The importance of genetic counseling, DNA diagnostics, and cardiologic family screening in left ventricular noncompaction cardiomyopathy

Identification of a novel likely pathogenic TPM1 variant linked to hypertrophic cardiomyopathy in a family with sudden cardiac death

AIMS

Hypertrophic cardiomyopathy (HCM) is an autosomal dominant genetic cardiac disorder characterized by unexplained left ventricular hypertrophy. It can cause a wide spectrum of clinical manifestations, ranging from asymptomatic to heart failure and sudden cardiac death (SCD). Approximately half of HCM cases are caused by variants in sarcomeric proteins, including α-tropomyosin (TPM1). In this study, we aimed to characterize the clinical and molecular phenotype of HCM in an Iranian pedigree with SCD.

METHODS AND RESULTS

The proband and available family members underwent comprehensive clinical evaluations, including echocardiography, cardiac magnetic resonance (CMR) imaging and electrocardiography (ECG). Whole-exome sequencing (WES) was performed in all available family members to identify the causal variant, which was validated, and segregation analysis was conducted via Sanger sequencing. WES identified a novel missense variant, c.761A>G:p.D254G (NM_001018005.2), in the TPM1 gene, in the proband, his father and one of his sisters. Bioinformatic analysis predicted it to be likely pathogenic. Clinical features in affected individuals were consistent with HCM.

CONCLUSIONS

The identification of a novel TPM1 variant in a family with HCM and SCD underscores the critical role of genetic screening in at-risk families. Early detection of pathogenic variants can facilitate timely intervention and management, potentially reducing the risk of SCD in individuals with HCM.

Left Ventricular Non-Compaction: Evolving Concepts

Left ventricular non-compaction (LVNC) is a rare heart muscle disease defined by the presence of prominent left ventricular trabeculation, deep intertrabecular recesses, and a thin compact layer. Several hypotheses have been proposed regarding its pathogenesis, with the most recently accepted one being that compact layer and trabeculated layers develop independently according to an "allometric growth". The current gold-standard diagnostic criteria (in particular, the Petersen index non-compaction/compaction ratio > 2.3) reflect an excess of myocardial trabeculation, which is not a specific morpho-functional feature of LVNC cardiomyopathy but merely a "phenotypic trait", even described in association with other myocardial disease and over-loading conditions. Accordingly, the European Society of Cardiology (ESC) guidelines have definitively abolished the term 'LVNC cardiomyopathy'. Recently, evolving perspectives led to the restoration of LVNC cardiomyopathy by distinguishing "hypertrabeculation phenotype" and "non-compaction phenotype". It has been proposed that the disease-specific pathophysiologic mechanism is a congenitally underdevelopment of the compact layer accounting for an impairment of the left ventricular systolic function. Future prospective research should focus on the clinical and prognostic relevance of compact layer thinning rather than excessive trabeculation, which could significantly influence the management of patients with LVNC. The review aims to update current knowledge on the pathogenesis, genetics, and diagnostic criteria of LVNC, offering modern insights for future perspectives.

Multidisciplinary approach in cardiomyopathies: From genetics to advanced imaging

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

Genetic, clinical and imaging implications of a noncompaction phenotype population with preserved ejection fraction

Introduction

The genotype of symptomatic left ventricular noncompaction phenotype (LVNC) subjects with preserved left ventricular ejection fraction (LVEF) and its effect on clinical presentation are less well studied. We aimed to characterize the genetic, cardiac magnetic resonance (CMR) and clinical background, and genotype-phenotype relationship in LVNC with preserved LVEF.

Methods

We included 54 symptomatic LVNC individuals (LVEF: 65 ± 5%) whose samples were analyzed with a 174-gene next-generation sequencing panel and 54 control (C) subjects. The results were evaluated using the criteria of the American College of Medical Genetics and Genomics. Medical data suggesting a higher risk of cardiovascular complications were considered "red flags".

Results

Of the LVNC population, 24% carried pathogenic or likely pathogenic (P) mutations; 56% carried variants of uncertain significance (VUS); and 20% were free from cardiomyopathy-related mutations. Regarding the CMR parameters, the LVNC and C groups differed significantly, while the three genetic subgroups were comparable. We found a significant relationship between red flags and genotype; furthermore, the number of red flags in a single subject differed significantly among the genetic subgroups (p = 0.002) and correlated with the genotype (r = 0.457, p = 0.01). In 6 out of 7 LVNC subjects diagnosed in childhood, P or VUS mutations were found.

Discussion

The large number of P mutations and the association between red flags and genotype underline the importance of genetic-assisted risk stratification in symptomatic LVNC with preserved LVEF.

Case report: A rare case of left ventricular noncompaction in two Chinese siblings with becker muscular dystrophy caused by deletion of exons 10 to 12 in the DMD gene

Background

Becker muscular dystrophy (BMD) is an inherited X-linked recessive condition resulting from mutations of the DMD gene encoding dystrophin. Left ventricular noncompaction (LVNC) is a rare cardiomyopathy morphologically characterized by abnormal myocardial trabeculae and deep recesses in the left ventricle. LVNC in BMD patients has only rarely been reported.

Case report

In the present study, we identified a deletion mutation in exons 10 to 12 (EX10_12 del) of the DMD gene (reference sequence NM_004006.2) in two Chinese siblings with BMD and LVNC by high throughput targeted next-generation sequencing (NGS) and quantitative polymerase chain reaction (qPCR). The proband was a 22-year-old man admitted with dyspnea, abdominal distention, and polyserositis. It is noteworthy that both the proband and his younger brother manifested progressive muscular atrophy and creatine kinase (CK) elevation. Light and electron microscopy examination of muscle biopsies showed the typical features of dystrophinopathies. Cardiac magnetic resonance imaging and echocardiography demonstrated that both brothers had an enlarged left ventricle, LVNC, and reduced left ventricular ejection fraction. Finally, the proband underwent heart transplantation at age 26 with an event-free follow-up over 4 years post-transplantation.

Conclusion

This case further enriches our knowledge of the symptoms, genotype, cardiac performance, management, and prognosis of BMD patients complicated by LVNC. It is recommended that early comprehensive cardiac evaluation should be considered for patients with BMD to exclude LVNC, as this may have a significant impact on their prognosis.

A novel mutation in the TTN gene resulted in left ventricular noncompaction: a case report and literature review

BACKGROUND

Left ventricular noncompaction (LVNC) is a specific type of cardiomyopathy characterized by coarse trabeculae and interspersed trabecular crypts within the ventricles. Clinical presentation varies widely and may be nonsignificant or may present with progressive heart failure, malignant arrhythmias, and multiorgan embolism. The mode of inheritance is highly heterogeneous but is most commonly autosomal dominant. The TTN gene encodes titin, which is not only an elastic component of muscle contraction but also mediates multiple signalling pathways in striated muscle cells. In recent years, mutations in the TTN gene have been found to be associated with LVNC, but the exact pathogenesis is still not fully clarified.

CASE PRESENTATION

In this article, we report a case of an adult LVNC patient with a TTN gene variant, c.87857G > A (p. Trp29286*), that has not been reported previously. This 43-year-old adult male was hospitalized repeatedly for heart failure. Echocardiography showed reduced myocardial contractility, dilated left ventricle with many prominent trabeculae, and a loose texture of the left ventricular layer of myocardium with crypt-like changes. During the out-of-hospital follow-up, the patient had no significant signs or symptoms of discomfort.

CONCLUSION

This case report enriches the mutational spectrum of the TTN gene in LVNC and provides a basis for genetic counselling and treatment of this patient. Clinicians should improve their understanding of LVNC, focusing on exploring its pathogenesis and genetic characteristics to provide new directions for future diagnosis and treatment.

