Clinical features of arrhythmogenic right ventricular dysplasia/cardiomyopathy associated with mutations in plakophilin-2

Clinical Guideline for Preimplantation Genetic Testing in Inherited Cardiac Diseases

BACKGROUND

Preimplantation genetic testing (PGT) is a reproductive technology that selects embryos without (familial) genetic variants. PGT has been applied in inherited cardiac disease and is included in the latest American Heart Association/American College of Cardiology guidelines. However, guidelines selecting eligible couples who will have the strongest risk reduction most from PGT are lacking. We developed an objective decision model to select eligibility for PGT and compared its results with those from a multidisciplinary team.

METHODS

All couples with an inherited cardiac disease referred to the national PGT center were included. A multidisciplinary team approved or rejected the indication based on clinical and genetic information. We developed a decision model based on published risk prediction models and literature, to evaluate the severity of the cardiac phenotype and the penetrance of the familial variant in referred patients. The outcomes of the model and the multidisciplinary team were compared in a blinded fashion.

RESULTS

Eighty-three couples were referred for PGT (1997-2022), comprising 19 different genes for 8 different inherited cardiac diseases (cardiomyopathies and arrhythmias). Using our model and proposed cutoff values, a definitive decision was reached for 76 (92%) couples, aligning with 95% of the multidisciplinary team decisions. In a prospective cohort of 11 couples, we showed the clinical applicability of the model to select couples most eligible for PGT.

CONCLUSIONS

The number of PGT requests for inherited cardiac diseases increases rapidly, without the availability of specific guidelines. We propose a 2-step decision model that helps select couples with the highest risk reduction for cardiac disease in their offspring after PGT.

De novo variants in PLCG1 are associated with hearing impairment, ocular pathology, and cardiac defects

Phospholipase C isozymes (PLCs) hydrolyze phosphatidylinositol 4,5-bisphosphate into inositol 1,4,5-trisphosphate and diacylglycerol, important signaling molecules involved in many cellular processes. PLCG1 encodes the PLCγ1 isozyme that is broadly expressed. Hyperactive somatic mutations of PLCG1 are observed in multiple cancers, but only one germline variant has been reported. Here we describe three unrelated individuals with de novo heterozygous missense variants in PLCG1 (p.Asp1019Gly, p.His380Arg, and p.Asp1165Gly) who exhibit variable phenotypes including hearing loss, ocular pathology and cardiac septal defects. To model these variants in vivo, we generated the analogous variants in the Drosophila ortholog, small wing (sl). We created a null allele slT2A and assessed the expression pattern. sl is broadly expressed, including in wing discs, eye discs, and a subset of neurons and glia. Loss of sl causes wing size reductions, ectopic wing veins and supernumerary photoreceptors. We document that mutant flies exhibit a reduced lifespan and age-dependent locomotor defects. Expressing wild-type sl in slT2A mutant rescues the loss-of-function phenotypes whereas expressing the variants causes lethality. Ubiquitous overexpression of the variants also reduces viability, suggesting that the variants are toxic. Ectopic expression of an established hyperactive PLCG1 variant (p.Asp1165His) in the wing pouch causes severe wing phenotypes, resembling those observed with overexpression of the p.Asp1019Gly or p.Asp1165Gly variants, further arguing that these two are gain-of-function variants. However, the wing phenotypes associated with p.His380Arg overexpression are mild. Our data suggest that the PLCG1 de novo heterozygous missense variants are pathogenic and contribute to the features observed in the probands.

The role of genetic testing in suspected fulminant myocarditis: A case report

ACM is a rare hereditary heart disease characterized by a progressive fibro-fatty replacement of the myocardium that can affect either the right or the left ventricle or both. It is mainly caused by variants in the desmosome genes with autosomal dominant transmission and incomplete penetrance. The disease shows a wide spectrum of clinical manifestations, including ventricular arrhythmias, HF and myocarditis. The latter is considered a 'hot phase' in the natural history of the disease and must therefore be distinguished from the isolated AM, which is frequently due to viral infections. Our case report is an example of how an AM, as the first manifestation of the disease, helped to reach a diagnosis of ACM through the genetic analysis. In fact, the multi-parametric investigation, which also included CMR and EMB, revealed controversial aspects that led us to perform the genetic test. The latter revealed a heterozygous pathogenic variant in the PKP2 that was considered definitive proof of ACM.

Myocarditis as a trigger for the expression of biventricular arrhythmogenic cardiomyopathy in desmosomal gene mutation

Arrhythmogenic-cardiomyopathy (ACM) is an inherited heart disease with right, left, or biventricular (BVACM) involvement based on EKG, imaging, family history, and genetic testing. We present a 64-year-old woman with prior myocarditis and diagnosis of BVACM 29 years later. We propose myocarditis as a promoter of gene expression of plakophilin-2 mutation.

Clinical and Genetic Characteristics of Arrhythmogenic Right Ventricular Cardiomyopathy Patients: A Single-Center Experience

Background

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited progressive cardiomyopathy. We aimed to define the long-term clinical outcome and genetic characteristics of patients and family members with positive genetic tests for ARVC in a single tertiary care cardiac center in Saudi Arabia.

Methods

We enrolled 46 subjects in the study, including 23 index-patients (probands) with ARVC based on the revised 2010 ARVC Task Force Criteria (TFC) and 23 family members who underwent a genetic test for the ARVC between 2016 and 2020.

Results

Of the probands, 17 (73.9%) were males with a mean age at presentation of 24.95 ± 13.9 years (7 to 55 years). Predominant symptoms were palpitations in 14 patients (60.9%), and syncope in 10 patients (43.47%). Sustained ventricular tachycardia (VT) was documented in 12 patients (52.2%). The mean left ventricular ejection fraction (LVEF) by echocardiogram was 52.81±6.311% (30-55%), and the mean right ventricular ejection fraction (RVEF) by cardiac MRI was 41.3±11.37% (23-64%). Implantable cardioverter-defibrillator (ICD) implantation was performed in 17 patients (73.9%), and over a mean follow-up of 13.65 ± 6.83 years, appropriate ICD therapy was noted in 12 patients (52.2%). Genetic variants were identified in 33 subjects (71.7%), 16 patients and 17 family members, with the most common variant of plakophilin 2 (PKP2) in 27 subjects (81.8%).

Conclusions

ARVC occurs during early adulthood in Saudi patients. It is associated with a significant arrhythmia burden in these patients. The PKP2 gene is the most common gene defect in Saudi patients, consistent with what is observed in other nations. We reported in this study two novel variants in PKP2 and desmocollin 2 (DSC2) genes. Genetic counseling is needed to include all first-degree family members for early diagnosis and management of the disease in our country.

