Arrhythmogenic right ventricular dysplasia/cardiomyopathy-three decades of progress

Basic and translational mechanisms in inflammatory arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is a familial, nonischemic heart disease typically inherited via an autosomal dominant pattern (Nava et al., [1]; Wlodarska et al., [2]). Often affecting the young and athletes, early diagnosis of ACM can be complicated as incomplete penetrance with variable expressivity are common characteristics (Wlodarska et al., [2]; Corrado et al., [3]). That said, of the five desmosomal genes implicated in ACM, pathogenic variants in desmocollin-2 (DSC2) and desmoglein-2 (DSG2) have been discovered in both an autosomal-recessive and autosomal-dominant pattern (Wong et al., [4]; Qadri et al., [5]; Chen et al., [6]). Originally known as arrhythmogenic right ventricular dysplasia (ARVD), due to its RV prevalence and manifesting in the young, the disease was first described in 1736 by Giovanni Maria Lancisi in his book "De Motu Cordis et Aneurysmatibus" (Lancisi [7]). However, the first comprehensive clinical description and recognition of this dreadful disease was by Guy Fontaine and Frank Marcus in 1982 (Marcus et al., [8]). These two esteemed pathologists evaluated twenty-two (n = 22/24) young adult patients with recurrent ventricular tachycardia (VT) and RV dysplasia (Marcus et al., [8]). Initially, ARVD was thought to be the result of partial or complete congenital absence of ventricular myocardium during embryonic development (Nava et al., [9]). However, further research into the clinical and pathological manifestations revealed acquired progressive fibrofatty replacement of the myocardium (McKenna et al., [10]); and, in 1995, ARVD was classified as a primary cardiomyopathy by the World Health Organization (Richardson et al., [11]). Thus, now classifying ACM as a cardiomyopathy (i.e., ARVC) rather than a dysplasia (i.e., ARVD). Even more recently, ARVC has shifted from its recognition as a primarily RV disease (i.e., ARVC) to include left-dominant (i.e., ALVC) and biventricular subtypes (i.e., ACM) as well (Saguner et al., [12]), prompting the use of the more general term arrhythmogenic cardiomyopathy (ACM). This review aims to discuss pathogenesis, clinical and pathological phenotypes, basic and translational research on the role of inflammation, and clinical trials aimed to prevent disease onset and progression.

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.

Arrhythmogenic Cardiomyopathy: A Review of a Rare Case of Biventricular Phenotype

Arrhythmogenic cardiomyopathy is a rare hereditary structural heart disease, with various phenotypes, which mostly affects the right ventricle of the heart, resulting in fibrofatty replacement of the heart muscles and a proclivity to create spontaneous malignant cardiac arrhythmias that may lead to sudden death. Most previous reports were noted on young people. We report a case of its biventricular phenotype in a 61-year-old heavy truck driver who has a current medical history of diabetes mellitus and smoking and was incidentally diagnosed based on the Padua criteria after presenting to the hospital with complaints of lightheadedness and syncope. He eventually had an implantable cardioverter defibrillator, hence preventing death. We were able to correctly diagnose the case and prevent sudden cardiac death by instituting the necessary management.

Motion-compensated fat-water imaging for 3D cardiac MRI at ultra-high fields

PURPOSE

Respiratory motion-compensated (MC) 3D cardiac fat-water imaging at 7T.

METHODS

Free-breathing bipolar 3D triple-echo gradient-recalled-echo (GRE) data with radial phase-encoding (RPE) trajectory were acquired in 11 healthy volunteers (7M\4F, 21-35 years, mean: 30 years) with a wide range of body mass index (BMI; 19.9-34.0 kg/m² ) and volunteer tailored B 1 + shimming. The bipolar-corrected triple-echo GRE-RPE data were binned into different respiratory phases (self-navigation) and were used for the estimation of non-rigid motion vector fields (MF) and respiratory resolved (RR) maps of the main magnetic field deviations (ΔB₀ ). RR ΔB₀ maps and MC ΔB₀ maps were compared to a reference respiratory phase to assess respiration-induced changes. Subsequently, cardiac binned fat-water images were obtained using a model-based, respiratory motion-corrected image reconstruction.

