Left-dominant arrhythmogenic cardiomyopathy: an under-recognized clinical entity

A case series of desmoplakin cardiomyopathy: a mimic of viral myocarditis

Background

Clinical features and imaging presentation of myocarditis can overlap with other inflammatory or arrhythmogenic cardiomyopathies. Desmoplakin (DSP) is an important structural cardiac protein. Mutations in the DSP gene are associated with a variant of arrhythmogenic right ventricular cardiomyopathy (ARVC). Interestingly, this distinct genetic cardiomyopathy can also present with a myocardial inflammation and fibrosis pattern that may mimic other forms of myocarditis including viral myocarditis, which can raise a clinical challenge. We report two cases of DSP cardiomyopathy, which were initially thought to represent coronavirus disease of 2019 (COVID-19) myocarditis.

Case summary

First patient is a 21-your-old woman with no past medical history but family history of presumed ‘viral myocarditis’ and ventricular tachycardia in her brother. She presented with acute chest pain and elevated cardiac enzymes. She tested positive for COVID-19 and given the suspicion for possible COVID-19 related acute myocarditis, cardiac magnetic resonance imaging obtained and revealed regional wall motion abnormalities, several areas of subepicardial and pericardial late gadolinium enhancement (LGE). Ambulatory cardiac monitoring showed runs of non-sustained ventricular tachycardia and considering her family history of arrhythmogenic myocarditis, genetic testing was performed that was positive for a likely pathogenic heterozygous mutation of DSP gene. She declined the recommended implantable cardioverter defibrillator (ICD).

Second patient is a 34-year-old physician with no significant past medical history who works at a COVID-19 unit and presented with syncope and was found to have ventricular tachycardia. Echocardiogram revealed severely dilated left ventricle and globally depressed systolic function with left ventricular ejection fraction of 20%. Coronary computed tomography angiography showed no evidence of coronary atherosclerosis. Cardiac magnetic resonance imaging revealed several areas of mid myocardial and pericardial LGE. Subcutaneous ICD was implanted and an endomyocardial biopsy had evidence of lymphocytic myocarditis and adipose tissue infiltration of the myocardium. Genetic testing revealed pathogenic heterozygous DSP mutation. He underwent epicardial ablation for the episodes of ventricular tachycardia despite medical therapy. He was able to return to work and has not had any further episodes of arrhythmia.

Conclusion

Mutations in the DSP gene are associated with left dominant arrhythmogenic cardiomyopathy, which is a variant of ARVC. Beside left ventricular systolic dysfunction and ventricular tachyarrhythmias, carriers of these mutations may present with episodes of chest pain associated with elevated cardiac enzymes and cardiac imaging findings indistinguishable from other forms of acute myocarditis including viral myocarditis. Currently, there are no guidelines for diagnosis and treatment of this entity.

Loss-of-Function FLNC Variants Are Associated With Arrhythmogenic Cardiomyopathy Phenotypes When Identified Through Exome Sequencing of a General Clinical Population

BACKGROUND

The FLNC gene has recently garnered attention as a likely cause of arrhythmogenic cardiomyopathy, which is considered an actionable genetic condition. However, the association with disease in an unselected clinical population is unknown. We hypothesized that individuals with loss-of-function variants in FLNC (FLNC_LOF) would have increased odds for arrhythmogenic cardiomyopathy-associated phenotypes versus variant-negative controls in the Geisinger MyCode cohort.

METHODS

We identified rare, putative FLNC_LOF among 171 948 individuals with exome sequencing linked to health records. Associations with arrhythmogenic cardiomyopathy phenotypes from available diagnoses and cardiac evaluations were investigated.

RESULTS

Sixty individuals (0.03%; median age 58 years [47-70 interquartile range], 43% male) harbored 27 unique FLNC_LOF. These individuals had significantly increased odds ratios for dilated cardiomyopathy (odds ratio, 4.9 [95% CI, 2.6-7.6]; P<0.001), supraventricular tachycardia (odds ratio, 3.2 [95% CI, 1.1-5.6]; P=0.048), and left-dominant arrhythmogenic cardiomyopathy (odds ratio, 4.2 [95% CI, 1.4-7.9]; P=0.03). Echocardiography revealed reduced left ventricular ejection fraction (52±13% versus 57±9%; P=0.001) associated with FLNC_LOF. Overall, at least 9% of FLNC_LOF patients demonstrated evidence of penetrant disease.

CONCLUSIONS

FLNC_LOF variants are associated with increased odds of ventricular arrhythmia and dysfunction in an unselected clinical population. These findings support genomic screening of FLNC for actionable secondary findings.

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.

Cardiac magnetic resonance imaging of arrhythmogenic cardiomyopathy: evolving diagnostic perspectives

Arrhythmogenic cardiomyopathy (ACM) is a genetically determined heart muscle disease characterized by fibro-fatty myocardial replacement, clinically associated with malignant ventricular arrhythmias and sudden cardiac death. Originally described a disease with a prevalent right ventricular (RV) involvement, subsequently two other phenotypes have been recognized, such as the left dominant and the biventricular phenotypes, for which a recent International Expert consensus document provided upgrade diagnostic criteria (the 2020 "Padua Criteria"). In this novel workup for the diagnosis of the entire spectrum of phenotypic variants of ACM, including left ventricular (LV) variants, cardiac magnetic resonance (CMR) has emerged as the cardiac imaging technique of choice, due to its capability of detailed morpho-functional and tissue characterization evaluation of both RV and LV. In this review, the key role of CMR in the diagnosis of ACM is outlined, including the supplemental value for the characterization of the disease variants. An ACM-specific CMR study protocol, as well as strengths and weaknesses of each imaging technique, is also provided. KEY POINTS: • Arrhythmogenic cardiomyopathy includes three different phenotypes: dominant right, biventricular, and dominant left. • In 2020, diagnostic criteria have been updated and cardiac magnetic resonance has emerged as the cardiac imaging technique of choice. • This aim of this review is to provide an update of the current state of art regarding the use of CMR in ACM, with a particular focus on novel diagnostic criteria, CMR protocols, and prognostic significance of CMR findings in ACM.

