Desmoplakin missense and non-missense mutations in arrhythmogenic right ventricular cardiomyopathy: Genotype-phenotype correlation

Desmoplakin CSM models unravel mechanisms regulating the binding to intermediate filaments and putative therapeutics for cardiocutaneous diseases

Arrhythmogenic cardiomyopathy (AC) is a common cause of sudden cardiac arrest and death in young adults. It can be induced by different types of mutations throughout the desmoplakin gene including the R2834H mutation in the extreme carboxyterminus tail of desmoplakin (DP CT) which remains structurally uncharacterized and poorly understood. Here, we have created 3D models of DP CT which show the structural effects of AC-inducing mutations as well as the implications of post-translational modifications (PTMs). Our results suggest that, in absence of PTMs, positively charged wildtype DP CT likely folds back onto negatively-charged plectin repeat 14 of nearby plakin repeat domain C (PRD C) contributing to the recruitment of intermediate filaments (IFs). When phosphorylated and methylated, negatively-charged wildtype DP CT would then fold back onto positively-charged plectin repeat 17 of PRD C, promoting the repulsion of intermediate filaments. However, by preventing PTMs, the R2834H mutation would lead to the formation of a cytoplasmic mutant desmoplakin with a constitutively positive DP CT tail that would be aberrantly recruited by cytoplasmic IFs instead of desmosomes, potentially weakening cell-cell contacts and promoting AC. Virtual screening of FDA-approved drug libraries identified several promising drug candidates for the treatment of cardiocutaneous diseases through drug repurposing.

The Desmoplakin Phenotype Spectrum: Is the Inflammation the "Fil Rouge" Linking Myocarditis, Arrhythmogenic Cardiomyopathy, and Uncommon Autoinflammatory Systemic Disease?

Myocarditis is an inflammatory condition of cardiac tissue presenting significant variability in clinical manifestations and outcomes. Its etiology is diverse, encompassing infectious agents (primarily viruses, but also bacteria, protozoa, and helminths) and non-infectious factors (autoimmune responses, toxins, and drugs), though often the specific cause remains unidentified. Recent research has highlighted the potential role of genetic susceptibility in the development of myocarditis (and in some cases the development of inflammatory dilated cardiomyopathy, i.e., the condition in which there is chronic inflammation (>3 months) and left ventricular dysfunction\dilatation), with several studies indicating a correlation between myocarditis and genetic backgrounds. Notably, pathogenic genetic variants linked to dilated or arrhythmic cardiomyopathy are found in 8-16% of myocarditis patients. Genetic predispositions can lead to recurrent myocarditis and a higher incidence of ventricular arrhythmias and heart failure. Moreover, the presence of DSP mutations has been associated with distinct pathological patterns and clinical outcomes in arrhythmogenic cardiomyopathy (hot phases). The interplay between genetic factors and environmental triggers, such as viral infections and physical stress, is crucial in understanding the pathogenesis of myocarditis. Identifying these genetic markers can improve the diagnosis, risk stratification, and management of patients with myocarditis, potentially guiding tailored therapeutic interventions. This review aims to synthesize current knowledge on the genetic underpinnings of myocarditis, with an emphasis on desmoplakin-related arrhythmogenic cardiomyopathy, to enhance clinical understanding and inform future research directions.

The role of genetic testing in management and prognosis of individuals with inherited cardiomyopathies

Inherited cardiomyopathies are a heterogeneous group of heart muscle conditions where disease classification has traditionally been based on clinical characteristics. However, this does not always align with genotype. While there are well described challenges of genetic testing, understanding the role of genotype in patient management is increasingly required. We take a gene-by-gene approach, reviewing current evidence for the role of genetic testing in guiding prognosis and management of individuals with inherited cardiomyopathies. In particular, focusing on causal variants in genes definitively associated with arrhythmogenic cardiomyopathy, dilated cardiomyopathy, and hypertrophic cardiomyopathy. This review identifies genotype-specific disease sub-groups with strong evidence supporting the use of genetics in clinical management and highlights that at present, the spectrum of clinical utility is not reflected in current guidelines. Of 13 guideline or expert consensus statements for management of cardiomyopathies, there are seven gene-specific therapeutic recommendations that have been published from four documents. Understanding how genotype influences phenotype provides evidence for the role of genetic testing for prognostic and therapeutic purposes, moving us closer to precision-medicine based care.

Sinus arrest in a p.Arg160X-DSP-positive patient without evidence of desmoplakin-mediated cardiomyopathy: a case report

Background

Pathogenic/Likely pathogenic variants in DSP-encoded desmoplakin are strongly associated with arrhythmogenic cardiomyopathy (ACM). However, their contribution towards sinus node dysfunction has not been well-delineated.

Case summary

A 74-year-old man with a pathogenic variant of DSP-encoded desmoplakin (c.478C >T; p.Arg160X) but no evidence of ACM presented with one episode of syncope in the setting of a gastrointestinal illness. Workup including echocardiography, cardiac magnetic resonance imaging, and Holter monitor did not show evidence of ACM or significant arrhythmias. One month later, he experienced several closely-spaced episodes of syncope associated with long sinus pauses and sinus arrest documented on telemetry. He underwent urgent dual chamber pacemaker implantation, during which a ventricular programmed stimulation study was performed and was negative for sustained ventricular arrhythmias. His syncopal episodes resolved and he had no recurrent events on three-month follow-up.

Discussion

As highlighted here, DSP-encoded desmoplakin pathogenic/Likely pathogenic variants may contribute to isolated sinus node dysfunction. This clinical link should be further explored in larger studies involving patients with DSP variants.

Management Strategies in Arrhythmogenic Cardiomyopathy across the Spectrum of Ventricular Involvement

Improved disease recognition through family screening and increased life expectancy with appropriate sudden cardiac death prevention has increased the burden of heart failure in arrhythmogenic cardiomyopathy (ACM). Heart failure management guidelines are well established but primarily focus on left ventricle function. A significant proportion of patients with ACM have predominant or isolated right ventricle (RV) dysfunction. Management of RV dysfunction in ACM lacks evidence but requires special considerations across the spectrum of heart failure regarding the initial diagnosis, subsequent management, monitoring for progression, and end-stage disease management. In this review, we discuss the unique aspects of heart failure management in ACM with a special focus on RV dysfunction.

The Many Faces of Arrhythmogenic Cardiomyopathy: An Overview

Arrhythmogenic cardiomyopathy (AC) is a disease that involves electromechanical uncoupling of cardiomyocytes. This leads to characteristic histologic changes that ultimately lead to the arrhythmogenic clinical features of the disease. Initially thought to affect the right ventricle predominantly, more recent data show that it can affect both the ventricles or the left ventricle alone. Throughout the recent era, diagnostic modalities and criteria for AC have continued to evolve and our understanding of its clinical features in different age groups as well as the genotype to the phenotype correlations have improved. In this review, we set out to detail the epidemiology, etiologies, presentations, evaluation, and management of AC across the age continuum.

Genetic Risk Stratification in Arrhythmogenic Left Ventricular Cardiomyopathy

Arrhythmogenic left ventricular cardiomyopathy is characterized by early malignant ventricular arrhythmia associated with varying degrees and times of onset of left ventricular dysfunction. Variants in numerous genes have been associated with this phenotype. Here, the authors review the literature on recent cohort studies of patients with variants in desmoplakin, lamin A/C, filamin-C, phospholamban, RBM20, TMEM43, and selected channelopathy genes also associated with structural disease. Unlike traditional sudden cardiac death risk assessment in nonischemic cardiomyopathy, left ventricular systolic function is an insensitive predictor of risk in patients with these genetic diagnoses.