RESULTS

The 3D cardiac fat-water imaging at 7T was successfully demonstrated. Local respiration-induced frequency shifts in MC ΔB₀ maps are small compared to the chemical shifts used in the multi-peak model. Compared to the reference exhale ΔB₀ map these changes are in the order of 10 Hz on average. Cardiac binned MC fat-water reconstruction reduced respiration induced blurring in the fat-water images, and flow artifacts are reduced in the end-diastolic fat-water separated images.

CONCLUSION

This work demonstrates the feasibility of 3D fat-water imaging at UHF for the entire human heart despite spatial and temporal B 1 + and B₀ variations, as well as respiratory and cardiac motion.

[Clinical and anamnestic characteristics of patients with an implanted cardioverter-defibrillator in real clinical practice (data from the Kuzbass register)]

Aim      To study the consistency of the practice of management, selection and routing of patients at high risk of sudden cardiac death (SCD) selected for cardioverter-defibrillator implantation (CDI) with current clinical guidelines and to evaluate the quality of subsequent outpatient follow-up and treatment based on a retrospective analysis of clinical amnestic data from the Kuzbass Registry of Patients with CDI.Material and methods  The study was based on the Registry of Patients with Implanted Cardioverter Defibrillator and included successive data of 28 patients hospitalized to the Kizbass Cardiological Center from 2015 through 2019. Social and clinical amnestic characteristics, indications for CVI, and concomitant drug therapy were analyzed retrospectively. Statistical analyses were performed with the Statistica 10.0 software (Statsoft, USA).Results Median age of patients was 59 (53; 66) years; 239 (83.6 %) men were included; 29 (10.1%) people were employed, CHI was performed in 182 (63.6 %) patients for prevention of SCC, and for secondary prevention in 104 (36.4 %) patients. 208 (72.7 %) patients were diagnosed with ischemic heart disease (IHD), and 145 (67.9 %) of them underwent myocardial revascularization. Noncoronarogenic diseases were found in 78 (27.3 %) patients, and most of them were diagnosed with dilated cardiomyopathy. All patients had chronic heart failure (CHF); half of them had stage IIA CHF. Median left ventricular ejection fraction was 30 (25; 36,5) % according to echocardiography using the Simpson method. Comorbidity was found in 151 (52.8 %) patients. 128 (44.8%) patients received a triple neurohormonal blockade for CHF treatment; titration to target doses was not performed in any of them. Antiarrhythmics were administered to 150 (52.4 %) patients.Conclusion      According to the data from the Kuzbass Registry of CVI, the main patient cohort consisted of men of pension age with IHD and CHF. Before CVI, more than a half of them had not received an optimum drug therapy and not all of them had received target lesion revascularization. Creating and analysis of Registries of CHI patients is an effective method for identifying existing problems in patient management before CVI and for optimizing their subsequent follow-up and treatment.

A 3D high resolution MRI method for the visualization of cardiac fibro-fatty infiltrations

Modifications of the myocardial architecture can cause abnormal electrical activity of the heart. Fibro-fatty infiltrations have been implicated in various cardiac pathologies associated with arrhythmias and sudden cardiac death, such as arrhythmogenic right ventricular cardiomyopathy (ARVC). Here, we report the development of an MRI protocol to observe these modifications at 9.4 T. Two fixed ex vivo human hearts, one healthy and one ARVC, were imaged with an Iterative decomposition with echo asymmetry and least-square estimations (IDEAL) and a magnetization transfer (MT) 3D sequences. The resulting fat fraction and MT ratio (MTR) were analyzed and compared to histological analysis of the three regions (“ARVC triangle”) primarily involved in ARVC structural remodeling. In the ARVC heart, high fat content was observed in the “ARVC triangle” and the superimposition of the MTR and fat fraction allowed the identification of fibrotic regions in areas without the presence of fat. The healthy heart exhibited twice less fat than the ARVC heart (31.9%, 28.7% and 1.3% of fat in the same regions, respectively). Localization of fat and fibrosis were confirmed by means of histology. This non-destructive approach allows the investigation of structural remodeling in human pathologies where fibrosis and/or fatty tissue infiltrations are expected to occur.