COVID-19 Vaccine-Induced Myocarditis: A Systemic Review and Literature Search

Myocarditis is one of the complications reported with COVID-19 vaccines, particularly both Pfizer-BioNTech and Moderna vaccines. Most of the published data about this association come from case reports and series. Integrating the geographical data, clinical manifestations, and outcomes is therefore important in patients with myocarditis to better understand the disease. A thorough literature search was conducted in Cochrane library, PubMed, ScienceDirect, and Google Scholar for published literature till 30 March 2022. We identified 26 patients eligible from 29 studies; the data were pooled from these qualifying case reports and case series. Around 94% of patients were male in this study, the median age for onset of myocarditis was 22 years and 85% developed symptoms after the second dose. The median time of admission for patients to hospitals post-vaccination was three days and chest pain was the most common presenting symptom in these patients. Most patients had elevated troponin on admission and about 90% of patients had cardiac magnetic resonance imaging (CMR) that showed late gadolinium enhancement. All patients admitted with myocarditis were discharged home after a median stay of four days. Results from this current analysis show that post-mRNA vaccination myocarditis is mainly seen in young males after the second dose of vaccination. The pathophysiology of vaccine-induced myocarditis is not entirely clear and late gadolinium enhancement is a common finding on CMR in these patients that may indicate myocardial fibrosis or necrosis. Prognosis remains good and all patients recovered from myocarditis, however further studies are advisable to assess long-term prognosis of myocarditis.

Dilated left ventricle with multiple outpouchings — a severe congenital ventricular diverticulum or left-dominant arrhythmogenic cardiomyopathy: A case report

BACKGROUND

Left-dominant arrhythmogenic cardiomyopathy (LDAC) is a relatively rare disease characterized by poor prognosis that exacerbates the incidence of sudden cardiac death and ventricular arrhythmias. Clinically, LDAC is constantly overlooked or misdiagnosed as myocardial infarction, myocarditis, and dilated cardiomyopathy, owing to atypical and nonspecific clinical manifestations at an early stage.

CASE SUMMARY

A 57-year-old woman was diagnosed with sinus bradycardia and chronic bifascicular block during a health check. She occasionally experienced mild chest pain and paroxysmal palpitation during activity in the past 2 years. Comprehensive auxiliary examinations, including electrocardiogram, echocardiography, coronary computerized tomography angiography, and magnetic resonance imaging, revealed that she had LDAC instead of congenital ventricular diverticulum. The physicians prescribed standard oral therapy for heart failure and implantable cardioverter-defibrillator. Consequently, her left ventricular systolic function and symptoms remained stable at the 2-year follow-up after discharge.

CONCLUSION

Based on this case, clinicians need to be aware of LDAC in patients with localized left ventricular lesions and multiple electrocardiographic abnormalities. Multimodality cardiovascular imaging is effective in identification of multiple types of cardiomyopathy and cardiac inner structures.

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

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

Arrhythmias as Presentation of Genetic Cardiomyopathy

There is increasing evidence regarding the prevalence of genetic cardiomyopathies, for which arrhythmias may be the first presentation. Ventricular and atrial arrhythmias presenting in the absence of known myocardial disease are often labelled as idiopathic, or lone. While ventricular arrhythmias are well-recognized as presentation for arrhythmogenic cardiomyopathy in the right ventricle, the scope of arrhythmogenic cardiomyopathy has broadened to include those with dominant left ventricular involvement, usually with a phenotype of dilated cardiomyopathy. In addition, careful evaluation for genetic cardiomyopathy is also warranted for patients presenting with frequent premature ventricular contractions, conduction system disease, and early onset atrial fibrillation, in which most detected genes are in the cardiomyopathy panels. Sudden death can occur early in the course of these genetic cardiomyopathies, for which risk is not adequately tracked by left ventricular ejection fraction. Only a few of the cardiomyopathy genotypes implicated in early sudden death are recognized in current indications for implantable cardioverter defibrillators which otherwise rely upon a left ventricular ejection fraction ≤0.35 in dilated cardiomyopathy. The genetic diagnoses impact other aspects of clinical management such as exercise prescription and pharmacological therapy of arrhythmias, and new therapies are coming into clinical investigation for specific genetic cardiomyopathies. The expansion of available genetic information and implications raises new challenges for genetic counseling, particularly with the family member who has no evidence of a cardiomyopathy phenotype and may face a potentially negative impact of a genetic diagnosis. Discussions of risk for both probands and relatives need to be tailored to their numeric literacy during shared decision-making. For patients presenting with arrhythmias or cardiomyopathy, extension of genetic testing and its implications will enable cascade screening, intervention to change the trajectory for specific genotype-phenotype profiles, and enable further development and evaluation of emerging targeted therapies.

Clinical presentations leading to arrhythmogenic left ventricular cardiomyopathy

OBJECTIVES

To describe a cohort of patients with arrhythmogenic left ventricular cardiomyopathy (ALVC), focusing on the spectrum of the clinical presentations.

METHODS

Patients were retrospectively evaluated between January 2012 and June 2020. Diagnosis was based on (1) ≥3 contiguous segments with subepicardial/midwall late gadolinium enhancement in the left ventricle (LV) at cardiac magnetic resonance plus a likely pathogenic/pathogenic arrhythmogenic cardiomyopathy (AC) associated genetic mutation and/or familial history of AC and/or red flags for ALVC (ie, negative T waves in V4-6/aVL, low voltages in limb leads, right bundle branch block like ventricular tachycardia) or (2) pathology examination of explanted hearts or autoptic cases suffering sudden cardiac death (SCD). Significant right ventricular involvement was an exclusion criterion.

RESULTS

Fifty-two patients (63% males, age 45 years (31-53)) composed the study cohort. Twenty-one (41%) had normal echocardiogram, 13 (25%) a hypokinetic non-dilated cardiomyopathy (HNDC) and 17 (33%) a dilated cardiomyopathy (DCM). Of 47 tested patients, 29 (62%) were carriers of a pathogenic/likely pathogenic DNA variant. Clinical contexts leading to diagnosis were SCD in 3 (6%), ventricular arrhythmias in 15 (29%), chest pain in 8 (15%), heart failure in 6 (12%) and familial screening in 20 (38%). Thirty patients (57%) had previously received a diagnosis other than ALVC with a diagnostic delay of 6 years (IQR 1-7).

CONCLUSIONS

ALVC is hidden in different clinical scenarios with a phenotypic spectrum ranging from normal LV to HNDC and DCM. Ventricular arrhythmias, chest pain, heart failure and SCD are the main clinical presentations, being familial screening essential for the affected relatives' identification.

Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) encompasses a group of conditions characterized by right ventricular fibrofatty infiltration, with a predominant arrhythmic presentation. First described in the late 1970s and early 1980s, it is now frequently recognized to have biventricular involvement. The prevalence is ∼1:2,000 to 1:5,000, depending on geographic location, and it has a slight male predominance. The diagnosis of ARVC is determined on the basis of fulfillment of task force criteria incorporating electrophysiological parameters, cardiac imaging findings, genetic factors, and histopathologic features. Risk stratification of patients with ARVC aims to identify those who are at increased risk of sudden cardiac death or sustained ventricular tachycardia. Factors including age, sex, electrophysiological features, and cardiac imaging investigations all contribute to risk stratification. The current management of ARVC includes exercise restriction, β-blocker therapy, consideration for implantable cardioverter-defibrillator insertion, and catheter ablation. This review summarizes our current understanding of ARVC and provides clinicians with a practical approach to diagnosis and management.

Diagnosis and Management of Rare Cardiomyopathies in Adult and Paediatric Patients. A Position Paper of the Italian Society of Cardiology (SIC) and Italian Society of Paediatric Cardiology (SICP)

Cardiomyopathies (CMPs) are myocardial diseases in which the heart muscle is structurally and functionally abnormal in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to cause the observed myocardial abnormality. Thought for a long time to be rare diseases, it is now clear that most of the CMPs can be easily observed in clinical practice. However, there is a group of specific heart muscle diseases that are rare in nature whose clinical/echocardiographic phenotypes resemble those of the four classical morphological subgroups of hypertrophic, dilated, restrictive, arrhythmogenic CMPs. These rare CMPs, often but not solely diagnosed in infants and paediatric patients, should be more properly labelled as specific CMPs. Emerging consensus exists that these conditions require tailored investigation and management. Indeed, an appropriate understanding of these conditions is mandatory for early treatment and counselling. At present, however, the multisystemic and heterogeneous presentation of these entities is a challenge for clinicians, and time delay in diagnosis is a significant concern. The aim of this paper is to define practical recommendations for diagnosis and management of the rare CMPs in paediatric or adult age. A modified Delphi method was adopted to grade the recommendations proposed by each member of the writing committee.

Arrhythmogenic Cardiomyopathy: Diagnosis, Evolution, Risk Stratification and Pediatric Population-Where Are We?

Arrhythmogenic cardiomyopathy (ACM) is a cardiomyopathy characterized by the occurrence of a high risk of life-threatening ventricular arrhythmias and sudden cardiac death even at presentation. Diagnosis, evolution and outcomes in adults have been extensively reported, but little data in pediatric population are available. Risk stratification in this particular setting is still a matter of debate and new risk factors are needed in a model of an ever more "individualized medicine".

Incidence and predictors of sudden cardiac death in arrhythmogenic right ventricular cardiomyopathy: a pooled analysis

AIMS

Arrhythmogenic right ventricular cardiomyopathy (ARVC), an inherited heart muscle abnormality, is a major cause of sudden cardiac death (SCD). However, the burden of SCD and risk factors in ARVC are not clearly described. Thus, we estimated the rates and predictors of SCD in ARVC in a meta-analysis.

METHODS AND RESULTS

PubMed, Embase, and Web of Science were searched through 7 April 2021. Prospective studies reporting SCD from ARVC cohorts were included. Data were independently extracted by two reviewers and pooled in a random-effects meta-analysis. Fifty-two studies (n = 5485 patients) with moderate-to-low risk of bias were included. The pooled annualized rates of SCD were 0.65 per 1000 [95% confidence interval 0.00-6.43, I2 0.00%] in those with an implantable cardioverter-defibrillator (ICD) and 7.21 (2.38-13.79, I2 0.0%) in non-ICD cohorts: 7.14 in probands and 8.44 for 2010 Task Force Criteria (TFC). Multivariable predictors of life-threatening arrhythmic events including SCD were: age at presentation [adjusted hazard ratio 0.98 (0.97-0.99)], male sex [2.08 (1.29-3.36)], right ventricular (RV) dysfunction [6.99 (2.17-22.49)], QRS fragmentation [6.55 (3.33-12.90)], T-wave inversion [1.12 (1.02-1.24)], syncope at presentation [2.83 (2.40-4.08)], previous non-sustained ventricular tachyarrhythmia [2.53 (1.44-4.45)], and the TFC score [1.96 (1.02-3.76)], (P < 0.05). Predictors of appropriate ICD therapy were RV dysfunction, syncope, and inducible ventricular arrhythmia (P < 0.01).

CONCLUSION

This meta-analysis demonstrates a high burden of SCD in ARVC patients, especially among probands and ARVC defined by the modified TFC. Better strategies are required to improve patient management and prevent SCD in ARVC. PROSPERO ID: CRD42020211761.

Prognostic Cardiac Magnetic Resonance Markers of Left Ventricular Involvement in Arrhythmogenic Cardiomyopathy for Predicting Heart Failure Outcomes

Background

Left ventricular (LV) involvement is frequently observed in arrhythmogenic cardiomyopathy (ACM). We investigated the association of LV myocardial assessment using cardiac magnetic resonance (CMR) with clinical outcomes including heart failure (HF)‐related events in ACM.

Methods and Results

We retrospectively analyzed 60 patients with ACM between 2005 and 2020 according to the 2010 Task Force Criteria and assessed HF‐related events (HF hospitalization, heart transplantation, and cardiac death) and ventricular tachycardia events. We analyzed CMR findings including late gadolinium enhancement (LGE) in all subjects and obtained mapping values (native T1, extracellular volume, and T2) on 30 (50%) patients out of them. Among the study population (mean age 49 years, 77% male), 41 (68%) patients had LV LGE. During a median follow‐up of 34 months, there were 13 (22%) HF‐related events, and 20 (30%) ventricular tachycardia events. Kaplan‐Meier survival analysis revealed that HF‐related events occurred only in patients with LV LGE (+) (versus LV LGE (‐), log‐rank P=0.006), and the events were not significantly different regarding right ventricular LGE (log‐rank P>0.999). When categorized by median value for each mapping parameter, HF‐related events occurred more in patients with higher native T1 (versus lower native T1, log‐rank P=0.002), and higher T2 (versus lower T2, log‐rank P=0.002), higher extracellular volume (versus lower extracellular volume, log‐rank P=0.002). However, regarding ventricular tachycardia events, there were no significant differences according to these CMR markers.

Conclusions

LV myocardial assessment using CMR with LGE imaging and native T1, T2, and extracellular volume markers were significantly associated with HF‐related event risk in patients with ACM.

Case report: DSP truncation variant p. R1951X leads to arrhythmogenic left ventricular cardiomyopathy

Background

Standardized diagnostic criteria for arrhythmogenic left ventricular cardiomyopathy (ALVC) have been recently proposed. The criteria emphasize structural left ventricle (LV) myocardial change on contrast-enhanced imaging and require the identification of gene variants associated with arrhythmogenic cardiomyopathy.

