Electromechanical and structural phenotypes from cardiac imaging and epicardial mapping in inherited arrhythmia syndromes

Inherited arrhythmia syndromes—including Brugada syndrome (BrS), long QT syndrome (LQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT), and short QT syndrome (SQTS)—can cause malignant arrhythmias and sudden cardiac death without overt structural heart disease on conventional evaluation. Advances in cardiac magnetic resonance imaging (CMR), speckle-tracking strain echocardiography, and epicardial electroanatomical mapping have revealed previously unrecognized electromechanical and structural abnormalities in these conditions. In BrS, right ventricular outflow tract (RVOT) fibrosis, connexin-43 downregulation, and progressive structural remodeling support the concept of a concealed subepicardial substrate. In LQTS, prolonged contraction duration, mechanical dispersion, and diastolic dysfunction represent an electromechanical phenotype beyond QT prolongation, and preliminary evidence of a right ventricular epicardial substrate has been reported. CPVT and SQTS largely preserve the classical electrical disease model, though limited CMR data suggest possible structural overlap in specific CPVT genotypes. This review summarizes disease-specific findings from advanced imaging, considers the role of genetic testing in guiding phenotypic assessment, and discusses the clinical implications of these evolving concepts.