PP2A-B55alpha controls keratinocyte adhesion through dephosphorylation of the Desmoplakin C-terminus

Critical for the maintenance of epidermal integrity and function are attachments between intermediate filaments (IF) and intercellular junctions called desmosomes. The desmosomal cytoplasmic plaque protein desmoplakin (DP) is essential for anchoring IF to the junction. DP-IF interactions are regulated by a phospho-regulatory motif within the DP C-terminus controlling keratinocyte intercellular adhesion. Here we identify the protein phosphatase 2A (PP2A)-B55α holoenzyme as the major serine/threonine phosphatase regulating DP's C-terminus and consequent intercellular adhesion. Using a combination of chemical and genetic approaches, we show that the PP2A-B55α holoenzyme interacts with DP at intercellular membranes in 2D- and 3D- epidermal models and human skin samples. Our experiments demonstrate that PP2A-B55α regulates the phosphorylation status of junctional DP and is required for maintaining strong desmosome-mediated intercellular adhesion. These data identify PP2A-B55α as part of a regulatory module capable of tuning intercellular adhesion strength and a candidate disease target in desmosome-related disorders of the skin and heart.

A truncating variant altering the extreme C-terminal region of desmoplakin (DSP) suggests the crucial functional role of the region: a case report study

BACKGROUND

Homozygous truncating mutations located in the C-terminal region of the desmoplakin gene (DSP) are known to mainly cause Carvajal syndrome, an autosomal recessive syndromic form of arrhythmogenic cardiomyopathy with an extra-cardiac cutaneous phenotype.

CASE PRESENTATION

Here we describe a female proband with a documented arrhythmogenic left ventricular cardiomyopathy and a syncopal episode at the age of 13, who was found homozygous for the novel DSP variant: NM_004415.4:c.8586delC, p.(Ser2863Hisfs*20) at the extreme C-terminal region of the protein, just 8 amino acids upstream the stop codon. She did not have any of the typical dermatological symptoms that characterize Carvajal syndrome. Her brother had died suddenly at the age of 18 during exercise and was found homozygous for the same variant at the post-mortem, while their parents were heterozygous. The region of origin of both parents was the same geographic area of Greece, but they were not aware of any common ancestor. Detailed clinical examination revealed that the mother displayed a mild arrhythmic phenotype, while the father was asymptomatic.

CONCLUSION

These observations pinpoint to a significant functional role of the extreme C-terminal tail of the protein.

From the phenotype to precision medicine: an update on the cardiomyopathies diagnostic workflow

Cardiomyopathies are disease of the cardiac muscle largely due to genetic alterations of proteins with 'structural' or 'functional' roles within the cardiomyocyte, going from the regulation of contraction-relaxation, metabolic and energetic processes to ionic fluxes. Modifications occurring to these proteins are responsible, in the vast majority of cases, for the phenotypic manifestations of the disease, including hypertrophic, dilated, arrhythmogenic and restrictive cardiomyopathies. Secondary nonhereditary causes to be excluded include infections, toxicity from drugs or alcohol or medications, hormonal imbalance and so on. Obtaining a phenotypic definition and an etiological diagnosis is becoming increasingly relevant and feasible, thanks to the availability of new tailored treatments and the diagnostic advancements made particularly in the field of genetics. This is, for example, the case for transthyretin cardiac amyloidosis, Fabry disease or dilated cardiomyopathies due to laminopathies. For these diseases, specific medications have been developed, and a more tailored arrhythmic risk stratification guides the implantation of a defibrillator. In addition, new medications directly targeting the altered protein responsible for the phenotype are becoming available (including the myosin inhibitors mavacantem and aficamten, monoclonal antibodies against Ras-MAPK, genetic therapies for sarcoglycanopathies), thus making a precision medicine approach less unrealistic even in the field of cardiomyopathies. For these reasons, a contemporary approach to cardiomyopathies must consider diagnostic algorithms founded on the clinical suspicion of the disease and developed towards a more precise phenotypic definition and etiological diagnosis, based on a multidisciplinary methodology putting together specialists from different disciplines, facilities for advanced imaging testing and genetic and anatomopathological competencies.

Cheek-Pro-Heart: What Can the Buccal Mucosa Do for Arrhythmogenic Cardiomyopathy?

Arrhythmogenic cardiomyopathy (ACM) is a heart muscle disease associated with ventricular arrhythmias and a high risk of sudden cardiac death (SCD). Although the disease was described over 40 years ago, its diagnosis is still difficult. Several studies have identified a set of five proteins (plakoglobin, Cx43, Nav1.5, SAP97 and GSK3β), which are consistently re-distributed in myocardial samples from ACM patients. Not all protein shifts are specific to ACM, but their combination has provided us with a molecular signature for the disease, which has greatly aided post-mortem diagnosis of SCD victims. The use of this signature, however, was heretofore restricted in living patients, as the analysis requires a heart sample. Recent studies have shown that buccal cells behave similarly to the heart in terms of protein re-localization. Protein shifts are associated with disease onset, deterioration and favorable response to anti-arrhythmic therapy. Accordingly, buccal cells can be used as a surrogate for the myocardium to aid diagnosis, risk stratification and even monitor response to pharmaceutical interventions. Buccal cells can also be kept in culture, hence providing an ex vivo model from the patient, which can offer insights into the mechanisms of disease pathogenesis, including drug response. This review summarizes how the cheek can aid the heart in the battle against ACM.

Desmoplakin Cardiomyopathy: Comprehensive Review of an Increasingly Recognized Entity

Desmoplakin (DSP) is a desmosomal protein that plays an essential role for cell-to-cell adhesion within the cardiomyocytes. The first association between DSP genetic variants and the presence of a myocardial disease referred to patients with Carvajal syndrome. Since then, several reports have linked the DSP gene to familial forms of arrhythmogenic (ACM) and dilated cardiomyopathies. Left-dominant ACM is the most common phenotype in individuals carrying DSP variants. More recently, a new entity—“Desmoplakin cardiomyopathy”—was described as a distinct form of cardiomyopathy characterized by frequent left ventricular involvement with extensive fibrosis, high arrhythmic risk, and episodes of acute myocardial injury. The purpose of this review was to summarize the available evidence on DSP cardiomyopathy and to identify existing gaps in knowledge that need clarification from upcoming research.

DSP c.6310delA p.(Thr2104Glnfs*12) associates with arrhythmogenic cardiomyopathy, increased trabeculation, curly hair, and palmoplantar keratoderma

Background

Pathogenic variants in DSP associate with cardiac and cutaneous manifestations including arrhythmogenic right ventricular cardiomyopathy, dilated cardiomyopathy, curly or wavy hair, and palmoplantar keratoderma (PPK). Episodes of myocardial inflammation associated with DSP cardiomyopathy might be confused in clinical work with myocarditis of other etiologies such as viral. Cardiac magnetic resonance imaging (CMR) may help in differential diagnosis.

Methods and results

This study comprised 49 Finnish patients: 34 participants from families with suspected DSP cardiomyopathy (9 index patients and 25 family members) and 15 patients with myocarditis. All 34 participants underwent genetic testing and cardiac evaluation, and 29 of them also underwent CMR. Participants with the DSP variant, numbering 22, were dermatologically examined. The 15 patients with myocarditis underwent CMR and were evaluated during their hospitalization.

A heterozygous truncating DSP c.6310delA p.(Thr2104Glnfs*12) variant was confirmed in 29 participants. Only participants with the DSP variant had pacemakers and life-threatening ventricular arrhythmias. Of the participants with the DSP variant, 24% fulfilled cardiomyopathy criteria, and the median age at diagnosis was 53. Upon CMR, myocardial edema was found to be more common in patients with myocarditis. Both groups had a substantial percentage of late gadolinium enhancement (LGE). A ring-like LGE and increased trabeculation were observed only in participants with the DSP variant. All the studied participants with the DSP variant had PPK and curly or wavy hair. Hyperkeratosis developed before the age of 20 in most patients.

Conclusions

The DSP c.6310delA p.(Thr2104Glnfs*12) variant associates with curly hair, PPK, and arrhythmogenic cardiomyopathy with increased trabeculation. Cutaneous symptoms developing in childhood and adolescence might help recognize these patients at an earlier stage. CMR, together with dermatologic characteristics, may help in diagnosis.