Case summary

A 21-year-old man presented for evaluation of exertional syncope and was found to have monomorphic ventricular tachycardia (VT) and an episode of polymorphic VT that degenerated to ventricular fibrillatory cardiac arrest. Documented premature ventricular contractions were of left bundle branch block, inferior axis morphology. Ventricular arrhythmias were successfully suppressed with β-blockade, amiodarone, and lidocaine, and a subcutaneous implantable cardioverter-defibrillator was implanted. Cardiac magnetic resonance imaging demonstrated normal-appearing right ventricle, reduced LV ejection fraction, and sub-epicardial scarring of basal-anterior and anterolateral LV segments. Endomyocardial biopsy showed lymphocytic myocarditis, and genetic testing revealed a pathogenic truncating mutation in the DSP gene, which encodes desmoplakin; this variant was also identified in the patient’s mother who carried a diagnosis of non-ischaemic cardiomyopathy. These findings are consistent with a diagnosis of ALVC.

Discussion

The clinical presentation of ALVC can be very dramatic. The differential for sub-epicardial LV myocardial fibrosis includes myocarditis, sarcoidosis, and in those with a suspicious family history or characteristic electrocardiogram findings, genetic cardiomyopathy. Prompt referral to a genetic counsellor can be lifesaving to patients and their family members.

Arrhythmogenic Right Ventricular Cardiomyopathy and Differential Diagnosis with Diseases Mimicking Its Phenotypes

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart muscle disease, which is characterized by fibro-fatty replacement of predominantly the right ventricle (RV). The disease can result in ventricular tachyarrhythmias and sudden cardiac death. Our understanding of the pathophysiology and clinical expressivity of ARVC has been continuously evolving. The diagnosis can be challenging due to its variable expressivity, incomplete penetrance and the lack of specific diagnostic criteria. Idiopathic RV outflow tract tachycardia, Brugada Syndrome, athlete’s heart, dilated cardiomyopathy, myocarditis, cardiac sarcoidosis, congenital aneurysms and diverticula may mimic clinical phenotypes of ARVC. This review aims to provide an update on the differential diagnosis of ARVC.

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

Background

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

Case presentation

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

Conclusions

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

Novel plasma biomarkers predicting biventricular involvement in arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart muscle disease characterized by fibrofatty replacement of the myocardium and ventricular arrhythmias. Biventricular involvement in ARVC may lead to heart failure. This study aimed to investigate the role of plasma biomarkers soluble (s)ST2, Galectin-3 (Gal-3) and GDF-15 in predicting biventricular involvement and adverse outcomes in ARVC.

METHODS AND RESULTS

ARVC patients from 2 independent cohorts, were studied. The Bejing (Chinese) cohort (n = 108) was the discovery cohort, whereas the Zurich (Swiss) cohort (n = 47) served as validation. All patients had a definite ARVC diagnosis at time of blood withdrawal. Biomarkers were independently correlated with NT-proBNP and left ventricular (LV)-function. ARVC patients with LV involvement had higher levels of sST2 and GDF-15 as compared to controls and patients with isolated right ventricle (RV) involvement. sST2 and GDF-15 were significantly correlated with late gadolinium enhancement in CMR and with adverse heart failure outcomes. Gal-3 was elevated in ARVC patients with and without LV involvement. The combined use of the three biomarkers (sST2, GDF-15 and NT-proBNP) showed the best performance in predicting LV involvement in both cohorts. Plasma drawn from the coronary arteries and coronary sinus indicated a transmyocardial elevation of sST2, but no transmyocardial gradient of GDF-15. After heart transplantation, both sST2 and GDF-15 returned to near-normal levels.

CONCLUSION

Our study showed that sST2 and GDF-15 may predict biventricular involvement in ARVC. The combined use of sST2, GDF-15 and NT-proBNP showed the best prediction of biventricular involvement in ARVC.

Understanding the molecular basis of cardiomyopathy

Inherited cardiomyopathies are a major cause of mortality and morbidity worldwide and can be caused by mutations in a wide range of proteins located in different cellular compartments. The present review is based on Dr. Ju Chen's 2021 Robert M. Berne Distinguished Lectureship of the American Physiological Society Cardiovascular Section, in which he provided an overview of the current knowledge on the cardiomyopathy-associated proteins that have been studied in his laboratory. The review provides a general summary of the proteins in different compartments of cardiomyocytes associated with cardiomyopathies, with specific focus on the proteins that have been studied in Dr. Chen's laboratory.

Diagnostic Challenges in Rare Causes of Arrhythmogenic Cardiomyopathy—The Role of Cardiac MRI

Arrhythmogenic right ventricular dysplasia (ARVD) is a rare genetic condition of the myocardium, with a significantly high risk of sudden death. Recent genetic research and improved understanding of the pathophysiology tend to change the ARVD definition towards a larger spectrum of myocardial involvement, which includes, in various proportions, both the right (RV) and left ventricle (LV), currently referred to as ACM (arrhythmogenic cardiomyopathy). Its pathological substrate is defined by the replacement of the ventricular myocardium with fibrous adipose tissue that further leads to inadequate electrical impulses and translates into varies degrees of malignant ventricular arrythmias and dyskinetic myocardium movements. Particularly, the cardio-cutaneous syndromes of Carvajal/Naxos represent rare causes of ACM that might be suspected from early childhood. The diagnostic is sometimes challenging, even with well-established rTFC or Padua criteria, especially for pediatric patients or ACM with LV involvement. Cardiac MRI gain more and more importance in ACM diagnostic especially in non-classical forms. Furthermore, MRI is useful in highlighting myocardial fibrosis, fatty replacement or wall movement with high accuracy, thus guiding not only the depiction, but also the patient’s stratification and management.

Genetic predisposition study of heart failure and its association with cardiomyopathy

Heart failure (HF) is a clinical condition distinguished by structural and functional defects in the myocardium, which genetic and environmental factors can induce. HF is caused by various genetic factors that are both heterogeneous and complex. The incidence of HF varies depending on the definition and area, but it is calculated to be between 1 and 2% in developed countries. There are several factors associated with the progression of HF, ranging from coronary artery disease to hypertension, of which observed the most common genetic cause to be cardiomyopathy. The main objective of this study is to investigate heart failure and its association with cardiomyopathy with their genetic variants. The selected novel genes that have been linked to human inherited cardiomyopathy play a critical role in the pathogenesis and progression of HF. Research sources collected from the human gene mutation and several databases revealed that numerous genes are linked to cardiomyopathy and thus explained the hereditary influence of such a condition. Our findings support the understanding of the genetics aspect of HF and will provide more accurate evidence of the role of changing disease accuracy. Furthermore, a better knowledge of the molecular pathophysiology of genetically caused HF could contribute to the emergence of personalized therapeutics in future.