[Clinical profile and therapeutic strategies in patients with arrhythmogenic cardiomyopathy treated in a national reference institute]

Objective

To determine the epidemiological, clinical, electrocardiographic, imaging characteristics and main therapeutic strategies performed in patients with arrhythmogenic cardiomyopathy treated in a national reference cardiovascular institute.

Materials and methods

Observational, descriptive and retrospective study that attempts to identify the clinical characteristics, complementary tests and therapeutic strategies performed in patients with arrhythmogenic cardiomyopathy treated at the Instituto Nacional Cardiovascular - INCOR EsSalud in Lima, Peru.

Results

Thirteen patients were found with arrhythmogenic cardiomyopathy. The median age at which the diagnosis was made was 38.2 years and 69.3% were male. The most frequent clinical manifestations were tachycardic palpitations (92.3%), presyncope (84.6%) and heart failure (69.2%). 23% of the patients suffered a cardiac arrest. All the patients presented at least one episode of ventricular tachycardia, 92.3% with complete left bundle branch block morphology and upper axis. 76.9% received an implantable cardioverter defibrillator (ICD), 15.3% underwent ablation and 15.3% received a heart transplant. 84.6% of the patients live to this day.

Conclusions

Arrhythmogenic cardiomyopathy predominantly affected the young and male population. All the patients had a potentially fatal ventricular arrhythmia. Biventricular disease by echocardiography and cardiac magnetic resonance occurred in 69.2% and 100% of the cases, respectively. The therapeutic strategies used were antiarrhythmic medical treatment, placement of an ICD as secondary prevention, ablation, and heart transplantation. To date, 84.6% of patients survive.

Safety and Utility of Cardiopulmonary Exercise Testing in Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia

Background

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is characterized by high arrhythmic burden and progressive heart failure, which can prompt referral for heart transplantation. Cardiopulmonary exercise testing (CPET) has an established role in risk stratification for advanced heart failure therapies, but has not been described in ARVC/D. This study sought to determine the safety and prognostic utility of CPET in patients with ARVC/D.

Methods and Results

Using the Johns Hopkins ARVC/D Registry, we examined patients with ARVC/D undergoing CPET. Baseline characteristics and transplant‐free survival were compared on the basis of peak oxygen consumption (pVO2) (≤14 or >14 mL/kg per minute) and ventilatory efficiency (Ve/VCO₂ slope ≤34 or >34). Thirty‐eight patients underwent 50 CPETs. There were no sustained arrhythmic events. Twenty‐nine patients achieved a maximal test. Patients with pVO2 ≤14 mL/kg per minute were more often men (P=0.042) compared with patients with pVO2 >14 mL/kg per minute. Patients with Ve/VCO₂ slope >34 tended to have more moderate/severe right ventricular dilation (7/9 [78%] versus 10/26 [38%]; P=0.060) and clinical heart failure (8/9 [89%] versus 13/26 [50%]; P=0.056) compared with patients with Ve/VCO₂ slope ≤34. Patients who underwent heart transplantation were more likely to have clinical heart failure (10/10 [100%] versus 13/28 [46%]; P=0.003). Patients with Ve/VCO₂ slope >34 had worse transplant‐free survival compared with patients with Ve/VCO₂ slope ≤34 (n=35; hazard ratio, 6.57 [95% CI, 1.28–33.72]; log‐rank P=0.010), whereas transplant‐free survival was similar on the basis of pVO2 groups (n=29; hazard ratio, 3.38 [95% CI, 0.75–15.19]; log‐rank P=0.092).

Conclusions

CPET is safe to perform in patients with ARVC/D. Ve/VCO₂ slope may be used for risk stratification and guide referral for heart transplantation in ARVC/D.