Circadian and Seasonal Pattern of Arrhythmic Events in Arrhythmogenic Cardiomyopathy Patients

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiac disease associated with an increased risk of life-threatening arrhythmias. The aim of the present study was to evaluate the association of ventricular arrhythmias (VA) with circadian and seasonal variation in ARVC. One hundred two ARVC patients with an implantable cardioverter defibrillator (ICD) were enrolled in the study. Arrhythmic events included (a) any initial ventricular tachycardia (VT) or fibrillation (VF) prompting ICD implantation, (b) any VT or non-sustained VT (NSVT) recorded by the ICD, and (c) appropriate ICD shocks/therapy. Differences in the annual incidence of events across seasons (winter, spring, summer, autumn) and period of the day (night, morning, afternoon, evening) were assessed both for all cardiac events and major arrhythmic events. In total, 67 events prior to implantation and 263 ICD events were recorded. These included 135 major (58 ICD therapies, 57 self-terminating VT, 20 sustained VT) and 148 minor (NSVT) events. A significant increase in the frequency of events was observed in the afternoon versus in the nights and mornings (p = 0.016). The lowest number of events was registered in the summer, with a peak in the winter (p < 0.001). Results were also confirmed when excluding NSVT. Arrhythmic events in ARVC follow a seasonal variation and a circadian rhythm. They are more prevalent in the late afternoon, the most active period of the day, and in the winter, supporting the role of physical activity and inflammation as triggers of events.

Clinical and echocardiographic evolution of patients with arrhythmogenic cardiomyopathy before heart transplantation

BACKGROUND

Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiomyopathy characterized by fibrofatty myocardial replacement, and accurate diagnosis can be challenging. The clinical course of patients expressing a severe phenotype of the disease needing heart transplantation (HTx) is not well described in the literature. Therefore, this study aims to describe the clinical and echocardiographic evolution of patients with ACM necessitating HTx.

METHODS

We retrospectively studied all patients who underwent HTx in our institution between 1998 and 2019 with a definite diagnosis of ACM according to the explanted heart examination.

RESULTS

Ten patients with confirmed ACM underwent HTx. Only four of them had a diagnosis of ACM before HTx. These patients were 28 ± 15 years old at the time of their first symptoms. Patients received a diagnosis of heart failure (HF) after 5.9 ± 8.7 years of symptom evolution. The mean age at transplantation was 40 ± 17 years old. All the patients experienced ventricular tachycardia (VT) at least once before their HTx and 50% were resuscitated after sudden death. The mean left ventricular ejection at diagnosis and before transplantation was similar (32% ± 21% vs. 35.0% ± 19.3%, p = NS). Right ventricular dysfunction was present in all patients at the time of transplantation.

CONCLUSION

Patients with ACM necessitating HTx show a high burden of ventricular arrhythmias and frequently present a biventricular involvement phenotype, making early diagnosis challenging. HF symptoms are the most frequent reason leading to the decision to transplant.

Clinical application of CMR in cardiomyopathies: evolving concepts and techniques : A position paper of myocardial and pericardial diseases and cardiac magnetic resonance working groups of Italian society of cardiology

Cardiac magnetic resonance (CMR) has become an essential tool for the evaluation of patients affected or at risk of developing cardiomyopathies (CMPs). In fact, CMR not only provides precise data on cardiac volumes, wall thickness, mass and systolic function but it also a non-invasive characterization of myocardial tissue, thus helping the early diagnosis and the precise phenotyping of the different CMPs, which is essential for early and individualized treatment of patients. Furthermore, several CMR characteristics, such as the presence of extensive LGE or abnormal mapping values, are emerging as prognostic markers, therefore helping to define patients' risk. Lastly new experimental CMR techniques are under investigation and might contribute to widen our knowledge in the field of CMPs. In this perspective, CMR appears an essential tool to be systematically applied in the diagnostic and prognostic work-up of CMPs in clinical practice. This review provides a deep overview of clinical applicability of standard and emerging CMR techniques in the management of CMPs.

Desmoplakin cardiomyopathy—an inherited cardiomyopathy presenting with recurrent episodes of acute myocardial injury

We present two female patients with recurrent episodes of myocardial injury, consisting of acute chest pain and elevated cardiac markers without coronary artery disease. Cardiovascular magnetic resonance imaging identified extensive late gadolinium enhancement suggestive of an inherited cardiomyopathy. Genetic testing showed heterozygous pathogenic variants in the desmoplakin (DSP) gene, the gene coding for the desmoplakin protein, a structural protein found in the cardiac desmosome. Pathogenic variants in the DSP gene are associated with dilated and arrhythmogenic cardiomyopathy. DSP cardiomyopathies may cause recurring myocardial injury mimicking an acute coronary syndrome or myocarditis. Cardiac magnetic resonance imaging is key in its diagnosis due to its specifying imaging features. Genetic testing is essential for the evaluation and confirmation of the diagnosis.

Genetic variants in Colombian patients with inherited cardiac conditions

BACKGROUND

Clinical and molecular diagnosis of inherited cardiac conditions is key to find at-risk subjects and avoid preventable deaths. This study aimed to identify genetic variants in a sample of Colombian patients diagnosed with inherited cardiac conditions.

METHODS

Next-generation sequencing (Illumina platform) using a 231 gene panel was performed in blood samples of 25 unrelated patients with age disease onset between 9 and 55 years.

RESULTS

Genetic testing yield was 52%. Two novel likely pathogenic/ pathogenic variants were found: a DSP nonsense variant in a patient with arrhythmogenic cardiomyopathy and a KCNE1 frameshift variant in two patients with long QT syndrome. Younger individuals (<18 years) had the highest genetic testing yield (66.6%) compared to 50% and 20% in young adults and patients over 40 years, respectively. All subjects affected with long QT syndrome with a severe event while exercising had a positive genetic test. They also had four times more loss of consciousness events and, resuscitated sudden cardiac arrest was more representative.

CONCLUSION

This study is the first one undertaken in Colombia to evaluate inherited cardiac conditions. It highlights the need to perform mutational analysis to provide adequate genetic counseling and to be able to identify patients at risk of severe events.

Case Report: A novel desmoplakin mutation in a taiwanese woman with familial dilated cardiomyopathy that necessitated heart transplantation

Around one-third of patients diagnosed with idiopathic dilated cardiomyopathy (DCM) turn out to be familial cases, in only a few of which the identification of a pathogenic/likely pathogenic variant could be achieved. Cardiomyopathy caused by desmoplakin gene mutations represents a distinct form with a high prevalence of left ventricle involvement. We report a novel desmoplakin mutation carried by two individuals in a Taiwanese family, in which the proband recovered well after heart transplantation and under medical control, while her son had received an implantable cardioverter defibrillator and has been under guideline-directed medical therapy. The present study broadens the genetic spectrum of this disease entity and strengthens the notion that a detailed family history with genetic study contributes to the early detection and treatment of inherited diseases.

Biological substrate modification suppresses ventricular arrhythmias in a porcine model of chronic ischaemic cardiomyopathy

AIMS

Cardiomyopathy patients are prone to ventricular arrhythmias (VA) and sudden cardiac death. Current therapies to prevent VA include radiofrequency ablation to destroy slowly conducting pathways of viable myocardium which support re-entry. Here, we tested the reverse concept, namely that boosting local tissue viability in zones of slow conduction might eliminate slow conduction and suppress VA in ischaemic cardiomyopathy.

METHODS AND RESULTS

Exosomes are extracellular vesicles laden with bioactive cargo. Exosomes secreted by cardiosphere-derived cells (CDCEXO) reduce scar and improve heart function after intramyocardial delivery. In a VA-prone porcine model of ischaemic cardiomyopathy, we injected CDCEXO or vehicle into zones of delayed conduction defined by electroanatomic mapping. Up to 1-month post-injection, CDCEXO, but not the vehicle, decreased myocardial scar, suppressed slowly conducting electrical pathways, and inhibited VA induction by programmed electrical stimulation. In silico reconstruction of electrical activity based on magnetic resonance images accurately reproduced the suppression of VA inducibility by CDCEXO. Strong anti-fibrotic effects of CDCEXO, evident histologically and by proteomic analysis from pig hearts, were confirmed in a co-culture assay of cardiomyocytes and fibroblasts.

CONCLUSION

Biological substrate modification by exosome injection may be worth developing as a non-destructive alternative to conventional ablation for the prevention of recurrent ventricular tachyarrhythmias.

