Atypical Dilated and Nonhypertrophic Cardiac Transthyretin Amyloidosis: Concept of Overlapping Cardiomyopathies

Transthyretin amyloid cardiomyopathy (ATTR-CM) is typically described as a restrictive cardiomyopathy characterized by deposition of insoluble amyloid proteins in the myocardium, resulting in heart failure (HF) with preserved left ventricular (LV) ejection fraction (EF). The usual echocardiographic pattern combines diffusely increased myocardial wall thickness (LV wall thickness ≥12 mm, right ventricular [RV] wall thickness ≥5 mm), and associated other cardiac structures thickening, normal LVEF, typical global longitudinal strain (GLS) reduction with relative apical sparing pattern, and pericardial effusion.