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

Background:

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

Methods:

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

Results:

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

Conclusions:

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

Clinical and genetic features of arrhythmogenic cardiomyopathy: diagnosis, management and the heart failure perspective

Background

Arrhythmogenic cardiomyopathy (ACM) is an emerging new concept of a life-threatening heart muscle disorder due not only to desmosome gene mutations, but also to non-desmosome genes, such as filamin C, lamin A/C, phospholamban, transmembrane protein 43, titin, SCN5A and RNA binding motif protein 20.Multi-modality imaging along with genetic testing are important tools for risk stratification to tailor treatment to a single patient. Cardiac magnetic resonance imaging (CMR) with late gadolinium enhancement (LGE) is the gold standard for evaluating left and right ventricular structure and function, edema, and fibrosis. The identification of regional fibrosis with LGE has prognostic value. The management of ACM involves several aspects: treatment of arrhythmias and heart failure, risk stratification, implantable cardioverter-defibrillator (ICD) placement, exercise restrictions, and life-style changes. The decision for ICD placement in ACM patients is not well established and should be made weighing risks and benefits. However, the presence of specific genotypes can allow a precision medicine approach. In ACM patients with only mild left ventricular dysfunction but phospholamban, filamin C or lamin A/C mutations, an ICD is now considered a reasonable approach.

Aim of Review

We sought to provide an overview of clinical and genetic feature of arrhythmogenic cardiomyopathy providing epidemiology, imaging, diagnostic and treatment information, using a systematic genetic approach.

Arrhythmogenic right ventricular cardiomyopathy in the pediatric population

PURPOSE OF REVIEW

Review the current state of the art of arrhythmogenic right ventricular cardiomyopathy (ARVC) diagnosis and risk stratification in the pediatric population.

RECENT FINDINGS

ARVC is an inherited cardiomyopathy characterized by progressive myocyte loss and fibrofatty replacement of predominantly the right ventricle and high risk of ventricular arrhythmias and sudden cardiac death (SCD). ARVC is one of the leading causes of arrhythmic cardiac arrest in young people. Early diagnosis and accurate risk assessment are challenging, especially in children who often exhibit little to no phenotype, even if genotype positive. Multimodal imaging provides more detailed assessment of the right ventricle and has been shown in pediatric patients to identify earlier preclinical disease expression. Identification of patients with ARVC allows the clinician to intervene early with appropriate exercise restrictions, even if genotype positive only without phenotypic expression. Emphasis should be placed on stratifying the patient's risk of ventricular arrhythmias and SCD.

SUMMARY

ARVC is a challenging diagnosis to make in adolescents who often do not exhibit clinical symptoms. Newer multimodal imaging techniques and improvements in genetic testing and biomarkers should help improve early diagnosis. Exercise restriction for children with ARVC has been shown to reduce disease advancement and decreases the risk of a life-threatening event.

Myocardial strain measured via two-dimensional speckle-tracking echocardiography in a family diagnosed with arrhythmogenic left ventricular cardiomyopathy

BACKGROUND

Arrhythmogenic cardiomyopathy is a myocardial disorder characterized by ventricular arrhythmias, right and/or left ventricular involvement, and fibrofatty infiltrations in the myocardium. We report a family diagnosed with arrhythmogenic left ventricular cardiomyopathy (ALVC) and depict their echocardiographic characteristics.

METHODS AND RESULTS

Fifteen family members were divided into three groups based on whether they carried the TMEM43 mutation and had been diagnosed with ALVC. Eight of them had TMEM43 mutations, and four were diagnosed with ALVC according to the Padua criteria. Only the proband experienced sudden cardiac death and had a dilated left ventricle. Left ventricular ejection fraction was reduced in two patients; however, left ventricular global longitudinal strain was depressed in three patients. Low QRS voltages in limb leads were evident in three patients, and five patients had frequent ventricular premature contractions. Late gadolinium enhancement was evident in three patients. Left ventricular layer-specific strain showed that the transmural strain gradient ratio was increased in patients diagnosed with ALVC, and it was elevated in the genotype-positive and phenotype-negative groups compared with healthy individuals.

CONCLUSION

Global left ventricular longitudinal strain better evaluated left ventricular function than left ventricular ejection fraction. The transmural strain gradient ratio was elevated in patients diagnosed with ALVC, suggesting that it was useful for the evaluation of ALVC.

Pathogenesis, Diagnosis and Risk Stratification in Arrhythmogenic Cardiomyopathy

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

Histopathological Features and Protein Markers of Arrhythmogenic Cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is a heritable heart muscle disease characterized by syncope, palpitations, ventricular arrhythmias and sudden cardiac death (SCD) especially in young individuals. It is estimated to affect 1:5,000 individuals in the general population, with >60% of patients bearing one or more mutations in genes coding for desmosomal proteins. Desmosomes are intercellular adhesion junctions, which in cardiac myocytes reside within the intercalated disks (IDs), the areas of mechanical and electrical cell-cell coupling. Histologically, ACM is characterized by fibrofatty replacement of cardiac myocytes predominantly in the right ventricular free wall though left ventricular and biventricular forms have also been described. The disease is characterized by age-related progression, vast phenotypic manifestation and incomplete penetrance, making proband diagnosis and risk stratification of family members particularly challenging. Key protein redistribution at the IDs may represent a specific diagnostic marker but its applicability is still limited by the need for a myocardial sample. Specific markers of ACM in surrogate tissues, such as the blood and the buccal epithelium, may represent a non-invasive, safe and inexpensive alternative for diagnosis and cascade screening. In this review, we shall cover the most relevant biomarkers so far reported and discuss their potential impact on the diagnosis, prognosis and management of ACM.

Imaging the "Hot Phase" of a Familiar Left-Dominant Arrhythmogenic Cardiomyopathy

We describe the case of a young man with an initial diagnosis of acute myocarditis that was finally recognized as a familial left-dominant arrhythmogenic cardiomyopathy. The diagnostic process was also based on demonstration, serial cardiac magnetic resonance imaging, and typical patterns of myocardial damage, including features of the disease’s inflammatory “hot phase”.