The Emergence of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes (hiPSC-CMs) as a Platform to Model Arrhythmogenic Diseases

There is a need for improved in vitro models of inherited cardiac diseases to better understand basic cellular and molecular mechanisms and advance drug development. Most of these diseases are associated with arrhythmias, as a result of mutations in ion channel or ion channel-modulatory proteins. Thus far, the electrophysiological phenotype of these mutations has been typically studied using transgenic animal models and heterologous expression systems. Although they have played a major role in advancing the understanding of the pathophysiology of arrhythmogenesis, more physiological and predictive preclinical models are necessary to optimize the treatment strategy for individual patients. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have generated much interest as an alternative tool to model arrhythmogenic diseases. They provide a unique opportunity to recapitulate the native-like environment required for mutated proteins to reproduce the human cellular disease phenotype. However, it is also important to recognize the limitations of this technology, specifically their fetal electrophysiological phenotype, which differentiates them from adult human myocytes. In this review, we provide an overview of the major inherited arrhythmogenic cardiac diseases modeled using hiPSC-CMs and for which the cellular disease phenotype has been somewhat characterized.

Ventricular Dysrhythmias During Long-Term Follow-Up in Patients With Inherited Cardiac Arrhythmia

Reports on development of frequent ventricular premature complexes (fVPC), (non)sustained ventricular tachycardias ([n]sVT), or ventricular fibrillation (VF) and their interrelationship in patients with different inherited cardiac arrhythmia (ICA) have sofar not been reported. The aim of this study is therefore to examine incidences and recurrences rates of sVT and VF ("malignant ventricular tachyarrhythmias, VTA") in addition to the incidence of fVPC and nsVT ("ventricular dysrhythmias, VDR") in patients with various ICA during long-term follow up. Patients (N = 167, 88 male, age 45 ± 15 years) with ICA including definite/borderline arrhythmogenic right ventricular cardiomyopathy (ARVC, N = 47), Brugada syndrome (BrS, N = 71), catecholaminergic polymorphic ventricular tachycardia (CPVT, N = 7), long QT syndrome (LQTS, N = 41) or short QT syndrome (SQTS, N = 1) who had frequent 24-hour Holter monitoring during a follow-up period of 4.6 ± 4.4 years. During the initial screening visit, 15 patients had a history of malignant VTA. fVPC and nsVT was observed in respectively 19% (OHCA/VF/sVT: N = 9) and 13% (OHCA/VF/sVT: N = 4) of all patients. Compared with the ARVC group, patients with BrS and LQTS had less frequent fVPC and nsVT (fVPC: odds ratio [OR] 0.20, 95% confidence interval [CI] 0.08 to 0.49, p <0.000 and OR 0.09, 95% CI 0.02 to 0.33, p <0.000; nsVT:OR 0.17, 95% CI 0.06 to 0.50, p = 0.001 and OR 0.09, 95% CI 0.02 to 0.46, p = 0.003). The recurrence rate of malignant VTA was 33%. In conclusion, variety of VDR and malignant VTA were found during long-term follow-up in patients with ICA. During nearly a 5 years follow-up period, the recurrence rate of malignant VTA was considerable. fVPC, nsVT, and malignant VTA were most often found in patients with an ARVC.

Cyclophilin A in Arrhythmogenic Cardiomyopathy Cardiac Remodeling

Arrhythmogenic cardiomyopathy (ACM) is a genetic disorder characterized by the progressive substitution of functional myocardium with noncontractile fibro-fatty tissue contributing to ventricular arrhythmias and sudden cardiac death. Cyclophilin A (CyPA) is a ubiquitous protein involved in several pathological mechanisms, which also characterize ACM (i.e., fibrosis, inflammation, and adipogenesis). Nevertheless, the involvement of CyPA in ACM cardiac remodeling has not been investigated yet. Thus, we first evaluated CyPA expression levels in the right ventricle (RV) tissue specimens obtained from ACM patients and healthy controls (HC) by immunohistochemistry. Then, we took advantage of ACM- and HC-derived cardiac mesenchymal stromal cells (C-MSC) to assess CyPA modulation during adipogenic differentiation. Interestingly, CyPA was more expressed in the RV sections obtained from ACM vs. HC subjects and positively correlated with the adipose replacement extent. Moreover, CyPA was upregulated at early stages of C-MSC adipogenic differentiation and was secreted at higher level over time in ACM- derived C-MSC. Our study provides novel ex vivo and in vitro information on CyPA expression in ACM remodeling paving the way for future C-MSC-based mechanistic and therapeutic investigations.