Understanding Arrhythmogenic Cardiomyopathy: Advances through the Use of Human Pluripotent Stem Cell Models

Cardiomyopathies (CMPs) represent a significant healthcare burden and are a major cause of heart failure leading to premature death. Several CMPs are now recognized to have a strong genetic basis, including arrhythmogenic cardiomyopathy (ACM), which predisposes patients to arrhythmic episodes. Variants in one of the five genes (PKP2, JUP, DSC2, DSG2, and DSP) encoding proteins of the desmosome are known to cause a subset of ACM, which we classify as desmosome-related ACM (dACM). Phenotypically, this disease may lead to sudden cardiac death in young athletes and, during late stages, is often accompanied by myocardial fibrofatty infiltrates. While the pathogenicity of the desmosome genes has been well established through animal studies and limited supplies of primary human cells, these systems have drawbacks that limit their utility and relevance to understanding human disease. Human induced pluripotent stem cells (hiPSCs) have emerged as a powerful tool for modeling ACM in vitro that can overcome these challenges, as they represent a reproducible and scalable source of cardiomyocytes (CMs) that recapitulate patient phenotypes. In this review, we provide an overview of dACM, summarize findings in other model systems linking desmosome proteins with this disease, and provide an up-to-date summary of the work that has been conducted in hiPSC-cardiomyocyte (hiPSC-CM) models of dACM. In the context of the hiPSC-CM model system, we highlight novel findings that have contributed to our understanding of disease and enumerate the limitations, prospects, and directions for research to consider towards future progress.

Abnormal developmental trajectory and vulnerability to cardiac arrhythmias in tetralogy of Fallot with DiGeorge syndrome

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease. Ventricular dysfunction and cardiac arrhythmias are well-documented complications in patients with repaired TOF. Whether intrinsic abnormalities exist in TOF cardiomyocytes is unknown. We establish human induced pluripotent stem cells (hiPSCs) from TOF patients with and without DiGeorge (DG) syndrome, the latter being the most commonly associated syndromal association of TOF. TOF-DG hiPSC-derived cardiomyocytes (hiPSC-CMs) show impaired ventricular specification, downregulated cardiac gene expression and upregulated neural gene expression. Transcriptomic profiling of the in vitro cardiac progenitors reveals early bifurcation, as marked by ectopic RGS13 expression, in the trajectory of TOF-DG-hiPSC cardiac differentiation. Functional assessments further reveal increased arrhythmogenicity in TOF-DG-hiPSC-CMs. These findings are found only in the TOF-DG but not TOF-with no DG (ND) patient-derived hiPSC-CMs and cardiac progenitors (CPs), which have implications on the worse clinical outcomes of TOF-DG patients.

Emerging Targeted Therapies for Inherited Cardiomyopathies and Arrhythmias

Inherited cardiomyopathy and arrhythmia syndromes are associated with significant morbidity and mortality, particularly in young people. Medical management of these conditions has primarily been limited to agents previously developed for more common forms of heart disease and not tailored to their distinct pathophysiology. As our understanding of their underlying genetics and disease mechanisms has improved, an era of targeted therapies for these rare conditions has begun to emerge. In recent years, several novel agents have been developed and tested in preclinical models and, in some cases, have advanced to both the clinical trial and clinical approval stages with exciting results. These new treatments are derived from multiple classes of therapeutics, including small molecules, antisense oligonucleotides, small interfering RNAs, adeno-associated virus-mediated gene therapies, and in vivo gene editing. Collectively, they carry the promise of revolutionizing management of affected patients and their families.

The Spectrum of the Heterozygous Effect in Biallelic Mendelian Diseases-The Symptomatic Heterozygote Issue

Heterozygous carriers of pathogenic/likely pathogenic variants in autosomal recessive disorders seem to be asymptomatic. However, in recent years, an increasing number of case reports have suggested that mild and unspecific symptoms can occur in some heterozygotes, as symptomatic heterozygotes have been identified across different disease types, including neurological, neuromuscular, hematological, and pulmonary diseases. The symptoms are usually milder in heterozygotes than in biallelic variants and occur "later in life". The status of symptomatic heterozygotes as separate entities is often disputed, and alternative diagnoses are considered. Indeed, often only a thin line exists between dual, dominant, and recessive modes of inheritance and symptomatic heterozygosity. Interestingly, recent population studies have found global disease effects in heterozygous carriers of some genetic variants. What makes the few heterozygotes symptomatic, while the majority show no symptoms? The molecular basis of this phenomenon is still unknown. Possible explanations include undiscovered deep-splicing variants, genetic and environmental modifiers, digenic/oligogenic inheritance, skewed methylation patterns, and mutational burden. Symptomatic heterozygotes are rarely reported in the literature, mainly because most did not undergo the complete diagnostic procedure, so alternative diagnoses could not be conclusively excluded. However, despite the increasing accessibility to high-throughput technologies, there still seems to be a small group of patients with mild symptoms and just one variant of autosomes in biallelic diseases. Here, we present some examples, the current state of knowledge, and possible explanations for this phenomenon, and thus argue against the existing dominant/recessive classification.

The Novel Variant NP_00454563.2 (p.Glu259Glyfs*77) in Gene PKP2 Associated with Arrhythmogenic Cardiomyopathy in 8 Families from Malaga, Spain

INTRODUCTION AND OBJECTIVES

Arrhythmogenic cardiomyopathy (ACM) is a hereditary heart disease defined by the progressive replacement of the ventricular myocardium with fibroadipose tissue, which can act as a substrate for arrhythmias, sudden death, or even give rise to heart failure (HF). Sudden death is frequently the first manifestation of the disease, particularly among young patients. The aim of this study is to describe a new pathogenic variant in the PKP2 gene.

METHODS

A descriptive observational study that included eight initially non-interrelated families with a diagnosis of ACM undergoing follow-up at our HF and Familial Cardiomyopathies Unit, who were carriers of the NM_004572.3:c.775_776insG; p.(Glu259Glyfs*77) variant in the PKP2 gene. The genetic testing employed next-generation sequencing for the index cases and the Sanger method for the targeted study with family members. We compiled personal and family histories, demographic and clinical characteristics, data from the additional tests at the time of diagnosis, and arrhythmic events at diagnosis and during follow-up.

