Truncations of titin causing dilated cardiomyopathy

Genetic analysis and family screening for dilated cardiomyopathy: a retrospective analysis of the stepwise pedigree approach

AIMS

This study aimed to assess the practicality of using a stepwise pedigree-based approach to differentiate between familial and sporadic Dilated Cardiomyopathy (DCM), while also considering timing of the genetic analysis. The analysis includes an examination of the extent to which complete family investigations were conducted in real-world scenarios as well as the length of the investigation.

METHODS

The stepwise pedigree approach involved conducting a comprehensive family history spanning 3 to 4 generations, reviewing medical records of relatives, and conducting clinical screening using echocardiography and electrocardiogram on first-degree relatives. Familial DCM was diagnosed when at least 2 family members were found to have DCM, and genetic analysis was considered as an option. This study involved a manual review of all DCM investigations conducted at the Centre of Cardiovascular Genetics at Umeå University Hospital, where the stepwise pedigree approach has been employed since 2007.

RESULTS

The investigation process had a mean duration of 643 days (95% CI 560.5-724.9). Of the investigations preformed, 94 (68%) were complete, 12 (9%) were ongoing, and 33 (24%) were prematurely terminated and thus incomplete. At the conclusion of the investigations, 55 cases (43%) were classified as familial DCM, 50 (39%) as sporadic DCM, and 22 (18%) remained unassessed due to incomplete pedigrees. Among the familial cases, genetic verification was achieved in 40%.

CONCLUSION

The stepwise pedigree approach is time consuming, and the investigations are often incomplete which may suggest that a more direct approach to genetic analysis, may be warranted.

Ultrastructural cardiac pathology: the wide (yet so very small) world of cardiac electron microscopy

Electron microscopy (EM) was a popular diagnostic tool in the 1970s and early 80s. With the adoption of newer, less expensive techniques, such as immunohistochemistry, the role of EM in diagnostic surgical pathology has dwindled substantially. Nowadays, even in academic centers, EM interpretation is relegated to renal pathologists and the handful of (aging) pathologists with experience using the technique. As such, EM interpretation is truly arcane-understood by few and mysterious to many. Nevertheless, there remain situations in which EM is the best or only ancillary test to ascertain a specific diagnosis. Thus, there remains a critical need for the younger generation of surgical pathologists to learn EM interpretation. Recognizing this need, cardiac EM was made the theme of the Cardiovascular Evening Specialty Conference at the 2023 United States and Canadian Academy of Pathology (USCAP) annual meeting in New Orleans, Louisiana. Each of the speakers contributed their part to this article, the purpose of which is to review EM as it pertains to myocardial tissue and provide illustrative examples of the spectrum of ultrastructural cardiac pathology seen in storage/metabolic diseases, cardiomyopathies, infiltrative disorders, and cardiotoxicities.

Dilated cardiomyopathy due to a novel combination of TTN and BAG3 genetic variants: From acute heart failure to subclinical phenotypes

Dilated cardiomyopathy (DCM) is defined as left ventricular enlargement accompanied by systolic dysfunction not explained by abnormal loading conditions or coronary heart disease. The DCM clinical spectrum is broad, ranging from subclinical to severe presentation with progression to end stage heart failure. To date, different genetic loci have been found to have moderate/definitive evidence for causality in DCM and pathogenic variants in the TTN gene represent the main genetic determinant. Here, we describe a family in which the co-occurrence of two genetic hits, one in the TTN and one in the BAG3 gene, was associated with heterogeneous clinical presentation ranging from subclinical phenotypes to acute cardiogenic shock mimicking fulminant myocarditis. We hypothesize that at least some specific BAG3 genotypes could be related to DCM presenting with acute heart failure and suggest that patients and relatives carrying BAG3 pathogenic variants should be addressed to a tertiary-level heart care center.

Integrated multi-omics approach revealed TTNtv c.13254T>G causing dilated cardiomyopathy in mice

Titin-truncating variant (TTNtv) is the most common genetic cause of dilated cardiomyopathy (DCM). In the previous study, we found a novel heterozygous TTNtv c.13254T>G (p.Tyr4418Ter) associated with DCM, but lacking functional evidence. The purpose of this study is to demonstrate the pathogenicity of TTNtv c.13254T>G. We constructed a mouse model with TTNtv Y4370* on exon 45 by CRISPR/Cas9-mediated genome engineering to imitate the TTNtv. c.13254T>G. Transmission electron microscope (TEM), immunohistochemistry, western blot (WB), Transcriptome sequencing (RNA-seq), and tandem Mass Tag (TMT) proteome analysis were performed on the mutant (KO) and WT mice cardiac tissue. Multi-omics association analysis was performed to observe the damages of cardiac tissue, and changes of inflammatory factors and Titin protein. TEM results showed that TTNtv Y4370* may lead to broken myofibrils, sparse myofilament structure, and broken Z-line and H-zone in many places of cardiac tissue of KO mice. Immunohistochemistry showed a significant increase in cTnT and TNF-α expression level in KO mice cardiac tissue. RNA-seq and TMT proteome enrichment analysis further strengthened that TTNtv Y4370* led to cardiac injury and inflammatory response in KO mice. In summary, TTNtv c.13254T>G contributed to the cardiac injury, inflammatory response and construct alterations in mice, that is TTNtv c.13254T>G may cause DCM in mice. These functional evidence of TTNtv c.13254T>G have important significance for follow-up genetic research of DCM in human.

Causal association between 1400 metabolites and dilated cardiomyopathy: a bidirectional two-sample Mendelian randomization analysis

Background

Dilated cardiomyopathy (DCM) is a cardiac disease with a poor prognosis of unclear etiology. Previous studies have shown that metabolism is associated with DCM. This study investigates the causal relationship between 1400 metabolites and DCM using a two-sample Mendelian randomization (MR) approach.

Methods

The study utilized data from the OpenGWAS database, comprising 355,381 Europeans, including 1,444 DCM cases. A total of 1,400 metabolites were evaluated for their causal association with DCM. Instrumental variables (IVs) were selected based on genetic variation and used in the MR analysis. The primary analysis method was inverse variance weighting (IVW), supplemented by weighted median-based estimation and sensitivity analyses.

Results

Of the 1,400 metabolites analyzed, 52 were identified as causally associated with DCM. The analysis revealed both positively and negatively correlated metabolites with DCM risk. Notable findings include the positive correlation of Tryptophan betaine and 5-methyluridine (ribothymidine) levels, and an inverse association of Myristoleate and Erythronate levels with DCM.

Conclusions

The study provides significant insights into the metabolites potentially involved in the pathogenesis of DCM. These findings could pave the way for new therapeutic strategies and biomarker identification in DCM management.

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.

Association of Multiple Nonhypertrophic Cardiomyopathy-Related Genetic Variants and Outcomes in Patients With Hypertrophic Cardiomyopathy

BACKGROUND

Approximately 10% of hypertrophic cardiomyopathy (HCM) patients have left ventricular systolic dysfunction (end-stage HCM) leading to severe heart-failure; however, risk stratification to identify patients at risk of progressing to end-stage HCM remains insufficient.

OBJECTIVES

In this study, the authors sought to elucidate whether the coexistence of other cardiovascular disease (CVD)-related variants is associated with progression to end-stage HCM in patients with HCM harboring pathogenic or likely pathogenic (P/LP) sarcomeric variants.

METHODS

The authors performed genetic analysis of 83 CVD-related genes in HCM patients from a Japanese multicenter cohort. P/LP variants in 8 major sarcomeric genes (MYBPC3, MYH7, TNNT2, TNNI3, TPM1, MYL2, MYL3, and ACTC1) definitive for HCM were defined as "sarcomeric variants." In addition, P/LP variants associated with other CVDs, such as dilated cardiomyopathy and arrhythmogenic cardiomyopathy, were referred to as "other CVD-related variants."