Divergent Molecular Phenotypes in Point Mutations at the Same Residue in Beta-Myosin Heavy Chain Lead to Distinct Cardiomyopathies

In genetic cardiomyopathies, a frequently described phenomenon is how similar mutations in one protein can lead to discrete clinical phenotypes. One example is illustrated by two mutations in beta myosin heavy chain (β-MHC) that are linked to hypertrophic cardiomyopathy (HCM) (Ile467Val, I467V) and left ventricular non-compaction (LVNC) (Ile467Thr, I467T). To investigate how these missense mutations lead to independent diseases, we studied the molecular effects of each mutation using recombinant human β-MHC Subfragment 1 (S1) in in vitro assays. Both HCM-I467V and LVNC-I467T S1 mutations exhibited similar mechanochemical function, including unchanged ATPase and enhanced actin velocity but had opposing effects on the super-relaxed (SRX) state of myosin. HCM-I467V S1 showed a small reduction in the SRX state, shifting myosin to a more actin-available state that may lead to the "gain-of-function" phenotype commonly described in HCM. In contrast, LVNC-I467T significantly increased the population of myosin in the ultra-slow SRX state. Interestingly, molecular dynamics simulations reveal that I467T allosterically disrupts interactions between ADP and the nucleotide-binding pocket, which may result in an increased ADP release rate. This predicted change in ADP release rate may define the enhanced actin velocity measured in LVNC-I467T, but also describe the uncoupled mechanochemical function for this mutation where the enhanced ADP release rate may be sufficient to offset the increased SRX population of myosin. These contrasting molecular effects may lead to contractile dysregulation that initiates LVNC-associated signaling pathways that progress the phenotype. Together, analysis of these mutations provides evidence that phenotypic complexity originates at the molecular level and is critical to understanding disease progression and developing therapies.

Nucleotide sequence variant of the TPM1 gene in a family with different phenotypes of left ventricular non-compaction

Left ventricular non-compaction (LVNC) is a rare, genetically and phenotypically heterogeneous disease, which is often accompanied by diagnostic difficulties.

Aim. To demonstrate several generations of a family with LVNC with various clinical and phenotypic manifestations of the disease (dilated and isolated types of LVNC) with an identified rs397516387 variant of the TPM1 gene.

Material and methods. Based on the multicenter registry "Myocardial Non-compaction", a family with a familial form of LVNC was selected. Next generation sequencing (NGS) was performed on an Ion S5 system (Thermo Fisher Scientific, USA) using Ampliseq technology. Variant was verified using Sanger sequencing on an Applied Biosystem 3500 Genetic Analyzer (Thermo Fisher Scientific, USA). For clinical interpretation, variants in the genes associated with LVNC with a minor allele frequency <0,1% were selected in the gnomAD database (v2.1.1). Results. Variant rs397516387 was found in 5 family members, including the proband. Further examination revealed LVNC in 2 additional family members. The proband and the proband’s uncle had a dilated type of LVNC, and the proband’s mother had an isolated type.

Conclusion. The paper presents several generations of a family with different phenotypic manifestations of LVNC and rs397516387 variant in the TPM1 gene. The beginning of genetic screening from a proband, a thorough collection of a family history and further detailed genetic screening of relatives led to the identification of rs397516387 variant in 4 more family members, which in turn made it possible to conduct an additional examination to confirm the diagnosis and prescribe timely drug therapy.

A Human Hereditary Cardiomyopathy Shares a Genetic Substrate With Bicuspid Aortic Valve

BACKGROUND

The complex genetics underlying human cardiac disease is evidenced by its heterogenous manifestation, multigenic basis, and sporadic occurrence. These features have hampered disease modeling and mechanistic understanding. Here, we show that 2 structural cardiac diseases, left ventricular noncompaction (LVNC) and bicuspid aortic valve, can be caused by a set of inherited heterozygous gene mutations affecting the NOTCH ligand regulator MIB1 (MINDBOMB1) and cosegregating genes.

METHODS

We used CRISPR-Cas9 gene editing to generate mice harboring a nonsense or a missense MIB1 mutation that are both found in LVNC families. We also generated mice separately carrying these MIB1 mutations plus 5 additional cosegregating variants in the ASXL3, APCDD1, TMX3, CEP192, and BCL7A genes identified in these LVNC families by whole exome sequencing. Histological, developmental, and functional analyses of these mouse models were carried out by echocardiography and cardiac magnetic resonance imaging, together with gene expression profiling by RNA sequencing of both selected engineered mouse models and human induced pluripotent stem cell-derived cardiomyocytes. Potential biochemical interactions were assayed in vitro by coimmunoprecipitation and Western blot.

RESULTS

Mice homozygous for the MIB1 nonsense mutation did not survive, and the mutation caused LVNC only in heteroallelic combination with a conditional allele inactivated in the myocardium. The heterozygous MIB1 missense allele leads to bicuspid aortic valve in a NOTCH-sensitized genetic background. These data suggest that development of LVNC is influenced by genetic modifiers present in affected families, whereas valve defects are highly sensitive to NOTCH haploinsufficiency. Whole exome sequencing of LVNC families revealed single-nucleotide gene variants of ASXL3, APCDD1, TMX3, CEP192, and BCL7A cosegregating with the MIB1 mutations and LVNC. In experiments with mice harboring the orthologous variants on the corresponding Mib1 backgrounds, triple heterozygous Mib1 Apcdd1 Asxl3 mice showed LVNC, whereas quadruple heterozygous Mib1 Cep192 Tmx3;Bcl7a mice developed bicuspid aortic valve and other valve-associated defects. Biochemical analysis suggested interactions between CEP192, BCL7A, and NOTCH. Gene expression profiling of mutant mouse hearts and human induced pluripotent stem cell-derived cardiomyocytes revealed increased cardiomyocyte proliferation and defective morphological and metabolic maturation.

CONCLUSIONS

These findings reveal a shared genetic substrate underlying LVNC and bicuspid aortic valve in which MIB1-NOTCH variants plays a crucial role in heterozygous combination with cosegregating genetic modifiers.

The Electrocardiogram in the Diagnosis and Management of Patients With Left Ventricular Non-Compaction

PURPOSE OF THE REVIEW

Left ventricular non-compaction (LVNC) is characterised by prominent left ventricular trabeculae and deep inter-trabecular recesses. Although considered a distinct cardiomyopathy, prominent trabeculations may also be found in other cardiomyopathies, in athletes or during pregnancy. Clinical presentation includes heart failure symptoms, systemic embolic events, arrhythmias and sudden cardiac death. Currently, LVNC diagnosis relies on imaging criteria, and clinicians face several challenges in the assessment of patients with prominent trabeculations. In this review, we summarise the available information on the role of the ECG in the diagnosis and management of LVNC.

RECENT FINDINGS

ECG abnormalities have been reported in 75-94% of adults and children with LVNC. The lack of specificity of these ECG abnormalities does not allow (in isolation) to diagnose the condition. However, when considered in a set of diagnostic criteria including family history, clinical information, and imaging features, the ECG may differentiate between physiological and pathological findings or may provide clues raising the possibility of specific underlying conditions. Finally, some ECG features in LVNC constitute ominous signs that require a stricter patient surveillance or specific therapeutic measures. The ECG remains a cornerstone in the diagnosis and management of patients with cardiomyopathies, including LVNC.

Left Ventricular Noncompaction in Children: The Role of Genetics, Morphology, and Function for Outcome

Left ventricular noncompaction (LVNC) is a ventricular wall anomaly morphologically characterized by numerous, excessively prominent trabeculations and deep intertrabecular recesses. Accumulating data now suggest that LVNC is a distinct phenotype but must not constitute a pathological phenotype. Some individuals fulfill the morphologic criteria of LVNC and are without clinical manifestations. Most importantly, morphologic criteria for LVNC are insufficient to diagnose patients with an associated cardiomyopathy (CMP). Genetic testing has become relevant to establish a diagnosis associated with CMP, congenital heart disease, neuromuscular disease, inborn error of metabolism, or syndromic disorder. Genetic factors play a more decisive role in children than in adults and severe courses of LVNC tend to occur in childhood. We reviewed the current literature and highlight the difficulties in establishing the correct diagnosis for children with LVNC. Novel insights show that the interplay of genetics, morphology, and function determine the outcome in pediatric LVNC.