RESULTS

We included 47 subjects, of whom 8 were index cases (17%). Among the evaluated family members, 16 (34%) were carriers of the genetic variant, 3 of whom also had a diagnosis of ACM. The majority were women (26 patients; 55.3%), with a mean age on diagnosis of 48.9 ± 18.6 years and a median follow-up of 39 [24-59] months. Worthy of note are the high incidences of arrhythmic events as the form of presentation and in follow-up (21.5% and 20.9%, respectively), and the onset of HF in 25% of the sample. The most frequent ventricular involvements were right (four patients, 16.7%) and biventricular (four patients, 16.7%); we found no statistical differences in any of the variables analysed.

CONCLUSIONS

This variant is a pathogenic variant of gene PKP2 that has not previously been described and is not present in the control groups associated with ACM. It has incomplete penetrance, a highly variable phenotypic expressivity, and was identified in eight families of our geographical area in Malaga (Andalusia, Spain), suggesting a founder effect in this area and describe the clinical and risk characteristics.

Determining the Likelihood of Disease Pathogenicity Among Incidentally Identified Genetic Variants in Rare Dilated Cardiomyopathy-Associated Genes

Background As utilization of clinical exome sequencing (ES) has expanded, criteria for evaluating the diagnostic weight of incidentally identified variants are critical to guide clinicians and researchers. This is particularly important in genes associated with dilated cardiomyopathy (DCM), which can cause heart failure and sudden death. We sought to compare the frequency and distribution of incidentally identified variants in DCM-associated genes between a clinical referral cohort with those in control and known case cohorts to determine the likelihood of pathogenicity among those undergoing genetic testing for non-DCM indications. Methods and Results A total of 39 rare, non-TTN DCM-associated genes were identified and evaluated from a clinical ES testing referral cohort (n=14 005, Baylor Genetic Laboratories) and compared with a DCM case cohort (n=9442) as well as a control cohort of population variants (n=141 456) derived from the gnomAD database. Variant frequencies in each cohort were compared. Signal-to-noise ratios were calculated comparing the DCM and ES cohort with the gnomAD cohort. The likely pathogenic/pathogenic variant yield in the DCM cohort (8.2%) was significantly higher than in the ES cohort (1.9%). Based on signal-to-noise and correlation analysis, incidental variants found in FLNC, RBM20, MYH6, DSP, ABCC9, JPH2, and NEXN had the greatest chance of being DCM-associated. Conclusions The distribution of pathogenic variants between the ES cohort and the DCM case cohort was gene specific, and variants found in the ES cohort were similar to variants found in the control cohort. Incidentally identified variants in specific genes are more associated with DCM than others.

Genetic Background and Clinical Features in Arrhythmogenic Left Ventricular Cardiomyopathy: A Systematic Review

In recent years a phenotypic variant of Arrhythmogenic cardiomyopathy has been described, characterized by predominant left ventricular (LV) involvement with no or minor right ventricular abnormalities, referred to as Arrhythmogenic left ventricular cardiomyopathy (ALVC). Different disease-genes have been identified in this form, such as Desmoplakin (DSP), Filamin C (FLNC), Phospholamban (PLN) and Desmin (DES). The main purpose of this critical systematic review was to assess the level of knowledge on genetic background and clinical features of ALVC. A search (updated to April 2022) was run in the PubMed, Scopus, and Web of Science electronic databases. The search terms used were “arrhythmogenic left ventricular cardiomyopathy” OR “arrhythmogenic cardiomyopathy” and “gene” OR “arrhythmogenic dysplasia” and “gene”. The most represented disease-gene turned out to be DSP, accounting for half of published cases, followed by FLNC. Overall, ECG abnormalities were reported in 58% of patients. Major ventricular arrhythmias were recorded in 26% of cases; an ICD was implanted in 29% of patients. A total of 6% of patients showed heart failure symptoms, and 15% had myocarditis-like episodes. DSP is confirmed to be the most represented disease-gene in ALVC patients. An analysis of reported clinical features of ALVC patients show an important degree of electrical instability, which frequently required an ICD implant. Moreover, myocarditis-like episodes are common.

Progressive Reduction in Right Ventricular Contractile Function Due to Altered Actin Expression in an Aging Mouse Model of Arrhythmogenic Cardiomyopathy

BACKGROUND

Arrhythmogenic cardiomyopathy (ACM) is an inherited genetic disorder of desmosomal dysfunction, and plakophilin-2 (PKP2) has been reported to be the most common disease-causing gene when mutation-positive. In the early "concealed" phase, the ACM heart is at high risk of sudden cardiac death before cardiac remodeling occurs due to mistargeted ion channels and altered Ca²⁺ handling. However, the results of pathogenic PKP2 variants on myocyte contraction in ACM pathogenesis remain unknown.

METHODS

We studied the outcomes of a human truncating variant of PKP2 on myocyte contraction using a novel knock-in mouse model with insertion of thymidine in exon 5 of Pkp2, which mimics a familial case of ACM (PKP2-L404fsX5). We used serial echocardiography, electrocardiography, blood pressure measurements, histology, cardiomyocyte contraction, intracellular calcium measurements, and gene and protein expression studies.

RESULTS

Serial echocardiography of Pkp2 heterozygous (Pkp2-Het) mice revealed progressive failure of the right ventricle (RV) in animals older than three months of age. By contrast, left ventricular (LV) function remained normal. Electrocardiograms of six-month-old anesthetized Pkp2-Het mice showed normal baseline heart rates and QRS complexes. Cardiac responses to β-adrenergic agonist isoproterenol (2 mg.kg^-1) plus caffeine (120 mg.kg^-1) were also normal. However, adrenergic stimulation enhanced the susceptibility of Pkp2-Het hearts to tachyarrhythmia and sudden cardiac death. Histologic staining showed no significant fibrosis or adipocyte infiltration in the RVs and LVs of six- and twelve-month-old Pkp2-Het hearts. Contractility assessment of isolated myocytes demonstrated progressively reduced Pkp2-Het RV cardiomyocyte function consistent with RV failure measured by echocardiography. However, aging Pkp2-Het and control RV myocytes loaded with intracellular Ca²⁺ indicator Fura-2 showed comparable Ca²⁺ transients. Western blotting of Pkp2-RV homogenates revealed a 40% decrease in actin, while actin immunoprecipitation followed by a 2, 4-dinitrophenylhydrazine staining showed doubled oxidation level. This correlated with a 39% increase in troponin-I phosphorylation. In contrast, Pkp2-Het LV myocytes had normal contraction, actin expression and oxidation, and troponin-I phosphorylation. Finally, Western blotting of cardiac biopsies revealed actin expression was 40% decreased in RVs of end-stage ACM patients.

