evidence regarding pharmacological cardioprotection. At the end, we focused our attention on the existing guidelines and strategies about the long-term follow-up of childhood cancer survivors.

Identification of a Novel de Novo Variant in the CASZ1 Causing a Rare Type of Dilated Cardiomyopathy

A new de novo frameshift variant has been identified in the CASZ1 gene leading to severe dilated cardiomyopathy. Methods: The proband was analyzed with WES NGS, post-mortem, using dried blood spots on filters. The variant was verified with Sanger sequencing for the proband and her parents. Results: We reported a proband with a new de novo frameshift mutation, c.3781del (p.(Trp1261GlyfsTer29)), in the CASZ1 gene. The clinical presentation was similar to the severe phenotype described in previous studies. Conclusions: In this study, we described a new case with a frameshift mutation in CASZ1 causing a severe phenotype of dilated cardiomyopathy.

Next-Generation Sequencing Gene Panels in Inheritable Cardiomyopathies and Channelopathies: Prevalence of Pathogenic Variants and Variants of Unknown Significance in Uncommon Genes

The diffusion of next-generation sequencing (NGS)-based approaches allows for the identification of pathogenic mutations of cardiomyopathies and channelopathies in more than 200 different genes. Since genes considered uncommon for a clinical phenotype are also now included in molecular testing, the detection rate of disease-causing variants has increased. Here, we report the prevalence of genetic variants detected by using a NGS custom panel in a cohort of 133 patients with inherited cardiomyopathies (n = 77) or channelopathies (n = 56). We identified 82 variants, of which 50 (61%) were identified in genes without a strong or definitive evidence of disease association according to the NIH-funded Clinical Genome Resource (ClinGen; "uncommon genes"). Among these, 35 (70%) were variants of unknown significance (VUSs), 13 (26%) were pathogenic (P) or likely pathogenic (LP) mutations, and 2 (4%) benign (B) or likely benign (LB) variants according to American College of Medical Genetics (ACMG) classifications. These data reinforce the need for the screening of uncommon genes in order to increase the diagnostic sensitivity of the genetic testing of inherited cardiomyopathies and channelopathies by allowing for the identification of mutations in genes that are not usually explored due to a currently poor association with the clinical phenotype.

Macrophage, a potential targeted therapeutic immune cell for cardiomyopathy

Cardiomyopathy is a major cause of heart failure, leading to systolic and diastolic dysfunction and promoting adverse cardiac remodeling. Macrophages, as key immune cells of the heart, play a crucial role in inflammation and fibrosis. Moreover, exogenous and cardiac resident macrophages are functionally and phenotypically different during cardiac injury. Although experimental evidence has shown that macrophage-targeted therapy is promising in cardiomyopathy, clinical translation remains challenging. In this article, the molecular mechanism of macrophages in cardiomyopathy has been discussed in detail based on existing literature. The issues and considerations of clinical treatment strategies for myocardial fibrosis has also been analyzed.

AAV-mediated gene therapy: Advancing cardiovascular disease treatment

Gene therapy has revolutionized the field of medicine, offering new hope for those with common and rare diseases. For nearly three decades, adeno-associated virus (AAV) has shown significant therapeutic benefits in multiple clinical trials, mainly due to its unique replication defects and non-pathogenicity in humans. In the field of cardiovascular disease (CVD), compared with non-viral vectors, lentiviruses, poxviruses, and adenovirus vectors, AAV possesses several advantages, including high security, low immunogenicity, sustainable and stable exogenous gene expression etc., which makes AAV one of the most promising candidates for the treatment of many genetic disorders and hereditary diseases. In this review, we evaluate the current information on the immune responses, transport pathways, and mechanisms of action associated with AAV-based CVD gene therapies and further explore potential optimization strategies to improve the efficiency of AAV transduction for the improved safety and efficiency of CVD treatment. In conclusion, AAV-mediated gene therapy has great potential for development in the cardiovascular system.