RESULTS

Among 394 HCM patients, 139 carried P/LP sarcomeric variants: 11 (7.9%) carried other CVD-related variants, 6 (4.3%) multiple sarcomeric variants, and 122 (87.8%) single sarcomeric variants. In a multivariable Cox regression analysis, presence of multiple sarcomeric variants (adjusted HR [aHR]: 3.35 [95% CI: 1.25-8.95]; P = 0.016) and coexistence of other CVD-related variants (aHR: 2.80 [95% CI: 1.16-6.78]; P = 0.022) were independently associated with progression to end-stage HCM. Coexisting other CVD-related variants were also associated with heart failure events (aHR: 2.75 [95% CI: 1.27-5.94]; P = 0.010).

CONCLUSIONS

Approximately 8% of sarcomeric HCM patients carried other CVD-related variants, which were associated with progression to end-stage HCM and heart failure events. Comprehensive surveillance of CVD-related variants within sarcomeric HCM patients contributes to risk stratification and understanding of mechanisms underlying end-stage HCM.

Plasma Olink Proteomics Reveals Novel Biomarkers for Prediction and Diagnosis in Dilated Cardiomyopathy with Heart Failure

In this study, we utilized the Olink Cardiovascular III panel to compare the expression levels of 92 cardiovascular-related proteins between patients with dilated cardiomyopathy combined with heart failure (DCM-HF) (n = 20) and healthy normal people (Normal) (n = 18). The top five most significant proteins, including SPP1, IGFBP7, F11R, CHI3L1, and Plaur, were selected by Olink proteomics. These proteins were further validated using ELISA in plasma samples collected from an additional cohort. ELISA validation confirmed significant increases in SPP1, IGFBP7, F11R, CHI3L1, and Plaur in DCM-HF patients compared to healthy controls. GO and KEGG analysis indicated that NT-pro BNP, SPP1, IGFBP7, F11R, CHI3L1, Plaur, BLM hydrolase, CSTB, Gal-4, CCL15, CDH5, SR-PSOX, and CCL2 were associated with DCM-HF. Correlation analysis revealed that these 13 differentially expressed proteins have strong correlations with clinical indicators such as LVEF and NT-pro BNP, etc. Additionally, in the GEO-DCM data sets, the combined diagnostic value of these five core proteins AUC values of 0.959, 0.773, and 0.803, respectively indicating the predictive value of the five core proteins for DCM-HF. Our findings suggest that these proteins may be useful biomarkers for the diagnosis and prediction of DCM-HF, and further research is prompted to explore their potential as therapeutic targets.

Rare genomic copy number variants implicate new candidate genes for bicuspid aortic valve

Bicuspid aortic valve (BAV), the most common congenital heart defect, is a major cause of aortic valve disease requiring valve interventions and thoracic aortic aneurysms predisposing to acute aortic dissections. The spectrum of BAV ranges from early onset valve and aortic complications (EBAV) to sporadic late onset disease. Rare genomic copy number variants (CNVs) have previously been implicated in the development of BAV and thoracic aortic aneurysms. We determined the frequency and gene content of rare CNVs in EBAV probands (n = 272) using genome-wide SNP microarray analysis and three complementary CNV detection algorithms (cnvPartition, PennCNV, and QuantiSNP). Unselected control genotypes from the Database of Genotypes and Phenotypes were analyzed using identical methods. We filtered the data to select large genic CNVs that were detected by multiple algorithms. Findings were replicated in a BAV cohort with late onset sporadic disease (n = 5040). We identified 3 large and rare (< 1,1000 in controls) CNVs in EBAV probands. The burden of CNVs intersecting with genes known to cause BAV when mutated was increased in case-control analysis. CNVs intersecting with GATA4 and DSCAM were enriched in cases, recurrent in other datasets, and segregated with disease in families. In total, we identified potentially pathogenic CNVs in 9% of EBAV cases, implicating alterations of candidate genes at these loci in the pathogenesis of BAV.

Identification of novel TTN gene variant in a patient exhibiting severe dilated cardiomyopathy co-occurring with acute fibrinoid organizing pneumonia

OBJECTIVES

Dilated cardiomyopathy (DCM) is often hereditary, with 20% to 40% of nonischemic cases showing familial linkage, yet genetic testing is underused. This report describes an unreported pathogenic nonsense variant in the Titin (TTN) gene (NM_001267550.2:c.92603G>A) in a 24-year-old man with severe DCM and acute fibrinoid organizing pneumonia, highlighting a unique cardiopulmonary pathology.

METHODS

We conducted detailed gross, histopathologic, immunophenotypic, and exome-based DNA sequencing analysis in the workup of this case. We also included the patient's clinical and radiologic findings in our study.

RESULTS

With rapid clinical deterioration and complex comorbidities, including substance abuse and psychiatric conditions, which precluded transplantation, the patient's cardiac function progressively worsened. Autopsy findings included extreme cardiomegaly, biventricular hypertrophy, and acute and chronic pericarditis. Significant pulmonary pathology consistent with acute fibrinoid organizing pneumonia was also noted. Molecular testing confirmed a deleterious maternally inherited TTN variant that was absent in the sibling of the proband and the extant medical literature, highlighting its rarity and significance.

CONCLUSIONS

This case contributes to the ongoing body of work on the impact of TTN variants on DCM. It suggests a potential link between genetic variants and complex cardiac injury patterns, emphasizing the need for further investigation into the interplay between cardiomyopathy and pulmonary pathology.

Toward the latest advancements in cardiac regeneration using induced pluripotent stem cells (iPSCs) technology: approaches and challenges

A novel approach to treating heart failures was developed with the introduction of iPSC technology. Knowledge in regenerative medicine, developmental biology, and the identification of illnesses at the cellular level has exploded since the discovery of iPSCs. One of the most frequent causes of mortality associated with cardiovascular disease is the loss of cardiomyocytes (CMs), followed by heart failure. A possible treatment for heart failure involves restoring cardiac function and replacing damaged tissue with healthy, regenerated CMs. Significant strides in stem cell biology during the last ten years have transformed the in vitro study of human illness and enhanced our knowledge of the molecular pathways underlying human disease, regenerative medicine, and drug development. We seek to examine iPSC advancements in disease modeling, drug discovery, iPSC-Based cell treatments, and purification methods in this article.

Genotype is associated with left ventricular reverse remodelling and early events in recent-onset dilated cardiomyopathy

AIMS

Recent-onset dilated cardiomyopathy (RODCM) is characterized by heterogeneous aetiology and diverse clinical outcomes, with scarce data on genotype-phenotype correlates. Our aim was to correlate individual RODCM genotypes with left ventricular reverse remodelling (LVRR) and clinical outcomes.

METHODS AND RESULTS

In this prospective study, a total of 386 Czech RODCM patients with symptom duration ≤6 months underwent genetic counselling and whole-exome sequencing (WES). The presence of pathogenic (class 5) or likely pathogenic (class 4) variants in a set of 72 cardiomyopathy-related genes was correlated with the occurrence of all-cause death, heart transplantation, or implantation of a ventricular assist device (primary outcome) and/or ventricular arrhythmia event (secondary outcome). LVRR was defined as an improvement of left ventricular ejection fraction to >50% or ≥10% absolute increase, with a left ventricular end-diastolic diameter ≤33 mm/m2 or ≥10% relative decrease. Median follow-up was 41 months. RODCM was familial in 98 (25%) individuals. Class 4-5 variants of interest (VOIs) were identified in 125 (32%) cases, with 69 (18%) having a single titin-truncating variant (TTNtv) and 56 (14%) having non-titin (non-TTN) VOIs. The presence of class 4-5 non-TTN VOIs, but not of TTNtv, heralded a lower probability of 12-month LVRR and proved to be an independent baseline predictor both of the primary and the secondary outcome. The negative result of genetic testing was a strong protective baseline variable against occurrence of life-threatening ventricular arrhythmias. Detection of class 4-5 VOIs in genes coding nuclear envelope proteins was another independent predictor of both study outcomes at baseline and also of life-threatening ventricular arrhythmias after 12 months. Class 4-5 VOIs of genes coding cytoskeleton were associated with an increased risk of life-threatening ventricular arrhythmias after baseline assessment. A positive family history of dilated cardiomyopathy alone only related to a lower probability of LVRR at 12 months and at the final follow-up.