CONCLUSIONS

During the early "concealed" phase of ACM, reduced actin expression drives loss of RV myocyte contraction, contributing to progressive RV dysfunction.

OUP accepted manuscript

AIMS

Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disorder that is characterized by progressive loss of myocardium that is replaced by fibro-fatty cells, arrhythmias, and sudden cardiac death. While myocardial degeneration and fibro-fatty replacement occur in specific locations, the underlying molecular changes remain poorly characterized. Here, we aim to delineate local changes in gene expression to identify new genes and pathways that are relevant for specific remodelling processes occurring during ACM.

METHODS AND RESULTS

Using Tomo-Seq, genome-wide transcriptional profiling with high spatial resolution, we created transmural epicardial-to-endocardial gene expression atlases of explanted ACM hearts to gain molecular insights into disease-driving processes. This enabled us to link gene expression profiles to the different regional remodelling responses and allowed us to identify genes that are potentially relevant for disease progression. In doing so, we identified distinct gene expression profiles marking regions of cardiomyocyte degeneration and fibro-fatty remodelling and revealed Zinc finger and BTB domain-containing protein 11 (ZBTB11) to be specifically enriched at sites of active fibro-fatty replacement of myocardium. Immunohistochemistry indicated ZBTB11 to be induced in cardiomyocytes flanking fibro-fatty areas, which could be confirmed in multiple cardiomyopathy patients. Forced overexpression of ZBTB11 induced autophagy and cell death-related gene programmes in human cardiomyocytes, leading to increased apoptosis.

CONCLUSION

Our study shows the power of Tomo-Seq to unveil new molecular mechanisms in human cardiomyopathy and uncovers ZBTB11 as a novel driver of cardiomyocyte loss.

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.

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.

Can Smartwatch Prevent Sudden Cardiac Deaths? A Case Of Smartwatch Failure in Arrhythmogenic Right Ventricular Dysplasia

Arrhythmogenic right ventricular dysplasia (ARVD) is caused by mutations in genes coding for components of desmosomes in the myocardium. Mutations in these genes make desmosomes dysfunctional and account for myocyte detachment, followed by inflammation and apoptosis when it encounters undue mechanical stress. This is why ARVD is a common cause of sudden cardiac death in athletes with undiagnosed ARVD, as increased physical activity exacerbates this progression of ARVD and associated arrhythmias. We describe a case of ARVD in a 36-year-old woman who presented with an unusual sensation in her chest due to non-sustaining ventricular tachycardia, which her smartwatch failed to pick up. Many smartwatches use photoplethysmography (PPG) to monitor heart rate (HR). A typical PPG device contains two light sources (green light and infrared) and a photodetector to measure the reflected light, proportional to the beat-to-beat variation in blood volume. HR is then calculated from these variations. In ambulatory settings, smartwatches underestimate HR in most tachyarrhythmias, mainly when the HR is more than 100 beats/min. Patients using smartwatches for ambulatory heart monitoring should know that the absence of an irregular pulse notification does not exclude possible arrhythmias. Management of ARVD is mainly focused on the prevention of syncope and cardiac arrest through antiarrhythmic medications and an implantable cardioverter defibrillator.

Gender-related differences in heart failure: beyond the "one-size-fits-all" paradigm

Cardiovascular diseases show many sex-related differences in prevalence, etiology, phenotype expression, and outcomes. Complex molecular mechanisms underlie this diverse pathological manifestation, from sex-determined differential gene expression to sex hormones interaction with their specific receptors in different tissues. More recently, differential non-coding RNAs regulation also turned out to be an involved mechanism. This review focuses on sex impact on the various heart failure syndromes, including coronary artery disease, heart failure with preserved ejection fraction and with reduced ejection fraction, with particular attention to dilated cardiomyopathy. Despite similar genetic predisposition in terms of identified causative mutations, other causes, such as cardiotoxic drugs exposure or stress-induced cardiomyopathy, are more prevalent in women. Beyond this, differences in disease presentation and natural history reveal a more severe clinical onset with otherwise better long-term outcomes in women compared to men. Understanding the varying characteristics of disease manifestation and outcomes is warranted for a prompt and tailored treatment for both men and women. This is a mandatory step in the road to the personalized medicine. Moreover, despite a higher enrollment in the last years, the under-representation of females in clinical trials is the first obstacle to overcome in the long way to develop appropriate sex-based therapy approach.

Screening relatives in arrhythmogenic right ventricular cardiomyopathy: yield of imaging and electrical investigations

AIMS

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited disease and presymptomatic screening of relatives is recommended. In 2010, the Task Force Criteria (TFC2010) introduced specific diagnostic imaging parameters. The aim of the study was to evaluate the diagnostic yield of family screening and the value of different diagnostic modalities.

METHODS AND RESULTS

Family evaluation, including cardiac magnetic resonance (CMR), is routinely offered to ARVC relatives at our institution. We retrospectively registered baseline characteristics, symptomatology, and results of non-invasive examinations from 2010 to 2016 and assessed the findings according to TFC2010. A total of 286 relatives (150 females; age 12-76 years; 251 first-degree) were included. A total of 103 (36%) individuals reported cardiovascular symptoms. The non-invasive workup showed that 101 (35%) relatives had ≥1 positive parameter on signal-averaged electrocardiogram (ECG), 40 (14%) had abnormal findings on Holter monitoring, 36 (13%) fulfilled an ECG criterion, six (2%) fulfilled CMR criteria, and echocardiographic abnormalities was seen in one (0.3%) relative. In total, 21 (7% overall; 13% among gene-positive subgroup) relatives were diagnosed with ARVC and 78 (27% overall; 49% among gene-positive subgroup) with borderline ARVC based on the combined non-invasive evaluations. Family history and electrical investigations alone diagnosed 20 out of 21 (95%) ARVC cases and 73 out of 78 (94%) borderline cases.

CONCLUSION

Consecutive evaluation of ARVC relatives diagnosed 7% with definite and 27% with borderline ARVC according to the TFC2010. Screening relatives for electrical abnormalities with 12 lead ECG, signal-averaged ECG, and Holter monitoring was more sensitive than imaging modalities.