Endocardial Regulation of Cardiac Development

The endocardium is a specialized form of endothelium that lines the inner side of the heart chambers and plays a crucial role in cardiac development. While comparatively less studied than other cardiac cell types, much progress has been made in understanding the regulation of and by the endocardium over the past two decades. In this review, we will summarize what is currently known regarding endocardial origin and development, the relationship between endocardium and other cardiac cell types, and the various lineages that endocardial cells derive from and contribute to. These processes are driven by key molecular mechanisms such as Notch and BMP signaling. These pathways in particular have been well studied, but other signaling pathways and mechanical cues also play important roles. Finally, we will touch on the contribution of stem cell modeling in combination with single cell sequencing and its potential translational impact for congenital heart defects such as bicuspid aortic valves and hypoplastic left heart syndrome. The detailed understanding of cellular and molecular processes in the endocardium will be vital to further develop representative stem cell-derived models for disease modeling and regenerative medicine in the future.

Cardiomyopathies in Children and Systemic Disorders When Is It Useful to Look beyond the Heart?

Cardiomyopathy (CMP) is a rare disease in the pediatric population, with a high risk of morbidity and mortality. The genetic etiology of CMPs in children is extremely heterogenous. These two factors play a major role in the difficulties of establishing standard diagnostic and therapeutic protocols. Isolated CMP in children is a frequent finding, mainly caused by sarcomeric gene variants with a detection rate that can reach up to 50% of analyzed cohorts. Complex multisystemic forms of pediatric CMP are even more heterogenous. Few studies in literature take into consideration this topic as the main core since it represents a rarity (systemic CMP) within a rarity (pediatric population CMP). Identifying etiology in this cohort is essential for understanding prognosis, risk stratification, eligibility to heart transplantation and/or mechanical-assisted procedures, preventing multiorgan complications, and relatives' recurrence risk calculation. The previous points represent a cornerstone in patients' empowerment and personalized medical care approach. The aim of this work is to propose a new approach for an algorithm in the setting of the diagnostic framework of systemic pediatric CMP. On the other hand, during the literature review, we noticed a relatively common etiologic pattern in some forms of complex/multisystem CMP. In other words, certain syndromes such as Danon, Vici, Alström, Barth, and Myhre syndrome share a common pathway of directly or indirectly defective "autophagy" process, which appears to be a possible initiating/triggering factor for CMPs. This conjoint aspect could be important for possible prognostic/therapeutic implications in this category of patients. However, multicentric studies detailed functional and experimental models are needed prior to deriving conclusions.

Combining whole exome sequencing with in silico analysis and clinical data to identify candidate variants in pediatric left ventricular noncompaction

BACKGROUND

Understanding the overall variant burden in pediatric patients with left ventricular noncompaction (LVNC) has clinical implications. Whole exome sequencing (WES) allows detection of coding variants in both candidate cardiomyopathy genes and those included on commercial panels. Other lines of evidence, including in silico analysis, are necessary to reduce the overwhelming number of variants to those most likely having a phenotypic impact.

METHODS

Five families, including five pediatric probands with LVNC, 5 other affected, and 10 unaffected family members, had WES performed, followed by bioinformatics filtering and Sanger sequencing. Review of the HGMD, variant classification by ACMG guidelines, and clinical information were used to further refine complex genotypes.

RESULTS

One nonsense and eleven missense variants were identified. In Family 1, affected siblings carried digenic heterozygous variants: E1350K-MYH7 and A276V-ANKRD1. The proband also carried heterozygous W143X-NRG1. Four affected members of Family 2 carried K184Q-MYH7 while unaffected members did not. In Family 3, homozygous A161T-MYH7 and heterozygous P4935T-OBSCN variants were identified in the proband with the latter being absent in his unaffected brother. In Family 4, proband's father and half-sibling have mild hypertrabeculation and carry T3796I-PLEC. The proband, carrying T3796I-PLEC and V2878A-OBSCN, demonstrated higher trabeculation burden. The proband in Family 5 carried four variants, R3247W-PLEC, C92Y-ERG, T1233M-NCOR2, and E54K-HIST1H4B. Application of ACMG criteria and clinical data revealed that W143X-NRG1, P4935T-OBSCN, and V2878A-OBSCN likely have no phenotypic role.

CONCLUSIONS

We report nine variants, including novel T3796I-PLEC and biallelic A161T-MYH7, likely contributing to phenotypes ranging from asymptomatic hypertrabeculation to severe LVNC with heart failure.

Case Report of Left Ventricular Noncompaction Cardiomyopathy Characterized by Undulating Phenotypes in Adult Patients

Left ventricular noncompaction cardiomyopathy (LVNC) is a heart muscle disorder morphologically characterized by reticulated trabeculations and intertrabecular recesses in the left ventricular (LV) cavity. LVNC is a genetically and phenotypically heterogeneous condition, which has been increasingly recognized with the accumulation of evidence provided by genotype-phenotype correlation analyses. Here, we report 2 sporadic adult cases of LVNC; both developed acute heart failure as an initial clinical manifestation and harbored causal sarcomere gene mutations. One case was a 57-year-old male with digenic heterozygote mutations, p.R1344Q in myosin heavy chain 7 (MYH7) and p.R144W in troponin T2, cardiac type (TNNT2), who showed morphological characteristics of LVNC in the lateral to apical regions of the LV together with a comorbidity of non-transmural myocardial infarction, resulting from a coronary artery stenosis. After the removal of ischemic insult and standard heart failure treatment, LVNC became less clear, and LV function gradually improved. The other case was a 36-year-old male with a heterozygote mutation, p.E334K in myosin binding protein C3 (MYBPC3), who exhibited cardiogenic shock on admission with morphological characteristics of LVNC being most prominent in the apical segment of the LV. The dosage of beta-blocker was deliberately increased in an outpatient clinic over 6 months following hospitalization, which remarkably improved the LV ejection fraction from 21% to 54.3%. Via a combination of imaging and histopathological and genetic tests, we have found that these cases are not compatible with a persistent phenotype of primary cardiomyopathy, but their morphological features are changeable in response to treatment. Thus, we point out phenotypic plasticity or undulation as a noticeable element of LVNC in this case report.

Overlap phenotypes of the left ventricular noncompaction and hypertrophic cardiomyopathy with complex arrhythmias and heart failure induced by the novel truncated DSC2 mutation

Background

The left ventricular noncompaction cardiomyopathy (LVNC) is a rare subtype of cardiomyopathy associated with a high risk of heart failure (HF), thromboembolism, arrhythmia, and sudden cardiac death.

Methods

The proband with overlap phenotypes of LVNC and hypertrophic cardiomyopathy (HCM) complicates atrial fibrillation (AF), ventricular tachycardia (VT), and HF due to the diffuse myocardial lesion, which were diagnosed by electrocardiogram, echocardiogram and cardiac magnetic resonance imaging. Peripheral blood was collected from the proband and his relatives. DNA was extracted from the peripheral blood of proband for high-throughput target capture sequencing. The Sanger sequence verified the variants. The protein was extracted from the skin of the proband and healthy volunteer. The expression difference of desmocollin2 was detected by Western blot.

Results

The novel heterozygous truncated mutation (p.K47Rfs*2) of the DSC2 gene encoding an important component of desmosomes was detected by targeted capture sequencing. The western blots showed that the expressing level of functional desmocollin2 protein (~ 94kd) was lower in the proband than that in the healthy volunteer, indicating that DSC2 p.K47Rfs*2 obviously reduced the functional desmocollin2 protein expression in the proband.

Conclusion

The heterozygous DSC2 p.K47Rfs*2 remarkably and abnormally reduced the functional desmocollin2 expression, which may potentially induce the overlap phenotypes of LVNC and HCM, complicating AF, VT, and HF.