Sex-specific influence on cardiac structural remodeling and therapy in cardiovascular disease

BACKGROUND

Cardiovascular diseases (CVDs) culminating into heart failure (HF) are major causes of death in men and women. Prevalence and manifestation, however, differ between sexes, since men mainly present with coronary artery disease (CAD) and myocardial infarction (MI), and post-menopausal women predominantly present with hypertension. These discrepancies are probably influenced by underlying genetic and molecular differences in structural remodeling pathways involved in hypertrophy, inflammation, fibrosis, and apoptosis. In general, men mainly develop eccentric forms, while women develop concentric forms of hypertrophy. Besides that, women show less inflammation, fibrosis, and apoptosis upon HF. This seems to emerge, at least partially, from the fact that the underlying pathways might be modulated by estrogen, which changes after menopause due to declining of the estrogen levels.

CONCLUSION

In this review, sex-dependent alterations in adverse cardiac remodeling are discussed for various CVDs. Moreover, potential therapeutic options, like estrogen treatment, are reviewed.

Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia (ARVC/D) - What We Have Learned after 40 Years of the Diagnosis of This Clinical Entity

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) was initially recognized as a clinical entity by Fontaine and Marcus, who evaluated a group of patients with ventricular tachyarrhythmia from a structurally impaired right ventricle (RV). Since then, there have been significant advances in the understanding of the pathophysiology, manifestation and clinical progression, and prognosis of the pathology. The identification of genetic mutations impairing cardiac desmosomes led to the inclusion of this entity in the classification of cardiomyopathies. Classically, ARVC/D is an inherited disease characterized by ventricular arrhythmias, right and / or left ventricular dysfunction; and fibro-fatty substitution of cardiomyocytes; its identification can often be challenging, due to heterogeneous clinical presentation, highly variable intra- and inter-family expressiveness, and incomplete penetrance.

In the absence of a gold standard that allows the diagnosis of ARVC/D, several diagnostic categories were combined and recently reviewed for a higher diagnostic sensitivity, without compromising the specificity. The finding that electrical abnormalities, particularly ventricular arrhythmias, usually precede structural abnormalities is extremely important for risk stratification in positive genetic members. Among the complementary exams, cardiac magnetic resonance imaging (CMR) allows the early diagnosis of left ventricular impairment, even before morpho-functional abnormalities. Risk stratification remains a major clinical challenge, and antiarrhythmic drugs, catheter ablation and implantable cardioverter defibrillator are the currently available therapeutic tools. The disqualification of the sport prevents cases of sudden death because the effort can trigger not only the electrical instability, but also the onset and progression of the disease.

Diagnostic and therapeutic strategies for arrhythmogenic right ventricular dysplasia/cardiomyopathy patient

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is a rare inherited heart muscle disease characterized by ventricular tachyarrhythmia, predominant right ventricular dysfunction, and sudden cardiac death. Its pathophysiology involves close interaction between genetic mutations and exposure to physical activity. Mutations in genes encoding desmosomal protein are the most common genetic basis. Genetic testing plays important roles in diagnosis and screening of family members. Syncope, palpitation, and lightheadedness are the most common symptoms. The 2010 Task Force Criteria is the standard for diagnosis today. Implantation of a defibrillator in high-risk patients is the only therapy that provides adequate protection against sudden death. Selection of patients who are best candidates for defibrillator implantation is challenging. Exercise restriction is critical in affected individuals and at-risk family members. Antiarrhythmic drugs and ventricular tachycardia ablation are valuable but palliative components of the management. This review focuses on the current diagnostic and therapeutic strategies in ARVD/C and outlines the future area of development in this field.

Advances in the Diagnosis and Management of Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is an inherited cardiomyopathy characterized by ventricular arrhythmias, right ventricular dysfunction, and sudden cardiac death. Since the first description of ARVD/C in 1982, there have been major advances in the diagnosis and management of the disease. For instance, the discovery of desmosomal abnormalities as a genetic basis for ARVD/C; the importance of proband status and ventricular ectopy for risk stratification of patients at risk for sudden cardiac death; and the critical role that exercise plays in the development and progression of ARVD/C, just to name a few. From a treatment perspective, the placement of implantable cardioverter defibrillators in those at risk for sudden cardiac death and ablation techniques have also evolved over time. In 2010, an update of the 1994 Task Force Diagnostic criteria for ARVD/C was published with the hope to increase diagnostic sensitivity. This update incorporates new knowledge and technology to assess structural cardiac abnormalities and is the standard for diagnosis today.