Risk stratification for ventricular arrhythmias and sudden cardiac death in arrhythmogenic right ventricular cardiomyopathy: an update

Introduction: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetically determined disease associated with a significant risk of ventricular arrhythmias and sudden cardiac death (SCD). Implantable cardioverter-defibrillators (ICDs) are the only effective preventive measure. Over the past 30 years, much effort has been invested in determining predictors of adverse arrhythmic events in these patients. Areas covered: This review summarizes available evidence on risk stratification for ARVC, with an emphasis on recent research findings. While efforts are ongoing to define risk predictors, several recent publications have synthetized and built on this knowledge base. A recently published meta-analysis has clarified the strongest predictors of ventricular arrhythmias in ARVC, which vary depending on the population included. Three management guidelines/expert consensus documents have integrated the previously described risk predictors into proposed ICD recommendations. Furthermore, a risk prediction model has allowed the integration of multiple risk factors to provide individualized risk prediction and to inform shared-decision making regarding ICD implantation. Expert opinion: Over the past few years, knowledge of risk prediction in ARVC has been consolidated and refined. Further improvements may be made by the considering additional predictors such as exercise and by targeting more specific surrogate outcomes for SCD.

Heart failure in patients with arrhythmogenic right ventricular cardiomyopathy: Genetic characteristics

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetically determined heart muscle disorder. The incidence of heart failure (HF) in ARVC has been reported at 5-13%. We aimed to define the genotype and disease progression of ARVC patients with HF.

METHODS

Patients with a definite diagnosis of ARVC who underwent genetic testing were consecutively recruited. Detailed clinical data was collected at baseline and during follow up. Clinical endpoint was a composite of heart transplantation and death due to HF.

RESULTS

135 patients were included. 8 (5.9%) patients reached the endpoint. Patients reaching the endpoint were significantly more likely to carry a Plakophilin 2 mutation than patients without HF, and 50% had multiple variants, however only one patient had 2 pathogenic mutations.

CONCLUSIONS

HF is a rare but significant outcome of patients with a definite diagnosis of ARVC. Patients with HF predominantly carried Plakophilin 2 mutations and often had multiple variants. RV dysfunction appears to be a determinant of heart transplantation and death.

PKP2 and DSG2 genetic variations in Latvian arrhythmogenic right ventricular dysplasia/cardiomyopathy registry patients

Objective:

The Latvian arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD-C) registry was established to determine the genetic background of ARVD-C for analyzing discovered genetic variation frequencies in the European and Latvian populations.

Methods:

In total, 38 patients with suspected ARVD-C were selected. The clinical parameters were defined according to the ARVD-C guidelines, PKP2 and DSG2 gene analysis was performed using the Sanger sequencing. Additionally, large deletions/duplications were analyzed using the multiplex ligation-dependent probe amplification (MLPA) analysis.

Results:

Twenty symptomatic patients were enrolled in the study. Typical ARVD abnormalities were found in electrocardiography for 10 (50%) patients, in Holter monitoring for 19 (95%), in transthoracic echocardiography for 20 (100%), and in cardiac magnetic resonance for 6 (30%). Different benign genetic variations were found. Three novel, unregistered, possibly benign variations were found in the PKP2 gene: c.2489+131G>A, c.2489+72delA, and c.1035-5T>C and three in the DSG2 gene: c.404G>A, c.1107G>A, and c.379-15A>G. Two genetic variations in the PKP2 gene: c.1592T>G, c.2489+1G>A are possibly pathogenic. For the first time, variation c.1592T>G, has been discovered in the homozygote form. Using the MLPA analysis, large deletions or duplications were not found.

Conclusion:

The prevalence of the majority of non-pathological genetic variations is similar in the Latvian ARVD-C patients and the European population. Possibly, pathogenic variations were found only in 10% of our registry patients, which could mean that PKP2 and DSG2 are not the most commonly affected genes in the Latvian population.

Genetics of and pathogenic mechanisms in arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart disease, associated with a high risk of sudden cardiac death. ARVC has been termed a 'disease of the desmosome' based on the fact that in many cases, it is caused by mutations in genes encoding desmosomal proteins at the specialised intercellular junctions between cardiomyocytes, the intercalated discs. Desmosomes maintain the structural integrity of the ventricular myocardium and are also implicated in signal transduction pathways. Mutated desmosomal proteins are thought to cause detachment of cardiac myocytes by the loss of cellular adhesions and also affect signalling pathways, leading to cell death and substitution by fibrofatty adipocytic tissue. However, mutations in desmosomal proteins are not the sole cause for ARVC as mutations in non-desmosomal genes were also implicated in its pathogenesis. This review will consider the pathology, genetic basis and mechanisms of pathogenesis for ARVC.

A novel PKP2 mutation and intrafamilial phenotypic variability in ARVC/D

Background: Arrhythmogenic ventricular cardiomyopathy (AVC) is an inherited cardiac disorder affecting 1 in 1000 individuals worldwide. The mean diagnosed age of disease is 31 years. In this article, an Iranian family reported that they were affected by ARVC due to a novel PKP2 mutation. Methods: Clinical evaluations, 12-lead ECG, CMR, and signal-averaged ECG were performed. After DNA extraction, genetic testing was done, and PCR-sequencing was applied to find causal mutations. Segregation analysis was also performed for the family. Results: ARVC criteria were documented in the patients. Genetic testing revealed a novel chain termination mutation (p.Tyr168Ter) in PKP2 gene; this mutation was transmitted from the mother to her 23-year-old son, but only the son was affected with ARVC. Conclusion: Modifier genes were indicated using interactome analysis of Plakophilin 2 protein (PKP2); they might have led to phenotypic variability through cellular mechanisms, such as nonsense-mediated mRNA decay. At least, 9 proteins were identified that might have affected Plakophilin 2 protein function, and consequently, rationalizing this intrafamilial phenotypic variability. This study highlighted the role of modifier genes involved in ARVC as well as the major role of PKP2 mutation in developing the disease in our population.

Massively Parallel Sequencing of Genes Implicated in Heritable Cardiac Disorders: A Strategy for a Small Diagnostic Laboratory

Sudden cardiac death (SCD) in people before the age of 35 years is a devastating event for any family. The causes of SCD in the young can be broadly divided into two groups: heritable cardiac disorders that affect the heart structure (cardiomyopathies) and primary electrical disorders (cardiac ion channelopathies). Genetic testing is vital as those suffering from cardiac ion channelopathies have structurally normal hearts, and those with cardiomyopathies may only show subtle abnormalities in the heart and these signs may not be detected during an autopsy. Post-mortem genetic testing of SCD victims is important to identify the underlying genetic cause. This is important as family cascade screening may be undertaken to identify those who may be at risk and provide vital information about risk stratification and clinical management. The development of massively parallel sequencing (MPS) has made it possible for the simultaneous screening of multiple patients for hundreds of genes. In light of this, we opted to develop an MPS approach for SCD analysis that would allow us to screen for mutations in genes implicated in cardiomyopathies and cardiac ion channelopathies. The rationale behind this panel was to limit it to genes carrying the greatest mutation load. If no likely pathogenic gene variant were found then testing could cascade to whole exome/genome sequencing as a gene-discovery exercise. The overarching aim was to design and validate a custom-cardiac panel that satisfies the diagnostic requirements of LabPLUS (Auckland City Hospital, Auckland, NZ) and the guidelines provided by the Royal College of Pathologists of Australasia and the Association for Clinical Genetic Science.

