Precision Medicine in the Management of Dilated Cardiomyopathy

Genetic testing in cardiovascular disease

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality globally and is responsible for an estimated one-third of deaths as well as significant morbidity and health care utilisation. Technological and bioinformatic advances have facilitated the discovery of pathogenic germline variants for some specific CVDs, including familial hypercholesterolaemia, cardiomyopathies and arrhythmic syndromes. Use of these genetic tests for earlier disease identification is increasing due, in part, to decreasing costs, Medicare rebates, and consumer comfort with genetic testing. However, CVDs that occur more commonly, including coronary artery disease and atrial fibrillation, do not display monogenic inheritance patterns. Genetically, these diseases have generally been associated with many genetic variants each with a small effect size. This complexity can be expressed mathematically as a polygenic risk score. Genetic testing kits that provide polygenic risk scoring are becoming increasingly available directly to private-paying consumers outside the traditional clinical setting. An improved understanding of the evidence of genetics in CVD will offer clinicians new opportunities for individualised risk prediction and preventive therapy.

Emerging Concepts of Mechanisms Controlling Cardiac Tension: Focus on Familial Dilated Cardiomyopathy (DCM) and Sarcomere-Directed Therapies

Novel therapies for the treatment of familial dilated cardiomyopathy (DCM) are lacking. Shaping research directions to clinical needs is critical. Triggers for the progression of the disorder commonly occur due to specific gene variants that affect the production of sarcomeric/cytoskeletal proteins. Generally, these variants cause a decrease in tension by the myofilaments, resulting in signaling abnormalities within the micro-environment, which over time result in structural and functional maladaptations, leading to heart failure (HF). Current concepts support the hypothesis that the mutant sarcomere proteins induce a causal depression in the tension-time integral (TTI) of linear preparations of cardiac muscle. However, molecular mechanisms underlying tension generation particularly concerning mutant proteins and their impact on sarcomere molecular signaling are currently controversial. Thus, there is a need for clarification as to how mutant proteins affect sarcomere molecular signaling in the etiology and progression of DCM. A main topic in this controversy is the control of the number of tension-generating myosin heads reacting with the thin filament. One line of investigation proposes that this number is determined by changes in the ratio of myosin heads in a sequestered super-relaxed state (SRX) or in a disordered relaxed state (DRX) poised for force generation upon the Ca2+ activation of the thin filament. Contrasting evidence from nanometer-micrometer-scale X-ray diffraction in intact trabeculae indicates that the SRX/DRX states may have a lesser role. Instead, the proposal is that myosin heads are in a basal OFF state in relaxation then transfer to an ON state through a mechano-sensing mechanism induced during early thin filament activation and increasing thick filament strain. Recent evidence about the modulation of these mechanisms by protein phosphorylation has also introduced a need for reconsidering the control of tension. We discuss these mechanisms that lead to different ideas related to how tension is disturbed by levels of mutant sarcomere proteins linked to the expression of gene variants in the complex landscape of DCM. Resolving the various mechanisms and incorporating them into a unified concept is crucial for gaining a comprehensive understanding of DCM. This deeper understanding is not only important for diagnosis and treatment strategies with small molecules, but also for understanding the reciprocal signaling processes that occur between cardiac myocytes and their micro-environment. By unraveling these complexities, we can pave the way for improved therapeutic interventions for managing DCM.

Penetrance of Dilated Cardiomyopathy in Genotype-Positive Relatives

BACKGROUND

Disease penetrance in genotype-positive (G+) relatives of families with dilated cardiomyopathy (DCM) and the characteristics associated with DCM onset in these individuals are unknown.

OBJECTIVES

This study sought to determine the penetrance of new DCM diagnosis in G+ relatives and to identify factors associated with DCM development.

METHODS

The authors evaluated 779 G+ patients (age 35.8 ± 17.3 years; 459 [59%] females; 367 [47%] with variants in TTN) without DCM followed at 25 Spanish centers.

RESULTS

After a median follow-up of 37.1 months (Q1-Q3: 16.3-63.8 months), 85 individuals (10.9%) developed DCM (incidence rate of 2.9 per 100 person-years; 95% CI: 2.3-3.5 per 100 person-years). DCM penetrance and age at DCM onset was different according to underlying gene group (log-rank P = 0.015 and P <0.01, respectively). In a multivariable model excluding CMR parameters, independent predictors of DCM development were: older age (HR per 1-year increase: 1.02; 95% CI: 1.0-1.04), an abnormal electrocardiogram (HR: 2.13; 95% CI: 1.38-3.29); presence of variants in motor sarcomeric genes (HR: 1.92; 95% CI: 1.05-3.50); lower left ventricular ejection fraction (HR per 1% increase: 0.86; 95% CI: 0.82-0.90) and larger left ventricular end-diastolic diameter (HR per 1-mm increase: 1.10; 95% CI: 1.06-1.13). Multivariable analysis in individuals with cardiac magnetic resonance and late gadolinium enhancement assessment (n = 360, 45%) identified late gadolinium enhancement as an additional independent predictor of DCM development (HR: 2.52; 95% CI: 1.43-4.45).

CONCLUSIONS

Following a first negative screening, approximately 11% of G+ relatives developed DCM during a median follow-up of 3 years. Older age, an abnormal electrocardiogram, lower left ventricular ejection fraction, increased left ventricular end-diastolic diameter, motor sarcomeric genetic variants, and late gadolinium enhancement are associated with a higher risk of developing DCM.

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.

Neuromuscular and cardiovascular phenotypes in paediatric titinopathies: a multisite retrospective study

BACKGROUND

Pathogenic variants in TTN cause a spectrum of autosomal dominant and recessive cardiovascular, skeletal muscle and cardioskeletal disease with symptom onset across the lifespan. The aim of this study was to characterise the genotypes and phenotypes in a cohort of TTN+paediatric patients.

METHODS

Retrospective chart review was performed at four academic medical centres. Patients with pathogenic or truncating variant(s) in TTN and paediatric-onset cardiovascular and/or neuromuscular disease were eligible.

RESULTS

31 patients from 29 families were included. Seventeen patients had skeletal muscle disease, often with proximal weakness and joint contractures, with average symptom onset of 2.2 years. Creatine kinase levels were normal or mildly elevated; electrodiagnostic studies (9/11) and muscle biopsies (11/11) were myopathic. Variants were most commonly identified in the A-band (14/32) or I-band (13/32). Most variants were predicted to be frameshift truncating, nonsense or splice-site (25/32). Seventeen patients had cardiovascular disease (14 isolated cardiovascular, three cardioskeletal) with average symptom onset of 12.9 years. Twelve had dilated cardiomyopathy (four undergoing heart transplant), two presented with ventricular fibrillation arrest, one had restrictive cardiomyopathy and two had other types of arrhythmias. Variants commonly localised to the A-band (8/15) or I-band (6/15) and were predominately frameshift truncating, nonsense or splice-site (14/15).

CONCLUSION

Our cohort demonstrates the genotype-phenotype spectrum of paediatric-onset titinopathies identified in clinical practice and highlights the risk of life-threatening cardiovascular complications. We show the difficulties of obtaining a molecular diagnosis, particularly in neuromuscular patients, and bring awareness to the complexities of genetic counselling in this population.