CONCLUSIONS

RODCM patients harbouring class 4-5 non-TTN VOIs are at higher risk of progressive heart failure and life-threatening ventricular arrhythmias. Genotyping may improve their early risk stratification at baseline assessment.

Genetic factors in the pathogenesis of cardio-oncology

In recent years, with advancements in medicine, the survival period of patients with tumours has significantly increased. The adverse effects of tumour treatment on patients, especially cardiac toxicity, have become increasingly prominent. In elderly patients with breast cancer, treatment-related cardiovascular toxicity has surpassed cancer itself as the leading cause of death. Moreover, in recent years, an increasing number of novel antitumour drugs, such as multitargeted agents, antibody‒drug conjugates (ADCs), and immunotherapies, have been applied in clinical practice. The cardiotoxicity induced by these drugs has become more pronounced, leading to a complex and diverse mechanism of cardiac damage. The risks of unintended cardiovascular toxicity are increased by high-dose anthracyclines, immunotherapies, and concurrent radiation, in addition to traditional cardiovascular risk factors such as smoking, hypertension, diabetes, hyperlipidaemia, and obesity. However, these factors do not fully explain why only a subset of individuals experience treatment-related cardiac toxicity, whereas others with similar clinical features do not. Recent studies indicate that genetics play a significant role in susceptibility to the development of cardiovascular toxicity from cancer therapies. These genes are involved in drug metabolism, oxidative damage, cardiac dysfunction, and other processes. Moreover, emerging evidence suggests that epigenetics also plays a role in drug-induced cardiovascular toxicity. We conducted a review focusing on breast cancer as an example to help oncologists and cardiologists better understand the mechanisms and effects of genetic factors on cardiac toxicity. In this review, we specifically address the relationship between genetic alterations and cardiac toxicity, including chemotherapy-related genetic changes, targeted therapy-related genetic changes, and immune therapy-related genetic changes. We also discuss the role of epigenetic factors in cardiac toxicity. We hope that this review will improve the risk stratification of patients and enable therapeutic interventions that mitigate these unintended adverse consequences of life-saving cancer treatments.

Titin truncating variants, cardiovascular risk factors and the risk of atrial fibrillation and heart failure

High-proportion spliced-in (hiPSI) titin truncating variant (TTNtv) carriers have a higher risk of atrial fibrillation and heart failure1. However, the role of cardiovascular risk factors in modifying the risk of atrial fibrillation and heart failure attributed to hiPSI TTNtv carriers is unknown. Here, we investigate the role of cardiovascular risk, quantified using the pooled cohort equations (PCEs), in influencing the hazard of outcomes attributed to hiPSI TTNtvs among UK Biobank participants without baseline cardiovascular disease. The cohort was stratified based on hiPSI TTNtv carrier status and cardiovascular risk (low: <5%, intermediate: 5.0-7.5% and high: >7.5%). The primary outcome was a composite of atrial fibrillation, heart failure or death. TTNtv noncarriers with low cardiovascular risk were used as the reference group for all analyses. Among 179,752 participants (median age: 56 (49, 62) years; 57.5% female), the risk of the primary outcome was lower in hiPSI TTNtv carriers with low cardiovascular risk (adjusted hazard ratio: 2.23 (95% confidence interval: 1.62-3.07)) than those with high cardiovascular risk (adjusted hazard ratio: 8.21 (95% confidence interval: 6.63-10.18)). A favorable cardiovascular risk factor profile may partially offset the risk of clinical outcomes among hiPSI TTNtv carriers.

Titin As the Culprit Behind Dilated Cardiomyopathy: A Case Series of Three Cases and a Comprehensive Literature Review

Nonischemic dilated cardiomyopathy (DCM) is a complex cardiovascular condition often characterized by genetic pathogenesis. Comprehensive genetic testing has become a crucial aspect of DCM diagnosis and management, offering insights into prognosis and the identification of at-risk individuals. We delve into distinct genetic pathways associated with DCM and their pathogenetic mechanisms, emphasizing the evolving significance of genetic markers, particularly in cases where arrhythmia risk is heightened. The historical reliance on cardiac morphology to subtype cardiomyopathies is being complemented by the identification of genetic variants, further refining DCM subtypes and aiding in clinical management. The first case is a 51-year-old male who presented with symptoms of heart failure and non-sustained ventricular tachycardia. The second case is a 65-year-old female who presented with chest pain, shortness of breath, and tachycardia-mediated cardiomyopathy. The third case was a 48-year-old male who had a history of heart failure and non-ischemic cardiomyopathy. Despite immediate and extensive resuscitative measures, the patients' protracted response to the treatment raised questions about the potential underlying genetic factors contributing to their clinical presentation. A genome study was done in all these reported cases, which showed a genetic mutation in the titin gene. These cases underscore the importance of genetic evaluation in unraveling the complexity of cardiomyopathies, ultimately enhancing our ability to manage and treat such challenging cases. This case series, with a comprehensive literature review, explores the mechanisms governing titin-based forces in healthy and diseased conditions. It highlights the influence of isoform diversity and post-translational modifications on myocardial stiffness and contractility.

Rare and Common Genetic Variation Underlying Atrial Fibrillation Risk

Importance

Atrial fibrillation (AF) has a substantial genetic component. The importance of polygenic risk is well established, while the contribution of rare variants to disease risk warrants characterization in large cohorts.

Objective

To identify rare predicted loss-of-function (pLOF) variants associated with AF and elucidate their role in risk of AF, cardiomyopathy (CM), and heart failure (HF) in combination with a polygenic risk score (PRS).

Design, Setting, and Participants

This was a genetic association and nested case-control study. The impact of rare pLOF variants was evaluated on the risk of incident AF. HF and CM were assessed in cause-specific Cox regressions. End of follow-up was July 1, 2022. Data were analyzed from January to October 2023. The UK Biobank enrolled 502 480 individuals aged 40 to 69 years at inclusion in the United Kingdom between March 13, 2006, and October 1, 2010. UK residents of European ancestry were included. Individuals with prior diagnosis of AF were excluded from analyses of incident AF.

Exposures

Rare pLOF variants and an AF PRS.

Main Outcomes and Measures

Risk of AF and incident HF or CM prior to and subsequent to AF diagnosis.

Results

A total of 403 990 individuals (218 489 [54.1%] female) with a median (IQR) age of 58 (51-63) years were included; 24 447 were diagnosed with incident AF over a median (IQR) follow-up period of 13.3 (12.4-14.0) years. Rare pLOF variants in 6 genes (TTN, RPL3L, PKP2, CTNNA3, KDM5B, and C10orf71) were associated with AF. Of these, TTN, RPL3L, PKP2, CTNNA3, and KDM5B replicated in an external cohort. Combined with high PRS, rare pLOF variants conferred an odds ratio of 7.08 (95% CI, 6.03-8.28) for AF. Carriers with high PRS also had a substantial 10-year risk of AF (16% in female individuals and 24% in male individuals older than 60 years). Rare pLOF variants were associated with increased risk of CM both prior to AF (hazard ratio [HR], 3.13; 95% CI, 2.24-4.36) and subsequent to AF (HR, 2.98; 95% CI, 1.89-4.69).

Conclusions and Relevance

Rare and common genetic variation were associated with an increased risk of AF. The findings provide insights into the genetic underpinnings of AF and may aid in future genetic risk stratification.

Prevalence of Genetically Associated Dilated Cardiomyopathy: A Systematic Literature Review and Meta-Analysis

Background

Dilated cardiomyopathy (DCM) is a leading cause of heart failure and cardiac transplantation globally. Disease-associated genetic variants play a significant role in the development of DCM. Accurately determining the prevalence of genetically associated DCM (genetic DCM) is important for developing targeted prevention strategies. This review synthesized published literature on the global prevalence of genetic DCM across various populations, focusing on two of the most common variants: titin (TTN) and myosin heavy chain 7 (MYH7).