Arrhythmogenic Right Ventricular Cardiomyopathy: Risk Stratification and Indications for Defibrillator Therapy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetically determined disease which predisposes to life-threatening ventricular arrhythmias. The main goal of ARVC therapy is prevention of sudden cardiac death (SCD). Implantable cardioverter defibrillator (ICD) is the most effective therapy for interruption of potentially lethal ventricular tachyarrhythmias. Despite its life-saving potential, ICD implantation is associated with a high rate of complications and significant impact on quality of life. Accurate risk stratification is needed to identify individuals who most benefit from the therapy. While there is general agreement that patients with a history of cardiac arrest or hemodynamically unstable ventricular tachycardia are at high risk of SCD and needs an ICD, indications for primary prevention remain a matter of debate. The article reviews the available scientific evidence and guidelines that may help to stratify the arrhythmic risk of ARVC patients and guide ICD implantation. Other therapeutic strategies, either alternative or additional to ICD, will be also addressed.

Arrhythmogenic Right Ventricular Cardiomyopathy in an Endurance Athlete Presenting with Ventricular Tachycardia and Normal Right Ventricular Function

Arrhythmogenic right ventricular cardiomyopathy, a genetically inherited disease that results in fibrofatty replacement of normal cardiac myocytes, has been associated with sudden cardiac death in athletes. Long-term participation in endurance exercise hastens the development of both the arrhythmic and structural arrhythmogenic right ventricular cardiomyopathy phenotypes. We describe the unusual case of a 34-year-old, symptomatic, female endurance athlete who had arrhythmogenic right ventricular cardiomyopathy in the presence of a structurally normal right ventricle. Clinicians should be aware of this infrequent presentation when evaluating athletic patients who have ventricular arrhythmias and normal findings on cardiac imaging studies.

Autosomal Recessive Nonsyndromic Arrhythmogenic Right Ventricular Cardiomyopathy without Cutaneous Involvements: A Novel Mutation

The arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is a genetic disease frequently associated with desmosomal mutations, mainly attributed to dominant mutations in the Plakophilin-2 (PKP2) gene. Naxos and Carvajal are the syndromic forms of ARVD/C due to recessive mutations. Herein, we report an autosomal recessive form of nonsyndromic ARVD/C caused by a mutation in the PKP2 gene. After examination and implementation of diagnostic modalities, the definite diagnosis of ARVD/C was confirmed by detection of ventricular tachycardia with a left bundle branch configuration and a superior axis, T-wave inversion in right precordial leads (i.e., V1-V3) in a 12-lead electrocardiogram, and a right ventricle outflow tract dilatation. Neither cutaneous involvement nor other abnormalities were observed. Genetic testing was performed during which an intronic mutation of c.2577+1G>T in the PKP2 gene was observed homozygously. The c.2577+1G>T disrupts PKP2 mRNA splicing and causes a nonsyndromic form of ARVD/C.

A classic case of arrhythmogenic right ventricular cardiomyopathy (ARVC) and literature review

Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) is a relatively under-recognized hereditary cardiomyopathy. It is characterized pathologically by fibro-fatty infiltration of right ventricular (RV) myocardium and clinically by consequences of RV electrical instability. Timely intervention with device therapy and pharmacotherapy may help reduce the risk of arrhythmic events or sudden cardiac death. Here, we describe a classic case of a young adult with ARVC and a brief literature review. The patient presented with exertional palpitations and ARVC was suspected after his routine electrocardiogram (EKG) revealed symmetric T wave inversions and possible epsilon waves in right precordial leads. Subsequent work up showed fatty infiltration of RV myocardium on cardiac magnetic resonance imaging and inducible ventricular tachycardia from the right ventricle during electrophysiologic study. Those findings confirmed the diagnosis of ARVC and warranted treatment with implantable cardioverter defibrillator. It is always exciting to encounter rare pathological entities with classic clinical findings, especially when they present as a diagnostic challenge.We were able to provide correct diagnosis and management, thereby preventing the potentially lethal consequences. Therefore, it is important to recognize the possible EKG findings of ARVC and to know when to pursue further investigations and to implement therapies.

Identification of established arrhythmogenic right ventricular cardiomyopathy mutation in a patient with the contrasting phenotype of hypertrophic cardiomyopathy

Background

Advances in the nucleic acid sequencing technologies have ushered in the era of genetic-based “precision medicine”. Applications of the genetic discoveries to practice of medicine, however, are hindered by phenotypic variability of the genetic variants. The report illustrates extreme pleiotropic phenotypes associated with an established causal mutation for hereditary cardiomyopathy.

Case presentation

We report a 61-year old white female who presented with syncope and echocardiographic and cardiac magnetic resonance (CMR) imaging findings consistent with the diagnosis of hypertrophic cardiomyopathy (HCM). The electrocardiogram, however, showed a QRS pattern resembling an Epsilon wave, a feature of arrhythmogenic right ventricular cardiomyopathy (ARVC). Whole exome sequencing (mean depth of coverage of exons 178X) analysis did not identify a pathogenic variant in the known HCM genes but identified an established causal mutation for ARVC. The mutation involves a canonical splice accepter site (c.2146-1G > C) in the PKP2 gene, which encodes plakophillin 2. Sanger sequencing confirmed the mutation. PKP2 is the most common causal gene for ARVC but has not been implicated in HCM. Findings on echocardiography and CMR during the course of 4-year follow up showed septal hypertrophy and a hyperdynamic left ventricle, consistent with the diagnosis of HCM. However, neither baseline nor follow up echocardiography and CMR studies showed evidence of ARVC. The right ventricle was normal in size, thickness, and function and there was no evidence of fibro-fatty infiltration in the myocardium.