A novel noninvasive surface ECG analysis using interlead QRS dispersion in arrhythmogenic right ventricular cardiomyopathy

Background

This study investigated the feasibility of using the precordial surface ECG lead interlead QRS dispersion (IQRSD) in the identification of abnormal ventricular substrate in arrhythmogenic right ventricular cardiomyopathy (ARVC).

Methods

Seventy-one consecutive patients were enrolled and reclassified into 4 groups: definite ARVC with epicardial ablation (Group 1), ARVC with ventricular tachycardia (VT, Group 2), idiopathic right ventricular outflow tract VT without ARVC (Group 3), and controls without VT (Group 4). IQRSD was quantified by the angular difference between the reconstruction vectors obtained from the QRS-loop decomposition, based on a principal component analysis (PCA). Electroanatomic mapping and simulated ECGs were used to investigate the relationship between QRS dispersion and abnormal substrate.

Results

The percentage of the QRS loop area in the Group 1–2 was smaller than the controls (P = 0.01). The IQRSD between V1-V2 could differentiate all VTs from control (P<0.01). Group 1–2 had a greater IQRSD than the Group 3–4 (V4-V5,P = 0.001), and Group 1 had a greater IQRSD than Group 3–4 (V6-Lead I, P<0.001). Both real and simulated data had a positive correlation between the maximal IQRSD (γ = 0.62) and the extent of corresponding abnormal substrate (γ = 0.71, both P<0.001).

Conclusions

The IQRSD of the surface ECG precordial leads successfully differentiated ARVC from controls, and could be used as a noninvasive marker to identify the abnormal substrate and the status of ARVC patients who can benefit from epicardial ablation.

Targeted next-generation sequencing detects novel gene-phenotype associations and expands the mutational spectrum in cardiomyopathies

Cardiomyopathies are a heterogeneous group of primary diseases of the myocardium, including hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and arrhythmogenic right ventricular cardiomyopathy (ARVC), with higher morbidity and mortality. These diseases are genetically diverse and associated with rare mutations in a large number of genes, many of which overlap among the phenotypes. To better investigate the genetic overlap between these three phenotypes and to identify new genotype–phenotype correlations, we designed a custom gene panel consisting of 115 genes known to be associated with cardiomyopathic phenotypes and channelopathies. A cohort of 38 unrelated patients, 16 affected by DCM, 14 by HCM and 8 by ARVC, was recruited for the study on the basis of more severe phenotypes and family history of cardiomyopathy and/or sudden death. We detected a total of 142 rare variants in 40 genes, and all patients were found to be carriers of at least one rare variant. Twenty-eight of the 142 rare variants were also predicted as potentially pathogenic variants and found in 26 patients. In 23 out of 38 patients, we found at least one novel potential gene–phenotype association. In particular, we detected three variants in OBSCN gene in ARVC patients, four variants in ANK2 gene and two variants in DLG1, TRPM4, and AKAP9 genes in DCM patients, two variants in PSEN2 gene and four variants in AKAP9 gene in HCM patients. Overall, our results confirmed that cardiomyopathic patients could carry multiple rare gene variants; in addition, our investigation of the genetic overlap among cardiomyopathies revealed new gene–phenotype associations. Furthermore, as our study confirms, data obtained using targeted next-generation sequencing could provide a remarkable contribution to the molecular diagnosis of cardiomyopathies, early identification of patients at risk for arrhythmia development, and better clinical management of cardiomyopathic patients.