Genetics of Cardiomyopathy: Clinical and Mechanistic Implications for Heart Failure

Genetic cardiomyopathies are an important cause of sudden cardiac death across all age groups. Genetic testing in heart failure clinics is useful for family screening and providing individual prognostic insight. Obtaining a family history of at least three generations, including the creation of a pedigree, is recommended for all patients with primary cardiomyopathy. Additionally, when appropriate, consultation with a genetic counsellor can aid in the success of a genetic evaluation. Clinical screening should be performed on all first-degree relatives of patients with genetic cardiomyopathy.

Genetics has played an important role in the understanding of different cardiomyopathies, and the field of heart failure (HF) genetics is progressing rapidly. Much research has also focused on distinguishing markers of risk in patients with cardiomyopathy using genetic testing. While these efforts currently remain incomplete, new genomic technologies and analytical strategies provide promising opportunities to further explore the genetic architecture of cardiomyopathies, afford insight into the early manifestations of cardiomyopathy, and help define the molecular pathophysiological basis for cardiac remodeling. Cardiovascular physicians should be fully aware of the utility and potential pitfalls of incorporating genetic test results into pre-emptive treatment strategies for patients in the preliminary stages of HF. Future work will need to be directed towards elucidating the biological mechanisms of both rare and common gene variants and environmental determinants of plasticity in the genotype-phenotype relationship. This future research should aim to further our ability to identify, diagnose, and treat disorders that cause HF and sudden cardiac death in young patients, as well as prioritize improving our ability to stratify the risk for these patients prior to the onset of the more severe consequences of their disease.

Ventricular non-compaction review

Left ventricular non-compaction cardiomyopathy (LVNC) is a rare and unclassified cardiomyopathy that carries the potential to cause heart failure, arrhythmias, and embolic events within adults. The diagnosis of this cardiomyopathy can be based off a variety of echocardiographic, cardiac magnetic resonance (CMR), and computed tomography (CT) imaging criteria; none of which have been standardized to establish a firm diagnosis. This is further complicated by the observation from prior studies that LVNC may present as different forms of cardiomyopathy, each with its own subset of nuances that may change treatment strategies. Management of such cardiomyopathy has been debated in terms of anticoagulation, electrophysiologic studies to prevent arrhythmia, as well as heart failure prevention. Not enough data exists in regard to establishing firm guidelines for management. The following article aims to provide a comprehensive review in regard to the etiologies, pathogenesis, diagnostic criteria, management, and treatment of LVNC.

The pivotal role of cardiovascular imaging in the identification and risk stratification of non-compaction cardiomyopathy patients

Non-compaction cardiomyopathy (NCM) is a heterogeneous myocardial disease that can finally lead to heart failure, arrhythmias, and/or embolic events. Therefore, early diagnosis and treatment is of paramount importance. Furthermore, genetic assessment and counseling are crucial for individual risk assessment and family planning. Echocardiography is the first-line imaging modality. However, it is hampered by interobserver variability, depends among others on the quality of the acoustic window, cannot assess reliably the right ventricle and the apex, and cannot provide tissue characterization. Cardiovascular magnetic resonance (CMR) provides a 3D approach allowing imaging of the entire heart, including both left and right ventricle, with low operator variability or limitations due to patient's body structure. Furthermore, tissue characterization, using late gadolinium enhancement (LGE), allows the detection of fibrotic areas possibly representing the substrate for potentially lethal arrhythmias, predicts the severity of LV systolic dysfunction, and differentiates apical thrombus from fibrosis. Conversely, besides being associated with high costs, CMR has long acquisition/processing times, lack of expertise among cardiologists/radiologists, and limited availability. Additionally, in cases of respiratory and/or cardiac motion artifacts or arrhythmias, the cine images may be blurred. However, CMR cannot be applied to patients with not CMR-compatible implanted devices and LGE may be not available in patients with severely reduced GFR. Nevertheless, native T1 mapping can provide detailed tissue characterization in such cases. This tremendous potential of CMR makes this modality the ideal tool for better risk stratification of NCM patient, based not only on functional but also on tissue characterization information.

Genetic Cardiomyopathies: The Lesson Learned from hiPSCs

Genetic cardiomyopathies represent a wide spectrum of inherited diseases and constitute an important cause of morbidity and mortality among young people, which can manifest with heart failure, arrhythmias, and/or sudden cardiac death. Multiple underlying genetic variants and molecular pathways have been discovered in recent years; however, assessing the pathogenicity of new variants often needs in-depth characterization in order to ascertain a causal role in the disease. The application of human induced pluripotent stem cells has greatly helped to advance our knowledge in this field and enabled to obtain numerous in vitro patient-specific cellular models useful to study the underlying molecular mechanisms and test new therapeutic strategies. A milestone in the research of genetically determined heart disease was the introduction of genomic technologies that provided unparalleled opportunities to explore the genetic architecture of cardiomyopathies, thanks to the generation of isogenic pairs. The aim of this review is to provide an overview of the main research that helped elucidate the pathophysiology of the most common genetic cardiomyopathies: hypertrophic, dilated, arrhythmogenic, and left ventricular noncompaction cardiomyopathies. A special focus is provided on the application of gene-editing techniques in understanding key disease characteristics and on the therapeutic approaches that have been tested.

Association Between Left Ventricular Noncompaction and Vigorous Physical Activity

BACKGROUND

Left ventricular (LV) hypertrabeculation fulfilling noncompaction cardiomyopathy criteria has been detected in athletes. However, the association between LV noncompaction (LVNC) phenotype and vigorous physical activity (VPA) in the general population is disputed.

OBJECTIVES

The aim of this study was to assess the relationship between LVNC phenotype on cardiac magnetic resonance (CMR) imaging and accelerometer-measured physical activity (PA) in a cohort of middle-aged nonathlete participants in the PESA (Progression of Early Subclinical Atherosclerosis) study.

METHODS

In PESA participants (n = 4,184 subjects free of cardiovascular disease), PA was measured by waist-secured accelerometers. CMR was performed in 705 subjects (mean age 48 ± 4 years, 16% women). VPA was recorded as total minutes per week. The study population was divided into 6 groups: no VPA and 5 sex-specific quintiles of VPA rate (Q1 to Q5). The Petersen criterion for LVNC was evaluated in all subjects undergoing CMR. For participants meeting this criterion (noncompacted-to-compacted ratio ≥2.3), 3 more restrictive LVNC criteria were also evaluated (Jacquier, Grothoff, and Stacey).

RESULTS

LVNC phenotype prevalence according to the Petersen criterion was significantly higher among participants in the highest VPA quintile (Q5 = 30.5%) than in participants with no VPA (14.2%). The Jacquier and Grothoff criteria were also more frequently fulfilled in participants in the highest VPA quintile (Jacquier Q5 = 27.4% vs. no VPA = 12.8% and Grothoff Q5 = 15.8% vs. no VPA = 7.1%). The prevalence of the systolic Stacey LVNC criterion was low (3.6%) and did not differ significantly between no VPA and Q5.

CONCLUSIONS

In a community-based study, VPA was associated with a higher prevalence of CMR-detected LVNC phenotype according to diverse established criteria. The association between VPA and LVNC phenotype was independent of LV volumes. According to these data, vigorous recreational PA should be considered as a possible but not uncommon determinant of LV hypertrabeculation in asymptomatic subjects.

High-Resolution Cryo-EM Structure of the Cardiac Actomyosin Complex

Heart contraction depends on a complicated array of interactions between sarcomeric proteins required to convert chemical energy into mechanical force. Cyclic interactions between actin and myosin molecules, controlled by troponin and tropomyosin, generate the sliding force between the actin-based thin and myosin-based thick filaments. Alterations in this sophisticated system due to missense mutations can lead to cardiovascular diseases. Numerous structural studies proposed pathological mechanisms of missense mutations at the myosin-myosin, actin-tropomyosin, and tropomyosin-troponin interfaces. However, despite the central role of actomyosin interactions a detailed structural description of the cardiac actomyosin interface remained unknown. Here, we report a cryo-EM structure of a cardiac actomyosin complex at 3.8 Å resolution. The structure reveals the molecular basis of cardiac diseases caused by missense mutations in myosin and actin proteins.