Conclusions

The patient carries an established pathogenic mutation for ARVC and a subtle finding of ARVC but exhibits the classic phenotype of HCM, a contrasting phenotype to ARVC. The case illustrates the need for detailed phenotypic characterization for patients with hereditary cardiomyopathies as well as the challenges physicians face in applying the genetic discoveries in practicing genetic-based “precision medicine”.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0385-8) contains supplementary material, which is available to authorized users.

Arrhythmogenic right-ventricular cardiomyopathy: molecular genetics into clinical practice in the era of next generation sequencing

Sudden death, ventricular arrhythmia and heart failure are common features in arrhythmogenic right-ventricular cardiomyopathy (ARVC), an inheritable heart muscle disease, characterized by clinical and genetic heterogeneity. So far, 13 disease genes have been identified, responsible for around 60% of all ARVC cases. In this review, we summarize the main clinical and pathological aspects of ARVC, focusing on the importance of the genetic testing and the application of the new sequencing techniques referred to next generation sequencing technology.

Genotype-phenotype relationship in patients with arrhythmogenic right ventricular cardiomyopathy caused by desmosomal gene mutations: A systematic review and meta-analysis

The relationship between clinical phenotypes and desmosomal gene mutations in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) is poorly characterized. Therefore, we performed a meta-analysis to explore the genotype-phenotype relationship in patients with ARVC. Any studies reporting this genotype-phenotype relationship were included. In total, 11 studies involving 1,113 patients were included. The presence of desmosomal gene mutations was associated with a younger onset age of ARVC (32.7 ± 15.2 versus 43.2 ± 13.3 years; P = 0.001), a higher incidence of T wave inversion in V_1–3 leads (78.5% versus 51.6%; P = 0.0002) or a family history of ARVC (39.5% versus 27.1%; P = 0.03). There was no difference in the proportion of males between desmosomal-positive and desmosomal-negative patients (68.3% versus 68.9%; P = 0.60). The presence of desmosomal gene mutations was not associated with global or regional structural and functional alterations (63.5% versus 60.5%; P = 0.37), epsilon wave (29.4% versus 26.2%; P = 0.51) or ventricular tachycardia of left bundle-branch morphology (62.6% versus 57.2%; P = 0.30). Overall, patients with desmosomal gene mutations are characterized by an earlier onset age, a higher incidence of T wave inversion in V_1–3 leads and a strong family history of ARVC.

2015 update on the diagnosis and management of arrhythmogenic right ventricular cardiomyopathy

PURPOSE OF REVIEW

This review will discuss the recent advances in the diagnosis and management of arrhythmogenic right ventricular cardiomyopathy (ARVC).

RECENT FINDINGS

Since the first detailed clinical description of the disease in 1982, we have learned much about the genetics, pathophysiology, diagnosis, and management of ARVC. We now appreciate that pathogenic mutations in desmosomal genes are the most common genetic finding. Although the right ventricle is mostly affected, left ventricular involvement is being increasingly recognized. Electrical instability precipitating sudden cardiac death often presents before structural abnormalities, and therefore early accurate diagnosis is of utmost importance. The broad spectrum of phenotypic variation, age-related penetrance, and lack of a definitive diagnostic test make the clinical diagnosis challenging. The diagnosis is made by fulfilling the 2010 Task Force criteria. Today, genetic testing and cardiac MRI play an important role in the diagnosis. Implantable cardioverter defibrillator implantation is the only lifesaving therapy available today for a subset of patients. In patients with recurrent ventricular arrhythmias, epicardial catheter ablation has demonstrated improved outcomes compared with endocardial ablation. Exercise restriction may delay the progression of disease.

SUMMARY

ARVC is predominantly associated with mutations in desmosomal genes with incomplete penetrance and variable expressivity. Ventricular electrical instability is the hallmark of ARVC, often occurring before structural abnormalities. Goals in the evaluation and management of ARVC are early diagnosis, risk stratification for sudden cardiac death, minimizing ventricular arrhythmias, and delaying the progression of disease.

Plakophilin-2 c.419C>T and risk of heart failure and arrhythmias in the general population

A rare genetic variant in the desmosomal gene plakophilin-2 (PKP2) c.419C>T(p.(S140F)) has repeatedly been identified in patients with dilated cardiomyopathy (DCM) and arrhythmogenic right ventricular cardiomyopathy (ARVC). Whether this is a disease-causing variant remains highly controversial. We tested this hypothesis using three approaches. Initially, in a prospective study of 10 407 individuals from the general population, including 2688 who developed heart failure or arrhythmias during >14 years of follow-up, PKP2 c.419C>T was identified in 98 individuals (0.94%). PKP2 genotype was not associated with electrocardiographic or echocardiographic changes, or with plasma levels of probrain natriuretic peptide (all P≥0.05). In c.419C>T carriers versus non-carriers, multifactorially adjusted hazard ratios were 1.26 (95% confidence interval: 0.77-2.07) for heart failure, 1.40 (0.90-2.17) for arrhythmias, 1.15 (0.78-1.71) for end points combined, and 1.33 (0.98-1.80) for all-cause mortality. The cumulative survival as a function of age and PKP2 genotype was similar among carriers and non-carriers (P=0.14). Second, comparing 517 patients referred for genetic testing with 1918 matched controls, odds ratios as a function of c.419C>T genotype were 2.11 (0.50-8.99) for ARVC, 0.72 (0.16-3.28) for hypertrophic cardiomyopathy (HCM)/DCM, and 1.28 (0.46-3.54) for end points combined. Third, in in vitro studies cellular localization of plakophilin-2, plakoglobin, connexin-43, or N-cadherin were similar in cells transfected with wild-type or mutant plakophilin-2. In conclusion, combining epidemiological data, with data on patients referred for genetic testing for ARVC or HCM/DCM, and data from in vitro studies, PKP2 c.419C>T did not associate with heart failure, arrhythmias, or premature death, with ARVC or HCM/DCM, or with effects in vitro, suggesting that this is not a disease-causing variant.

Toward Personalized Medicine: Does Genetic Diagnosis of Pediatric Cardiomyopathy Influence Patient Management?

A goal of personalized medicine is to provide increasingly sophisticated, individualized approaches to management and therapy for disease. Genetics is the engine that drives personalized medicine, holding the promise of therapeutics directed toward the unique needs of each patient. The 3^rd International Conference on Cardiomyopathy in Children provided a forum to discuss the current status of personalized approaches to diagnosis, management, and therapy in the pediatric cardiomyopathy population. This review will focus on the importance of genetic diagnosis in this population as a necessary first step toward understanding the best approach to management and influencing disease outcome. The genetic heterogeneity of cardiomyopathy in children, the implications of specific genotypes, the ability to risk stratify based on genotype, and the impact on cascade screening in family members will be discussed.