Identification of key genes for hypertrophic cardiomyopathy using integrated network analysis of differential lncRNA and gene expression

Objective

Hypertrophic cardiomyopathy (HCM) is a complex heterogeneous heart disease. Recent reports found that long non-coding RNAs (lncRNAs) play an important role in the progression of cardiovascular diseases. The present study aimed to identify the novel lncRNAs and messenger RNAs (mRNAs) and determine the key pathways involved in HCM.

Methods

The lncRNA and mRNA sequencing datasets of GSE68316 and GSE130036 were downloaded from the Gene Expression Omnibus (GEO) database. An integrated co-expression network analysis was conducted to identify differentially expressed lncRNAs and differentially expressed mRNAs in patients with HCM. Then, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were explored to identify the biological functions and signaling pathways of the co-expression network. Protein–protein interaction (PPI) and hub gene networks were constructed by using Cytoscape software. Plasma samples of patients with HCM and the GSE89714 dataset were used to validate the bioinformatics results.

Results

A total of 1,426 differentially expressed long non-coding RNAs (lncRNAs) and 1,715 differentially expressed mRNAs were obtained from GSE68316, of which 965 lncRNAs and 896 mRNAs were upregulated and 461 lncRNAs and 819 mRNAs were downregulated. A total of 469 differentially expressed lncRNAs and 2,407 differentially expressed mRNAs were screened from GSE130036, of which 183 lncRNAs and 1,283 mRNAs were upregulated and 286 lncRNAs and 1,124 mRNAs were downregulated. A co-expression network was constructed and contained 30 differentially expressed lncRNAs and 63 differentially expressed mRNAs, which were primarily involved in ‘G-protein beta/gamma-subunit complex binding,' ‘polyubiquitin modification-dependent protein binding,' ‘Apelin signaling pathway,' and ‘Wnt signaling pathway.' The 10 hub genes in the upregulated network [G Protein Subunit Alpha I2 (GNAI2), G Protein Subunit Alpha I1 (GNAI1), G Protein Subunit Alpha I3 (GNAI3), G Protein Subunit Gamma 2 (GNG2), G Protein Subunit Beta 1 (GNB1), G Protein Subunit Gamma 13 (GNG13), G Protein Subunit Gamma Transducin 1 (GNGT1), G Protein Subunit Gamma 12 (GNG12), AKT Serine/Threonine Kinase 1 (AKT1) and GNAS Complex Locus (GNAS)] and the 10 hub genes in the downregulated network [Nucleotide-Binding Oligomerization Domain Containing Protein 2 (NOD2), Receptor-Interacting Serine/Threonine Kinase 2 (RIPK2), Nucleotide-Binding Oligomerization Domain Containing Protein 1 (NOD1), Mitochondrial Antiviral Signaling Protein (MAVS), Autophagy Related 16-Like 1 (ATG16L1), Interferon Induced With Helicase C Domain 1 (IFIH1), Autophagy Related 5 (ATG5), TANK-Binding Kinase 1 (TBK1), Caspase Recruitment Domain Family Member 9 (CARD9), and von Willebrand factor (VWF)] were screened using cytoHubba. The expression of LA16c-312E8.2 and RP5-1160K1.3 in the plasma of patients with HCM was elevated, and the expression of the MIR22 host gene (MIR22HG) was decreased, which was consistent with our analysis, while the expression of LINC00324 and Small Nucleolar RNA Host Gene 12 (SNHG12) was not significantly different between the two groups. Verification analyses performed on GSE89714 showed the upregulated mRNAs of Chloride Voltage-Gated Channel 7 (CLCN7), N-Acetylglucosamine-1-Phosphate Transferase Subunit Gamma (GNPTG), Unk Like Zinc Finger (UNKL), Adenosine Monophosphate Deaminase 2 (AMPD2), GNAI3, WD Repeat Domain 81 (WDR81), and Serpin Family F Member 1 (SERPINF1) and downregulated mRNAs of TATA-Box Binding Protein Associated Factor 12 (TAF12) co-expressed with five crucial lncRNAs. Moreover, GNAI2, GNAI3, GNG12, and vWF were upregulated and GNAS was downregulated in the top 10 hub genes of upregulated and downregulated PPI networks.