Acute Myocardial Infarction-Like Events in Related Patients With a Desmoplakin-Associated Arrhythmogenic Cardiomyopathy

Patients with familial arrhythmogenic cardiomyopathy typically present with ventricular arrhythmias or progressive heart failure. This paper characterizes a rare presentation of an underlying genetic cardiomyopathy with clinical manifestations mimicking an acute myocardial infarction in 2 siblings, each with the same mutation in the desmoplakin (DSP) gene. (Level of Difficulty: Advanced.)

Cardiac arrest as first presentation of arrhythmogenic left ventricular cardiomyopathy due to Filamin C mutation: a case report

Background

Arrhythmogenic left ventricular cardiomyopathy (ALVC) is a rare form of arrhythmogenic cardiomyopathy characterized by fibrofatty replacement of left ventricular myocardium, malignant arrhythmia, and sudden cardiac death. The definition incorporates several genetic causes, including pathogenic variation in the Filamin C gene (FLNC). Although awareness of ALVC has improved, identification remains challenging and diagnostic criteria continue to evolve.

Case summary

A 50-year-old athletic male was admitted following an out-of-hospital cardiac arrest due to ventricular tachycardia (VT) whilst playing football. Coronary angiography revealed unobstructed epicardial vessels and the diagnosis of ALVC was suggested by cardiovascular magnetic resonance imaging, which demonstrated a mildly dilated and moderately impaired left ventricle with epicardial late gadolinium enhancement in the basal to mid-lateral walls and subendocardial septum. Initial testing with a cardiomyopathy and arrhythmia gene panel was negative but extended testing uncovered a likely pathogenic variant in FLNC. Subsequently, the patient experienced a recurrence of sustained VT necessitating implantable cardioverter-defibrillator (ICD) therapies, ultimately undergoing a combined epicardial and endocardial VT ablation 4 years after presentation. Six months post-ablation, he was asymptomatic and his arrhythmia rendered quiescent.

Discussion

Arrhythmogenic cardiomyopathy should be considered in the evaluation of an initially unexplained cardiac arrest. This case characterizes the clinical features of a patient with FLNC cardiomyopathy and emphasizes the utility of genetic testing using modern gene panels in patients with comparable phenotypes. We also demonstrate that optimal medical therapy with antiarrhythmic drugs, exercise restriction, ICD insertion, and catheter ablation can be useful in the management of ALVC with positive outcomes

Left Ventricular Longitudinal Dyssynchrony by CMR Feature Tracking Is Related to Adverse Prognosis in Advanced Arrhythmogenic Cardiomyopathy

Objectives: Left ventricular (LV) involvement has been associated with unfavorable prognosis in arrhythmogenic cardiomyopathy (ACM). We aim to evaluate LV mechanics by cardiovascular magnetic resonance-feature tracking (CMR-FT) in ACM patients with right ventricular (RV) dysfunction. Methods: We retrospectively recruited ACM patients diagnosed according to the revised Task Force Criteria (rTFC) from January 2015 to July 2017. All patients underwent CMR examinations and collections of clinical, electrocardiographic data. The strain and dyssynchrony parameters of LV and RV were analyzed. These patients were followed, and primary study outcome was defined as a composite of cardiovascular events (arrhythmic events and heart transplantation), secondary study outcome included arrhythmic events. Results: Eighty-nine ACM patients (40.40 ± 13.98 years, 67.42% male) were included. LV and RV ejection fractions were 49.12 ± 12.02% and 22.28 ± 10.11%, respectively. During a median (IQR) follow-up for 18.20 (11.60-30.04) months, 30 patients experienced cardiovascular events which included 22 patients who experienced arrhythmic events. Patients with cardiovascular events had impaired LV global longitudinal strain (-10.82 ± 2.77 vs. -12.61 ± 3.18%, p = 0.010), impaired LV global circumferential strain (-11.81 ± 2.40 vs. -13.04 ± 2.83%, p = 0.044), and greater LV longitudinal dyssynchrony (LVLD) (80.98 ± 30.98 vs. 64.23 ± 25.51 ms, p = 0.012) than those without. After adjusting for age, sex, and other confounding factors, LVLD ≥89.15 ms was an independent risk factor for cardiovascular events (HR: 4.50, 95% CI: 1.94 to 10.42; p = 0.001) and for arrhythmic events (HR: 4.79, 95% CI: 1.74 to 13.20; p = 0.003). Conclusions: LVLD by CMR-FT was an independent risk factor for cardiovascular and arrhythmic events in ACM patients in advanced stage, which could provide prognostic value for this subtype.

Arrhythmogenic right ventricular cardiomyopathy in Bulldogs: Evaluation of clinical and histopathologic features, progression, and outcome in 71 dogs (2004-2016)

OBJECTIVES

This study aimed to characterize the clinical and histopathological features of arrhythmogenic right ventricular cardiomyopathy (ARVC) in English Bulldogs, American Bulldogs, and Bulldog-type mixed breed dogs and assess affected Bulldogs for a striatin gene mutation previously reported in Boxers with ARVC.

ANIMALS

Seventy-one Bulldogs fit the inclusion criteria. Genetic analysis was performed on five dogs. Cardiac post-mortem evaluations were performed on two dogs.

METHODS

Medical records from a single veterinary cardiology group (CVCA) were retrospectively evaluated. Tissue and blood samples were submitted for histopathological analysis and genetic testing in select patients.

RESULTS

Presenting complaints included syncope (38%), arrhythmia (81.7%), or murmur (34.2%) documented on examination. On presentation, congestive heart failure (CHF) was diagnosed in 22 (31%) dogs, and 58 (81.7%) had ventricular arrhythmias. On bivariable analyses, the two-dimensional (2D) left atrial-to-aortic root ratio (LA:Ao) was the only prognostic variable significantly associated with survival time. Dogs with 2D LA:Ao below the mean (1.41) had longer median survival to all-cause mortality (12 months; 95% confidence interval [CI] 6.0-15.0 months) than those with 2D LA:Ao above the mean (four months; 95% CI 2.0-6.0 months; p=0.0384). Most dogs (54%) died from cardiac disease, with 42.1% experiencing sudden death. The median time from diagnosis to cardiac death was four months.

CONCLUSIONS

Arrhythmogenic right ventricular cardiomyopathy affects Bulldogs with both arrhythmogenic and dilated-type phenotypes. Despite variable arrhythmia severity and predominantly right-sided involvement in many dogs, an increase in left atrial size was the only significant predictor of mortality in this sample of dogs.