Breaking genetic shackles: The advance of base editing in genetic disorder treatment

The rapid evolution of gene editing technology has markedly improved the outlook for treating genetic diseases. Base editing, recognized as an exceptionally precise genetic modification tool, is emerging as a focus in the realm of genetic disease therapy. We provide a comprehensive overview of the fundamental principles and delivery methods of cytosine base editors (CBE), adenine base editors (ABE), and RNA base editors, with a particular focus on their applications and recent research advances in the treatment of genetic diseases. We have also explored the potential challenges faced by base editing technology in treatment, including aspects such as targeting specificity, safety, and efficacy, and have enumerated a series of possible solutions to propel the clinical translation of base editing technology. In conclusion, this article not only underscores the present state of base editing technology but also envisions its tremendous potential in the future, providing a novel perspective on the treatment of genetic diseases. It underscores the vast potential of base editing technology in the realm of genetic medicine, providing support for the progression of gene medicine and the development of innovative approaches to genetic disease therapy.

Natural History of Dilated Cardiomyopathy Due to c.77T>C (p.Val26Ala) in Emerin Protein

(1) Introduction: Dilated cardiomyopathy (DCM) mainly affects young individuals and is the main indication of heart transplantation. The variant c.77T>C (p.Val26Ala) of the gene coding for emerin (EMD) in chromosome Xq28 has been catalogued as a pathogenic variant for the development of DCM, exhibiting an X-linked inheritance pattern. (2) Methods: A retrospective study was conducted covering the period 2015-2023 in patients with DCM of genetic origin. The primary endpoint was patient age at onset of the first composite major cardiac event, in the form of a first episode of heart failure, malignant ventricular arrhythmia, or end-stage heart failure, according to the presence of truncating variant in titin gene (TTNtv) versus the p.Val26Ala mutation in the EMD protein. (3) Results: A total of 31 and 22 patients were included in the EMD group and TTNtv group, respectively. The primary endpoint was significantly higher in the EMD group, with a hazard ratio of 4.16 (95% confidence interval: 1.83-9.46; p = 0.001). At 55 years of age, all the patients in the EMD group had already presented heart failure, nine presented malignant ventricular arrhythmia (29%), and 13 required heart transplantation (42%). (4) Conclusions: DCM secondary to the c.77T>C (p.Val26Ala) mutation in the EMD gene is associated to an increased risk of major cardiac events compared to patients with DCM due to TTNtv, with a large proportion of transplanted patients in the fifth decade of life.

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.

Titin domains with reduced core hydrophobicity cause dilated cardiomyopathy

The underlying genetic defect in most cases of dilated cardiomyopathy (DCM), a common inherited heart disease, remains unknown. Intriguingly, many patients carry single missense variants of uncertain pathogenicity targeting the giant protein titin, a fundamental sarcomere component. To explore the deleterious potential of these variants, we first solved the wild-type and mutant crystal structures of I21, the titin domain targeted by pathogenic variant p.C3575S. Although both structures are remarkably similar, the reduced hydrophobicity of deeply buried position 3575 strongly destabilizes the mutant domain, a scenario supported by molecular dynamics simulations and by biochemical assays that show no disulfide involving C3575. Prompted by these observations, we have found that thousands of similar hydrophobicity-reducing variants associate specifically with DCM. Hence, our results imply that titin domain destabilization causes DCM, a conceptual framework that not only informs pathogenicity assessment of gene variants but also points to therapeutic strategies counterbalancing protein destabilization.

Your Heart Function Has Normalized-What Next After TRED-HF?

PURPOSE OF REVIEW

With the widespread implementation of contemporary disease-modifying heart failure therapy, the rates of normalization of ejection fraction are continuously increasing. The TRED-HF trial confirmed that heart failure remission rather than complete recovery is typical in patients with dilated cardiomyopathy who respond to therapy. The present review outlines key points related to the management and knowledge gaps of this growing patient group, focusing on patients with non-ischaemic dilated cardiomyopathy.

RECENT FINDINGS

There is substantial heterogeneity among patients with normalized ejection fraction. The specific etiology is likely to affect the outcome, although a multiple-hit phenotype is frequent and may not be identified without comprehensive characterization. A monogenic or polygenic genetic susceptibility is common. Ongoing pathophysiological processes may be unraveled with advanced cardiac imaging, biomarkers, multi-omics, and machine learning technologies. There are limited studies that have investigated the withdrawal of specific heart failure therapies in these patients. Diuretics may be safely withdrawn if there is no evidence of congestion, while continued therapy with at least some disease-modifying therapy is likely to be required to reduce myocardial workload and sustain remission for the vast majority. Understanding the underlying disease mechanisms of patients with normalized ejection fraction is crucial in identifying markers of myocardial relapse and guiding individualized therapy in the future. Ongoing clinical trials should inform personalized approaches to therapy.

Insulin-like growth factor binding protein 2: a core biomarker of left ventricular dysfunction in dilated cardiomyopathy

BACKGROUND

RNA modifications, especially N6-methyladenosine, N1-methyladenosine and 5-methylcytosine, play an important role in the progression of cardiovascular disease. However, its regulatory function in dilated cardiomyopathy (DCM) remains to be undefined.

METHODS

In the study, key RNA modification regulators (RMRs) were screened by three machine learning models. Subsequently, a risk prediction model for DCM was developed and validated based on these important genes, and the diagnostic efficiency of these genes was assessed. Meanwhile, the relevance of these genes to clinical traits was explored. In both animal models and human subjects, the gene with the strongest connection was confirmed. The expression patterns of important genes were investigated using single-cell analysis.

RESULTS

A total of 4 key RMRs were identified. The risk prediction models were constructed basing on these genes which showed a good accuracy and sensitivity in both the training and test set. Correlation analysis showed that insulin-like growth factor binding protein 2 (IGFBP2) had the highest correlation with left ventricular ejection fraction (LVEF) (R = -0.49, P = 0.00039). Further validation expression level of IGFBP2 indicated that this gene was significantly upregulated in DCM animal models and patients, and correlation analysis validation showed a significant negative correlation between IGFBP2 and LVEF (R = -0.87; P = 6*10-5). Single-cell analysis revealed that this gene was mainly expressed in endothelial cells.

CONCLUSION

In conclusion, IGFBP2 is an important biomarker of left ventricular dysfunction in DCM. Future clinical applications could possibly use it as a possible therapeutic target.

Genetic Contribution to End-Stage Cardiomyopathy Requiring Heart Transplantation

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

The Genetic Evaluation of Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is a common cause of heart failure and is the primary indication for heart transplantation. A genetic etiology can be found in 20-35% of patients with DCM, especially in those with a family history of cardiomyopathy or sudden cardiac death at an early age. With advancements in genome sequencing, the understanding of genotype-phenotype relationships in DCM has expanded with over 60 genes implicated in the disease. Subsequently, these findings have increased adoption of genetic testing in the management of DCM, which has allowed for improved risk stratification and identification of at risk family members. In this review, we discuss the genetic evaluation of DCM with a focus on practical genetic testing considerations, genotype-phenotype associations, and insights into upcoming personalized therapies.