Methods

MEDLINE® and Embase were searched from database inception to September 19, 2022 for English-language studies reporting the prevalence of genetic DCM within any population. Studies using family history as a proxy for genetic DCM were excluded.

Results

Of 2,736 abstracts, 57 studies were included. Among the global adult or mixed (mostly adults with few pediatric patients) DCM population, median prevalence was 20.2% (interquartile range (IQR): 16.3-36.0%) for overall genetic DCM, 11.4% (IQR: 8.2-17.8%) for TTN-associated DCM, and 3.2% (IQR: 1.8-5.2%) for MYH7-associated DCM. Global prevalence of overall pediatric genetic DCM within the DCM population was similar (weighted mean: 21.3%). Few studies reported data on the prevalence of genetic DCM within the general population.

Conclusions

Our study identified variable prevalence estimates of genetic DCM across different populations and geographic locations. The current evidence may underestimate the genetic contributions due to limited screening and detection of potential DCM patients. Epidemiological studies using long-read whole genome sequencing to identify structural variants or non-coding variants are needed, as well as large cohort datasets with genotype-phenotype correlation analyses.

ClinGen Hereditary Cardiovascular Disease Gene Curation Expert Panel: Reappraisal of Genes associated with Hypertrophic Cardiomyopathy

Background

Hypertrophic cardiomyopathy (HCM) is an inherited cardiac condition affecting ~1 in 500 and exhibits marked genetic heterogeneity. Previously published in 2019, 57 HCM-associated genes were curated providing the first systematic evaluation of gene-disease validity. Here we report work by the ClinGen Hereditary Cardiovascular Disorders Gene Curation Expert Panel (HCVD-GCEP) to reappraise the clinical validity of previously curated and new putative HCM genes.

Methods

The ClinGen systematic gene curation framework was used to re-classify the gene-disease relationships for HCM and related syndromic entities involving left ventricular hypertrophy. Genes previously curated were included if their classification was not definitive, and if the time since curation was >2-3 years. New genes with literature assertions for HCM were included for initial evaluation. Existing genes were curated for new inheritance patterns where evidence existed. Curations were presented on twice monthly calls, with the HCVD-GCEP composed of 29 individuals from 21 institutions across 6 countries.

Results

Thirty-one genes were re-curated and an additional 5 new potential HCM-associated genes were curated. Among the re-curated genes, 17 (55%) genes changed classification: 1 limited and 4 disputed (from no known disease relationship), 9 disputed (from limited), and 3 definitive (from moderate). Among these, 3 (10%) genes had a clinically relevant upgrade, including TNNC1, a 9th sarcomere gene with definitive HCM association. With new evidence, two genes were curated for multiple inheritance patterns (TRIM63, disputed for autosomal dominant but moderate for autosomal recessive; ALPK3, strong for autosomal dominant and definitive for recessive). CSRP3 was curated for a semi-dominant mode of inheritance (definitive). Nine (29%) genes were downgraded to disputed, further discouraging clinical reporting of variants in these genes. Five genes recently reported to cause HCM were curated: RPS6KB1 and RBM20 (limited), KLHL24 and MT-TI (moderate), and FHOD3 (definitive).

Conclusions

We report 29 genes with definitive, strong or moderate evidence of causation for HCM or isolated LVH, including sarcomere, sarcomere-associated and syndromic conditions.

Prognostic implications of genotype findings in non-ischaemic dilated cardiomyopathy: A network meta-analysis

AIMS

Evidence on the relative impact of diverse genetic backgrounds associated with non-ischaemic dilated cardiomyopathy (DCM) remains contradictory. This study sought to synthesize the available data regarding long-term outcomes of different gene groups in DCM.

METHODS AND RESULTS

Electronic databases were systematically screened to identify studies reporting prognostic data on pre-specified gene groups. Those included pathogenic/likely pathogenic (P/LP) variants, truncating titin variants (TTNtv), lamin A/C variants (LMNA), and desmosomal proteins. Outcomes were divided into composite adverse events (CAEs), malignant ventricular arrhythmic events (MVAEs) and heart failure events (HFEs). A total of 26 studies (n = 7255) were included in the meta-analysis and 6791 patients with genotyped DCM were analysed. Patients with P/LP variants had a higher risk for CAEs (odds ratio [OR] 2.10, 95% confidence interval [CI] 1.67-2.65), MVAEs (OR 1.86, 95% CI 1.52-2.26), and HFEs (OR 2.01, 95% CI 1.08-3.73) than genotype-negative patients. The presence of TTNtv was linked to a higher risk for CAEs (OR 1.78, 95% CI 1.20-2.63), but not MVAEs or HFEs. LMNA and desmosomal groups suffered a higher risk for CAEs, MVAEs, and HFEs compared to non-LMNA and non-desmosomal groups, respectively. When genes were indirectly compared, the presence of LMNA resulted in a more detrimental effect that TTNtv, with respect to all composite outcomes but no significant difference was found between LMNA and desmosomal genes. Desmosomal genes harboured a higher risk for MVAEs compared to TTNtv.

CONCLUSIONS

Different genetic substrates associated with DCM result in divergent natural histories. Routine utilization of genetic testing should be employed to refine risk stratification and inform therapeutic strategies in DCM.

Gut microbiota as a residual risk factor causally influencing cardiac structure and function: Mendelian randomization analysis and biological annotation

Background

The gut microbiota (GM) is widely acknowledged to have a significant impact on cardiovascular health and may act as a residual risk factor affecting cardiac structure and function. However, the causal relationship between GM and cardiac structure and function remains unclear.

Objective

This study aims to employ a two-sample Mendelian randomization (MR) approach to investigate the causal association between GM and cardiac structure and function.

Methods

Data on 119 GM genera were sourced from a genome-wide association study (GWAS) meta-analysis (13,266 European participants) conducted by the MiBioGen consortium, while data on 16 parameters of cardiac structure and function were obtained from the UK Biobank's GWAS of cardiac magnetic resonance imaging (up to 41,135 European participants). Inverse variance weighted (IVW), MR-Egger, and weighted median (WM) methods were utilized for causal association assessments, with sensitivity analyses conducted to reinforce the findings. Finally, biological annotation was performed on the GWAS data of GM and cardiac phenotypes with causal associations to explore potential mechanisms.

Results

The MR analysis, predominantly based on the IVW model, revealed 93 causal associations between the genetically predicted abundance of 44 GM genera and 16 cardiac structure and function parameters. These associations maintained consistent directions in MR-Egger and WM models, with no evidence of pleiotropy detected. Biological annotations suggest that GM may influence cardiac structure and function through pathways involved in myocardial cell development, cardiac contractility, and apoptosis.

Conclusion

The MR analysis supports a causal association between certain abundances of genetically predicted GM and cardiac structure and function, suggesting that GM could be a residual risk factor impacting cardiac phenotypes.

Risk Assessment and Personalized Treatment Options in Inherited Dilated Cardiomyopathies: A Narrative Review

Considering the worldwide impact of heart failure, it is crucial to develop approaches that can help us comprehend its root cause and make accurate predictions about its outcome. This is essential for lowering the suffering and death rates connected with this widespread illness. Cardiomyopathies frequently result from genetic factors, and the study of heart failure genetics is advancing quickly. Dilated cardiomyopathy (DCM) is the most prevalent kind of cardiomyopathy, encompassing both genetic and nongenetic abnormalities. It is distinguished by the enlargement of the left ventricle or both ventricles, accompanied by reduced contractility. The discovery of the molecular origins and subsequent awareness of the molecular mechanism is broadening our knowledge of DCM development. Additionally, it emphasizes the complicated nature of DCM and the necessity to formulate several different strategies to address the diverse underlying factors contributing to this disease. Genetic variants that can be transmitted from one generation to another can be a significant contributor to causing family or sporadic hereditary DCM. Genetic variants also play a significant role in determining susceptibility for acquired triggers for DCM. The genetic causes of DCM can have a large range of phenotypic expressions. It is crucial to select patients who are most probable to gain advantages from genetic testing. The purpose of this research is to emphasize the significance of identifying genetic DCM, the relationships between genotype and phenotype, risk assessment, and personalized therapy for both those affected and their relatives. This approach is expected to gain importance once treatment is guided by genotype-specific advice and disease-modifying medications.

