THE CONTEXT
Magnetic resonance imaging (MRI) assesses cardiac anatomy, function, perfusion and myocardial tissue characteristics.
Image formation and tissue differentiation
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MRI generates cross-sectional images of the heart, lungs and mediastinal structures.
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MRI differentiates soft tissues better than computed tomography (CT), but demonstrates calcification poorly.
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MRI scans are gated to the electrocardiogram (ECG) to produce moving images throughout the cardiac cycle.
Functional assessment
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Signals from moving blood allow quantification of flow across regurgitant or stenotic valves.
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Regional wall motion can be analysed in patients with suspected coronary disease or cardiomyopathy.
Perfusion, viability and delayed enhancement
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MRI can assess myocardial perfusion and viability.
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Gadolinium-based contrast identifies myocardial hypoperfusion with better spatial resolution than nuclear medicine techniques.
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Delayed enhancement reflects later redistribution of contrast and identifies myocardial scarring and fibrosis, a particular strength of cardiac MRI.
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These findings can help select patients for revascularisation or identify myocardial infiltration, including that described with sarcoid heart disease and arrhythmogenic right ventricular cardiomyopathy.