Introduction

Phenotype is defined as a set of observable characteristics of an individual resulting from the interaction of their genotype with the environment. It differs from ‘disease’ in that it does not reflect the mechanism by which it is produced. In 1982, the term arrhythmogenic right ventricular dysplasia was first used to describe a clinical phenotype characterised by ventricular arrhythmias of left bundle branch block (LBBB) configuration accompanied by right ventricular dilatation, wall motion abnormalities and fibrofatty replacement of the myocardium.1 Arrhythmogenic right ventricular cardiomyopathy (ARVC) became the preferred descriptor when subsequent histopathological analysis revealed that myocyte atrophy as a consequence of progressive cell death occurred after birth.2 3 Initial clinical diagnostic criteria for ARVC were based on descriptions of patients with advanced disease,4 but discovery of its genetic basis, and the phenotyping of large patient cohorts including relatives, revealed a broader disease spectrum in which right ventricle (RV) and left ventricle (LV) can be involved.5 The disease paradigm has expanded further with the recognition of new disease genes causing similar phenotypes. Hence, terms such as left-dominant arrhythmogenic cardiomyopathy, arrhythmic dilated cardiomyopathy or simply arrhythmogenic cardiomyopathy (AC) are increasingly used to describe the clinical phenotype observed in a family of disorders in which frequent ventricular arrhythmia and dysfunction of one or both ventricles are the defining features. In this article, we review this emerging concept with a focus on the …