Conclusion

These findings from integrative biological analysis of lncRNA-mRNA co-expression networks explored the key genes and pathways and provide new insights into the understanding of the mechanism and discovering new therapeutic targets for HCM. Three differentially expressed pivotal lncRNAs (LA16c-312E8.2, RP5-1160K1.3, and MIR22HG) in the co-expression network may serve as biomarkers and intervention targets for the diagnosis and treatment of HCM.

Evaluation of Exercise Tolerance in Non-obstructive Hypertrophic Cardiomyopathy With Myocardial Work and Peak Strain Dispersion by Speckle-Tracking Echocardiography

Background

The aim of this study was to evaluate exercise tolerance in non-obstructive hypertrophic cardiomyopathy (HCM) by investigating the value of myocardial work (MW) combined with strain peak dispersion.

Methods

A total of 65 patients with non-obstructive HCM and normal left ventricular ejection fraction were enrolled and 60 healthy subjects were selected as controls. The automated function imaging (AFI)-two-dimensional ultrasonic speckle-tracking technology was used to obtain the values for peak global longitudinal strain (GLS), longitudinal strain peak time dispersion (PSD), 18-segment systolic longitudinal peak strain (LPS), 18-segment longitudinal strain peak time (TTPLS), global waste work (GWW), global constructive work (GCW), global work index (GWI), global work efficiency (GWE), and exercise metabolic equivalents (METS).

Results

(1) Values for LV-GLS (−17.77 ± 0.20 vs. −21.66 ± 0.42%) were lower and PSD (95.10 ± 8.15 vs. 28.97 ± 1.50 ms) was prolonged in patients with HCM (p &lt; 0.01). (2) An increasing trend was shown in the basal segment &lt; intermediate segment &lt; apical segment for both patients with HCM and controls, although each segment had lower values in the HCM group. (3) TTPLS was prolonged in the HCM group (p &lt; 0.01). (4) GWE, GWI, and GCW were all lower (p &lt; 0.01) and GWW was higher in patients with HCM (p &lt; 0.01). (5) Values of GWE were less than 92.5%, GWI less than 1,200 mmHg, GCW less than 1,399 mmHg, these abnormal values are helpful for the diagnosis of impaired exercise tolerance and poor prognosis (6) The METS and LV-GLS of HCM in the asymmetric group were significantly lower than that in AHCM group, but the PSD was significantly greater than that in the AHCM group. Values of LPS-BL (−13.13% ± 2.51% vs −10.17% ± 2.20%) in the apical HCM group were better than in the asymmetric HCM group (p &lt; 0.05).

Conclusion

GCW, GWI, and GWE can be safely measured by resting echocardiography to evaluate exercise tolerance in patients with HCM who cannot perform an exercise-based examination. Such measurements provide a basis for clinical decisions regarding exercise and drug prescription.

Construction of Prediction Model for Atrial Fibrillation with Valvular Heart Disease Based on Machine Learning

Background

Valvular heart disease (VHD) is a major precipitating factor of atrial fibrillation (AF) that contributes to decreased cardiac function, heart failure, and stroke. Stroke induced by VHD combined with atrial fibrillation (AF-VHD) is a much more serious condition in comparison to VHD alone. The aim of this study was to explore the molecular mechanism governing VHD progression and to provide candidate treatment targets for AF-VHD.

Methods

Four public mRNA microarray datasets were downloaded and differentially expressed genes (DEGs) screening was performed. Weighted gene correlation network analysis was carried out to detect key modules and explore their relationships and disease status. Candidate hub signature genes were then screened within the key module using machine learning methods. The receiver operating characteristic curve and nomogram model analysis were used to determine the potential clinical significance of the hub genes. Subsequently, target gene protein levels in independent human atrial tissue samples were detected using western blotting. Specific expression analysis of the hub genes in the tissue and cell samples was performed using single-cell sequencing analysis in the Human Protein Atlas tool.

