How to evaluate cardiomyopathies by cardiovascular magnetic resonance parametric mapping and late gadolinium enhancement

BACKGORUND : Cardiomyopathies (CMPs), defined as a myocardial disorder in which the heart muscle is structurally and functionally abnormal, in the absence of coronary artery disease, hypertension, valvular disease, and congenital heart disease sufficient to cause the observed myocardial abnormality are broadly classified in dilated CMP (DCM), hypertrophic CMP (HCM), restrictive CMP, and arrhythmogenic CMP (ACM). The aetiology is heterogeneous, both genetic as well as (or triggered by) acquired causes. Genetic causes include the known DCM, HCM, and ACM mutations, but also lysosomal (e.g. Anderson-Fabry disease etc.), infiltrative (amyloidosis, sarcoidosis, and haemochromatosis), and neuromuscular diseases (e.g. Duchenne muscular and Becker dystrophy etc.). Acquired causes include toxins (e.g. alcohol, cocaine etc.), drugs (e.g. chemotherapy such as anthracyclines etc.), infectious/inflammatory diseases (viruses, or autoimmune mediated), and peripartum CMP. Cardiovascular magnetic resonance (CMR) imaging is now firmly established for comprehensive evaluation of CMPs. Its unique advantage over other imaging techniques is the ability to provide comprehensive tissue characterization. Focal necrosis/fibrosis and amyloid infiltration and oedema can be identified by late gadolinium enhancement (LGE), whereas diffuse fibrosis and, amyloid can be detected by increased T1 and extracellular volume (ECV) fraction. Oedema increases T2 values. Fat and lysosomal storage disease decrease T1 times while iron infiltration lowers T1, T2, and especially T2*. Furthermore, CMR is the gold standard for the assessment of myocardial volumes, mass, wall thickness, and trabeculation for both the left and right ventricle. These features not only allow differential diagnosis of different types of CMPs but were also shown to have important prognostic value in many of such CMPs