RYR2-ryanodinopathies: from calcium overload to calcium deficiency

The sarcoplasmatic reticulum (SR) cardiac ryanodine receptor/calcium release channel RyR2 is an essential regulator of cardiac excitation-contraction coupling and intracellular calcium homeostasis. Mutations of the RYR2 are the cause of rare, potentially lethal inherited arrhythmia disorders. Catecholaminergic polymorphic ventricular tachycardia (CPVT) was first described more than 20 years ago and is the most common and most extensively studied cardiac ryanodinopathy. Over time, other distinct inherited arrhythmia syndromes have been related to abnormal RyR2 function. In addition to CPVT, there are at least two other distinct RYR2-ryanodinopathies that differ mechanistically and phenotypically from CPVT: RYR2 exon-3 deletion syndrome and the recently identified calcium release deficiency syndrome (CRDS). The pathophysiology of the different cardiac ryanodinopathies is characterized by complex mechanisms resulting in excessive spontaneous SR calcium release or SR calcium release deficiency. While the vast majority of CPVT cases are related to gain-of-function variants of the RyR2 protein, the recently identified CRDS is linked to RyR2 loss-of-function variants. The increasing number of these cardiac 'ryanodinopathies' reflects the complexity of RYR2-related cardiogenetic disorders and represents an ongoing challenge for clinicians. This state-of-the-art review summarizes our contemporary understanding of RYR2-related inherited arrhythmia disorders and provides a systematic and comprehensive description of the distinct cardiac ryanodinopathies discussing clinical aspects and molecular insights. Accurate identification of the underlying type of cardiac ryanodinopathy is essential for the clinical management of affected patients and their families.

Transcriptome studies of inherited dilated cardiomyopathies

Dilated cardiomyopathy (DCM) is a group of heart muscle diseases that often lead to heart failure, with more than 50 causative genes have being linked to DCM. The heterogenous nature of the inherited DCMs suggest the need of precision medicine. Consistent with this emerging concept, transcriptome studies in human patients with DCM indicated distinct molecular signature for DCMs of different genetic etiology. To facilitate this line of research, we reviewed the status of transcriptome studies of inherited DCMs by focusing on three predominant DCM causative genes, TTN, LMNA, and BAG3. Besides studies in human patients, we summarized transcriptomic analysis of these inherited DCMs in a variety of model systems ranging from iPSCs to rodents and zebrafish. We concluded that the RNA-seq technology is a powerful genomic tool that has already led to the discovery of new modifying genes, signaling pathways, and related therapeutic avenues. We also pointed out that both temporal (different pathological stages) and spatial (different cell types) information need to be considered for future transcriptome studies. While an important bottle neck is the low throughput in experimentally testing differentially expressed genes, new technologies in efficient animal models such as zebrafish starts to be developed. It is anticipated that the RNA-seq technology will continue to uncover both unique and common pathological events, aiding the development of precision medicine for inherited DCMs.

Role of non-coding variants in cardiovascular disease

Cardiovascular diseases (CVDs) constitute one of the significant causes of death worldwide. Different pathological states are linked to CVDs, which despite interventions and treatments, still have poor prognoses. The genetic component, as a beneficial tool in the risk stratification of CVD development, plays a role in the pathogenesis of this group of diseases. The emergence of genome-wide association studies (GWAS) have led to the identification of non-coding parts associated with cardiovascular traits and disorders. Variants located in functional non-coding regions, including promoters/enhancers, introns, miRNAs and 5'/3' UTRs, account for 90% of all identified single-nucleotide polymorphisms associated with CVDs. Here, for the first time, we conducted a comprehensive review on the reported non-coding variants for different CVDs, including hypercholesterolemia, cardiomyopathies, congenital heart diseases, thoracic aortic aneurysms/dissections and coronary artery diseases. Additionally, we present the most commonly reported genes involved in each CVD. In total, 1469 non-coding variants constitute most reports on familial hypercholesterolemia, hypertrophic cardiomyopathy and dilated cardiomyopathy. The application and identification of non-coding variants are beneficial for the genetic diagnosis and better therapeutic management of CVDs.

Integrated genomic analysis defines molecular subgroups in dilated cardiomyopathy and identifies novel biomarkers based on machine learning methods

Aim: As the most common cardiomyopathy, dilated cardiomyopathy (DCM) often leads to progressive heart failure and sudden cardiac death. This study was designed to investigate the molecular subgroups of DCM. Methods: Three datasets of DCM were downloaded from GEO database (GSE17800, GSE79962 and GSE3585). After log2-transformation and background correction with "limma" package in R software, the three datasets were merged into a metadata cohort. The consensus clustering was conducted by the "Consensus Cluster Plus" package to uncover the molecular subgroups of DCM. Moreover, clinical characteristics of different molecular subgroups were compared in detail. We also adopted Weighted gene co-expression network analysis (WGCNA) analysis based on subgroup-specific signatures of gene expression profiles to further explore the specific gene modules of each molecular subgroup and its biological function. Two machine learning methods of LASSO regression algorithm and SVM-RFE algorithm was used to screen out the genetic biomarkers, of which the discriminative ability of molecular subgroups was evaluated by receiver operating characteristic (ROC) curve. Results: Based on the gene expression profiles, heart tissue samples from patients with DCM were clustered into three molecular subgroups. No statistical difference was found in age, body mass index (BMI) and left ventricular internal diameter at end-diastole (LVIDD) among three molecular subgroups. However, the results of left ventricular ejection fraction (LVEF) statistics showed that patients from subgroup 2 had a worse condition than the other group. We found that some of the gene modules (pink, black and grey) in WGCNA analysis were significantly related to cardiac function, and each molecular subgroup had its specific gene modules functions in modulating occurrence and progression of DCM. LASSO regression algorithm and SVM-RFE algorithm was used to further screen out genetic biomarkers of molecular subgroup 2, including TCEAL4, ISG15, RWDD1, ALG5, MRPL20, JTB and LITAF. The results of ROC curves showed that all of the genetic biomarkers had favorable discriminative effectiveness. Conclusion: Patients from different molecular subgroups have their unique gene expression patterns and different clinical characteristics. More personalized treatment under the guidance of gene expression patterns should be realized.

Natural History of MYH7-Related Dilated Cardiomyopathy

BACKGROUND

Variants in myosin heavy chain 7 (MYH7) are responsible for disease in 1% to 5% of patients with dilated cardiomyopathy (DCM); however, the clinical characteristics and natural history of MYH7-related DCM are poorly described.

OBJECTIVES

We sought to determine the phenotype and prognosis of MYH7-related DCM. We also evaluated the influence of variant location on phenotypic expression.

METHODS

We studied clinical data from 147 individuals with DCM-causing MYH7 variants (47.6% female; 35.6 ± 19.2 years) recruited from 29 international centers.

RESULTS

At initial evaluation, 106 (72.1%) patients had DCM (left ventricular ejection fraction: 34.5% ± 11.7%). Median follow-up was 4.5 years (IQR: 1.7-8.0 years), and 23.7% of carriers who were initially phenotype-negative developed DCM. Phenotypic expression by 40 and 60 years was 46% and 88%, respectively, with 18 patients (16%) first diagnosed at <18 years of age. Thirty-six percent of patients with DCM met imaging criteria for LV noncompaction. During follow-up, 28% showed left ventricular reverse remodeling. Incidence of adverse cardiac events among patients with DCM at 5 years was 11.6%, with 5 (4.6%) deaths caused by end-stage heart failure (ESHF) and 5 patients (4.6%) requiring heart transplantation. The major ventricular arrhythmia rate was low (1.0% and 2.1% at 5 years in patients with DCM and in those with LVEF of ≤35%, respectively). ESHF and major ventricular arrhythmia were significantly lower compared with LMNA-related DCM and similar to DCM caused by TTN truncating variants.

CONCLUSIONS

MYH7-related DCM is characterized by early age of onset, high phenotypic expression, low left ventricular reverse remodeling, and frequent progression to ESHF. Heart failure complications predominate over ventricular arrhythmias, which are rare.

Clinical Risk Score to Predict Pathogenic Genotypes in Patients With Dilated Cardiomyopathy

BACKGROUND

Although genotyping allows family screening and influences risk-stratification in patients with nonischemic dilated cardiomyopathy (DCM) or isolated left ventricular systolic dysfunction (LVSD), its result is negative in a significant number of patients, limiting its widespread adoption.

