Arrhythmogenic Cardiomyopathy: Focus on Imaging

Abstract

Abstract Arrhythmogenic cardiomyopathy (AC) is a broad term denoting subclinical or clinical heart muscle disease which presents predominantly with serious arrhythmias. Heart muscle disease or cardiomyopathy can present as an abnormal electrocardiogram, heart failure, syncope, arrhythmias, or sudden cardiac death. Ventricular arrhythmogenesis is the hallmark of this entity. A small but significant number of athletes experiencing sudden cardiac death have AC. AC has complex and ill-understood pathophysiology. Usually, arrhythmogenic cardiomyopathies are genetic or hereditary. In these patients, muscle hypertrophy, dilatation, cardiac fat metaplasia, and fibrosis provide the anatomic substrate for arrhythmias. Hereditary cardiomyopathies are considered primary diseases of the cardiac myocytes and their intercellular junctions. Secondary diseases of the myocardium due to coronary artery disease, hypertension, valvular heart disease, etc., are excluded from this nomenclature. Channelopathies are also not included in the spectrum of AC. Initially, AC was reported as a single phenotype and labeled arrhythmogenic right ventricular dysplasia, and it was considered a desmosomal disorder. Our current knowledge about this entity has expanded to include multiple variants of this entity with diverse genetic mutations. Its genotypes and phenotypes are still evolving. As of now, distinct desmosomal, cytoskeletal, nuclear, and sarcomeric ACs have been reported. Geography-specific syndromic ACs have also been described. It is a cell-to-cell disjunction cardiomyopathy impairing the inter- and intracellular signal transduction. Gap junctions make AC unique in the sense that arrhythmias precede structural alterations or heart failure in the vast majority. There is also a distinct arrhythmogenic atrial cardiomyopathy. Diagnostic algorithms include morphofunctional, depolarization and repolarization abnormalities, distinct genetic mutations, and typical arrhythmias which serve as the basis of scoring systems devised to diagnose AC. This review discusses salient aspects of AC focusing on imaging observations.