Research landscape of genetics in dilated cardiomyopathy: insight from a bibliometric analysis

Background

Dilated cardiomyopathy (DCM) is a heterogeneous myocardial disorder with diverse genetic or acquired origins. Notable advances have been achieved in discovering and understanding the genetics of DCM. This study aimed to depict the distribution of the main research forces, hotspots, and frontiers in the genetics of DCM, thus shaping future research directions.

Methods

Based on the documents published in the Web of Science Core Collection database from 2013 to 2022, co-authorship of authors, institutions, and countries/regions, co-citation of references, and co-occurrence of keywords were conducted respectively to present the distribution of the leading research forces, research hotspots, and emerging trends in the genetics of DCM.

Results

4,141 documents were included, and the annual publications have steadily increased. Seidman, Christine E, Meder, Benjamin, Sinagra, Gianfranco were the most productive authors, German Centre for Cardiovascular Research was the most productive institution, and the USA, China, and Germany were the most prolific countries. The co-occurrence of keywords has generated 8 clusters, including DCM, lamin a/c, heart failure, sudden cardiac death, hypertrophic cardiomyopathy, cardiac hypertrophy, arrhythmogenic cardiomyopathy, and next-generation sequencing. Frequent keywords with average publication time after 2019 mainly included arrhythmogenic cardiomyopathy, whole-exome sequencing, RBM 20, phenotype, risk stratification, precision medicine, genotype, and machine learning.

Conclusion

The research landscape of genetics in DCM is continuously evolving. Deciphering the genetic profiles by next-generation sequencing and illustrating pathogenic mechanisms of gene variants, establishing innovative treatments for heart failure and improved risk stratification for SCD, uncovering the genetic overlaps between DCM and other inherited cardiomyopathies, as well as identifying genotype-phenotype correlations are the main research hotspots and frontiers in this field.

Characterization and Long-Term Prognosis of Patients with Different Phenotypes of Dilated Cardiomyopathy

BACKGROUND

Long-term prognosis of dilated cardiomyopathy (DCM) in the Chinese population is lacking, and the left ventricular (LV) hypertrabeculation phenotype usually overlaps with DCM.

OBJECTIVES

The study aims to investigate whether the presence of the LV hypertrabeculation phenotype confers additional adverse prognostic information for DCM patients.

METHODS

We retrospectively reviewed all DCM patients (≥18 years of age at diagnosis) hospitalized in the Peking Union Medical College Hospital between September 2002 and September 2022. The eligible patients were divided into two groups based on echocardiography at diagnosis: the isolated DCM (n = 353), and DCM with the LV hypertrabeculation phenotype (n = 97). The primary endpoint was major adverse cardiac events (MACEs), and multivariate Cox hazards regression models were used to compare the endpoints between the two groups.

RESULTS

During a mean follow-up time of 4.6 years, there was no significant difference in the primary endpoint between the isolated DCM and DCM with the LV hypertrabeculation phenotype (p = 0.19). The risk of MACEs in the first 5 years was significantly higher in DCM with the LV hypertrabeculation phenotype than isolated DCM (adjusted HR [95%CI]: 1.83 [1.21-2.77]) and after 5 years the effect of the LV hypertrabeculation phenotype as a prognostic attenuated. Subgroup analysis found a significant interaction for the incidence of MACEs between sex and DCM subtypes (p for interaction = 0.01).

CONCLUSIONS

DCM with LV hypertrabeculation phenotypes had a higher early (first 5 years) risk of MACEs. For males, the presence of LV hypertrabeculation phenotypes might be an important clue for identifying high-risk DCM patients.

Clinical Characteristics and Mechanisms of Acute Myocarditis

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT05335928.

Hearts apart: sex differences in cardiac remodeling in health and disease

Biological sex is an important modifier of physiology and influences pathobiology in many diseases. While heart disease is the number one cause of death worldwide in both men and women, sex differences exist at the organ and cellular scales, affecting clinical presentation, diagnosis, and treatment. In this Review, we highlight baseline sex differences in cardiac structure, function, and cellular signaling and discuss the contribution of sex hormones and chromosomes to these characteristics. The heart is a remarkably plastic organ and rapidly responds to physiological and pathological cues by modifying form and function. The nature and extent of cardiac remodeling in response to these stimuli are often dependent on biological sex. We discuss organ- and molecular-level sex differences in adaptive physiological remodeling and pathological cardiac remodeling from pressure and volume overload, ischemia, and genetic heart disease. Finally, we offer a perspective on key future directions for research into cardiac sex differences.

Titin Cardiomyopathy Associated With Refractory Ventricular Tachycardia: A Case Report

Cardiomyopathy is defined as structural and functional myocardial abnormality not attributed to ischemic, valvular, hypertensive, or congenital cardiac causes. The main phenotypes of cardiomyopathy include hypertrophic, dilated, non-dilated left ventricular, restrictive, arrhythmogenic right ventricular, Takotsubo, and left ventricular noncompaction cardiomyopathies. A significant proportion of dilated cardiomyopathy (DCM) cases represents patients with genetic mutations, most commonly titin gene truncating variants (TTNtv). It has been shown that TTNtv mutation contributes to the development of certain types of DCM such as alcohol, chemotherapy, and peripartum. We present a case of DCM where genetic workup revealed TTNtv without other contributing factors. The course was complicated by multiple ventricular tachycardias (VTs) refractory to medical management, despite treatment with amiodarone, sotalol, dofetilide, mexiletine, and propranolol. Interestingly, endocardial mapping failed to delineate the substrate of tachycardia. This report underscores the importance of genetic testing in DCM and highlights the potential association of titin cardiomyopathy with refractory VTs, possibly of epicardial origin.

Unexpected Genetic Twists in Patients with Cardiac Devices

Objective: To assess the frequency and types of genetic mutations in patients with arrhythmias who underwent cardiac device implantation. Methods: Retrospective observational study, including 38 patients with different arrhythmias and cardiac arrest as a first cardiac event. Treatment modalities encompass pacemakers, transvenous defibrillators, loop recorders, subcutaneous defibrillators, and cardiac resynchronization therapy. All patients underwent genetic testing, using commercially available panels (106-174 genes). Outcome measures include mortality, arrhythmia recurrence, and device-related complications. Results: Clinical parameters revealed a family history of sudden cardiac death in 19 patients (50%), who were predominantly male (58%) and had a mean age of 44.5 years and a mean left ventricle ejection fraction of 40.3%. Genetic testing identified mutations in various genes, predominantly TMEM43 (11%). In two patients (3%) with arrhythmogenic cardiomyopathy, complete subcutaneous defibrillator extraction with de novo transvenous implantable cardioverter-defibrillator implantation was needed. The absence of multiple associations among severe gene mutations was crucial for cardiac resynchronization therapy response. Mortality in this group was around 3% in titin dilated cardiomyopathy patients. Conclusions: Integration of genetic testing into the decision-making process for patients with electronic devices represents a paradigm shift in personalized medicine. By identifying genetic markers associated with arrhythmia susceptibility, heart failure etiology, and cardiac resynchronization therapy response, clinicians can tailor device choices to optimize patient outcomes.

