Imaging Phenotype vs Genotype in Nonhypertrophic Heritable Cardiomyopathies

Advances in cardiovascular imaging increasingly afford unique insights into heritable myocardial disease. As clinical presentation of genetic cardiomyopathies may range from nonspecific symptoms to sudden cardiac death, accurate diagnosis has implications for individual patients as well as related family members. The initial consideration of genetic cardiomyopathy may occur in the imaging laboratory, where one must recognize the patient with arrhythmogenic right ventricular cardiomyopathy (ARVC) among the many with ventricular arrhythmia referred to define myocardial substrate. Accurate diagnosis of the patient presenting with dyspnea and palpitations whose first-degree relatives have lamin A/C cardiomyopathy may warrant genetic testing1, 2 plus imaging of diastolic function and myocardial fibrosis3. As advances in cardiac imaging afford detection of subclinical structural and functional changes, the imaging specialist must be attuned to signatures of specific genetic disorders. With increased availability of both advanced imaging as well as genotyping techniques, this review seeks to provide cardiovascular imaging specialists and clinicians with the contemporary information needed for more precise diagnosis and treatment of heritable myocardial disease. A companion paper in this series covers imaging phenotype and genotype considerations in hypertrophic cardiomyopathy (HCM). This review details clinical features, imaging phenotype and current genetic understanding for two of the most common non-HCM conditions that prompt myocardial imaging - dilated cardiomyopathy (DCM) and arrhythmogenic right ventricular cardiomyopathy (ARVC). While all modalities are considered herein, considerable focus is given to CMR with its unique capabilities for myocardial tissue characterization.