Endomyocardial Biopsy: The Forgotten Piece in the Arrhythmogenic Cardiomyopathy Puzzle

Background Endomyocardial biopsy (EMB) is part of 2010 Task Force Criteria (TFC) for arrhythmogenic right ventricular cardiomyopathy (ARVC). However, its usage has been curtailed because of its low presumed diagnostic yield, and it is now a poorly used tool. This study aims to analyze the contribution of EMB to the final diagnosis of ARVC. Methods and Results We included 104 consecutive patients evaluated for a suspicion of ARVC, who were referred for EMB. Patients with suspected left dominant pattern were excluded from the primary analysis. Subjects were initially stratified according to TFC without considering EMB. After EMB, patients were reclassified accordingly, and the reclassification rate was calculated. EMB yielded a diagnostic finding in 92 patients (85.5%). After including EMB evaluation, 20 (43%) more patients "at risk" received a definite diagnosis of ARVC. Overall, 59 patients received a definite diagnosis of ARVC, 34% only after EMB. EMB appeared to be the better-performing exam with respect to the final diagnosis (β, 2.2; area uder the curve, 0.73; P<0.05). The reclassification improvement after EMB measured 28%. TFC score increased from 3.5±1.3 to 4.3±1.4 (P<0.001). Notably, active inflammation was present in 6 (10%) patients. Minor complications were reported in only 2% of the cohort. In patients with suspected left-dominant disease, conventional TFC performed poorly. Conclusions Electroanatomic voltage mapping-guided EMB was safe and yielded an optimal diagnostic yield. It allowed upgrading of the diagnosis of nearly one-third of the patients considered "at risk." Classical TFC without EMB performed poorly in patients with the left dominant form of ARVC.

Myocardial fibrosis: morphologic patterns and role of imaging in diagnosis and prognostication

Myocardial fibrosis is defined as an increased amount of collagen in the myocardium relative to cardiac myocytes. Two main morphologic patterns are recognized: 1) replacement fibrosis, which occurs in response to myocyte necrosis (myocardial scarring); and 2) interstitial fibrosis, which is usually a diffuse process and has been shown to be reversible and treatable. Replacement and interstitial fibrosis often coexist and are a constant feature of pathologic cardiac remodeling. In the last twenty years, there has been significant interest in developing objective non-invasive methods to identify and quantitatively assess myocardial fibrosis in vivo, both for diagnostic purposes and to improve stratification of patients. The present Review focuses on the morphologic patterns of myocardial fibrosis observed either at autopsy and heart transplant, or in vivo by non-invasive imaging techniques. Main aim is to provide clues for the differential diagnosis, with emphasis on entities whose diagnosis may be challenging. An update on the diagnostic and prognostic role of imaging, along with recent data on available biomarkers, is also proposed.

Evolving Diagnostic Criteria for Arrhythmogenic Cardiomyopathy

Criteria for diagnosis of arrhythmogenic cardiomyopathy (ACM) were first proposed in 1994 and revised in 2010 by a Task Force. Although the Task Force criteria demonstrated a good accuracy for diagnosis of the original right ventricular phenotype (arrhythmogenic right ventricular cardiomyopathy), they lacked sensitivity for identification of the expanding phenotypic spectrum of ACM, which includes left‐sided variants and did not incorporate late‐gadolinium enhancement findings by cardiac magnetic resonance. The 2020 International criteria (“Padua criteria”) have been developed by International experts with the aim to improve the diagnosis of ACM by providing new criteria for the diagnosis of left ventricular phenotypic features. The key upgrade was the incorporation of tissue characterization findings by cardiac magnetic resonance for noninvasive detection of late‐gadolinium enhancement/myocardial fibrosis that are determinants for characterization of arrhythmogenic biventricular and left ventricular cardiomyopathy. The 2020 International criteria are heavily dependent on cardiac magnetic resonance, which has become mandatory to characterize the ACM phenotype and to exclude other diagnoses. New criteria regarding left ventricular depolarization and repolarization ECG abnormalities and ventricular arrhythmias of left ventricular origin were also provided. This article reviews the evolving approach to diagnosis of ACM, going back to the 1994 and 2010 International Task Force criteria and then grapple with the modern 2020 International criteria.

Cardiac magnetic resonance features of left dominant arrhythmogenic cardiomyopathy: differential diagnosis with myocarditis

Cardiac magnetic resonance (CMR) findings suggesting a suspected left-dominant arrhythmogenic cardiomyopathy (LDAC) may be difficult to distinguish from those related to previous myocarditis; however, especially in patients with ventricular arrhythmias (VA) with ECG morphology consistent with a left ventricle (LV) origin differential diagnosis is fundamental. Aim of the study was to identify potential imaging features at CMR specific for LDAC diagnosis. Between January 2011 and December 2019, we enrolled 15 consecutive stable patients with a recent diagnosis of significant VA and ECG morphology consistent with a LV origin, detection of potential LV arrhythmic substrate at CMR and undergoing a clinically-indicated LV endomyocardial biopsy showing tissue abnormalities consistent with the diagnosis of LDAC. From the same CMR-endomyocardial biopsy registry, a second group of 30 consecutive patients who underwent CMR and biopsy with a histological diagnosis of previous myocarditis were identified. (1) Subepicardial LGE at the level of the posterolateral wall of the LV was detected in 13 cases of LDAC vs. 21 cases of myocarditis; (2) fat infiltration, and particularly subepicardial posterolateral fat infiltration, was found in almost all LDAC patients vs. one myocarditis only (p < 0.01). (3) No differences in other CMR findings or in any clinical or echocardiographic parameters were found between patients with a biopsy consistent with LDAC vs. myocarditis. In patients with significant VA and ECG morphology consistent with a LV origin, the presence of morpho-functional involvement of the subepicardial layer of LV posterolateral wall at CMR (LGE, fat infiltration, wall dyskinesis) supports LDAC diagnosis.

MicroRNAs in Hypertrophic, Arrhythmogenic and Dilated Cardiomyopathy

MicroRNAs (miRNAs) are a class of non-coding RNAs of about 20 nucleotides in length, involved in the regulation of many biochemical pathways in the human body. The level of miRNAs in tissues and circulation can be deregulated because of altered pathophysiological mechanisms; thus, they can be employed as biomarkers for different pathological conditions, such as cardiac diseases. This review summarizes published findings of these molecular biomarkers in the three most common structural cardiomyopathies: human dilated, arrhythmogenic and hypertrophic cardiomyopathy.