Connecting the Dots: Exploring the Interplay Between Preeclampsia and Peripartum Cardiomyopathy

Preeclampsia and peripartum cardiomyopathy (PPCM) are significant obstetric problems that can arise during or after pregnancy. Both are known to be causes of maternal mortality and morbidity. Several recent studies have suggested a link between preeclampsia and the pathophysiology of PPCM. However, the common thread that connects the two has yet to be thoroughly and fully articulated. Here, we investigate the complex dynamics of preeclampsia and PPCM in this review. Our analysis focuses mainly on inflammatory and immunological responses, endothelial dysfunction as a shared pathway, and potential genetic predisposition to both diseases. To begin, we will look at how excessive inflammatory and immunological responses can lead to clinical symptoms of both illnesses, emphasizing the role of proinflammatory cytokines and immune cells in modifying vascular and tissue responses. Second, we consider endothelial dysfunction to be a crucial point at which endothelial damage and activation contribute to pathogenesis through increased vascular permeability, vascular dysfunction, and thrombus formation. Finally, we examine recent information suggesting genetic predispositions to preeclampsia and PPCM, such as genetic variants in genes involved in the management of blood pressure, the inflammatory response, and heart structural integrity. With this synergistic study, we seek to encourage more research and creative therapy solutions by emphasizing the need for an interdisciplinary approach to understanding and managing the connection between preeclampsia and PPCM.

Reanalysis of RNA sequencing data ends diagnostic odyssey and expands the phenotypic spectrum of congenital titinopathy

Although next-generation sequencing has enabled diagnoses for many patients with Mendelian disorders, the majority remain undiagnosed. Here, we present a sibling pair who were clinically diagnosed with Escobar syndrome, however targeted gene testing was negative. Exome sequencing (ES), and later genome sequencing (GS), revealed compound heterozygous TTN variants in both siblings, a maternally inherited frameshift variant [(NM_133378.4):c.36812del; p.(Asp12271Valfs*10)], and a paternally inherited missense variant [(NM_133378.4):c.12322G > A; p.(Asp4108Asn)]. This result was considered nondiagnostic due to poor clinical fit and limited pathogenicity evidence for the missense variant of uncertain significance (VUS). Following initial nondiagnostic RNA sequencing (RNAseq) on muscle and further pursuit of other variants detected on the ES/GS, a reanalysis of noncanonical splice sites in the muscle transcriptome identified an out-of-frame exon retraction in TTN, near the known VUS. Interim literature included reports of patients with similar TTN variants who had phenotypic concordance with the siblings, and a diagnosis of a congenital titinopathy was given 4 years after the TTN variants had been initially reported. This report highlights the value of reanalysis of RNAseq with a different approach, expands the phenotypic spectrum of congenital titinopathy and also illustrates how a perceived phenotypic mismatch, and failure to consider known variants, can result in a prolongation of the diagnostic journey.

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

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

Diagnosis and cardiac transplantation of a Carney syndrome-induced cardiac myxoma combined with dilated cardiomyopathy: a case report

BACKGROUND

Carney syndrome is an uncommon autosomal disorder closely linked to mutations in the PRKAR1A gene. Skin lesions are the most pronounced feature of Carney syndrome, affecting over 80% of individuals with this condition. This syndrome is characterized by a triad of myxomas, skin pigmentation, and endocrine hyperfunction, featuring multiple endocrine neoplasms with skin and cardiac involvement. Dilated cardiomyopathy, a primary cardiomyopathy, is defined as the dilation and impaired systolic function of the left or both ventricles. Its clinical presentation varies from being asymptomatic to heart failure or sudden cardiac death, making it a leading global cause of heart failure. Currently, Dilated cardiomyopathy has an estimated prevalence of 1/2500-1/250 individuals, predominantly affecting those aged 30-40 years, with a male-to-female ratio of 3:1. This case report describes a heart failure patient with cardiac myxoma caused by Carney syndrome combined with dilated cardiomyopathy. The patient was successfully treated for heart failure by heart transplantation.

CASE PRESENTATION

Herein, we report a case of heart failure due to Carney syndrome that resulted in cardiac myxoma combined with dilated cardiomyopathy. A 35-year-old male was admitted to the hospital three years ago because of sudden chest tightness and shortness of breath. Echocardiography indicated myxoma, and a combination of genetic screening and physical examination confirmed Carney syndrome with cardiac myxoma. Following symptomatic management, he was discharged. Surgical interventions were not considered at the time. However, the patient's chest tightness and shortness of breath symptoms worsened, and he returned to the hospital. A New York Heart Association grade IV heart function was confirmed, and echocardiography indicated the presence of dilated cardiomyopathy accompanied by cardiac myxoma. Ultimately, the patient's heart failure was successfully treated with heart transplantation.

CONCLUSIONS

Cardiac myxoma caused by Carney syndrome combined with heart failure caused by dilated cardiomyopathy can be resolved by heart transplantation.

TTN novel splice variant in familial dilated cardiomyopathy and splice variants review: a case report

This case report details the identification of a novel likely pathogenic splicing variant in the TTN gene, associated with dilated cardiomyopathy (DCM), in a 42-year-old male patient presenting with early-onset heart failure and reduced ejection fraction. DCM is a nonischemic heart condition characterized by left biventricular dilation and systolic dysfunction, with approximately one-third of cases being familial and often linked to genetic mutations. The TTN gene, encoding the largest human protein essential for muscle contraction and sarcomere structure, is implicated in about 25% of DCM cases through mutations, especially truncating variants. Our investigation revealed a previously unreported G > C mutation at the splice acceptor site in intron 356 of TTN, confirmed by Sanger sequencing and not found in population databases, suggesting a novel contribution to the understanding of DCM etiology. The case emphasizes the critical role of the TTN gene in cardiac function and the genetic complexity underlying DCM. A comprehensive literature review highlighted the prevalence and significance of splice variants in the TTN gene, particularly those affecting the titin A-band, which is known for its role in muscle contraction and stability. This variant's identification underscores the importance of genetic screening in patients with DCM, offering insights into the disease's familial transmission and potential therapeutic targets. Our findings contribute to the expanding knowledge of genetic factors in DCM, demonstrating the necessity of integrating genetic diagnostics in cardiovascular medicine. This case supports the growing evidence linking splicing mutations in specific regions of the TTN gene to DCM development and underscores the importance of genetic counseling and testing in managing heart disease.

Cocaine, amphetamine, or titin: Unraveling the genetic underpinnings of dilated cardiomyopathy

Key Clinical Message

An interesting case that shows the importance of identifying a pathogenic TTN gene mutation through genetic assessment in unexplained cardiomyopathy, especially with family history. This case highlights the need for genetic counseling and testing for at-risk relatives, and advocates for personalized management considering both genetic and lifestyle factors.

Abstract

This case report examines a 33-year-old Hispanic male with bipolar disorder, schizophrenia, and a history of substance use, presenting with acute respiratory failure and cardiac arrest. The patient's nonischemic dilated cardiomyopathy (DCM) highlights the critical role of genetic factors, particularly titin gene (TTN) mutations, in cardiomyopathy pathogenesis. Through genetic analysis, we explore the intersection of lifestyle factors and genetic predisposition in DCM, underscoring the importance of comprehensive genetic testing for accurate diagnosis and targeted therapy. This case contributes to the evolving understanding of DCM etiology, emphasizing the necessity of considering both environmental and genetic factors in clinical assessment and management.

Sex differences in heart transplantation - analysis of the national inpatient sample 2012-2019

INTRODUCTION

Advanced heart failure therapies and heart transplantation (HT) have been underutilized in women. Therefore, we aimed to explore the clinical characteristics and outcomes of HT by sex.

METHODS

We conducted a retrospective analysis of adult discharges from the National Inpatient Sample (NIS) between 2012 and 2019. International Classification of Disease (ICD) procedure codes were used to identify those who underwent HT.