Left Ventricular Noncompaction: New Insights into a Poorly Understood Disease

Left ventricular noncompaction (LVNC) is a congenital pathology that directly affects the lining walls of myocardial tissue, causing trabeculations with blood filling in the inner wall of the heart, concomitantly with the development of a mesocardial thinning. Although LVNC was described for the first time as long ago as 1984, our understanding of the disease with regard to its genetic pattern, diagnosis, clinical presentation and treatment is still scanty. LVNC can present as an isolated condition or associated with congenital heart disease, genetic syndromes or neuromuscular disease. This suggests that LVNC is not a distinct form of cardiomyopathy, but rather a morphological expression of different diseases. Recognition of the disease is of fundamental importance because its clinical manifestations are variable, ranging from the absence of any symptom to congestive heart failure, lethal arrhythmias and thromboembolic events. The study of this disease has emphasized its genetic aspects, as it may be of sporadic origin or hereditary, in which case it most commonly has an autosomal dominant inheritance or one linked to the X chromosome. Echocardiography is the gold standard for diagnosis, and magnetic resonance imaging may refine the identification of the disease, especially in those patients with non-conclusive echocardiography. This article sets out to review the main characteristics of LVNC and present updates, especially in the genetic pattern, diagnosis and treatment of the disease.

2019 HRS expert consensus statement on evaluation, risk stratification, and management of arrhythmogenic cardiomyopathy: Executive summary

Arrhythmogenic cardiomyopathy (ACM) is an arrhythmogenic disorder of the myocardium not secondary to ischemic, hypertensive, or valvular heart disease. ACM incorporates a broad spectrum of genetic, systemic, infectious, and inflammatory disorders. This designation includes, but is not limited to, arrhythmogenic right/left ventricular cardiomyopathy, cardiac amyloidosis, sarcoidosis, Chagas disease, and left ventricular noncompaction. The ACM phenotype overlaps with other cardiomyopathies, particularly dilated cardiomyopathy with arrhythmia presentation that may be associated with ventricular dilatation and/or impaired systolic function. This expert consensus statement provides the clinician with guidance on evaluation and management of ACM and includes clinically relevant information on genetics and disease mechanisms. PICO questions were utilized to evaluate contemporary evidence and provide clinical guidance related to exercise in arrhythmogenic right ventricular cardiomyopathy. Recommendations were developed and approved by an expert writing group, after a systematic literature search with evidence tables, and discussion of their own clinical experience, to present the current knowledge in the field. Each recommendation is presented using the Class of Recommendation and Level of Evidence system formulated by the American College of Cardiology and the American Heart Association and is accompanied by references and explanatory text to provide essential context. The ongoing recognition of the genetic basis of ACM provides the opportunity to examine the diverse triggers and potential common pathway for the development of disease and arrhythmia.

Clinical Implications of the Genetic Architecture of Dilated Cardiomyopathy

PURPOSE OF REVIEW

Dilated cardiomyopathy (DCM) frequently involves an underlying genetic etiology, but the clinical approach for genetic diagnosis and application of results in clinical practice can be complex.

RECENT FINDINGS

International sequence databases described the landscape of genetic variability across populations, which informed guidelines for the interpretation of DCM gene variants. New evidence indicates that loss-of-function mutations in filamin C (FLNC) contribute to DCM and portend high risk of ventricular arrhythmia. A clinical framework aids in referring patients for DCM genetic testing and applying results to patient care. Results of genetic testing can change medical management, particularly in a subset of genes that increase risk for life-threatening ventricular arrhythmias, and can influence decisions for defibrillator therapy. Clinical screening and cascade genetic testing of family members should be diligently pursued to identify those at risk of developing DCM.

Bridging the gap between hypertrabeculation phenotype, noncompaction phenotype and left ventricular noncompaction cardiomyopathy

Left ventricular noncompaction (LVNC) is an increasingly recognised cardiomyopathy characterised by excessive trabeculation and deep intertrabecular recesses in direct communication with the left ventricular cavity. In LVNC, hypertrabeculation has been associated with heart failure, ventricular arrhythmia, and systemic thromboembolism. However, hypertrabeculation alone is not sufficient to define a subject as at risk for such complications and thus should not be sufficient to diagnose LVNC. Despite several studies having investigated parameters to predict adverse cardiovascular events, physicians have no effective tools to differentiate between clinically silent hypertrabeculation and LVNC. The aim of this paper was to review literature on LVNC diagnostic criteria and to provide an easy and accessible diagnostic algorithm to distinguish between hypertrabeculation phenotype, non-compaction phenotype and LVNC cardiomyopathy.

Characterization of Left Ventricular Non-Compaction Cardiomyopathy

Left ventricle non-compaction cardiomyopathy (LVNC) has gained great interest in recent years, being one of the most controversial cardiomyopathies. There are several open debates, not only about its genetic heterogeneity, or about the possibility to be an acquired cardiomyopathy, but also about its possible overdiagnosis based on imaging techniques. In order to better understand this entity, we identified 38 LVNC patients diagnosed by cardiac MRI (CMRI) or anatomopathological study that could underwent NGS-sequencing and clinical study. Anatomopathological exam was performed in eight available LVNC hearts. The genetic yield was 34.2%. Patients with negative genetic testing had better left ventricular ejection fraction (LVEF) or it showed a tendency to improve in follow-up, and a possible trigger factor for LVNC was identified in 1/3 of them. Nonetheless, cerebrovascular accidents occurred in similar proportions in both groups. We conclude that in LVNC there seem to be different ways to achieve the same final phenotype. Genetic testing has a good genetic yield and provides valuable information. LVNC without an underlying genetic cause may have a better prognosis in terms of LVEF evolution. However, anticoagulation to prevent cerebrovascular accident (CVA) should be carefully evaluated in all patients. Larger series with pathologic examination are needed to help better understand this entity.

Cardiac Emerinopathy: A Nonsyndromic Nuclear Envelopathy With Increased Risk of Thromboembolic Stroke Due to Progressive Atrial Standstill and Left Ventricular Noncompaction

BACKGROUND

Mutations in the nuclear envelope genes encoding LMNA and EMD are responsible for Emery-Dreifuss muscular dystrophy. However, LMNA mutations often manifest dilated cardiomyopathy with conduction disturbance without obvious skeletal myopathic complications. On the contrary, the phenotypic spectrums of EMD mutations are less clear. Our aims were to determine the prevalence of nonsyndromic forms of emerinopathy, which may underlie genetically undefined isolated cardiac conduction disturbance, and the etiology of thromboembolic complications associated with EMD mutations.

METHODS

Targeted exon sequencing was performed in 87 probands with familial sick sinus syndrome (n=36) and a progressive cardiac conduction defect (n=51).

RESULTS

We identified 3 X-linked recessive EMD mutations (start-loss, splicing, missense) in families with cardiac conduction disease. All 3 probands shared a common clinical phenotype of progressive atrial arrhythmias that ultimately resulted in atrial standstill associated with left ventricular noncompaction (LVNC), but they lacked early contractures and progressive muscle wasting and weakness characteristic of Emery-Dreifuss muscular dystrophy. Because the association of LVNC with EMD has never been reported, we further genetically screened 102 LVNC patients and found a frameshift EMD mutation in a boy with progressive atrial standstill and LVNC without complications of muscular dystrophy. All 6 male EMD mutation carriers of 4 families underwent pacemaker or defibrillator implantation, whereas 2 female carriers were asymptomatic. Notably, a strong family history of stroke observed in these families was probably due to the increased risk of thromboembolism attributable to both atrial standstill and LVNC.

CONCLUSIONS

Cardiac emerinopathy is a novel nonsyndromic X-linked progressive atrial standstill associated with LVNC and increased risk of thromboembolism.