Molecular genetic testing in athletes: Why and when a position statement from the Italian society of sports cardiology

Molecular genetic testing is an increasingly available test to support the clinical diagnosis of inherited cardiovascular diseases through identification of pathogenic gene variants and to make a preclinical genetic diagnosis among proband's family members (so-called "cascade family screening"). In athletes, the added value of molecular genetic testing is to assist in discriminating between physiological adaptive changes of the athlete's heart and inherited cardiovascular diseases, in the presence of overlapping phenotypic features such as ECG changes, imaging abnormalities or arrhythmias ("grey zone"). Additional benefits of molecular genetic testing in the athlete include the potential impact on the disease risk stratification and the implications for eligibility to competitive sports. This position statement of the Italian Society of Sports Cardiology aims to guide general sports medical physicians and sports cardiologists on clinical decision as why and when to perform a molecular genetic testing in the athlete, highlighting strengths and weaknesses for each inherited cardiovascular disease at-risk of sudden cardiac death during sport. The importance of early (preclinical) diagnosis to prevent the negative effects of exercise on phenotypic expression, disease progression and worsening of the arrhythmogenic substrate is also addressed.

A novel desmoplakin mutation causes dilated cardiomyopathy with palmoplantar keratoderma as an early clinical sign

Background

PPKs represent a heterogeneous group of disorders with hyperkeratosis of palmar and/or plantar skin. PPK, hair shaft abnormalities, cardiomyopathy and arrhythmias can be caused by mutations in desmosomal genes, e.g. desmoplakin (DSP). PPK should trigger genetic testing to reveal mutations with possible related cardiac disease.

Objectives

To report a large multigenerational family with a novel DSP mutation associated with early‐onset PPK and adult‐onset cardiomyopathy and arrhythmias.

Methods

A custom‐designed in‐house panel of 35 PPK related genes was used to screen mutations in the index patient with focal PPK. The identified DSP mutation was verified by Sanger sequencing. DNA samples from 20 members of the large multigenerational family were sequenced for the DSP mutation. Medical records were reviewed. Clinical dermatological evaluation was performed, including light microscopy of hair samples. Cardiac evaluation included clinical examination, echocardiography, cardiac magnetic resonance imaging (CMR), electrocardiogram (ECG), Holter monitoring and laboratory tests.

Results

We identified a novel autosomal dominant truncating DSP c.2493delA p.(Glu831Aspfs*33) mutation associated with dilated cardiomyopathy (DCM) with arrhythmia susceptibility and focal PPK as an early cutaneous sign. The mutation was found in nine affected family members, but not in any unaffected members. Onset of dermatological findings preceded cardiac symptoms which were variable and occurred at adult age.

Conclusions

We report a novel truncating DSP mutation causing focal PPK with varying severity and left ventricular dilatation and ventricular extrasystoles. This finding emphasizes the importance of genetic diagnosis in patients with PPK for clinical counselling and management of cardiomyopathies and arrhythmias.

A 45-year-old man with sudden cardiac death, cutaneous abnormalities and a rare desmoplakin mutation: a case report and literature review

Background

Arrhythmogenic cardiomyopathy (AC) is a rare, heritable myocardial disorder that is a leading cause of ventricular arrhythmia and sudden cardiac death (SCD) in young people. Desmoplakin (DSP) mutations account for 3–20% of AC cases. However, the number of patients with DSP mutations is extremely small in all published reports and genotype–phenotype correlations are scant and mostly non-gene-specific.

Case presentation

A 45-year-old man was admitted after an out-of-hospital cardiac arrest, with documented ventricular fibrillation. He had no previous history of heart disease or family history of SCD or cardiomyopathy. The cardiac magnetic resonance showed a mildly dilated left ventricle with an ejection fraction of 30% and a non-dilated right ventricle with mildly depressed systolic function, and extensive subepicardial late gadolinium enhancement. Genetic screening identified a heterozygote nonsense mutation in DSP (NM_004415.2: c.478 C > T; p.Arg160Ter). Cascade genetic screening of the relatives revealed a high prevalence of the genotype and cutaneous phenotype, but a very low penetrance of the cardiac phenotype.

Conclusions

We report a case of SCD and an autosomal dominant mutation in DSP that causes arrhythmogenic dilated cardiomyopathy/AC. Like the recessive mutation in DSP known to cause Carvajal syndrome, Arg160Ter may be associated with cutaneous abnormalities.

Cardiovascular Characteristics of Patients with Genetic Variation in Desmoplakin (DSP)

Background:

Variants in the desmoplakin (DSP) gene have been recognized in association with the pathogenesis of arrhythmogenic right ventricular cardiomyopathy (ARVC) for nearly 20 years. More recently, genetic variation in DSP has also been associated with left-dominant arrhythmogenic cardiomyopathy. Data regarding the cardiac phenotypes associated with genetic variation in DSP have been largely accumulated from phenotype-first studies of ARVC.

Methods:

We aimed to evaluate the clinical manifestations of cardiac disease associated with variants in DSP through a genotype-first approach employed in the University of Pennsylvania Center for Inherited Cardiovascular Disease registry. We performed a retrospective study of 19 individuals with “pathogenic” or “likely pathogenic” variants in DSP identified by clinical genetic testing. Demographics and clinical characteristics were collected.

Results:

Among individuals with disease-causing variants in DSP, nearly 40% had left ventricular enlargement at initial assessment. Malignant arrhythmias were prevalent in this cohort (42%) with a high proportion of individuals undergoing primary and secondary prevention implantable cardioverter defibrillator implantation (68%) and ablation of ventricular arrhythmias (16%). Probands also experienced end-stage heart failure requiring heart transplantation (11%).

Conclusions:

Our data suggest DSP cardiomyopathy may manifest with a high burden of heart failure and arrhythmic events, highlighting its importance in the pathogenesis of dilated and arrhythmogenic cardiomyopathies. Targeted strategies for diagnosis and risk stratification for DSP cardiomyopathy should be investigated.

Pathogenesis, Diagnosis and Risk Stratification in Arrhythmogenic Cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is a genetically determined myocardial disease associated with sudden cardiac death (SCD). It is most frequently caused by mutations in genes encoding desmosomal proteins. However, there is growing evidence that ACM is not exclusively a desmosome disease but rather appears to be a disease of the connexoma. Fibroadipose replacement of the right ventricle (RV) had long been the hallmark of ACM, although biventricular involvement or predominant involvement of the left ventricle (LD-ACM) is increasingly found, raising the challenge of differential diagnosis with arrhythmogenic dilated cardiomyopathy (a-DCM). A-DCM, ACM, and LD-ACM are increasingly acknowledged as a single nosological entity, the hallmark of which is electrical instability. Our aim was to analyze the complex molecular mechanisms underlying arrhythmogenic cardiomyopathies, outlining the role of inflammation and autoimmunity in disease pathophysiology. Secondly, we present the clinical tools used in the clinical diagnosis of ACM. Focusing on the challenge of defining the risk of sudden death in this clinical setting, we present available risk stratification strategies. Lastly, we summarize the role of genetics and imaging in risk stratification, guiding through the appropriate patient selection for ICD implantation.

Heart Failure in Patients with Arrhythmogenic Cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is a rare inherited cardiomyopathy characterized as fibro-fatty replacement, and a common cause for sudden cardiac death in young athletes. Development of heart failure (HF) has been an under-recognized complication of ACM for a long time. The current clinical management guidelines for HF in ACM progression have nowadays been updated. Thus, a comprehensive review for this great achievement in our understanding of HF in ACM is necessary. In this review, we aim to describe the research progress on epidemiology, clinical characteristics, risk stratification and therapeutics of HF in ACM.

Genotype-phenotype correlation in arrhythmogenic right ventricular cardiomyopathy-risk of arrhythmias and heart failure

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is predominantly caused by desmosomal genetic variants, and clinical hallmarks include arrhythmias and systolic dysfunction. We aimed at studying the impact of the implicated gene(s) on the disease course.

METHODS

The Nordic ARVC Registry holds data on a multinational cohort of ARVC families. The effects of genotype on electrocardiographic features, imaging findings and clinical events were analysed.