RESULTS

A total of 20,180 HT hospitalizations were identified from 2012-2019. Among them, 28 % were female. Women undergoing HT were younger (mean age 51 vs. 54.5 years, p<0.001). HT hospitalizations among men were more likely to have atrial fibrillation, diabetes, hypertension, renal failure, dyslipidemia, smoking, and ischemic heart disease. HT hospitalizations among women were more likely to have hypothyroidism and valvular heart disease. HT hospitalizations in women were associated with no significant difference in risk of in-hospital mortality (adjusted odds ratio [OR] 0.82; 95 % confidence interval [CI] 0.58-1.16, p=0.271), no significant difference in length of stay or inflation-adjusted cost. Men were more likely to develop acute kidney injury during HT hospitalization (69.2 % vs. 59.7 %, adjusted OR 0.71, 95 % CI 0.61-0.83, p<0.001).

CONCLUSIONS

HT utilization is lower in women. However, most major in-hospital outcomes for HT are similar between the sexes. Further studies are need to explore the causes of lower rates of HT in women.

Prevalence of Pathogenic Variants in Cardiomyopathy-Associated Genes in Acute Myocarditis: A Systematic Review and Meta-Analysis

BACKGROUND

Acute myocarditis is an inflammatory condition that may precede the development of dilated or arrhythmogenic cardiomyopathy.

OBJECTIVES

The aim of this study was to investigate the reported prevalence of pathogenic or likely pathogenic (P/LP) variants in cardiomyopathy-associated genes in patients with acute myocarditis.

METHODS

For this systematic review and meta-analysis, the PubMed and Embase databases were searched on March 4, 2023. Observational studies evaluating the prevalence of P/LP variants in cardiomyopathy-associated genes in patients with acute myocarditis were included. Studies were stratified into adult and pediatric age groups and for the following scenarios: 1) complicated myocarditis (ie, presenting with acute heart failure, reduced left ventricular ejection fraction, or life-threatening ventricular arrhythmias); and 2) uncomplicated myocarditis. The study was registered with the International Prospective Register of Systematic Reviews (CRD42023408668) and followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

Of 732 studies identified, 8 met the inclusion criteria, providing data for 586 patients with acute myocarditis. A total of 89 P/LP variants in cardiomyopathy-associated genes were reported in 85 patients. For uncomplicated myocarditis, the pooled prevalence was 4.2% (95% CI: 1.8%-7.4%; I2 = 1.4%), whereas for complicated myocarditis, the pooled prevalence was 21.9% (95% CI: 14.3%-30.5%; I2 = 38.8%) and 44.5% (95% CI: 22.7%-67.4%; I2 = 52.8%) in adults and children, respectively. P/LP variants in desmosomal genes were predominant in uncomplicated myocarditis (64%), whereas sarcomeric gene variants were more prevalent in complicated myocarditis (58% in adults and 71% in children).

CONCLUSIONS

Genetic variants are present in a large proportion of patients with acute myocarditis. The prevalence of genetic variants and the genes involved vary according to age and clinical presentation.

Myocardial Recovery and Relapse in Heart Failure With Improved Ejection Fraction

Purpose of review

The purpose of this review is to discuss myocardial recovery in heart failure with reduced ejection fraction (HFrEF) and to summarize the contemporary insights regarding heart failure with improved ejection fraction (HFimpEF).

Recent findings

Improvement in left ventricular ejection fraction (LVEF ≥ 40%) with improved prognosis can be achieved in one out of three (10-40%) patients with HFrEF treated with guideline-directed medical therapy. Clinical predictors include non-ischemic etiology of HFrEF, less abnormal blood or imaging biomarkers, and lack of specific pathogenic genetic variants. However, a subset of patients may ultimately relapse, suggesting that many patients are merely in remission rather than having fully recovered.

Summary

Patients with HFimpEF have improved prognosis but nonetheless remain at risk of relapse and long-term adverse events. Future studies will hopefully chart the natural history of HFimpEF and identify clinical predictors such as blood or novel imaging biomarkers that distinguish subgroups of patients based on differential trajectory and prognosis.

Homozygous TNNI3 frameshift variant in a consanguineous family with lethal infantile dilated cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is characterized by dilatation of the left ventricle, systolic dysfunction, and normal or reduced thickness of the left ventricular wall. It is a leading cause of heart failure and cardiac death at a young age. Cases with neonatal onset DCM were correlated with severe clinical presentation and poor prognosis. A monogenic molecular etiology accounts for nearly half of cases.

FAMILY DESCRIPTION

Here, we report a family with three deceased offspring at the age of 1 year old. The autopsy of the first deceased infant revealed a DCM. The second infant presented a DCM phenotype with a severely reduced Left Ventricular Ejection Fraction (LVEF) of 10%. Similarly, the third infant showed a severe DCM phenotype with LVEF of 30% as well, in addition to eccentric mitral insufficiency.

RESULTS

Exome sequencing was performed for the trio (the second deceased infant and her parents). Data analysis following the autosomal dominant and recessive patterns of inheritance was carried out along with a mitochondrial pathways-based analysis. We identified a homozygous frameshift variant in the TNNI3 gene (c.204delG; p.(Arg69AlafsTer8)). This variant has been recently reported in the ClinVar database in association with cardiac phenotypes as pathogenic or likely pathogenic and classified as pathogenic according to ACMG.

CONCLUSION

Genetic counseling was provided for the family and a prenatal diagnosis of choronic villus was proposed in the absence of pre-implantation genetic diagnosis possibilities. Our study expands the case series of early-onset DCM patients with a protein-truncating variant in the TNNI3 gene by reporting three affected infant siblings.

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.

Life at the crossroads: the nuclear LINC complex and vascular mechanotransduction

Vascular endothelial cells line the inner surface of all blood vessels, where they are exposed to polarized mechanical forces throughout their lifespan. Both basal substrate interactions and apical blood flow-induced shear stress regulate blood vessel development, remodeling, and maintenance of vascular homeostasis. Disruption of these interactions leads to dysfunction and vascular pathologies, although how forces are sensed and integrated to affect endothelial cell behaviors is incompletely understood. Recently the endothelial cell nucleus has emerged as a prominent force-transducing organelle that participates in vascular mechanotransduction, via communication to and from cell-cell and cell-matrix junctions. The LINC complex, composed of SUN and nesprin proteins, spans the nuclear membranes and connects the nuclear lamina, the nuclear envelope, and the cytoskeleton. Here we review LINC complex involvement in endothelial cell mechanotransduction, describe unique and overlapping functions of each LINC complex component, and consider emerging evidence that two major SUN proteins, SUN1 and SUN2, orchestrate a complex interplay that extends outward to cell-cell and cell-matrix junctions and inward to interactions within the nucleus and chromatin. We discuss these findings in relation to vascular pathologies such as Hutchinson-Gilford progeria syndrome, a premature aging disorder with cardiovascular impairment. More knowledge of LINC complex regulation and function will help to understand how the nucleus participates in endothelial cell force sensing and how dysfunction leads to cardiovascular disease.

Circular RNAs: a small piece in the heart failure puzzle

Cardiovascular disease, specifically heart failure (HF), remains a significant concern in the realm of healthcare, necessitating the development of new treatments and biomarkers. The RNA family consists of various subgroups, including microRNAs, PIWI-interacting RNAs (piRAN) and long non-coding RNAs, which have shown potential in advancing personalized healthcare for HF patients. Recent research suggests that circular RNAs, a lesser-known subgroup of RNAs, may offer a novel set of targets and biomarkers for HF. This review will discuss the biogenesis of circular RNAs, their unique characteristics relevant to HF, their role in heart function, and their potential use as biomarkers in the bloodstream. Furthermore, future research directions in this field will be outlined. The stability of exosomal circRNAs makes them suitable as biomarkers, pathogenic regulators, and potential treatments for cardiovascular diseases such as atherosclerosis, acute coronary syndrome, ischemia/reperfusion injury, HF, and peripheral artery disease. Herein, we summarized the role of circular RNAs and their exosomal forms in HF diseases.

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.