OBJECTIVES

This study sought to develop and externally validate a score that predicts the probability for a positive genetic test result (G+) in DCM/LVSD.

METHODS

Clinical, electrocardiogram, and echocardiographic variables were collected in 1,015 genotyped patients from Spain with DCM/LVSD. Multivariable logistic regression analysis was used to identify variables independently predicting G+, which were summed to create the Madrid Genotype Score. The external validation sample comprised 1,097 genotyped patients from the Maastricht and Trieste registries.

RESULTS

A G+ result was found in 377 (37%) and 289 (26%) patients from the derivation and validation cohorts, respectively. Independent predictors of a G+ result in the derivation cohort were: family history of DCM (OR: 2.29; 95% CI: 1.73-3.04; P < 0.001), low electrocardiogram voltage in peripheral leads (OR: 3.61; 95% CI: 2.38-5.49; P < 0.001), skeletal myopathy (OR: 3.42; 95% CI: 1.60-7.31; P = 0.001), absence of hypertension (OR: 2.28; 95% CI: 1.67-3.13; P < 0.001), and absence of left bundle branch block (OR: 3.58; 95% CI: 2.57-5.01; P < 0.001). A score containing these factors predicted a G+ result, ranging from 3% when all predictors were absent to 79% when ≥4 predictors were present. Internal validation provided a C-statistic of 0.74 (95% CI: 0.71-0.77) and a calibration slope of 0.94 (95% CI: 0.80-1.10). The C-statistic in the external validation cohort was 0.74 (95% CI: 0.71-0.78).

CONCLUSIONS

The Madrid Genotype Score is an accurate tool to predict a G+ result in DCM/LVSD.

Basal oxidation of conserved cysteines modulates cardiac titin stiffness and dynamics

Titin, as the main protein responsible for the passive stiffness of the sarcomere, plays a key role in diastolic function and is a determinant factor in the etiology of heart disease. Titin stiffness depends on unfolding and folding transitions of immunoglobulin-like (Ig) domains of the I-band, and recent studies have shown that oxidative modifications of cryptic cysteines belonging to these Ig domains modulate their mechanical properties in vitro. However, the relevance of this mode of titin mechanical modulation in vivo remains largely unknown. Here, we describe the high evolutionary conservation of titin mechanical cysteines and show that they are remarkably oxidized in murine cardiac tissue. Mass spectrometry analyses indicate a similar landscape of basal oxidation in murine and human myocardium. Monte Carlo simulations illustrate how disulfides and S-thiolations on these cysteines increase the dynamics of the protein at physiological forces, while enabling load- and isoform-dependent regulation of titin stiffness. Our results demonstrate the role of conserved cysteines in the modulation of titin mechanical properties in vivo and point to potential redox-based pathomechanisms in heart disease.

Arrhythmias as Presentation of Genetic Cardiomyopathy

There is increasing evidence regarding the prevalence of genetic cardiomyopathies, for which arrhythmias may be the first presentation. Ventricular and atrial arrhythmias presenting in the absence of known myocardial disease are often labelled as idiopathic, or lone. While ventricular arrhythmias are well-recognized as presentation for arrhythmogenic cardiomyopathy in the right ventricle, the scope of arrhythmogenic cardiomyopathy has broadened to include those with dominant left ventricular involvement, usually with a phenotype of dilated cardiomyopathy. In addition, careful evaluation for genetic cardiomyopathy is also warranted for patients presenting with frequent premature ventricular contractions, conduction system disease, and early onset atrial fibrillation, in which most detected genes are in the cardiomyopathy panels. Sudden death can occur early in the course of these genetic cardiomyopathies, for which risk is not adequately tracked by left ventricular ejection fraction. Only a few of the cardiomyopathy genotypes implicated in early sudden death are recognized in current indications for implantable cardioverter defibrillators which otherwise rely upon a left ventricular ejection fraction ≤0.35 in dilated cardiomyopathy. The genetic diagnoses impact other aspects of clinical management such as exercise prescription and pharmacological therapy of arrhythmias, and new therapies are coming into clinical investigation for specific genetic cardiomyopathies. The expansion of available genetic information and implications raises new challenges for genetic counseling, particularly with the family member who has no evidence of a cardiomyopathy phenotype and may face a potentially negative impact of a genetic diagnosis. Discussions of risk for both probands and relatives need to be tailored to their numeric literacy during shared decision-making. For patients presenting with arrhythmias or cardiomyopathy, extension of genetic testing and its implications will enable cascade screening, intervention to change the trajectory for specific genotype-phenotype profiles, and enable further development and evaluation of emerging targeted therapies.

Combination of late gadolinium enhancement and genotype improves prediction of prognosis in non-ischemic dilated cardiomyopathy

Aims

Genotype and left ventricular scar on cardiac magnetic resonance (CMR) are increasingly recognized as risk markers for adverse outcomes in non‐ischaemic dilated cardiomyopathy (DCM). We investigated the combined influence of genotype and late gadolinium enhancement (LGE) in assessing prognosis in a large cohort of patients with DCM.

Methods and results

Outcomes of 600 patients with DCM (53.3 ± 14.1 years, 66% male) who underwent clinical CMR and genetic testing were retrospectively analysed. The primary endpoints were end‐stage heart failure (ESHF) and malignant ventricular arrhythmias (MVA). During a median follow‐up of 2.7 years (interquartile range 1.3–4.9), 24 (4.00%) and 48 (8.00%) patients had ESHF and MVA, respectively. In total, 242 (40.3%) patients had pathogenic/likely pathogenic variants (positive genotype) and 151 (25.2%) had LGE. In survival analysis, positive LGE was associated with MVA and ESHF (both, p < 0.001) while positive genotype was associated with ESHF (p = 0.034) but not with MVA (p = 0.102). Classification of patients according to genotype (G+/G−) and LGE presence (L+/L−) revealed progressively increasing events across L−/G−, L−/G+, L+/G− and L+/G+ groups and resulted in optimized MVA and ESHF prediction (p < 0.001 and p = 0.001, respectively). Hazard ratios for MVA and ESHF in patients with either L+ or G+ compared with those with L−/G− were 4.71 (95% confidence interval: 2.11–10.50, p < 0.001) and 7.92 (95% confidence interval: 1.86–33.78, p < 0.001), respectively.

Conclusion

Classification of patients with DCM according to genotype and LGE improves MVA and ESHF prediction. Scar assessment with CMR and genotyping should be considered to select patients for primary prevention implantable cardioverter‐defibrillator placement.

Study on Risk Factors for Death from Cardiomyopathy and Effectiveness of Health Information Management

Objective

To explore risk factors for death from cardiomyopathy and the effectiveness of health information management (HIM).

Methods

A total of 80 patients with cardiomyopathy admitted in ICU of our hospital (January 2016–January 2020) were selected as study subjects, and the clinical data of the patients were retrospectively analyzed. The patients were divided into the survival group (n = 72) and the death group (n = 14) according to the treatment outcome. Then, according to the management mode, the survival group was further equally divided into the conventional group and the HIM group to investigate the influence of risk factors on prognosis of patients with cardiomyopathy and the effectiveness of HIM.