RESULTS

We evaluated 419 patients (55% men), with a mean follow-up of 11.2±7.4 years. A pathogenic desmosomal variant was identified in 62% of the 230 families: PKP2 in 41%, DSG2 in 13%, DSP in 7% and DSC2 in 3%. Reduced left ventricular ejection fraction (LVEF) ≤45% on cardiac MRI was more frequent among patients with DSC2/DSG2/DSP than PKP2 ARVC (27% vs 4%, p<0.01). In contrast, in Cox regression modelling of patients with definite ARVC, we found a higher risk of arrhythmias among PKP2 than DSC2/DSG2/DSP carriers: HR 0.25 (0.10-0.68, p<0.01) for atrial fibrillation/flutter, HR 0.67 (0.44-1.0, p=0.06) for ventricular arrhythmias and HR 0.63 (0.42-0.95, p<0.05) for any arrhythmia. Gene-negative patients had an intermediate risk (16%) of LVEF ≤45% and a risk of the combined arrhythmic endpoint comparable with DSC2/DSG2/DSP carriers. Male sex was a risk factor for both arrhythmias and reduced LVEF across all genotype groups (p<0.01).

CONCLUSION

In this large cohort of ARVC families with long-term follow-up, we found PKP2 genotype to be more arrhythmic than DSC2/DSG2/DSP or gene-negative carrier status, whereas reduced LVEF was mostly seen among DSC2/DSG2/DSP carriers. Male sex was associated with a more severe phenotype.

Desmoplakin cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy: two distinct forms of cardiomyopathy?

The confirmation of a hypothesis that desmoplakin-related (DSP) cardiomyopathy could represent a distinct clinical entity from the classical, RV-dominant, form of arrhythmogenic cardiomyopathy (ACM), most frequently caused by PKP2 mutations, would without any shadow of doubt signify a turning point in the history of this disease. The concept of gene-specific diseases underneath the umbrella diagnosis of ACM would bring fundamental changes not only in the clinical, diagnostic and therapeutic approach, but also in terms of risk stratification, pushing the scientific community towards a more patient-centred view of the disease, similarly to what has already been done in other inherited arrhythmogenic disease (e.g., Long QT Syndrome; LQTS). We provide a state-of-the-art review, starting with a brief historical framework to give the necessary context and better focus the question. Then, we proceed with a novel, genotype-tophenotype-based comparison of the most important aspects of DSP-related cardiomyopathy with the classical, RV-dominant ACM: this allows us to ascertain not only that the differences between the forms exist, but are also clinically relevant and actionable, leading to the underrecognition of the atypical, DSP-related, LV-dominant forms when applying the current diagnostic criteria. These findings will usher an exciting era, in which the scientific community will try to answer a range of questions, starting from the reasons why different desmosomal mutations cause such different phenotypes.

Desmoplakin and clinical manifestations of desmoplakin cardiomyopathy

Desmoplakin (DSP), encoded by the DSP gene, is the main desmosome component and is abundant in the myocardial tissue. There are three DSP isoforms that assume the role of supporting structural stability through intercellular adhesion. It has been found that DSP regulates the transcription of adipogenic and fibrogenic genes, and maintains appropriate electrical conductivity by regulating gap junctions and ion channels. DSP is essential for normal myocardial development and the maintenance of its structural functions. Studies have suggested that DSP gene mutations are associated with a variety of hereditary cardiomyopathy, such as arrhythmia cardiomyopathy, dilated cardiomyopathy (DCM), left ventricular noncompaction, and is also closely associated with the Carvajal syndrome, Naxos disease, and erythro-keratodermia-cardiomyopathy syndrome with skin and heart damage. The structure and function of DSP, as well as the clinical manifestations of DSP-related cardiomyopathy were reviewed in this article.

Pathogenic variants in plakophilin-2 gene (PKP2) are associated with better survival in arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is mainly caused by mutations in genes encoding desmosomal proteins. Variants in plakophilin-2 gene (PKP2) are the most common cause of the disease, associated with conventional ARVC phenotype. The study aims to evaluate the prevalence of PKP2 variants and examine genotype-phenotype correlation in Polish ARVC cohort. All 56 ARVC patients fulfilling the current criteria were screened for genetic variants in PKP2 using denaturing high-performance liquid chromatography or next-generation sequencing. The clinical evaluation involved medical history, electrocardiogram, echocardiography, and follow-up. Ten variants (5 frameshift, 2 nonsense, 2 splicing, and 1 missense) in PKP2 were found in 28 (50%) cases. All truncating variants are classified as pathogenic/likely pathogenic, while the missense variant is classified as variant of uncertain significance. Patients carrying a PKP2 mutation were younger at diagnosis (p = 0.003), more often had negative T waves in V1-V3 (p = 0.01), had higher left ventricular ejection fraction (p = 0.04), and were less likely to present symptoms of heart failure (p = 0.01) and left ventricular damage progression (p = 0.04). Combined endpoint of death or heart transplant was more frequent in subgroup without PKP2 mutation (p = 0.03). Pathogenic variants in PKP2 are responsible for 50% of ARVC cases in the Polish population and are associated with a better prognosis. ARVC patients with PKP2 mutation are less likely to present left ventricular involvement and heart failure symptoms. Combined endpoint of death or heart transplant was less frequent in this group.

Pitfalls in arrhythmogenic left ventricular cardiomyopathy (ALVC). A review of the literature with considerations on a single case of sudden death in a juvenile athlete

Sudden cardiac death (SCD) in young athletes represents a challenging issue in forensic practice. The pathologist is frequently asked to establish the cause of death basing upon anatomical findings and to evaluate the role of the physician in preparticipation evaluation (PPE) and eligibility decision. Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a leading cause of SCD during sport activity. However, in the last few years, forms with predominant or even isolated involvement of the left ventricle (LV) have progressively been correlated with a high risk of SCD. We present a case of SCD in an apparently healthy 19-year-old semi-professional football player. Annual PPEs performed in accordance with international and Italian recommendations, were unremarkable. At autopsy, a 1-cm area of subepicardial fibro-fatty replacement was observed at the postero-lateral wall of the LV. The finding was diagnostic of arrhythmogenic left ventricular cardiomyopathy (ALVC). A review of this rare pathology has been performed under a forensic perspective, focusing on the evaluation of the medico-legal responsibility of the physician in the PPE and on the morphological aspects of the disease. Current diagnostic criteria and recommendations result to be focused on the right ventricular pattern, with a risk of misdiagnosis for isolated LV forms. Furthermore, few detailed autopsies cases concerning ALVC have been published. There is a need, therefore, to study this rare disease with a careful and revised approach.

The EP300/TP53 pathway, a suppressor of the Hippo and canonical WNT pathways, is activated in human hearts with arrhythmogenic cardiomyopathy in the absence of overt heart failure

AIM

Arrhythmogenic cardiomyopathy (ACM) is a primary myocardial disease that typically manifests with cardiac arrhythmias, progressive heart failure and sudden cardiac death (SCD). ACM is mainly caused by mutations in genes encoding desmosome proteins. Desmosomes are cell-cell adhesion structures and hubs for mechanosensing and mechanotransduction. The objective was to identify the dysregulated molecular and biological pathways in human ACM in the absence of overt heart failure.

METHODS AND RESULTS

Transcriptomes in the right ventricular endomyocardial biopsy samples from three independent individuals carrying truncating mutations in the DSP gene and 5 control samples were analyzed by RNA-Seq (discovery group). These cases presented with cardiac arrhythmias and had a normal right ventricular function. The RNA-Seq analysis identified ∼5,000 differentially expressed genes (DEGs), which predicted suppression of the Hippo and canonical WNT pathways, among others.Dysregulated genes and pathways, identified by RNA-Seq, were tested for validation in the right and left ventricular tissues from 5 independent autopsy-confirmed ACM cases with defined mutations (validation group), who were victims of SCD and had no history of heart failure. Protein levels and nuclear localization of the cWNT and Hippo pathway transcriptional regulators were reduced in the right and left ventricular validation samples. In contrast, levels of acetyltransferase EP300, known to suppress the Hippo and canonical WNT pathways, were increased and its bona fide target TP53 was acetylated. RNA-Seq data identified apical junction, reflective of cell-cell attachment, as the most disrupted biological pathway, which was corroborated by disrupted desmosomes and intermediate filament structures. Moreover, the DEGs also predicted dysregulation of over a dozen canonical signal transduction pathways, including the Tec kinase and integrin signaling pathways. The changes were associated with increased apoptosis and fibro-adipogenesis in the ACM hearts.

