Detection of enterovirus RNA in the myocardium of a patient with arrhythmogenic right ventricular cardiomyopathy by in situ hybridization

Circadian and Seasonal Pattern of Arrhythmic Events in Arrhythmogenic Cardiomyopathy Patients

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

Inflammation in the Pathogenesis of Arrhythmogenic Cardiomyopathy: Secondary Event or Active Driver?

Arrhythmogenic cardiomyopathy (ACM) is a rare inherited cardiac disease characterized by arrhythmia and progressive fibro-fatty replacement of the myocardium, which leads to heart failure and sudden cardiac death. Inflammation contributes to disease progression, and it is characterized by inflammatory cell infiltrates in the damaged myocardium and inflammatory mediators in the blood of ACM patients. However, the molecular basis of inflammatory process in ACM remains under investigated and it is unclear whether inflammation is a primary event leading to arrhythmia and myocardial damage or it is a secondary response triggered by cardiomyocyte death. Here, we provide an overview of the proposed players and triggers involved in inflammation in ACM, focusing on those studied using in vivo and in vitro models. Deepening current knowledge of inflammation-related mechanisms in ACM could help identifying novel therapeutic perspectives, such as anti-inflammatory therapy.

Molecular mechanisms of arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy is a genetic disorder characterized by the risk of life-threatening arrhythmias, myocardial dysfunction and fibrofatty replacement of myocardial tissue. Mutations in genes that encode components of desmosomes, the adhesive junctions that connect cardiomyocytes, are the predominant cause of arrhythmogenic cardiomyopathy and can be identified in about half of patients with the condition. However, the molecular mechanisms leading to myocardial destruction, remodelling and arrhythmic predisposition remain poorly understood. Through the development of animal, induced pluripotent stem cell and other models of disease, advances in our understanding of the pathogenic mechanisms of arrhythmogenic cardiomyopathy over the past decade have brought several signalling pathways into focus. These pathways include canonical and non-canonical WNT signalling, the Hippo-Yes-associated protein (YAP) pathway and transforming growth factor-β signalling. These studies have begun to identify potential therapeutic targets whose modulation has shown promise in preclinical models. In this Review, we summarize and discuss the reported molecular mechanisms underlying the pathogenesis of arrhythmogenic cardiomyopathy.

Arrhythmogenic right ventricular cardiomyopathy/dysplasia: is there a role for viruses?

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a primary heart muscle disease characterized structurally by progressive fibrofatty replacement of the right ventricle and clinically by life-threatening ventricular arrhythmias with left bundle branch block morphology. Recently, there has been a great deal of interest on ARVC/D as a cause of sudden death in young people, and it has been reported as the most common cause of exercise-related sudden death among competitive athletes in Italy. An autosomic dominant familial occurrence has been recognized, and four disease-causing genes have been recently identified in the dominant forms: ryanodinic cardiac receptor 2, desmoplakin, plakophilin 2, and transforming growth factor (TGF)-beta3. Furthermore, plakoglobin has been identified as the first gene responsible for the recessive variant of ARVC/D associated with palmoplantar keratosis and woolly hair (Naxos disease). However, although much progress has been made in molecular genetics, up to today, the pathogenesis of the disease is still unclear. The occurrence of myocyte apoptosis has been documented, suggesting that recurrent bouts of apoptosis may account for progressive atrophy of the myocardium, which is then replaced by fibrofatty tissue. Considering the frequent finding of myocarditis at histology, an inflammatory theory has been advanced, and infective mechanisms have been postulated to contribute to the onset and the progression of the disease. Cardiotropic viruses have been detected in some ARVC/D cases, and they have been proposed as possible etiologic agents. Several etiopathogenetic theories are herein presented in detail with particular attention to the inflammatory/infective one and its possible links between this and the genetic/dystrophic theories are discussed.

[Arrhythmogenic cardiomyopathy as cause of sudden death in Spain. Report of 21 cases]

INTRODUCTION AND OBJECTIVES

Arrhythmogenic cardiomyopathy is a myocardial disease of unknown origin characterized by progressive replacement of right and/or left ventricular myocardium by fibrofatty tissue. Young adult people are more frequently affected and symptoms include palpitations, syncopes or sudden death. The objective of this study is to assess the frequency and characteristics of arrhythmogenic cardiomyopathy as a cause of sudden death in a series of cases in Spain.

MATERIAL AND METHODS

Among the sudden death cases studied at the Toxicology Institute of Madrid between 1991 and 1997, those with arrhythmogenic cardiomyopathy diagnosis were analysed.

RESULTS

21 cases were diagnosed (0.62% of all sudden deaths and 6.8% of sudden deaths under 35 years). There were 20 males and one female (mean age 24.5 +/- 9.37 years); eleven (52.3%) died during sport activity and 8 (38%) had previous exercise related symptoms. In only two cases other members of the family had died suddenly and only one had been diagnosed in life. Biventricular involvement was observed in 13 cases; isolated involvement of the left ventricle in 4, and isolated involvement of the right ventricle in 4.

CONCLUSIONS

Arrhythmogenic cardiomyopathy is a relatively frequent cause of sudden death in the young population in Spain. It is very often the first manifestation of the disease. The myocardial involvement is more frequently biventricular than isolated in the right ventricle. The diagnosis could be difficult for cardiologists, pathologists and forensic doctors.