Results

No significant difference was found in baseline body mass, myocardial enzymes, troponin, infection factors, history of heart disease, and gender between the survival group and the death group (P > 0.05). Compared with the survival group, the patients of the death group were older (P < 0.05), LVEF of the death group was obviously lower (P < 0.05), and the scores of APACHE II and SOFA of the death group were obviously higher (P < 0.05). Further logistic regression analysis of the univariate factors influencing the risk of death from cardiomyopathy led to the conclusion that LVEF was an independent risk factor for death in patients with cardiomyopathy. LVEF below 24.69% examined by echocardiography had a high predictive value, with a sensitivity of 98.6% and a specificity of 78.6%. No obvious difference was found in general data between the conventional group and the HIM group (P > 0.05). Compared with the conventional group, the disease remission rate, complication rate, awareness rate of health knowledge, ICU length of stay, and scores of self-management efficacy of the HIM group were obviously better (P < 0.05). No significant difference was found in 5-year mean survival rate between the conventional group and the HIM group (P > 0.05).

Conclusion

Older age, lower LVEF, and higher scores of APACHE II and SOFA are all risk factors for death from cardiomyopathy. Lower LVEF is an independent risk factor, and LVEF below 24.69% is an important indicator of increased risk of death. Moreover, HIM can effectively improve short-term treatment efficacy but has little effect on the long-term survival rate.

Identification of the distinctive role of DPT in dilated cardiomyopathy: a study based on bulk and single-cell transcriptomic analysis

Background

Dilated cardiomyopathy (DCM) is a common cause of heart failure. Cardiac remodeling is the main pathological change in DCM, yet the molecular mechanism is still unclear. Therefore, the present study aims to find potential crucial genes and regulators through bulk and single-cell transcriptomic analysis.

Methods

Three microarray datasets of DCM (GSE57338, GSE42955, GSE79962) were chosen from gene expression omnibus (GEO) to analyze the differentially expressed genes (DEGs). LASSO regression, SVM-RFE, and PPI network methods were then carried out to identify key genes. Another dataset (GSE116250) was used to validate these findings. To further identify DCM-associated specific cell types, transcription factors, and cell-cell interaction networks, GSEA, SCENIC, and CellPhoneDB were conducted on public datasets for single-cell RNA sequencing analysis of DCM (GSE109816 and GSE121893). Finally, reverse transcription-polymerase chain reaction (RT-PCR), western blot, and immunohistochemical were performed to validate DPT expression in fibroblasts and DCM.

Results

There were 281 DEGs between DCM and non-failing donors. CCL5 and DPT were identified to be key genes and both genes had a 0.844 area under the receiver operating curve (AUC) in the validation dataset. Further single-cell sequencing analysis revealed three main findings: (I) DPT was mainly expressed in fibroblasts and was significantly upregulated in DCM fibroblasts; (II) DPT⁺ fibroblasts were involved in the organization of the extracellular matrix (ECM) and collagen fibrils and were regulated by the transcription factor STAT3; and (III) DPT⁺ fibroblasts had high interactions with endothelial cells through including Ephrin-Eph, ACKR-CXCL, and JAG-NOTCH signal pathways. RT-PCR, western blot, and immunohistochemical confirmed that DPT was highly expressed and co-localized with Vimentin and p-STAT3 in DCM patients. STAT3 inhibitor S3I-201 reduced the expression of DPT in mouse cardiac fibroblasts.

Conclusions

DPT could be used as a diagnostic marker and therapeutic target of DCM. DPT⁺ fibroblasts could be a novel regulator of the cardiac remodeling process in DCM.

Depletion of m6 A reader protein YTHDC1 induces dilated cardiomyopathy by abnormal splicing of Titin

N⁶ -methyladenosine (m⁶ A) is the most prevalent modification in mRNA and engages in multiple biological processes. Previous studies indicated that m⁶ A methyltransferase METTL3 ('writer') and demethylase FTO ('eraser') play critical roles in heart-related disease. However, in the heart, the function of m⁶ A 'reader', such as YTH (YT521-B homology) domain-containing proteins remains unclear. Here, we report that the defect in YTHDC1 but not other YTH family members contributes to dilated cardiomyopathy (DCM) in mice. Cardiac-specific conditional Ythdc1 knockout led to obvious left ventricular chamber enlargement and severe systolic dysfunction. YTHDC1 deficiency also resulted in the decrease of cardiomyocyte contractility and disordered sarcomere arrangement. By means of integrating multiple high-throughput sequence technologies, including m⁶ A-MeRIP, RIP-seq and mRNA-seq, we identified 42 transcripts as potential downstream targets of YTHDC1. Amongst them, we found that Titin mRNA was decorated with m⁶ A modification and depletion of YTHDC1 resulted in aberrant splicing of Titin. Our study suggests that Ythdc1 plays crucial role in regulating the normal contractile function and the development of DCM. These findings clarify the essential role of m⁶ A reader in cardiac biofunction and provide a novel potential target for the treatment of DCM.

Association of Genetic Variants With Outcomes in Patients With Nonischemic Dilated Cardiomyopathy

BACKGROUND

The clinical relevance of genetic variants in nonischemic dilated cardiomyopathy (DCM) is unsettled.

OBJECTIVES

The study sought to assess the prognostic impact of disease-causing genetic variants in DCM.

METHODS

Baseline and longitudinal clinical data from 1,005 genotyped DCM probands were retrospectively collected at 20 centers. A total of 372 (37%) patients had pathogenic or likely pathogenic variants (genotype positive) and 633 (63%) were genotype negative. The primary endpoint was a composite of major adverse cardiovascular events. Secondary endpoints were end-stage heart failure (ESHF), malignant ventricular arrhythmia (MVA), and left ventricular reverse remodeling (LVRR).

RESULTS

After a median follow-up of 4.04 years (interquartile range: 1.70-7.50 years), the primary endpoint had occurred in 118 (31.7%) patients in the genotype-positive group and in 125 (19.8%) patients in the genotype-negative group (hazard ratio [HR]: 1.51; 95% confidence interval [CI]: 1.17-1.94; P = 0.001). ESHF occurred in 60 (16.1%) genotype-positive patients and in 55 (8.7%) genotype-negative patients (HR: 1.67; 95% CI: 1.16-2.41; P = 0.006). MVA occurred in 73 (19.6%) genotype-positive patients and in 77 (12.2%) genotype-negative patients (HR: 1.50; 95% CI: 1.09-2.07; P = 0.013). LVRR occurred in 39.6% in the genotype-positive group and in 46.2% in the genotype-negative group (P = 0.047). Among individuals with baseline left ventricular ejection fraction ≤35%, genotype-positive patients exhibited more major adverse cardiovascular events, ESHF, and MVA than their genotype-negative peers (all P < 0.02). LVRR and clinical outcomes varied depending on the underlying affected gene.

CONCLUSIONS

In this study, DCM patients with pathogenic or likely pathogenic variants had worse prognosis than genotype-negative individuals. Clinical course differed depending on the underlying affected gene.

Controlling my genome with my smartphone: first clinical experiences of the PROMISE system

Background

The development of Precision Medicine strategies requires high-dimensional phenotypic and genomic data, both of which are highly privacy-sensitive data types. Conventional data management systems lack the capabilities to sufficiently handle the expected large quantities of such sensitive data in a secure manner. PROMISE is a genetic data management concept that implements a highly secure platform for data exchange while preserving patient interests, privacy, and autonomy.

Methods

The concept of PROMISE to democratize genetic data was developed by an interdisciplinary team. It integrates a sophisticated cryptographic concept that allows only the patient to grant selective access to defined parts of his genetic information with single DNA base-pair resolution cryptography. The PROMISE system was developed for research purposes to evaluate the concept in a pilot study with nineteen cardiomyopathy patients undergoing genotyping, questionnaires, and longitudinal follow-up.