Arrhythmogenic right ventricular dysplasia: Atypical clinical presentation

A 67-year-old man was admitted to our hospital after episodes of syncope preceded by malaise and diffuse neck and chest discomfort. No family history of cardiac disease was reported. Laboratory workup was within normal limits, including D-dimers, serum troponin I and arterial blood gases. The electrocardiogram showed sinus rhythm with T-wave inversion in leads V1 to V3. Computed tomography angiography to investigate pulmonary embolism showed no abnormal findings. Transthoracic echocardiography (TTE) displayed massive enlargement of the right ventricle with intact interatrial septum and no pulmonary hypertension. Cardiac magnetic resonance imaging (MRI) confirmed right ventricular (RV) dilatation and revealed marked hypokinesia/akinesia of the lateral wall. Exercise stress testing was negative for ischemia. According to the 2010 Task Force criteria for arrhythmogenic right ventricular dysplasia (ARVD), this patient presented two major criteria (global or regional dysfunction and structural alterations: by MRI, regional RV akinesia or dyskinesia or dyssynchronous RV contraction and RV ejection fraction ≤40%, and repolarization abnormalities: inverted T waves in right precordial leads [V1, V2, and V3]); and one minor criterion (>500 ventricular extrasystoles per 24 hours by Holter), and so a diagnosis of ARVD was made. After electrophysiologic study (EPS) the patient received an implantable cardioverter-defibrillator (ICD). This late clinical presentation of ARVD highlights the importance of TTE screening, possibly complemented by MRI. The associated risk of sudden death was assessed by EPS leading to the implantation of an ICD. Genetic association studies should be offered to the offspring of all ARVD patients.

Human iPSC-derived cardiomyocytes and tissue engineering strategies for disease modeling and drug screening

Improved methodologies for modeling cardiac disease phenotypes and accurately screening the efficacy and toxicity of potential therapeutic compounds are actively being sought to advance drug development and improve disease modeling capabilities. To that end, much recent effort has been devoted to the development of novel engineered biomimetic cardiac tissue platforms that accurately recapitulate the structure and function of the human myocardium. Within the field of cardiac engineering, induced pluripotent stem cells (iPSCs) are an exciting tool that offer the potential to advance the current state of the art, as they are derived from somatic cells, enabling the development of personalized medical strategies and patient specific disease models. Here we review different aspects of iPSC-based cardiac engineering technologies. We highlight methods for producing iPSC-derived cardiomyocytes (iPSC-CMs) and discuss their application to compound efficacy/toxicity screening and in vitro modeling of prevalent cardiac diseases. Special attention is paid to the application of micro- and nano-engineering techniques for the development of novel iPSC-CM based platforms and their potential to advance current preclinical screening modalities.

Arrhythmogenic right ventricular dysplasia/cardiomyopathy

Arrhythmogenic right ventricular dysplasia/cardiomyopathy is an inherited cardiomyopathy characterised by ventricular arrhythmias and an increased risk of sudden cardiac death. Arrhythmogenic right ventricular dysplasia/cardiomyopathy diagnosis is based on criteria that take into account electrical and structural cardiac abnormalities, as well as mutation analysis. Appropriate pharmacological therapy and the prevention of sudden death with implantable defibrillators are important in the management of these patients. Exercise is considered an important environmental factor for the development and progression of the disease.

Right ventricular thrombus formation in a patient with arrhythmogenic right ventricular dysplasia following radiofrequency ablation

A middle-aged female suffering from ARVD presented for routine follow-up 8 weeks after right ventricular radiofrequency ablation of recurring ventricular tachycardia. Echocardiography revealed two right ventricular thrombi in the scar area of right ventricular radiofrequency ablation. Ablation-related thromboembolic events should be considered as possible complication in patients suffering from ARVD.

Animal Models of Congenital Cardiomyopathies Associated With Mutations in Z-Line Proteins

The cardiac Z-line at the boundary between sarcomeres is a multiprotein complex connecting the contractile apparatus with the cytoskeleton and the extracellular matrix. The Z-line is important for efficient force generation and transmission as well as the maintenance of structural stability and integrity. Furthermore, it is a nodal point for intracellular signaling, in particular mechanosensing and mechanotransduction. Mutations in various genes encoding Z-line proteins have been associated with different cardiomyopathies, including dilated cardiomyopathy, hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, restrictive cardiomyopathy, and left ventricular noncompaction, and mutations even within the same gene can cause widely different pathologies. Animal models have contributed to a great advancement in the understanding of the physiological function of Z-line proteins and the pathways leading from mutations in Z-line proteins to cardiomyopathy, although genotype-phenotype prediction remains a great challenge. This review presents an overview of the currently available animal models for Z-line and Z-line associated proteins involved in human cardiomyopathies with special emphasis on knock-in and transgenic mouse models recapitulating the clinical phenotypes of human cardiomyopathy patients carrying mutations in Z-line proteins. Pros and cons of mouse models will be discussed and a future outlook will be given. J. Cell. Physiol. 232: 38-52, 2017. © 2016 Wiley Periodicals, Inc.