A bibliometric and visual analysis of research trends and hotspots of familial hypertrophic cardiomyopathy: A review

Familial hypertrophic cardiomyopathy (FHCM) is an inherited cardiac disease caused by mutations of sarcomere proteins and can be the underlining substrate for major cardiovascular events. Early identification and diagnosis of FHCM are essential to reduce sudden cardiac death. So, this paper summarized the current knowledge on FHCM, and displayed the analysis via bibliometrics method. The relevant literature on FHCM were screened searched via the Web of Science Core Collection database from 2012 to 2022. The literatures were was summarized and analyzed via the bibliometrics method analyzed via CiteSpace and VOSviewer according to topic categories, distribution of spatiotemporal omics and authors, as well as references. Since 2012, there are 909 research articles and reviews related to FHCM. The number of publication for the past 10 years have shown that the development of FHCM research has been steady, with the largest amount of literature in 2012. The most published papers were from the United States, followed by the United Kingdom and Italy. The University of London (63 papers) was the institution that published the most research articles, followed by Harvard University (45 papers) and University College London (45 papers). Keywords formed 3 clusters, focused on the pathogenesis of FHCM, the diagnosis of FHCM, FHCM complications, respectively. The bibliometric analysis and visualization techniques employed herein highlight key trends and focal points in the field, predominantly centered around FHCM's pathogenesis, diagnostic approaches, and its complications. These insights are instrumental in steering future research directions in this area.

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.

Translating myosin-binding protein C and titin abnormalities to whole-heart function using a novel calcium-contraction coupling model

Mutations in cardiac myosin-binding protein C (cMyBP-C) or titin may respectively lead to hypertrophic (HCM) or dilated (DCM) cardiomyopathies. The mechanisms leading to these phenotypes remain unclear because of the challenge of translating cellular abnormalities to whole-heart and system function. We developed and validated a novel computer model of calcium-contraction coupling incorporating the role of cMyBP-C and titin based on the key assumptions: 1) tension in the thick filament promotes cross-bridge attachment mechanochemically, 2) with increasing titin tension, more myosin heads are unlocked for attachment, and 3) cMyBP-C suppresses cross-bridge attachment. Simulated stationary calcium-tension curves, isotonic and isometric contractions, and quick release agreed with experimental data. The model predicted that a loss of cMyBP-C function decreases the steepness of the calcium-tension curve, and that more compliant titin decreases the level of passive and active tension and its dependency on sarcomere length. Integrating this cellular model in the CircAdapt model of the human heart and circulation showed that a loss of cMyBP-C function resulted in HCM-like hemodynamics with higher left ventricular end-diastolic pressures and smaller volumes. More compliant titin led to higher diastolic pressures and ventricular dilation, suggesting DCM-like hemodynamics. The novel model of calcium-contraction coupling incorporates the role of cMyBP-C and titin. Its coupling to whole-heart mechanics translates changes in cellular calcium-contraction coupling to changes in cardiac pump and circulatory function and identifies potential mechanisms by which cMyBP-C and titin abnormalities may develop into HCM and DCM phenotypes. This modeling platform may help identify distinct mechanisms underlying clinical phenotypes in cardiac diseases.

Variants in structural cardiac genes in patients with cancer therapy-related cardiac dysfunction after anthracycline chemotherapy: a case control study

BACKGROUND

Variants in cardiomyopathy genes have been identified in patients with cancer therapy-related cardiac dysfunction (CTRCD), suggesting a genetic predisposition for the development of CTRCD. The diagnostic yield of genetic testing in a CTRCD population compared to a cardiomyopathy patient cohort is not yet known and information on which genes should be assessed in this population is lacking.

METHODS

We retrospectively included 46 cancer patients with a history of anthracycline induced CTRCD (defined as a decrease in left ventricular ejection fraction (LVEF) to < 50% and a ≥ 10% reduction from baseline by echocardiography). Genetic testing was performed for 59 established cardiomyopathy genes. Only variants of uncertain significance and (likely) pathogenic variants were included. Diagnostic yield of genetic testing was compared with a matched cohort of patients with dilated cardiomyopathy (DCM, n = 46) and a matched cohort of patients without cardiac disease (n = 111).

RESULTS

Average LVEF at time of CTRCD diagnosis was 30.1 ± 11.0%. Patients were 52.9 ± 14.6 years old at time of diagnosis and 30 (65.2%) were female. Most patients were treated for breast cancer or lymphoma, with a median doxorubicin equivalent dose of 300 mg/m2 [112.5-540.0]. A genetic variant, either pathogenic, likely pathogenic or of uncertain significance, was identified in 29/46 (63.0%) of patients with CTRCD, which is similar to the DCM cohort (34/46, 73.9%, p = 0.262), but significantly higher than in the negative control cohort (47/111, 39.6%, p = 0.018). Variants in TTN were the most prevalent in the CTRCD cohort (43% of all variants). All (likely) pathogenic variants identified in the CTRCD cohort were truncating variants in TTN. There were no significant differences in severity of CTRCD and in recovery rate in variant-harbouring individuals versus non-variant harbouring individuals.

CONCLUSIONS

In this case-control study, cancer patients with anthracycline-induced CTRCD have an increased burden of genetic variants in cardiomyopathy genes, similar to a DCM cohort. If validated in larger prospective studies, integration of genetic data in risk prediction models for CTRCD may guide cancer treatment. Moreover, genetic results have important clinical impact, both for the patient in the setting of precision medicine, as for the family members that will receive genetic counselling.

CRISPR Activation Reverses Haploinsufficiency and Functional Deficits Caused by TTN Truncation Variants

BACKGROUND

TTN truncation variants (TTNtvs) are the most common genetic lesion identified in individuals with dilated cardiomyopathy, a disease with high morbidity and mortality rates. TTNtvs reduce normal TTN (titin) protein levels, produce truncated proteins, and impair sarcomere content and function. Therapeutics targeting TTNtvs have been elusive because of the immense size of TTN, the rarity of specific TTNtvs, and incomplete knowledge of TTNtv pathogenicity.

METHODS

We adapted CRISPR activation using dCas9-VPR to functionally interrogate TTNtv pathogenicity and develop a therapeutic in human cardiomyocytes and 3-dimensional cardiac microtissues engineered from induced pluripotent stem cell models harboring a dilated cardiomyopathy-associated TTNtv. We performed guide RNA screening with custom TTN reporter assays, agarose gel electrophoresis to quantify TTN protein levels and isoforms, and RNA sequencing to identify molecular consequences of TTN activation. Cardiomyocyte epigenetic assays were also used to nominate DNA regulatory elements to enable cardiomyocyte-specific TTN activation.

RESULTS

CRISPR activation of TTN using single guide RNAs targeting either the TTN promoter or regulatory elements in spatial proximity to the TTN promoter through 3-dimensional chromatin interactions rescued TTN protein deficits disturbed by TTNtvs. Increasing TTN protein levels normalized sarcomere content and contractile function despite increasing truncated TTN protein. In addition to TTN transcripts, CRISPR activation also increased levels of myofibril assembly-related and sarcomere-related transcripts.

CONCLUSIONS

TTN CRISPR activation rescued TTNtv-related functional deficits despite increasing truncated TTN levels, which provides evidence to support haploinsufficiency as a relevant genetic mechanism underlying heterozygous TTNtvs. CRISPR activation could be developed as a therapeutic to treat a large proportion of TTNtvs.

Titin: roles in cardiac function and diseases

The giant protein titin is an essential component of muscle sarcomeres. A single titin molecule spans half a sarcomere and mediates diverse functions along its length by virtue of its unique domains. The A-band of titin functions as a molecular blueprint that defines the length of the thick filaments, the I-band constitutes a molecular spring that determines cell-based passive stiffness, and various domains, including the Z-disk, I-band, and M-line, serve as scaffolds for stretch-sensing signaling pathways that mediate mechanotransduction. This review aims to discuss recent insights into titin's functional roles and their relationship to cardiac function. The role of titin in heart diseases, such as dilated cardiomyopathy and heart failure with preserved ejection fraction, as well as its potential as a therapeutic target, is also discussed.