Cardiac MRI (CMR)

Cardiovascular magnetic resonance (CMR) is the reference standard for quantifying left- and right-ventricular volumes, ejection fraction and myocardial mass, because volumetric measurement does not rely on geometric assumptions. Beyond function, CMR characterises tissue: late gadolinium enhancement (LGE) maps focal scar and fibrosis, T1 and T2 parametric mapping quantify diffuse fibrosis and oedema, and the extracellular volume (ECV) fraction is calculated from pre- and post-contrast T1 with haematocrit. These techniques diagnose and risk-stratify ischaemic and non-ischaemic cardiomyopathy, myocarditis, cardiac amyloidosis, sarcoidosis and Fabry disease. CMR uses no ionising radiation; limitations include cost, scanner availability, gadolinium contraindications in advanced renal failure, and reduced image quality with arrhythmia or implanted devices. Standardised acquisition protocols are published by the Society for Cardiovascular Magnetic Resonance (SCMR).