CONCLUSION

Altered apical junction structures is associated with activation of the EP300-TP53 and suppression of the Hippo/cWNT pathways in human ACM caused by defined mutations in the absence of an overt heart failure. The findings implicate altered mechanotransduction in the pathogenesis of ACM.

TRANSLATIONAL PERSPECTIVE

The findings suggest that altered mechanosensing at the cell-cell junction instigates a cascade of molecular events through the activation of acetyltransferase EP300/TP53 and suppression of gene expression through the Hippo/canonical WNT pathways in human arrhythmogenic cardiomyopathy (ACM) caused by defined mutations. These molecular changes occur early and in the absence of overt heart failure. Consequently, one may envision cell type-specific interventions to target the dysregulated transcriptional, mechanosensing, and mechanotransduction pathways to prevent the evolving phenotype in human ACM.

Arrhythmogenic Right Ventricular Cardiomyopathy Presenting as Clinical Myocarditis in Women

Patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) classically initially present with ventricular arrhythmias or, less commonly, heart failure. Myocardial inflammation has been implicated in pathogenesis, but clinical myocarditis in ARVC is less described. We therefore studied clinical myocarditis as an initial ARVC presentation, and hypothesized that these patients have distinct clinical and genetic characteristics. Using the Johns Hopkins ARVC Registry, we identified 12 patients (all female, median age 20) referred between 2014 and 2019 diagnosed with myocarditis at presentation who were subsequently diagnosed with ARVC by Task Force Criteria. Majority presented with chest pain (n = 7, 58%) or ventricular arrhythmia (n = 3, 25%). All patients had troponin elevations and left ventricular (LV) function was reduced in 5 (42%). Magnetic resonance imaging demonstrated LV delayed gadolinium enhancement and/or pericardial enhancement in 10 (83%); only 3 (25%) patients had right ventricular abnormalities. Pathogenic genetic variants were identified in 11 (92%) patients: 10 desmoplakin (DSP) and 1 desmoglein-2 (DSG2). Thus, nearly 1/3 (10/32, 31%) of overall DSP ARVC patients were originally diagnosed with myocarditis. Patients were diagnosed with ARVC 1.8 years (IQR 2.7 years) after presentation and 8 (75%) patients did not meet Task Force Criteria without genetic testing. ARVC diagnosis led to an additional 5 (42%) patients referred for implantable cardiac defibrillator and 17 family member diagnoses. In conclusion, ARVC may initially present as myocarditis and these patients have distinct characteristics including female gender, LV involvement and DSP gene variants. Genetic testing is key to ARVC diagnosis and should be considered in select myocarditis patients.

Single-Cell RNA Sequencing Uncovers Paracrine Functions of the Epicardial-Derived Cells in Arrhythmogenic Cardiomyopathy

BACKGROUND

Arrhythmogenic cardiomyopathy (ACM) manifests with sudden death, arrhythmias, heart failure, apoptosis, and myocardial fibro-adipogenesis. The phenotype typically starts at the epicardium and advances transmurally. Mutations in genes encoding desmosome proteins, including DSP (desmoplakin), are major causes of ACM.

METHODS

To delineate contributions of the epicardium to the pathogenesis of ACM, the Dsp allele was conditionally deleted in the epicardial cells in mice upon expression of tamoxifen-inducible Cre from the Wt1 locus. Wild type (WT) and Wt1-Cre^ERT2:Dsp^W/F were crossed to Rosa26^mT/mG (R26^mT/mG) dual reporter mice to tag the epicardial-derived cells with the EGFP (enhanced green fluorescent protein) reporter protein. Tagged epicardial-derived cells from adult Wt1-Cre^ERT2:R26^mT/mG and Wt1-Cre^ERT2: R26^mT/mG:Dsp^W/F mouse hearts were isolated by fluorescence-activated cell staining and sequenced by single-cell RNA sequencing.

RESULTS

WT1 (Wilms tumor 1) expression was progressively restricted postnatally and was exclusive to the epicardium by postnatal day 21. Expression of Dsp was reduced in the epicardial cells but not in cardiac myocytes in the Wt1-Cre^ERT2:Dsp^W/F mice. The Wt1-Cre^ERT2:Dsp^W/F mice exhibited premature death, cardiac dysfunction, arrhythmias, myocardial fibro-adipogenesis, and apoptosis. Single-cell RNA sequencing of ≈18 000 EGFP-tagged epicardial-derived cells identified genotype-independent clusters of endothelial cells, fibroblasts, epithelial cells, and a very small cluster of cardiac myocytes, which were confirmed on coimmunofluorescence staining of the myocardial sections. Differentially expressed genes between the paired clusters in the 2 genotypes predicted activation of the inflammatory and mitotic pathways-including the TGFβ1 (transforming growth factor β1) and fibroblast growth factors-in the epicardial-derived fibroblast and epithelial clusters, but predicted their suppression in the endothelial cell cluster. The findings were corroborated by analysis of gene expression in the pooled RNA-sequencing data, which identified predominant dysregulation of genes involved in epithelial-mesenchymal transition, and dysregulation of 146 genes encoding the secreted proteins (secretome), including genes in the TGFβ1 pathway. Activation of the TGFβ1 and its colocalization with fibrosis in the Wt1-Cre^ERT2:R26^mT/mG:Dsp^W/F mouse heart was validated by complementary methods.

CONCLUSIONS

Epicardial-derived cardiac fibroblasts and epithelial cells express paracrine factors, including TGFβ1 and fibroblast growth factors, which mediate epithelial-mesenchymal transition, and contribute to the pathogenesis of myocardial fibrosis, apoptosis, arrhythmias, and cardiac dysfunction in a mouse model of ACM. The findings uncover contributions of the epicardial-derived cells to the pathogenesis of ACM.

Cadherin 2-Related Arrhythmogenic Cardiomyopathy: Prevalence and Clinical Features

BACKGROUND

Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disease characterized by fibrofatty replacement of the right and left ventricle, often causing ventricular dysfunction and life-threatening arrhythmias. Variants in desmosomal genes account for up to 60% of cases. Our objective was to establish the prevalence and clinical features of ACM stemming from pathogenic variants in the nondesmosomal cadherin 2 (CDH2), a novel genetic substrate of ACM.

METHODS

A cohort of 500 unrelated patients with a definite diagnosis of ACM and no disease-causing variants in the main ACM genes was assembled. Genetic screening of CDH2 was performed through next-generation or Sanger sequencing. Whenever possible, cascade screening was initiated in the families of CDH2-positive probands, and clinical evaluation was performed.

RESULTS

Genetic screening of CDH2 led to the identification of 7 rare variants: 5, identified in 6 probands, were classified as pathogenic or likely pathogenic. The previously established p.D407N pathogenic variant was detected in 2 additional probands. Probands and family members with pathogenic/likely pathogenic variants in CDH2 were clinically evaluated, and along with previously published cases, altogether contributed to the identification of gene-specific features (13 cases from this cohort and 11 previously published, for a total of 9 probands and 15 family members). Ventricular arrhythmic events occurred in most CDH2-positive subjects (20/24, 83%), while the occurrence of heart failure was rare (2/24, 8.3%). Among probands, sustained ventricular tachycardia and sudden cardiac death occurred in 5/9 (56%).

CONCLUSIONS

In this worldwide cohort of previously genotype-negative ACM patients, the prevalence of probands with CDH2 pathogenic/likely pathogenic variants was 1.2% (6/500). Our data show that this cohort of CDH2-ACM patients has a high incidence of ventricular arrhythmias, while evolution toward heart failure is rare.