[Overlapping Phenotype: Left Ventricular non-Compaction and Hypertrophic Cardiomyopathy]

Aim To study the clinical course of the mixed phenotype (hypertrophic cardiomyopathy, HCMP, and left ventricular noncompaction, LVNC); to determine its genetic causes; and to evaluate incidence of cardiovascular complications (CVC) during the follow-up period.Material and methods In screening of 286 patients with HCMP, 8 of them (2.8 %; median age, 41.5 years; 4 men and 4 women) from unrelated families were found to have the mixed phenotype (combination of HCMP and LVNC). For their 10 first-degree relatives, the most frequent phenotype was HCMP without LVNC; however, both isolated LVNC and the mixed phenotype were also observed. Criteria for HCMP and LVNC were confirmed by echocardiography and cardiac magnetic resonance imaging Genotyping was performed by high-throughput sequencing NGT using the TruSight Cardio Sequencing Panel kit.Results Probands with the HCMP+LVNC combination compared to first-degree relatives with isolated HCMP and LVNC were characterized by more pronounced left ventricular dysfunction (ejection fraction, 43.57±7.6 and 53.64±6.51 %, respectively; p&lt;0.001), a higher risk of CVC, and a higher incidence of ventricular tachyarrhythmias (7.9 and 2.2 %, respectively; p&lt;0.01). 11 mutations in 5 genes were found in 8 patients with the mixed phenotype. 72.7 % of mutations were in the MYH7 and MYBPC3 genes that encode the heavy chain of β-myosin and myosin-binding protein C, respectively; however, in some cases, replacements in other genes (DTNA, TGFB2) were also found.Conclusion The mixed phenotype (HCMP and LVNC) is associated with more severe clinical course of the disease and unfavorable CVC.

Left Ventricular Noncompaction and Congenital Heart Disease Increases the Risk of Congestive Heart Failure

BACKGROUND

Left ventricular noncompaction (LVNC) is a hereditary cardiomyopathy that is associated with high morbidity and mortality rates. Recently, LVNC was classified into several phenotypes including congenital heart disease (CHD). However, although LVNC and CHD are frequently observed, the role and clinical significance of genetics in these cardiomyopathies has not been fully evaluated. Therefore, we aimed to evaluate the impact on the perioperative outcomes of children with concomitant LVNC and CHD using next-generation sequencing (NGS).

METHODS

From May 2000 to August 2018, 53 Japanese probands with LVNC (25 males and 28 females) were enrolled and we screened 182 cardiomyopathy-associated genes in these patients using NGS.

RESULTS

The age at diagnosis of the enrolled patients ranged from 0 to 14 years (median: 0.3 months). A total of 23 patients (43.4%) were diagnosed with heart failure, 14 with heart murmur (26.4%), and 6 with cyanosis (11.3%). During the observation period, 31 patients (58.5%) experienced heart failure and 13 (24.5%) developed arrhythmias such as ventricular tachycardia, supraventricular tachycardia, and atrioventricular block. Moreover, 29 patients (54.7%) had ventricular septal defects (VSDs), 17 (32.1%) had atrial septal defects, 10 had patent ductus arteriosus (PDA), and 7 (13.2%) had Ebstein's anomaly and double outlet right ventricle. Among the included patients, 30 underwent surgery, 19 underwent biventricular repair, and 2 underwent pulmonary artery banding, bilateral pulmonary artery banding, and PDA ligation. Overall, 30 genetic variants were identified in 28 patients with LVNC and CHD. Eight variants were detected in MYH7 and two in TPM1. Echocardiography showed lower ejection fractions and more thickened trabeculations in the left ventricle in patients with LVNC and CHD than in age-matched patients with VSDs. During follow-up, 4 patients died and the condition of 8 worsened postoperatively. The multivariable proportional hazards model showed that heart failure, LV ejection fraction of < 24%, LV end-diastolic diameter z-score of > 8.56, and noncompacted-to-compacted ratio of the left ventricular apex of > 8.33 at the last visit were risk factors for survival.

CONCLUSIONS

LVNC and CHD are frequently associated with genetic abnormalities. Knowledge of the association between CHD and LVNC is important for the awareness of clinical implications during the preoperative and postoperative periods to identify the populations who are at an increased risk of additional morbidity.

Cardiac Phenotypes, Genetics, and Risks in Familial Noncompaction Cardiomyopathy

BACKGROUND

There is overlap in genetic causes and cardiac features in noncompaction cardiomyopathy (NCCM), hypertrophic cardiomyopathy (HCM), and dilated cardiomyopathy (DCM).

OBJECTIVES

The goal of this study was to predict phenotype and outcome in relatives according to the clinical features and genotype of NCCM index cases.

METHODS

Retrospective DNA and cardiac screening of relatives of 113 families from 143 index patients were used to classify NCCM cases according to the cardiac phenotype. These cases were classified as isolated NCCM, NCCM with left ventricular (LV) dilation (DCM), and NCCM with LV hypertrophy (HCM).

RESULTS

In 58 (51%) families, screening identified 73 relatives with NCCM and 34 with DCM or HCM without NCCM. The yield of family screening was higher in families with a mutation (p < 0.001). Fifty-four families had a mutation. Nonpenetrance was observed in 37% of the relatives with a mutation. Index cases were more often symptomatic than affected relatives (p < 0.001). NCCM with DCM (53%) was associated with LV systolic dysfunction (p < 0.001), increased risk for major adverse cardiac events, mutations in the tail of MYH7 (p < 0.001), and DCM without NCCM in relatives (p < 0.001). Isolated NCCM (43%) was associated with a milder course, mutations in the head of MYH7, asymptomatic NCCM (42%) (p = 0.018), and isolated NCCM in relatives (p = 0.004). NCCM with HCM (4%) was associated with MYBPC3 and HCM without NCCM in relatives (p < 0.001).

CONCLUSIONS

The phenotype of relatives may be predicted according to the NCCM phenotype and the mutation of index patients. NCCM phenotypes were related to outcome. In this way, clinical and genetic features of index patients may help prediction of outcome in relatives.

Genotype-Positive Status Is Associated With Poor Prognoses in Patients With Left Ventricular Noncompaction Cardiomyopathy

Background Left ventricular noncompaction cardiomyopathy ( LVNC ) is a genetically and phenotypically heterogeneous disease. This study aims to investigate the genetic basis and genotype-phenotype correlations in a cohort of Chinese patients with LVNC . Methods and Results A total of 72 cardiomyopathy-associated genes were comprehensively screened in 83 adults and 17 children with LVNC by targeted sequencing. Pathogenicity of the detected variants was determined according to their prevalence and American College of Medical Genetics and Genomics recommendations. Baseline and follow-up clinical data were collected. The primary end point was a composite of death and heart transplantation. Overall, 42 pathogenic variants were identified in 38 patients (38%), with TTN , MYH 7, MYBPC 3, and DSP being the most commonly involved genes. At baseline, genotype-positive adults had higher rates of atrial fibrillation and family history, and lower left ventricular ejection fraction, compared with genotype-negative adults. During a median follow-up of 4.2 years, more primary end points occurred in genotype-positive adults than in genotype-negative adults (50.0% versus 23.5%; P=0.013). Multivariable analysis demonstrated that genotype-positive status was associated with higher risks of death and heart transplantation, independent of age, sex, and cardiac function at baseline in patients with LVNC (adjusted hazards ratio, 2.49; 95% confidence interval, 1.15-5.37; P=0.020). Conclusions Our study revealed a distinct genetic spectrum in Chinese patients with LVNC , with variants in TTN , MYH 7, MYBPC 3, and DSP being the most common. The presence of pathogenic variants is an independent risk factor for adverse outcomes and may aid in risk stratification in adult patients. Larger studies are needed to confirm these findings.

Genetics, Clinical Features, and Long-Term Outcome of Noncompaction Cardiomyopathy

BACKGROUND

The clinical outcomes of noncompaction cardiomyopathy (NCCM) range from asymptomatic to heart failure, arrhythmias, and sudden cardiac death. Genetics play an important role in NCCM.

OBJECTIVES

This study investigated the correlations among genetics, clinical features, and outcomes in adults and children diagnosed with NCCM.