Results

The safety of genetic data was very important to 79%, and patients generally regarded the data as highly sensitive. More than half the patients reported that their attitude towards the handling of genetic data has changed after using the PROMISE app for 4 months (median). The patients reported higher confidence in data security and willingness to share their data with commercial third parties, including pharmaceutical companies (increase from 5 to 32%).

Conclusion

PROMISE democratizes genomic data by a transparent, secure, and patient-centric approach. This clinical pilot study evaluating a genetic data infrastructure is unique and shows that patient’s acceptance of data sharing can be increased by patient-centric decision-making.

Graphic abstract

The Role of Computer Skills in Personal Health Record Adoption Among Patients With Heart Disease: Multidimensional Evaluation of Users Versus Nonusers

Background

In the era of precision medicine, it is critical for health communication efforts to prioritize personal health record (PHR) adoption.

Objective

The objective of this study was to describe the characteristics of patients with heart disease that choose to adopt a PHR.

Methods

A total of 79 patients with chronic cardiovascular disease participated in this study: 48 PHR users and 31 nonusers. They completed 5 surveys related to their choice to use or not use the PHR: demographics, patient activation, medication adherence, health literacy, and computer self-efficacy (CSE).

Results

There was a significant difference between users and nonusers in the sociodemographic measure education (P=.04). There was no significant difference between users and nonusers in other sociodemographic measures: age (P=.20), sex (P=.35), ethnicity (P=.43), race (P=.42), and employment (P=.63). There was a significant difference between PHR users and PHR nonusers in CSE (P=.006).

Conclusions

In this study, we demonstrate that sociodemographic characteristics were not an important factor in patients’ use of their PHR, except for education. This study had a small sample size and may not have been large enough to detect differences between groups. Our results did demonstrate that there is a difference between PHR users and nonusers related to their CSE. This work suggests that incorporating CSE into the design of PHRs is critical. The design of patient-facing tools must take into account patients’ preferences and abilities when developing effective user-friendly health information technologies.

Dilated cardiomyopathy in the era of precision medicine: latest concepts and developments

Dilated cardiomyopathy (DCM) is an umbrella term entailing a wide variety of genetic and non-genetic etiologies, leading to left ventricular systolic dysfunction and dilatation, not explained by abnormal loading conditions or coronary artery disease. The clinical presentation can vary from asymptomatic to heart failure symptoms or sudden cardiac death (SCD) even in previously asymptomatic individuals. In the last 2 decades, there has been striking progress in the understanding of the complex genetic basis of DCM, with the discovery of additional genes and genotype-phenotype correlation studies. Rigorous clinical work-up of DCM patients, meticulous family screening, and the implementation of advanced imaging techniques pave the way for a more efficient and earlier diagnosis as well as more precise indications for implantable cardioverter defibrillator implantation and prevention of SCD. In the era of precision medicine, genotype-directed therapies have started to emerge. In this review, we focus on updates of the genetic background of DCM, characteristic phenotypes caused by recently described pathogenic variants, specific indications for prevention of SCD in those individuals and genotype-directed treatments under development. Finally, the latest developments in distinguishing athletic heart syndrome from subclinical DCM are described.

Omics phenotyping in heart failure: the next frontier

This state-of-the-art review aims to provide an up-to-date look at breakthrough omic technologies that are helping to unravel heart failure (HF) disease mechanisms and heterogeneity. Genomics, transcriptomics, proteomics, and metabolomics in HF are reviewed in depth. In addition, there is a thorough, expert discussion regarding the value of omics in identifying novel disease pathways, advancing understanding of disease mechanisms, differentiating HF phenotypes, yielding biomarkers for diagnosis or prognosis, or identifying new therapeutic targets in HF. The combination of multiple omics technologies may create a more comprehensive picture of the factors and physiology involved in HF than achieved by either one alone and provides a rich resource for predictive phenotype modelling. However, the successful translation of omics tools as solutions to clinical HF requires that the observations are robust and reproducible and can be validated across multiple independent populations to ensure confidence in clinical decision-making.

The Complex and Diverse Genetic Architecture of Dilated Cardiomyopathy

Our insight into the diverse and complex nature of dilated cardiomyopathy (DCM) genetic architecture continues to evolve rapidly. The foundations of DCM genetics rest on marked locus and allelic heterogeneity. While DCM exhibits a Mendelian, monogenic architecture in some families, preliminary data from our studies and others suggests that at least 20% to 30% of DCM may have an oligogenic basis, meaning that multiple rare variants from different, unlinked loci, determine the DCM phenotype. It is also likely that low-frequency and common genetic variation contribute to DCM complexity, but neither has been examined within a rare variant context. Other types of genetic variation are also likely relevant for DCM, along with gene-by-environment interaction, now established for alcohol- and chemotherapy-related DCM. Collectively, this suggests that the genetic architecture of DCM is broader in scope and more complex than previously understood. All of this elevates the impact of DCM genetics research, as greater insight into the causes of DCM can lead to interventions to mitigate or even prevent it and thus avoid the morbid and mortal scourge of human heart failure.

Cardiac organoid - a promising perspective of preclinical model

Human cardiac organoids (hCOs), three-dimensional (3D) cellular constructs similar to in vivo organ, are new-generation models. To a large extent, a hCO retains the biological characteristics and functions of cells in vivo more accurately than previous models. With the continuous development of biotechnology, the hCO model is becoming increasingly complex and mature. High-fidelity hCOs help us better explore the mysteries of human physiology and integrate phenotypes with living functions into models. Here, we discuss recent advances in the methods of constructing human cardiac organoids and introduce applications of hCOs, especially in modeling cardiovascular diseases, including myocardial infarction, heart failure, genetic cardiac diseases, and arrhythmia. In addition, we propose the prospects for and the limitations of hCOs. In conclusion, a greater understanding of hCOs will provide ways to improve hCO construction and make these models useful for future preclinical studies.

Genetic variant burden and adverse outcomes in pediatric cardiomyopathy

BACKGROUND

Previous genetic research in pediatric cardiomyopathy (CM) has focused on pathogenic variants for diagnostic purposes, with limited data evaluating genotype-outcome correlations. We explored whether greater genetic variant burden (pathogenic or variants of unknown significance, VUS) correlates with worse outcomes.

METHODS

Children with dilated CM (DCM) and hypertrophic CM (HCM) who underwent multigene testing between 2010 and 2018 were included. Composite endpoint was freedom from major adverse cardiac event (MACE).

RESULTS

Three hundred and thirty-eight subjects were included [49% DCM, median age 5.7 (interquartile range (IQR) 0.2-13.4) years, 51% HCM, median age 3.0 (IQR 0.1-12.5) years]. Pathogenic variants alone were not associated with MACE in either cohort (DCM p = 0.44; HCM p = 0.46). In DCM, VUS alone [odds ratio (OR) 4.0, 95% confidence interval (CI) 1.9-8.3] and in addition to pathogenic variants (OR 5.2, 95% CI 1.7-15.9) was associated with MACE. The presence of VUS alone or in addition to pathogenic variants were not associated with MACE in HCM (p = 0.22 and p = 0.33, respectively).

CONCLUSION

Increased genetic variant burden (pathogenic variants and VUS) is associated with worse clinical outcomes in DCM but not HCM. Genomic variants that influence DCM onset may be distinct from those driving disease progression, highlighting the potential value of universal genetic testing to improve risk stratification.

IMPACT

In pediatric CM, inconsistent findings historically have been shown between genotype and phenotype severity when only pathogenic variants have been considered. Increased genetic variant burden (including both pathogenic variants and VUS) is associated with worse clinical outcomes in DCM but not HCM. Genomic variants that influence CM onset may be distinct from those variants that drive disease progression and influence outcomes in phenotype-positive individuals. Incorporation of both pathogenic variants and VUS may improve risk stratification models in pediatric CM.