Clinical Presentation, Long-Term Follow-Up, and Outcomes of 1001 Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy Patients and Family Members

Background—

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is a progressive cardiomyopathy. We aimed to define long-term outcome in a transatlantic cohort of 1001 individuals.

Methods and Results—

Clinical and genetic characteristics and follow-up data of ARVD/C index-patients (n=439, fulfilling of 2010 criteria in all) and family members (n=562) were assessed. Mutations were identified in 276 index-patients (63%). Index-patients presented predominantly with sustained ventricular arrhythmias (268; 61%). During a median follow-up of 7 years, 301 of the 416 index-patients presenting alive (72%) experienced sustained ventricular arrhythmias. Sudden cardiac death during follow-up occurred more frequently among index-patients without an implantable cardioverter-defibrillator (10/63, 16% versus 2/335, 0.6%). Overall, cardiac mortality and the need for cardiac transplantation were low (6% and 4%, respectively). Clinical characteristics and outcomes were similar in index-patients with and without mutations, as well as in those with familial and nonfamilial ARVD/C. ARVD/C was diagnosed in 207 family members (37%). Symptoms at first evaluation correlated with disease expression. Family members with mutations were more likely to meet Task Force Criteria for ARVD/C (40% versus 18%), experience sustained ventricular arrhythmias (11% versus 1%), and die from a cardiac cause (2% versus 0%) than family members without mutations.

Conclusions—

Long-term outcome was favorable in diagnosed and treated ARVD/C index-patients and family members. Outcome in index-patients was modulated by implantable cardioverter-defibrillator implantation, but not by mutation status and familial background of disease. One third of family members developed ARVD/C. Outcome in family members was determined by symptoms at first evaluation and mutations.

Maturation-Based Model of Arrhythmogenic Right Ventricular Dysplasia Using Patient-Specific Induced Pluripotent Stem Cells

Cellular reprogramming of somatic cells to patient-specific induced pluripotent stem cells (iPSCs) enables in-vitro modeling of human cardiac disorders for pathogenic and therapeutic investigations. However, using iPSC-derived cardiomyocytes (iPSC-CMs) to model an adult-onset heart disease remains challenging because of the uncertainty regarding the ability of relatively immature iPSC-CMs to fully recapitulate adult disease phenotypes. Arrhythmogenic right ventricular dysplasia (ARVD) is an inherited cardiomyopathy characterized by pathological fibrofatty infiltration and cardiomyocyte (CM) loss predominantly in the right ventricle (RV), leading to heart failure and lethal arrhythmias. Over 50% of affected individuals have desmosome gene mutations, most commonly inPKP2encoding plakophilin-2. Using Yamanaka's pluripotent factors, we generated iPSC lines from ARVD patients withPKP2mutations. We first developed a method to induce metabolic maturation of iPSC-CMs and showed that induction of adult-like metabolic energetics from an embryonic/glycolytic state is essential to model an adult-onset cardiac disease using patient-specific iPSCs. Furthermore, we showed that coactivation of normal peroxisome proliferator-activated receptor (PPAR)-α and abnormal PPARγ pathways in ARVD iPSC-CMs resulted in exaggerated CM lipogenesis, CM apoptosis, Na(+)channel downregulation and defective intracellular calcium handling, recapitulating the pathological signatures of ARVD. Using this model, we revealed novel pathogenic insights that metabolic derangement in an adult-like metabolic milieu underlies ARVD pathologies, enabling us to propose novel disease-modifying therapeutic strategies.

Feasibility of combined unipolar and bipolar voltage maps to improve sensitivity of endomyocardial biopsy

BACKGROUND

Endomyocardial biopsy (EMB) has a low sensitivity. Electroanatomic voltage mapping (EVM) is effective in guiding EMB thanks to its ability in identifying and locating low-voltage regions. The analysis of unipolar EVM can correlate with epicardial pathological involvement. We evaluated the unipolar EVM in EMB areas to determine whether it can increase EMB sensitivity in diagnosing epicardial diseases.

METHODS AND RESULTS

We performed endocardial bipolar EVM-guided EMBs in 29 patients and we analyzed unipolar EVM at withdrawal sites. Eighty myocardial samples were collected (mean, 2.8±0.9; median, 3 fragments per patient) and 60 were suitable for histological analysis. Ten specimens (17%) were collected from an area with discordant normal bipolar/low-voltage unipolar EVM and they were diagnostic or suggestive for arrhythmogenic right ventricular dysplasia/cardiomyopathy in 6 patients, for myocarditis and sarcoidosis in 1 patient each. Six samples (10%) were collected from an area with discordant low-voltage bipolar/normal unipolar EVM and they showed nonspecific features. The sensitivity of unipolar EVMs for a diagnostic biopsy finding EMB was significantly higher compared with bipolar EVMs analyzed according to samples (P<0.01) and patients (P=0.008). The specificity of unipolar EMB was better than bipolar EMB when analyzed for all samples (P=0.0014) but the difference did not reach statistical significance when analyzed by patient (P=0.083). The diagnostic yield was 63.3% for the bipolar and 83.3% for the unipolar EVM.

CONCLUSIONS

These findings suggest that use of a combined bipolar/unipolar map may be able to improve the diagnostic yield of endomyocardial ventricular biopsy.

Epigenetics and Metabolism

The molecular signatures of epigenetic regulation and chromatin architectures are fundamental to genetically determined biological processes. Covalent and post-translational chemical modification of the chromatin template can sensitize the genome to changing environmental conditions to establish diverse functional states. Recent interest and research focus surrounds the direct connections between metabolism and chromatin dynamics, which now represents an important conceptual challenge to explain many aspects of metabolic dysfunction. Several components of the epigenetic machinery require intermediates of cellular metabolism for enzymatic function. Furthermore, changes to intracellular metabolism can alter the expression of specific histone methyltransferases and acetyltransferases conferring widespread variations in epigenetic modification patterns. Specific epigenetic influences of dietary glucose and lipid consumption, as well as undernutrition, are observed across numerous organs and pathways associated with metabolism. Studies have started to define the chromatin-dependent mechanisms underlying persistent and pathophysiological changes induced by altered metabolism. Importantly, numerous recent studies demonstrate that gene regulation underlying phenotypic determinants of adult metabolic health is influenced by maternal and early postnatal diet. These emerging concepts open new perspectives to combat the rising global epidemic of metabolic disorders.