METHODS

A retrospective multicenter study from 4 cardiogenetic centers in the Netherlands classified 327 unrelated NCCM patients into 3 categories: 1) genetic, with a mutation in 32% (81 adults; 23 children) of patients; 2) probably genetic, familial cardiomyopathy without a mutation in 16% (45 adults; 8 children) of patients; or 3) sporadic, no family history, without mutation in 52% (149 adults; 21 children) of patients. Clinical features and major adverse cardiac events (MACE) during follow-up were compared across the children and adults.

RESULTS

MYH7, MYBPC3, and TTN mutations were the most common mutations (71%) found in genetic NCCM. The risk of having reduced left ventricular (LV) systolic dysfunction was higher for genetic patients compared with the probably genetic and sporadic cases (p = 0.024), with the highest risk in patients with multiple mutations and TTN mutations. Mutations were more frequent in children (p = 0.04) and were associated with MACE (p = 0.025). Adults were more likely to have sporadic NCCM. High risk for cardiac events in children and adults was related to LV systolic dysfunction in mutation carriers, but not in sporadic cases. Patients with MYH7 mutations had low risk for MACE (p = 0.03).

CONCLUSIONS

NCCM is a heterogeneous condition, and genetic stratification has a role in clinical care. Distinguishing genetic from nongenetic NCCM complements prediction of outcome and may lead to management and follow-up tailored to genetic status.

Molecular autopsy and family screening in a young case of sudden cardiac death reveals an unusually severe case of FHL1 related hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a genetic cardiomyopathy with a prevalence of about 1:200. It is characterized by left ventricular hypertrophy, diastolic dysfunction and interstitial fibrosis; HCM might lead to sudden cardiac death (SCD) especially in the young. Due to low autopsy frequencies of sudden unexplained deaths (SUD) the true prevalence of SCD and especially of HCM among SUD remains unclear. Even in cases of proven SCD genetic testing is not a routine procedure precluding appropriate risk stratification and counseling of relatives.

METHODS

Here we report a case of SCD in a 19-year-old investigated by combined forensic and molecular autopsy.

RESULTS

During autopsy of the index-patient HCM was detected. As no other possible cause of death could be uncovered by forensic autopsy the event was classified as SCD. Molecular autopsy identified two (probably) pathogenic genetic variants in FHL1 and MYBPC3. The MYBPC3 variant had an incomplete penetrance. The FHL1 variant was a de novo mutation. We detected reduced FHL1 mRNA levels and no FHL1 protein in muscle samples suggesting nonsense-mediated mRNA decay and/or degradation of the truncated protein in the SCD victim revealing a plausible disease mechanism.

CONCLUSION

The identification of the genetic cause of the SCD contributed to the rational counseling of the relatives and risk assessment within the family. Furthermore our study revealed evidences for the pathomechanism of FHL1 mutations.

Cardiomyopathy in Children: Classification and Diagnosis: A Scientific Statement From the American Heart Association

In this scientific statement from the American Heart Association, experts in the field of cardiomyopathy (heart muscle disease) in children address 2 issues: the most current understanding of the causes of cardiomyopathy in children and the optimal approaches to diagnosis cardiomyopathy in children. Cardiomyopathies result in some of the worst pediatric cardiology outcomes; nearly 40% of children who present with symptomatic cardiomyopathy undergo a heart transplantation or die within the first 2 years after diagnosis. The percentage of children with cardiomyopathy who underwent a heart transplantation has not declined over the past 10 years, and cardiomyopathy remains the leading cause of transplantation for children >1 year of age. Studies from the National Heart, Lung, and Blood Institute-funded Pediatric Cardiomyopathy Registry have shown that causes are established in very few children with cardiomyopathy, yet genetic causes are likely to be present in most. The incidence of pediatric cardiomyopathy is ≈1 per 100 000 children. This is comparable to the incidence of such childhood cancers as lymphoma, Wilms tumor, and neuroblastoma. However, the published research and scientific conferences focused on pediatric cardiomyopathy are sparcer than for those cancers. The aim of the statement is to focus on the diagnosis and classification of cardiomyopathy. We anticipate that this report will help shape the future research priorities in this set of diseases to achieve earlier diagnosis, improved clinical outcomes, and better quality of life for these children and their families.

Molecular dynamics simulation of tropomyosin bound to actins/myosin in the closed and open states

Tropomyosin (Tpm) is a dimeric coiled-coil protein that binds to filamentous actin, and regulates actin-myosin interaction by moving between three positions corresponding to the blocked, closed, and open states. To elucidate how Tpm undergoes transitions between these functional states, we have built structural models and conducted extensive molecular dynamics simulations of the Tpm-actins/myosin complex in the closed and open states (total simulation time >1.4 μs). Based on the simulation trajectories, we have analyzed the dynamics and energetics of a truncated Tpm interacting with actins/myosin under the physiological conditions. Our simulations have shown distinct dynamics of four Tpm periods (P3-P6), featuring pronounced biased fluctuations of P4 and P5 toward the open position in the closed state, which is consistent with a conformational selection mechanism for Tpm-regulated myosin binding. Additionally, we have identified key residues of Tpm specifically binding to actins/myosin in the closed and open state. Some of them were validated as functionally important in comparison with past functional/clinical studies, and the rest will make promising targets for future mutational experiments.

2019 HRS expert consensus statement on evaluation, risk stratification, and management of arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is an arrhythmogenic disorder of the myocardium not secondary to ischemic, hypertensive, or valvular heart disease. ACM incorporates a broad spectrum of genetic, systemic, infectious, and inflammatory disorders. This designation includes, but is not limited to, arrhythmogenic right/left ventricular cardiomyopathy, cardiac amyloidosis, sarcoidosis, Chagas disease, and left ventricular noncompaction. The ACM phenotype overlaps with other cardiomyopathies, particularly dilated cardiomyopathy with arrhythmia presentation that may be associated with ventricular dilatation and/or impaired systolic function. This expert consensus statement provides the clinician with guidance on evaluation and management of ACM and includes clinically relevant information on genetics and disease mechanisms. PICO questions were utilized to evaluate contemporary evidence and provide clinical guidance related to exercise in arrhythmogenic right ventricular cardiomyopathy. Recommendations were developed and approved by an expert writing group, after a systematic literature search with evidence tables, and discussion of their own clinical experience, to present the current knowledge in the field. Each recommendation is presented using the Class of Recommendation and Level of Evidence system formulated by the American College of Cardiology and the American Heart Association and is accompanied by references and explanatory text to provide essential context. The ongoing recognition of the genetic basis of ACM provides the opportunity to examine the diverse triggers and potential common pathway for the development of disease and arrhythmia.

Advanced Evolution of Pathogenesis Concepts in Cardiomyopathies

Cardiomyopathy is a group of heterogeneous cardiac diseases that impair systolic and diastolic function, and can induce chronic heart failure and sudden cardiac death. Cardiomyopathy is prevalent in the general population, with high morbidity and mortality rates, and contributes to nearly 20% of sudden cardiac deaths in younger individuals. Genetic mutations associated with cardiomyopathy play a key role in disease formation, especially the mutation of sarcomere encoding genes and ATP kinase genes, such as titin, lamin A/C, myosin heavy chain 7, and troponin T1. Pathogenesis of cardiomyopathy occurs by multiple complex steps involving several pathways, including the Ras-Raf-mitogen-activated protein kinase-extracellular signal-activated kinase pathway, G-protein signaling, mechanotransduction pathway, and protein kinase B/phosphoinositide 3-kinase signaling. Excess biomechanical stress induces apoptosis signaling in cardiomyocytes, leading to cell loss, which can induce myocardial fibrosis and remodeling. The clinical features and pathophysiology of cardiomyopathy are discussed. Although several basic and clinical studies have investigated the mechanism of cardiomyopathy, the detailed pathophysiology remains unclear. This review summarizes current concepts and focuses on the molecular mechanisms of cardiomyopathy, especially in the signaling from mutation to clinical phenotype, with the aim of informing the development of therapeutic interventions.