Arrhythmogenic Right Ventricular Cardiomyopathy in Pediatric Patients: An Important but Underrecognized Clinical Entity

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy characterized by fibrofatty infiltration of predominantly the right ventricular (RV) myocardium. Affected patients typically present as young adults with hemodynamically stable ventricular tachycardia, although pediatric cases are increasingly recognized. These young subjects often have a more severe phenotype with a high risk of sudden cardiac death (SCD) and progression toward heart failure. Diagnosis of ARVC is made by combining multiple sources of information as prescribed by the consensus-based Task Force Criteria. The description of Naxos disease, a fully penetrant autosomal recessive disorder that is associated with ARVC and a cutaneous phenotype of palmoplantar keratoderma and wooly hair facilitated the identification of the genetic cause of ARVC. At present, approximately 60% of patients are found to carry a pathogenic variant in one of five genes associated with the cardiac desmosome. The incomplete penetrance and variable expressivity of these variants however implies an important role for environmental factors, of which participation in endurance exercise is a strong risk factor. Since there currently is no definite cure for ARVC, disease management is directed toward symptom reduction, delay of disease progression, and prevention of SCD. This clinically focused review describes the spectrum of ARVC among children and adolescents, the genetic architecture underlying this disease, the cardio-cutaneous syndromes that led to its identification, and current diagnostic and therapeutic strategies in pediatric ARVC subjects.

Characteristics of Patients With Arrhythmogenic Left Ventricular Cardiomyopathy

Background:

Arrhythmogenic left ventricular cardiomyopathy (ALVC) is an under-characterized phenotype of arrhythmogenic cardiomyopathy involving the LV ab initio. ALVC was not included in the 2010 International Task Force Criteria for arrhythmogenic right ventricular cardiomyopathy diagnosis and data regarding this phenotype are scarce.

Methods:

Clinical characteristics were reported from all consecutive patients diagnosed with ALVC, defined as a LV isolated late gadolinium enhancement and fibro-fatty replacement at cardiac magnetic resonance plus genetic variants associated with arrhythmogenic right ventricular cardiomyopathy and of an endomyocardial biopsy showing fibro-fatty replacement complying with the 2010 International Task Force Criteria in the LV.

Results:

Twenty-five patients ALVC (53 [48–59] years, 60% male) were enrolled. T wave inversion in infero-lateral and left precordial leads were the most common ECG abnormalities. Overall arrhythmic burden at study inclusion was 56%. Cardiac magnetic resonance showed LV late gadolinium enhancement in the LV lateral and posterior basal segments in all patients. In 72% of the patients an invasive evaluation was performed, in which electroanatomical voltage mapping and electroanatomical voltage mapping-guided endomyocardial biopsy showed low endocardial voltages and fibro-fatty replacement in areas of late gadolinium enhancement presence. Genetic variants in desmosomal genes (desmoplakin and desmoglein-2) were identified in 12/25 of the cohort presenting pathogenic/likely pathogenic variants. A definite/borderline 2010 International Task Force Criteria arrhythmogenic right ventricular cardiomyopathy diagnosis was reached only in 11/25 patients.

Conclusions:

ALVC presents with a preferential involvement of the lateral and postero-lateral basal LV and is associated mostly with variants in desmoplakin and desmoglein-2 genes. An amendment to the current International Task Force Criteria is reasonable to better diagnose patients with ALVC.

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

Background

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

Methods

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

Results

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

Conclusion

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

Missense variants in the spectrin repeat domain of DSP are associated with arrhythmogenic cardiomyopathy: A family report and systematic review

Rare loss of function variants in DSP, which codes for the desmosomal protein desmoplakin, have been implicated in dilated and arrhythmogenic right ventricular cardiomyopathies. We present a family with arrhythmogenic cardiomyopathy associated with a novel missense variant in DSP (NM_004415.4): c.877G>A, p.(Glu293Lys). The phenotype is characterized by predominant involvement of the left ventricle with systolic dysfunction, fibrosis, and life-threatening arrhythmias. We performed a systematic review of literature collecting all cardiomyopathy cases with rare missense variants in DSP. We demonstrate that the distribution of missense variants across the protein domains in cardiomyopathy cases differs from that in gnomAD (p = .04), with a case enrichment of rare missense variants in the spectrin repeat domain (36/78 [46%] in cases vs. 449/1495 [30%] in gnomAD; p = .004). Our findings highlight the predominance of cardiac arrhythmia and left ventricular involvement in desmoplakin cardiomyopathy and pinpoint to a potential mutation hotspot in DSP thereby facilitating missense variant interpretation in the diagnostic setting.

Genetic Risk of Arrhythmic Phenotypes in Patients With Dilated Cardiomyopathy

BACKGROUND

Genotype-phenotype correlations in dilated cardiomyopathy (DCM) and, in particular, the effects of gene variants on clinical outcomes remain poorly understood.

OBJECTIVES

The purpose of this study was to investigate the prognostic role of genetic variant carrier status in a large cohort of DCM patients.

METHODS

A total of 487 DCM patients were analyzed by next-generation sequencing and categorized the disease genes into functional gene groups. The following composite outcome measures were assessed: 1) all-cause mortality; 2) heart failure-related death, heart transplantation, or destination left ventricular assist device implantation (DHF/HTx/VAD); and 3) sudden cardiac death/sustained ventricular tachycardia/ventricular fibrillation (SCD/VT/VF).

RESULTS

A total of 183 pathogenic/likely pathogenic variants were found in 178 patients (37%): 54 (11%) Titin; 19 (4%) Lamin A/C (LMNA); 24 (5%) structural cytoskeleton-Z disk genes; 16 (3.5%) desmosomal genes; 46 (9.5%) sarcomeric genes; 8 (1.6%) ion channel genes; and 11 (2.5%) other genes. All-cause mortality was no different between variant carriers and noncarriers (p = 0.99). A trend toward worse SCD/VT/VF (p = 0.062) and DHF/HTx/VAD (p = 0.061) was found in carriers. Carriers of desmosomal and LMNA variants experienced the highest rate of SCD/VT/VF, which was independent of the left ventricular ejection fraction.

CONCLUSIONS

Desmosomal and LMNA gene variants identify the subset of DCM patients who are at greatest risk for SCD and life-threatening ventricular arrhythmias, regardless of the left ventricular ejection fraction.

Desmoplakin Cardiomyopathy, a Fibrotic and Inflammatory Form of Cardiomyopathy Distinct From Typical Dilated or Arrhythmogenic Right Ventricular Cardiomyopathy

BACKGROUND

Mutations in desmoplakin (DSP), the primary force transducer between cardiac desmosomes and intermediate filaments, cause an arrhythmogenic form of cardiomyopathy that has been variably associated with arrhythmogenic right ventricular cardiomyopathy. Clinical correlates of DSP cardiomyopathy have been limited to small case series.

METHODS

Clinical and genetic data were collected on 107 patients with pathogenic DSP mutations and 81 patients with pathogenic plakophilin 2 (PKP2) mutations as a comparison cohort. A composite outcome of severe ventricular arrhythmia was assessed.

RESULTS

DSP and PKP2 cohorts included similar proportions of probands (41% versus 42%) and patients with truncating mutations (98% versus 100%). Left ventricular (LV) predominant cardiomyopathy was exclusively present among patients with DSP (55% versus 0% for PKP2, P<0.001), whereas right ventricular cardiomyopathy was present in only 14% of patients with DSP versus 40% for PKP2 (P<0.001). Arrhythmogenic right ventricular cardiomyopathy diagnostic criteria had poor sensitivity for DSP cardiomyopathy. LV late gadolinium enhancement was present in a primarily subepicardial distribution in 40% of patients with DSP (23/57 with magnetic resonance images). LV late gadolinium enhancement occurred with normal LV systolic function in 35% (8/23) of patients with DSP. Episodes of acute myocardial injury (chest pain with troponin elevation and normal coronary angiography) occurred in 15% of patients with DSP and were strongly associated with LV late gadolinium enhancement (90%), even in cases of acute myocardial injury with normal ventricular function (4/5, 80% with late gadolinium enhancement). In 4 DSP cases with 18F-fluorodeoxyglucose positron emission tomography scans, acute LV myocardial injury was associated with myocardial inflammation misdiagnosed initially as cardiac sarcoidosis or myocarditis. Left ventricle ejection fraction <55% was strongly associated with severe ventricular arrhythmias for DSP cases (P<0.001, sensitivity 85%, specificity 53%). Right ventricular ejection fraction <45% was associated with severe arrhythmias for PKP2 cases (P<0.001) but was poorly associated for DSP cases (P=0.8). Frequent premature ventricular contractions were common among patients with severe arrhythmias for both DSP (80%) and PKP2 (91%) groups (P=non-significant).