Results

A total of 819 common DEGs in combined datasets were screened. Fourteen modules were identified using the cut tree dynamic function. The cyan and purple modules were considered the most clinically significant for AF-VHD. Then, 25 hub genes in the cyan and purple modules were selected for further analysis. The pathways related to dilated cardiomyopathy, hypertrophic cardiomyopathy, and heart contraction were concentrated in the purple and cyan modules of the AF-VHD. Genes of importance (CSRP3, MCOLN3, SLC25A5, and FIBP) were then identified based on machine learning. Of these, CSRP3 had a potential clinical significance and was specifically expressed in the heart tissue.

Conclusions

The identified genes may play critical roles in the pathophysiological process of AF-VHD, providing new insights into VHD development to AF and helping to determine potential biomarkers and therapeutic targets for treating AF-VHD.

Myosin Heavy Chain Converter Domain Mutations Drive Early-Stage Changes in Extracellular Matrix Dynamics in Hypertrophic Cardiomyopathy

More than 60% of hypertrophic cardiomyopathy (HCM)-causing mutations are found in the gene loci encoding cardiac myosin-associated proteins including myosin heavy chain (MHC) and myosin binding protein C (MyBP-C). Moreover, patients with more than one independent HCM mutation may be at increased risk for more severe disease expression and adverse outcomes. However detailed mechanistic understanding, especially at early stages of disease progression, is limited. To identify early-stage HCM triggers, we generated single (MYH7 c.2167C > T [R723C] with a known pathogenic significance in the MHC converter domain) and double (MYH7 c.2167C > T [R723C]; MYH6 c.2173C > T [R725C] with unknown significance) myosin gene mutations in human induced pluripotent stem cells (hiPSCs) using a base-editing strategy. Cardiomyocytes (CMs) derived from hiPSCs with either single or double mutation exhibited phenotypic characteristics consistent with later-stage HCM including hypertrophy, multinucleation, altered calcium handling, metabolism, and arrhythmia. We then probed mutant CMs at time points prior to the detection of known HCM characteristics. We found MYH7/MYH6 dual mutation dysregulated extracellular matrix (ECM) remodeling, altered integrin expression, and interrupted cell-ECM adhesion by limiting the formation of focal adhesions. These results point to a new phenotypic feature of early-stage HCM and reveal novel therapeutic avenues aimed to delay or prohibit disease onset.

Adult-Onset Sandhoff Disease in a Filipino Patient: Asymmetric Weakness, Whole HEXB Gene Deletion, and Coexisting MYH7 Pathogenic Variant

Objective

To describe a Filipino patient with adult-onset Sandhoff disease manifesting with an atypical asymmetric lower motor neuron syndrome due to a novel whole HEXB deletion in trans with a pathogenic missense variant and with a coexisting MYH7 pathogenic variant.

Methods

We performed clinical, laboratory, myopathologic, and genetic evaluation with next-generation sequencing in the proband and targeted mutational analysis in an asymptomatic sibling.

Results

A 59-year-old Filipino woman presented with 15 years of slowly progressive, asymmetric, proximal-predominant, lower greater than upper extremity weakness, mildly elevated creatine kinase, and generalized cerebellar atrophy. Serum total β-hexosaminidase was significantly reduced, and hexosaminidase A percentage was increased. We identified a novel HEXB whole gene deletion in compound heterozygosity with a pathogenic missense variant (c.1513C>T, p.Arg505Trp) previously described in 1 patient with adult-onset Sandhoff disease. The patient, with a family history of cardiomyopathy, has a coexisting MYH7 pathogenic variant (c.3134G>A, p.Arg1045His), causative of cardiomyopathy but without cardiac involvement, likely due to variable penetrance. Myopathic features were absent from skeletal muscle biopsy.

Discussion

This patient expands the genotypic, phenotypic, and ethnic spectrum of Sandhoff disease and highlights challenges generated by low-penetrant pathogenic variants, especially when considering a potentially polygenic phenotype.