Clinical and genetic insights into non-compaction: a meta-analysis and systematic review on 7598 individuals

BACKGROUND

Left ventricular non-compaction has been increasingly diagnosed in recent years. However, it is still debated whether non-compaction is a pathological condition or a physiological trait. In this meta-analysis and systematic review, we compare studies, which investigated these two different perspectives. Furthermore, we provide a comprehensive overview on the clinical outcome as well as genetic background of left ventricular non-compaction cardiomyopathy in adult patients.

METHODS AND RESULTS

We retrieved PubMed/Medline literatures in English language from 2000 to 19/09/2018 on clinical outcome and genotype of patients with non-compaction. We summarized and extensively reviewed all studies that passed selection criteria and performed a meta-analysis on key phenotypic parameters. Altogether, 35 studies with 2271 non-compaction patients were included in our meta-analysis. The mean age at diagnosis was the mid of their fifth decade. Two-thirds of patients were male. Congenital heart diseases including atrial or ventricular septum defect or Ebstein anomaly were reported in 7% of patients. Twenty-four percent presented with family history of cardiomyopathy. The mean frequency of neuromuscular diseases was 5%. Heart rhythm abnormalities were reported frequently: conduction disease in 26%, supraventricular tachycardia in 17%, and sustained or non-sustained ventricular tachycardia in 18% of patients. Three important outcome measures were reported including systemic thromboembolic events with a mean frequency of 9%, heart transplantation with 4%, and adequate ICD therapy with 15%. Nine studies investigated the genetics of non-compaction cardiomyopathy. The most frequently mutated gene was TTN with a pooled frequency of 11%. The average frequency of MYH7 mutations was 9%, for MYBPC3 mutations 5%, and for CASQ2 and LDB3 3% each. TPM1, MIB1, ACTC1, and LMNA mutations had an average frequency of 2% each. Mutations in PLN, HCN4, TAZ, DTNA, TNNT2, and RBM20 were reported with a frequency of 1% each. We also summarized the results of eight studies investigating the non-compaction in altogether 5327 athletes, pregnant women, patients with sickle cell disease, as well as individuals from population-based cohorts, in which the presence of left ventricular hypertrabeculation ranged from 1.3 to 37%.

CONCLUSION

The summarized data indicate that non-compaction may lead to unfavorable outcome in different cardiomyopathy entities. The presence of key features in a multimodal diagnostic approach could distinguish between benign morphological trait and manifest cardiomyopathy.

Noncompaction cardiomyopathy is caused by a novel in-frame desmin (DES) deletion mutation within the 1A coiled-coil rod segment leading to a severe filament assembly defect

Mutations in DES, encoding desmin protein, are associated with different kinds of skeletal and/or cardiac myopathies. However, it is unknown, whether DES mutations are associated with left ventricular hypertrabeculation (LVHT). Here, we performed a clinical examination and subsequent genetic analysis in a family, with two individuals presenting LVHT with conduction disease and skeletal myopathy. The genetic analysis revealed a novel small in-frame deletion within the DES gene, p.Q113_L115del, affecting the α-helical rod domain. Immunohistochemistry analysis of explanted myocardial tissue from the index patient revealed an abnormal cytoplasmic accumulation of desmin and a degraded sarcomeric structure. Cell transfection experiments with wild-type and mutant desmin verified the cytoplasmic aggregation and accumulation of mutant desmin. Cotransfection experiments were performed to model the heterozygous state of the patients and revealed a dominant negative effect of the mutant desmin on filament assembly. DES:p.Q113_L115del is classified as a pathogenic mutation associated with dilated cardiomyopathy with prominent LVHT.

Thickness and Ratio of Noncompacted and Compacted Layers of the Left Ventricular Myocardium Evaluated in 56 Normal Fetuses by Two-Dimensional Echocardiography

The thickness and ratio of noncompacted and compacted layers of the left ventricular (LV) myocardium in the normal fetus were investigated by fetal echocardiography. We aimed to investigate the compaction process of the LV myocardium during the normal gestation period and provide reference for echocardiographic diagnosis of a fetus with ventricular myocardium noncompaction. A total of 56 pregnant women in the gestational period of 23–30 weeks were included. Complete fetal echocardiography was performed with system ultrasonographic examination to exclude congenital heart malformation or extracardiac malformation. All 56 fetuses showed normal development. In the short-axis view of the fetal heart, the LV wall was divided into an upper and lower section at the level of the papillary muscle. Each section was then further divided into four segments, namely, anterior, posterior, lateral, and inferior wall. Thus, the LV wall was divided into eight segments. The thickness of the ventricular noncompacted and compacted layers and the ratio of the ventricular noncompacted to compacted layers of these segments at end-systole were measured and calculated. In echocardiography, the fetal LV myocardium is a two-layered structure: the endocardial noncompact myocardium (NC) with higher echo and the epicardium compact myocardium (C) with lower echo. The noncompacted layer is thinner than the compacted layer in the anterior wall, but thicker than the compacted layers in the posterior, lateral, and inferior wall. With respect to the upper and lower sections of the LV myocardium, the noncompacted layer in each segment of the upper section is thinner than that in each segment of the lower section, whereas the compacted layer of the upper section is thicker than that of the lower section. This study suggests that the densification of the fetal LV myocardium occurs gradually from base to apex and from the anterior to lateral, posterior, and inferior walls. This finding aids in further understanding the process of myocardial densification and provides a diagnostic reference for noncompaction of noncompaction cardiomyopathy (NCCM).

Left ventricular noncompaction: a distinct cardiomyopathy or a composite anatomical syndrome?

Left ventricular non-compaction (LVNC) is characterized by hypertrabecularity (thickened non-compact layer) with deep intertrabecular recesses that are continuous with the ventricle cavity, and a thin compact layer. The phenotypes of LVNС are extremely variable: the left or right ventricular variant, biventricular form, LVNC with symptoms of heart failure or arrhythmia, asymptomatic forms or variants with thromboembolic events. In 30-50 % of patients with LVNC genetic mutations of genes encoding sarcomeric or cytoskeletal proteins are revealed by a genetic study. The article presents a literature review on the problems of diagnosis, visualization, pathogenesis, variability of clinical manifestations of LVNC and its genetic heterogeneity. Clinical cases demonstrating LVNC as a concomitant anatomical syndrome due to monogenic Danone disease, as well as the family cardiomyopathy with the digenic inheritance of two phenotypes (LVNC with DCM) and the unique case of peripartum evolution of the acquired LVNC syndrome, all these cases are reflect the current uncertainty regarding to the pathogenesis and significance of LVNC. The main question is whether LVNC is a distinct cardiomyopathy or a morphologic trait and a composite anatomical syndrome of congenital heart disease or other cardiomyopathies (DCM, HCM, ARVC) remains controversial. Achievement of professional consensus guidelines about unification of diagnostic criteria and risk-stratification of LVNC, improvement of visualization tools and expansion of genetic testing will help to significantly expand our knowledge and understanding of the pathogenesis, clinical significance and prognosis of LVNC for optimization of the treatment strategy.

The importance of preconception and prenatal genetic evaluation in heart transplant individuals and fetal and postnatal cardiac monitoring in their offspring

A 24-year-old woman with a history of idiopathic dilated cardiomyopathy status post heart transplant gave birth to a healthy term female infant. At 5 months of age, the infant was diagnosed with severe left ventricular dysfunction with an ejection fraction of 18% and moderate non-compaction of the left ventricle. She received a heart transplant at 7 months of age. Familial dilated cardiomyopathy was diagnosed. Genetic testing revealed a likely pathogenic variant in the TPM1 gene. Fetal cardiac screening is critical for offspring of heart transplant recipients, especially when the reason for transplant was cardiomyopathy. Early genetic consultation and counselling is necessary for all heart transplant recipients, preferably prenatally. Postnatal screening of offspring is essential at birth, at 3-month intervals until 1 year of age, and then annually until the risk for familial cardiomyopathy is assessed.