Contemporary and Future Approaches to Precision Medicine in Inherited Cardiomyopathies: JACC Focus Seminar 3/5

Inherited cardiomyopathies are commonly occurring myocardial disorders that are associated with substantial morbidity and mortality. Clinical management strategies have focused on treatment of heart failure and arrhythmic complications in symptomatic patients according to standardized guidelines. Clinicians are now being urged to implement precision medicine, but what does this involve? Advances in understanding of the genetic underpinnings of inherited cardiomyopathies have brought new possibilities for interventions that are tailored to genes, specific variants, or downstream mechanisms. However, the phenotypic variability that can occur with any given pathogenic variant suggests that factors other than single driver gene mutations are often involved. This is propelling a new imperative to elucidate the nuanced ways in which individual combinations of genetic variation, comorbidities, and lifestyle may influence cardiomyopathy phenotypes. Here, Part 3 of a 5-part precision medicine Focus Seminar series reviews the current status and future opportunities for precision medicine in the inherited cardiomyopathies.

Clinical Insights Into Heritable Cardiomyopathies

Cardiomyopathies (CMs) encompass a heterogeneous group of structural and functional abnormalities of the myocardium. The phenotypic characteristics of these myocardial diseases range from silent to symptomatic heart failure, to sudden cardiac death due to malignant tachycardias. These diseases represent a leading cause of cardiovascular morbidity, cardiac transplantation, and death. Since the discovery of the first locus associated with hypertrophic cardiomyopathy 30 years ago, multiple loci and molecular mechanisms have been associated with these cardiomyopathy phenotypes. Conversely, the disparity between the ever-growing landscape of cardiovascular genetics and the lack of awareness in this field noticeably demonstrates the necessity to update training curricula and educational pathways. This review summarizes the current understanding of heritable CMs, including the most common pathogenic gene variants associated with the morpho-functional types of cardiomyopathies: dilated, hypertrophic, arrhythmogenic, non-compaction, and restrictive. Increased understanding of the genetic/phenotypic associations of these heritable diseases would facilitate risk stratification to leveraging appropriate surveillance and management, and it would additionally provide identification of family members at risk of avoidable cardiovascular morbidity and mortality.

Mechanical dysfunction of the sarcomere induced by a pathogenic mutation in troponin T drives cellular adaptation

Familial hypertrophic cardiomyopathy (HCM), a leading cause of sudden cardiac death, is primarily caused by mutations in sarcomeric proteins. The pathogenesis of HCM is complex, with functional changes that span scales, from molecules to tissues. This makes it challenging to deconvolve the biophysical molecular defect that drives the disease pathogenesis from downstream changes in cellular function. In this study, we examine an HCM mutation in troponin T, R92Q, for which several models explaining its effects in disease have been put forward. We demonstrate that the primary molecular insult driving disease pathogenesis is mutation-induced alterations in tropomyosin positioning, which causes increased molecular and cellular force generation during calcium-based activation. Computational modeling shows that the increased cellular force is consistent with the molecular mechanism. These changes in cellular contractility cause downstream alterations in gene expression, calcium handling, and electrophysiology. Taken together, our results demonstrate that molecularly driven changes in mechanical tension drive the early disease pathogenesis of familial HCM, leading to activation of adaptive mechanobiological signaling pathways.

The Genetic Pathways Underlying Immunotherapy in Dilated Cardiomyopathy

Heart failure (HF) is a global public health threat affecting 26 million individuals worldwide with an estimated prevalence increase of 46% by 2030. One of the main causes of HF and sudden death in children and adult is Dilated Cardiomyopathy (DCM). DCM is characterized by dilation and systolic dysfunction of one or both ventricles. It has an underlying genetic basis or can develop subsequent to various etiologies that cause myocardium inflammation (secondary causes). The morbidity and mortality rates of DCM remains high despite recent advancement to manage the disease. New insights have been dedicated to better understand the pathogenesis of DCM in respect to genetic and inflammatory basis by linking the two entities together. This cognizance in the field of cardiology might have an innovative approach to manage DCM through targeted treatment directed to the causative etiology. The following review summarizes the genetical and inflammatory causes underlying DCM and the pathways of the novel precision-medicine-based immunomodulatory strategies to salvage and prevent the associated heart failure linked to the disease.

Complexity in genetic cardiomyopathies and new approaches for mechanism-based precision medicine

Genetic cardiomyopathies have been studied for decades, and it has become increasingly clear that these progressive diseases are more complex than originally thought. These complexities can be seen both in the molecular etiologies of these disorders and in the clinical phenotypes observed in patients. While these disorders can be caused by mutations in cardiac genes, including ones encoding sarcomeric proteins, the disease presentation varies depending on the patient mutation, where mutations even within the same gene can cause divergent phenotypes. Moreover, it is challenging to connect the mutation-induced molecular insult that drives the disease pathogenesis with the various compensatory and maladaptive pathways that are activated during the course of the subsequent progressive, pathogenic cardiac remodeling. These inherent complexities have frustrated our ability to understand and develop broadly effective treatments for these disorders. It has been proposed that it might be possible to improve patient outcomes by adopting a precision medicine approach. Here, we lay out a practical framework for such an approach, where patient subpopulations are binned based on common underlying biophysical mechanisms that drive the molecular disease pathogenesis, and we propose that this function-based approach will enable the development of targeted therapeutics that ameliorate these effects. We highlight several mutations to illustrate the need for mechanistic molecular experiments that span organizational and temporal scales, and we describe recent advances in the development of novel therapeutics based on functional targets. Finally, we describe many of the outstanding questions for the field and how fundamental mechanistic studies, informed by our more nuanced understanding of the clinical disorders, will play a central role in realizing the potential of precision medicine for genetic cardiomyopathies.

Detection and functional characterization of a novel MEF2A variation responsible for familial dilated cardiomyopathy

OBJECTIVES

Dilated cardiomyopathy (DCM) represents the most frequent form of cardiomyopathy, leading to heart failure, cardiac arrhythmias and death. Accumulating evidence convincingly demonstrates the crucial role of genetic defects in the pathogenesis of DCM, and over 100 culprit genes have been implicated with DCM. However, DCM is of substantial genetic heterogeneity, and the genetic determinants underpinning DCM remain largely elusive.

METHODS

Whole-exome sequencing and bioinformatical analyses were implemented in a consanguineous Chinese family with DCM. A total of 380 clinically annotated control individuals and 166 more DCM index cases then underwent Sanger sequencing analysis for the identified genetic variation. The functional characteristics of the variant were delineated by utilizing a dual-luciferase assay system.

RESULTS

A heterozygous variation in the MEF2A gene (encoding myocyte enhancer factor 2A, a transcription factor pivotal for embryonic cardiogenesis and postnatal cardiac adaptation), NM_001365204.1: c.718G>T; p. (Gly240*), was identified, and verified by Sanger sequencing to segregate with autosome-dominant DCM in the family with complete penetrance. The nonsense variation was neither detected in 760 control chromosomes nor found in 166 more DCM probands. Functional analyses revealed that the variant lost transactivation on the validated target genes MYH6 and FHL2, both causally linked to DCM. Furthermore, the variation nullified the synergistic activation between MEF2A and GATA4, another key transcription factor involved in DCM.

CONCLUSIONS

The findings firstly indicate that MEF2A loss-of-function variation predisposes to DCM in humans, providing novel insight into the molecular mechanisms of DCM and suggesting potential implications for genetic testing and prognostic evaluation of DCM patients.