CONCLUSIONS

DSP cardiomyopathy is a distinct form of arrhythmogenic cardiomyopathy characterized by episodic myocardial injury, left ventricular fibrosis that precedes systolic dysfunction, and a high incidence of ventricular arrhythmias. A genotype-specific approach for diagnosis and risk stratification should be used.

Clinical predictors of left ventricular involvement in arrhythmogenic right ventricular cardiomyopathy

AIM

The impact of clinical characteristics for predicting patterns of ventricular involvement in arrhythmogenic right ventricular cardiomyopathy (ARVC) are not well defined. The aims of this study were to characterize different patterns of ventricular involvement in patients with ARVC and to stratify them based on clinical characteristics exercise and underlying genetic mutations.

METHODS

Sixty-four patients with definite ARVC from the Swiss ARVC Registry were enrolled. Right and left ventricular functions were assessed at baseline and most recent follow-up. All patients received genetic testing. Serum high-sensitivity cardiac Troponin T (hs-cTNT) and N-terminal of pro-brain natriuretic peptide (NT-proBNP) were determined at baseline.

RESULTS

Thirty-five patients (55%) had isolated right ventricular (RV) involvement, 12 patients (19%) had biventricular (BiV) involvement at baseline and 17 patients (26%) had no left ventricular (LV) involvement at baseline, but revealed new onset LV involvement at mean follow-up of 7.5 years. Patients with BiV involvement at baseline harbored significantly more desmoplakin and multiple mutations and patients with new-onset LV involvement at follow-up frequently showed non-desmosomal mutations. Patients engaging in competitive sports more often showed LV involvement during follow-up. Baseline hs-cTNT and NT-proBNP levels were higher in patients developing BiV involvement.

CONCLUSION

Multiple mutations are more common in ARVC patients with BiV involvement. Competitive exercise is associated with disease progression resulting in BiV involvement. Hs-cTNT and NT-proBNP are elevated in patients with BiV involvement and may help to identify ARVC patients at risk for developing BiV disease.

Monozygotic twins with myocarditis and a novel likely pathogenic desmoplakin gene variant

Myocarditis most often affects otherwise healthy athletes and is one of the leading causes of sudden death in children and young adults. Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetically determined heart muscle disorder with increased risk for paroxysmal ventricular arrhythmias and sudden cardiac death. The clinical picture of myocarditis and ARVC may overlap during the early stages of cardiomyopathy, which may lead to misdiagnosis. In the literature, we found several cases that presented with episodes of myocarditis and ended up with a diagnosis of arrhythmogenic cardiomyopathy, mostly of the left predominant type. The aim of this case presentation is to shed light upon a possible link between myocarditis, a desmoplakin (DSP) gene variant, and ARVC by describing a case of male monozygotic twins who presented with symptoms and signs of myocarditis at 17 and 18 years of age, respectively. One of them also had a recurrent episode of myocarditis. The twins and their family were extensively examined including electrocardiograms (ECG), biochemistry, multimodal cardiac imaging, myocardial biopsy, genetic analysis, repeated cardiac magnetic resonance (CMR) and echocardiography over time. Both twins presented with chest pain, ECG with slight ST-T elevation, and increased troponin T levels. CMR demonstrated an affected left ventricle with comprehensive inflammatory, subepicardial changes consistent with myocarditis. The right ventricle did not appear to have any abnormalities. Genotype analysis revealed a nonsense heterozygous variant in the desmoplakin (DSP) gene [NM_004415.2:c.2521_2522del (p.Gln841Aspfs*9)] that is considered likely pathogenic and presumably ARVC related. There was no previous family history of heart disease. There might be a common pathophysiology of ARVC, associated with desmosomal dysfunction, and myocarditis. In our case, both twins have an affected left ventricle without any right ventricular involvement, and they are carriers of a novel DSP variant that is likely associated with ARVC. The extensive inflammation of the LV that was apparent in the CMR may or may not be the primary event of ARVC. Nevertheless, our data suggest that irrespective of a possible link here to ARVC, genetic testing for arrhythmogenic cardiomyopathy might be advisable for patients with recurrent myocarditis associated with a family history of myocarditis.

Emerging concepts in arrhythmogenic dilated cardiomyopathy

Dilated cardiomyopathy (DCM) represents one of the primary cardiomyopathies and may lead to heart failure and sudden death. Until recently, ventricular arrhythmias were considered to be a direct consequence of the systolic dysfunction of the left ventricle (LV) and guidelines for implantable cardioverter defibrillator implantation were established on this basis. However, the identification of heritable dilated cardiomyopathy phenotypes that presented with mildly impaired or moderate LV dysfunction, with or without chamber dilatation, and ventricular arrhythmias exceeding the degree of the underlying morphological abnormalities lead to the identification of the arrhythmogenic phenotypes and genotypes of DCM. This subset of DCM patients presents phenotypic and in many cases genotypic overlaps with left dominant arrhythmogenic cardiomyopathy (LDAC). LMNA, SCN5A, FLNC, TTN, and RBM20 are the main genes responsible for arrhythmogenic DCM. Moreover, desmosomal genes such as DSP and other non-desmosomal such as DES and PLN have been associated with both LDAC and arrhythmogenic DCM. The aim of this review is to highlight the importance of genetic profiling among DCM patients with disproportionate arrhythmic burden and the significance of the electrocardiogram, cardiac magnetic resonance, Holter monitoring, detailed family history, and other assays in order to identify red flags for arrhythmogenic DCM and proceed to an early preventive approach for sudden cardiac death. A special consideration was given to the phenotypic and genotypic overlap with LDAC. The role of myocarditis as a common disease expression of LDAC and arrhythmogenic DCM is also analyzed supporting the premise of their phenotypic overlap.

Next-generation sequencing identified novel Desmoplakin frame-shift variant in patients with Arrhythmogenic cardiomyopathy

Background

Arrhythmogenic cardiomyopathy (AC) is one of the leading causes for sudden cardiac death (SCD). Recent studies have identified mutations in cardiac desmosomes as key players in the pathogenesis of AC. However, the specific etiology in individual families remains largely unknown.

Methods

A 4-generation family presenting with syncope, lethal ventricular arrhythmia and SCD was recruited. Targeted next generation sequencing (NGS) was performed and validated by Sanger sequencing. Plasmids containing the mutation and wild type (WT) were constructed. Real-time PCR, western-blot and immunofluorescence were performed to detect the functional change due to the mutation.

Results

The proband, a 56-year-old female, presented with recurrent palpitations and syncope. An ICD was implanted due to her family history of SCD/ aborted SCD. NGS revealed a novel heterozygous frame-shift variant (c.832delG) in Desmoplakin (DSP) among 5 family members. The variant led to frame-shift and premature termination, producing a truncated protein. Cardiac magnetic resonance (CMR) of the family members carrying the same variant shown myocardium thinning and fatty infiltration in the right ventricular, positive bi-ventricular late gadolinium enhancement and severe RV dysfunction, fulfilling the diagnostic criteria of AC. HEK293T cells transfected with mutant plasmids expressed truncated DSP mRNA and protein, upregulation of nuclear junction plakoglobin (JUP) and downregulation of β-catenin, when compared with WT.

Conclusion

We infer that the novel c.832delG variant in DSP was associated with AC in this family, likely through Wnt/β-catenin signaling pathway.

Novel Basic Science Insights to Improve the Management of Heart Failure: Review of the Working Group on Cellular and Molecular Biology of the Heart of the Italian Society of Cardiology

Despite important advances in diagnosis and treatment, heart failure (HF) remains a syndrome with substantial morbidity and dismal prognosis. Although implementation and optimization of existing technologies and drugs may lead to better management of HF, new or alternative strategies are desirable. In this regard, basic science is expected to give fundamental inputs, by expanding the knowledge of the pathways underlying HF development and progression, identifying approaches that may improve HF detection and prognostic stratification, and finding novel treatments. Here, we discuss recent basic science insights that encompass major areas of translational research in HF and have high potential clinical impact.