Brugada Syndrome and PKP2: Evidences and uncertainties

Common electrocardiographic patterns in Brugada Syndrome and Arrhythmogenic Cardiomyopathy have been reported despite phenotypic alterations during its clinical course. Recently, potentially pathogenic variants in the PKP2 gene, the most prevalent gene associated with Arrhythmogenic Cardiomyopathy, have been associated with Brugada Syndrome. In addition, in vitro studies demonstrated the interaction between plakophilin-2 and sodium channel, the most prevalent gene associated with Brugada Syndrome. All these facts reinforce the suggested overlapping between both entities but little is known about the pathophysiological mechanisms. We have performed a comprehensive genetic revision of all PKP2 genetic variants currently associated with Brugada Syndrome. In all variants we identified a lack of solid evidences in order to establish a definite genotype-phenotype association. Hence, despite we believe that PKP2 analysis should be considered as a part of molecular genetic testing in Brugada Syndrome patients, comprehensive clinical and molecular studies should be performed before establish pathogenic association. Therefore, PKP2 variants in Brugada Syndrome cases should be interpreted carefully and additional studies including family segregation should be performed before translation into clinical practice.

Recent advances in genetic testing and counseling for inherited arrhythmias

Inherited arrhythmias, such as cardiomyopathies and cardiac ion channelopathies, along with coronary heart disease (CHD) are three most common disorders that predispose adults to sudden cardiac death. In the last three decades, causal genes in inherited arrhythmias have been successfully identified. At the same time, it has become evident that the genetic architectures are more complex than previously known. Recent advancements in DNA sequencing technology (next generation sequencing) have enabled us to study such complex genetic traits.

This article discusses indications for genetic testing of patients with inherited arrhythmias. Further, it describes the benefits and challenges that we face in the era of next generation sequencing. Finally, it briefly discusses genetic counseling, in which a multidisciplinary approach is required due to the increased complexity of the genetic information related to inherited arrhythmias.

Nature and Nurture in Arrhythmogenic Right Ventricular Cardiomyopathy - A Clinical Perspective

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is an inherited cardiomyopathy characterised by frequent ventricular arrhythmias and slowly progressive predominant RV dysfunction. Up to two-thirds of ARVD/C patients have mutations in genes encoding the cardiac desmosome. Mutations in other genes are increasingly recognised. Inheritance of ARVD/C is generally autosomal dominant with reduced age-related penetrance and significant variable expressivity. While the full explanation for this phenotypic heterogeneity remains unclear, there is increasing evidence that exercise plays a major role in disease penetrance and arrhythmic risk. The disproportionate representation of athletes among ARVD/C patients has long been noted. Recently, the association of exercise with earlier onset and more severe arrhythmic and structural disease has been documented. This article reviews current evidence regarding the association of genotype, exercise and clinical outcomes and discusses the emerging paradigm in which genetic predisposition and environmental factors (exercise) interact around a threshold for phenotypic expression of ARVD/C.

Unusual Serial Electrocardiographic Changes which Progressed to Arrhythmogenic Right Ventricular Cardiomyopathy

Left ventricular (LV) involvement in the advanced stage of arrhythmogenic right ventricular cardiomyopathy (ARVC) is a well recognized phenomenon. T wave inversion in the lateral leads has been reported to be an electrocardiographic marker of LV involvement. Variants of ARVC that preferentially affect the left ventricle (left-dominant subtype of arrhythmogenic cardiomyopathy) have recently been recognized. We herein report a case in which an initial electrocardiogram that was similar to the left-dominant subtype of arrhythmogenic cardiomyopathy progressed to definitive ARVC over a period of 7 years. This case supports the hypothesis that LV involvement in ARVC may precede the evident onset of significant RV dysfunction.