Modeling Inherited Cardiomyopathies in Adult Zebrafish for Precision Medicine

Cardiomyopathies are a highly heterogeneous group of heart muscle disorders. More than 100 causative genes have been linked to various cardiomyopathies, which explain about half of familial cardiomyopathy cases. More than a dozen candidate therapeutic signaling pathways have been identified; however, precision medicine is not being used to treat the various types of cardiomyopathy because knowledge is lacking for how to tailor treatment plans for different genetic causes. Adult zebrafish (Danio rerio) have a higher throughout than rodents and are an emerging vertebrate model for studying cardiomyopathy. Herein, we review progress in the past decade that has proven the feasibility of this simple vertebrate for modeling inherited cardiomyopathies of distinct etiology, identifying effective therapeutic strategies for a particular type of cardiomyopathy, and discovering new cardiomyopathy genes or new therapeutic strategies via a forward genetic approach. On the basis of this progress, we discuss future research that would benefit from integrating this emerging model, including discovery of remaining causative genes and development of genotype-based therapies. Studies using this efficient vertebrate model are anticipated to significantly accelerate the implementation of precision medicine for inherited cardiomyopathies.

Traditional Chinese Medicine Formulation Huangqi Jianzhong Tang Improves Cardiac Function after Myocardial Infarction in Rats

Huangqi Jianzhong Tang (HQJZT) is a traditional Chinese herbal formula consisting of seven different herbs: Radix Astragali, Radix Paeoniae Alba, Ramulus Cinnamomi, Fructus Jujubae, Glycyrrhizae Radix Et Rhizoma Praeparata Cum Melle, Rhizoma Zingiberis Recens, and Saccharum Granorum. The present study aims to evaluate the possible effects of HQJZT on cardiac function in acute myocardial infarction (AMI) and related mechanism. AMI model was established by ligation of the left anterior descending coronary artery followed by one-week HQJZT treatment. Survival rate was calculated. Rat heart function was assessed by heart performance analysis system. 5-Triphenyltetrazolium chloride (TTC) staining was used to observe myocardial infarct size. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining and western blot were applied to evaluate tissue apoptotic level. Treatment with high dose of HQJZT improved cardiac function, reduced infarct size, number of apoptotic cells and expression of apoptotic proteins, Bax (a proapoptotic protein), and increased expression of antiapoptotic protein, Bcl2. However, enalapril (an angiotensin-converting enzyme inhibitor) treatment did not show marked improvement of these parameters. Our present data suggest that HQJZT has potential therapeutic effects to improve cardiac function by regulation of apoptotic signaling pathway.

Genomic study of dilated cardiomyopathy in a group of Mexican patients using site-directed next generation sequencing

Background

Dilated cardiomyopathy (DCM) is a major cause of nonischemic heart failure and death in young adults. Next generation sequencing (NGS) has become part of the diagnostic workup in idiopathic and familial DCM. More than 50 DCM genes have been identified, revealing great molecular heterogeneity and variable diagnostic yield. Interpretation of variant pathogenicity is challenging particularly in underrepresented populations, as pathogenic variant databases include studies mainly from European/Caucasian populations. To date, no studies on genomic diagnosis of DCM have been conducted in Mexico.

Methods

We recruited 55 unrelated DCM patients, 22 familial (F‐DCM), and 33 idiopathic (I‐DCM), and performed site‐directed NGS seeking causal mutations. Diagnostic yield was defined as the proportion of individuals with at least one pathogenic (P) or likely pathogenic (LP) variant in DCM genes.

Results

Overall diagnostic yield was 47.3%, and higher in F‐DCM (63.6%) than in I‐DCM (36.4%, p = 0.047). Overall, NGS disclosed 41 variants of clinical interest (61.0% novel), 27 were classified as P/LP and 14 of unknown clinical significance. Of P/LP variants, 10 were A‐band region TTN truncating variants, five were found in DSP (18.5%), five in MYH7 (18.5%), two in LMNA (7.4%), and one in RBM20, ABCC9, FKTN, ACTA1, and TNNT2. NGS findings suggested autosomal recessive inheritance in three families, two with DSP loss of function mutations in affected individuals. The increasing number of mutation reports in DCM, increasing knowledge on the functional consequences of mutations, mutational hotspots and functional domains of DCM‐related proteins, the recent refinement ACMG/ClinGen Guidelines, and co‐segregation analysis in DCM families helped increase the diagnostic yield.

Conclusion

This is the first NGS study performed in a group of Mexican DCM patients, contributing to understand the mutational spectrum and complexity of DCM molecular diagnosis.

Editor-in-Chief's Top Picks From 2019

Each week, I record audio summaries for every paper in JACC, as well as an issue summary. Although this process is quite time-consuming, I have become familiar with every paper that we publish. Thus, I have personally selected the top 100 papers (both Original Investigations and Review Articles, and an occasional Editorial Comment) from the distinct specialties each year. In addition to my personal choices, I have included papers that have been the most accessed or downloaded on our websites, as well as those selected by the JACC Editorial Board members. In order to present the full breadth of this important research in a consumable fashion, we will present these abstracts in this issue of JACC, as well as most of the central illustrations, with the realization that a magnifying glass will be be needed for appropriate visualization. The highlights comprise the following sections: Basic & Translational Research, Cardiac Failure & Myocarditis, Cardiomyopathies/Congenital & Genetics, Cardio-Oncology, Coronary Disease & Interventions, Hypertension, Imaging, Metabolic & Lipid Disorders, Neurovascular Disease & Dementia, Promoting Health & Prevention, Rhythm Disorders & Thromboembolism, Valvular Heart Disease, and Vascular Medicine (1-100).

Beyond genomics-technological advances improving the molecular characterization and precision treatment of heart failure

Dilated cardiomyopathy (DCM) is a major cause of heart failure and cardiovascular mortality. In the past 20 years, there has been an overwhelming focus on developing therapeutics that target common downstream disease pathways thought to be involved in all forms of heart failure independent of the initial etiology. While this strategy is effective at the population level, individual responses vary tremendously and only approximately one third of patients receive benefit from modern heart failure treatments. In this perspective, we propose that DCM should be considered as a collection of diseases with a common phenotype of left ventricular dilation and systolic dysfunction rather than a single disease entity, and that mechanism-based classification of disease subtypes will revolutionize our understanding and clinical approach towards DCM. We discuss how these efforts are central to realizing the potential of precision medicine and how they are empowered by the development of new tools that allow investigators to strategically employ genomic and transcriptomic information. Finally, we outline an investigational strategy to (1) define DCM at the patient level, (2) develop new tools to model and mechanistically dissect subtypes of human heart failure, and (3) harness these insights for the development of precision therapeutics.

Personalized medicine for cardiovascular diseases

Personalized medicine is an emerging concept involving managing the health of patients based on their individual characteristics, including particular genotypes. Cardiovascular diseases are heritable traits, and family history information is useful for risk prediction. As such, determining genetic information (germline genetic mutations) may also be applied to risk prediction. Furthermore, accumulating evidence suggests that genetic background can provide guidance for selecting effective treatments and preventive strategies in individuals with particular genotypes. These concepts may be applicable both to rare Mendelian diseases and to common complex traits. In this review, we define the concept and provide examples of personalized medicine based on human genetics for cardiovascular diseases, including coronary artery disease, arrhythmia, and cardiomyopathies. We also provide a particular focus on Mendelian randomization studies, especially those examining loss-of function genetic variations, for identifying high-risk individuals, as well as signaling pathways that may be useful targets for improving healthy living without cardiovascular events.