The prevalence of left and right bundle branch block morphology ventricular tachycardia amongst patients with arrhythmogenic cardiomyopathy and sustained ventricular tachycardia: insights from the European Survey on Arrhythmogenic Cardiomyopathy

AIMS

In arrhythmogenic cardiomyopathy (ACM), sustained ventricular tachycardia (VT) typically displays a left bundle branch block (LBBB) morphology while a right bundle branch block (RBBB) morphology is rare. The present study assesses the VT morphology in ACM patients with sustained VT and their clinical and genetic characteristics.

METHODS AND RESULTS

Twenty-six centres from 11 European countries provided information on 954 ACM patients who had ≥1 episode of sustained VT spontaneously documented during patients' clinical course. Arrhythmogenic cardiomyopathy was defined according to the 2010 Task Force Criteria, and VT morphology according to the QRS pattern in V1. Overall, 882 (92.5%) patients displayed LBBB-VT alone and 72 (7.5%) RBBB-VT [alone in 42 (4.4%) or in combination with LBBB-VT in 30 (3.1%)]. Male sex prevalence was 79.3%, 88.1%, and 56.7% in the LBBB-VT, RBBB-VT, and LBBB + RBBB-VT groups, respectively (P = 0.007). First RBBB-VT occurred 5 years after the first LBBB-VT (46.5 ± 14.4 vs 41.1 ± 15.8 years, P = 0.011). An implanted cardioverter-defibrillator was more frequently implanted in the RBBB-VT (92.9%) and the LBBB + RBBB-VT groups (90%) than in the LBBB-VT group (68.1%) (P < 0.001). Mutations in PKP2 predominated in the LBBB-VT (65.2%) and the LBBB + RBBB-VT (41.7%) groups while DSP mutations predominated in the RBBB-VT group (45.5%). By multivariable analysis, female sex was associated with LBBB + RBBB-VT (P = 0.011) while DSP mutations were associated with RBBB-VT (P < 0.001). After a median follow-up of 103 (51-185) months, death occurred in 106 (11.1%) patients with no intergroup difference (P = 0.176).

CONCLUSION

RBBB-VT accounts for a significant proportion of sustained VTs in ACM. Sex and type of pathogenic mutations were associated with VT type, female sex with LBBB + RBBB-VT, and DSP mutation with RBBB-VT.

Insights Into Genetics and Pathophysiology of Arrhythmogenic Cardiomyopathy

Purpose of Review

Arrhythmogenic cardiomyopathy (ACM) is a genetic disease characterized by life-threatening ventricular arrhythmias and sudden cardiac death (SCD) in apparently healthy young adults. Mutations in genes encoding for cellular junctions can be found in about half of the patients. However, disease onset and severity, risk of arrhythmias, and outcome are highly variable and drug-targeted treatment is currently unavailable.

Recent Findings

This review focuses on advances in clinical risk stratification, genetic etiology, and pathophysiological concepts. The desmosome is the central part of the disease, but other intercalated disc and associated structural proteins not only broaden the genetic spectrum but also provide novel molecular and cellular insights into the pathogenesis of ACM. Signaling pathways and the role of inflammation will be discussed and targets for novel therapeutic approaches outlined.

Summary

Genetic discoveries and experimental-driven preclinical research contributed significantly to the understanding of ACM towards mutation- and pathway-specific personalized medicine.

Acute myocarditis: aetiology, diagnosis and management

Acute myocarditis is a serious, likely underdiagnosed condition affecting people of all ages and for which the number of UK hospital admissions is rising. A primary diagnosis of myocarditis accounted for 0.04% (36.5 per 100,000) of all hospital admissions in England between 1998 and 2017, although this is likely to be an underestimate of the true burden of myocarditis. The aetiology is broad, including infective and inflammatory conditions as well as exposure to toxic agents. Clinical features are varied and overlap with other acute cardiac conditions making diagnosis a challenge. Cardiovascular magnetic resonance imaging currently serves as the gold standard non-invasive diagnostic modality. If an underlying aetiological process is identified, then therapy may be directed at the cause; however, for most, treatment is supportive and aimed at managing any complications such as heart failure or arrhythmias. There is emerging evidence for immunosuppressive therapy in certain cases. Prognosis is generally good with recovery in most; however, up to 30% with biopsy-proven myocarditis progress to develop a dilated cardiomyopathy and its potential associated complications. All-cause mortality in the UK for patients presenting to hospital with acute myocarditis is approximately 4%.

Pharmacological suppression of the WNT signaling pathway attenuates age-dependent expression of the phenotype in a mouse model of arrhythmogenic cardiomyopathy

Introduction

Arrhythmogenic cardiomyopathy (ACM) is a genetic disease of the myocardium, characterized by cardiac arrhythmias, dysfunction, and sudden cardiac death. The pathological hallmark of ACM is fibro-adipocytes replacing cardiac myocytes. The canonical WNT pathway is implicated in the pathogenesis of ACM.

Aim

The study aimed to determine the effects of the suppression of the WNT pathway on cardiac phenotype in a mouse model of ACM.

Methods and Results

One copy of the Dsp gene, a known cause of ACM in humans, was deleted specifically in cardiac myocytes (Myh6-Cre-Dsp ^W/F). Three-month-old wild type and Myh6-Cre-Dsp ^W/F mice, without a discernible phenotype, were randomized to either untreated or daily administration of a vehicle (placebo), or WNT974, the latter an established inhibitor of the WNT pathway, for three months. The Myh6-Cre-Dsp ^W/F mice in the untreated or placebo-treated groups exhibited cardiac dilatation and dysfunction, increased myocardial fibrosis, and apoptosis upon completion of the study, which was verified by complementary methods. Daily administration of WNT974 prevented and/or attenuated evolving cardiac dilatation and dysfunction, normalized myocardial fibrosis, and reduced apoptosis, compared to the untreated or placebo-treated groups. However, administration of WNT974 increased the number of adipocytes only in the Myh6-Cre-Dsp ^W/F hearts. There were no differences in the incidence of cardiac arrhythmias and survival rates.

Conclusion

Suppression of the WNT pathway imparts salutary phenotypic effects by preventing or attenuating age-dependent expression of cardiac dilatation and dysfunction, myocardial fibrosis, and apoptosis in a mouse model of ACM. The findings set the stage for large-scale studies and studies in larger animal models to test the beneficial effects of the suppression of the WNT pathway in ACM.

One sentence summary

Suppression of the WNT signaling pathway has beneficial effects on cardiac dysfunction, myocardial apoptosis, and fibrosis in a mouse model of arrhythmogenic cardiomyopathy.