CardiologyTier 2Topic

Cardiac MRI

Role

Provides detailed structural, functional, and tissue-characterisation imaging of the heart without ionising radiation - increasingly central to cardiomyopathy and myocarditis diagnosis
The reference standard for ventricular volumes/function (more accurate/reproducible than echo); complements but does not replace echo as first-line

Tissue characterisation

Late gadolinium enhancement (LGE) identifies fibrosis/scar - the pattern distinguishes ischaemic (subendocardial/transmural, coronary territory) from non-ischaemic (mid-wall/epicardial, non-coronary distribution) causes of cardiomyopathy
T1/T2 mapping detects diffuse fibrosis, oedema (myocarditis), and infiltration (amyloid - characteristic gadolinium kinetics)

Diagnostic uses

Myocarditis (Lake Louise criteria - oedema + LGE), hypertrophic cardiomyopathy (wall thickness + fibrosis pattern, prognostic), cardiac amyloidosis (characteristic diffuse subendocardial LGE + abnormal gadolinium kinetics), ARVC (RV structural/functional criteria), sarcoidosis (patchy mid-wall LGE)
Myocarditis, hypertrophic/dilated/restrictive cardiomyopathy, cardiac amyloidosis, sarcoidosis

Prognosis and contraindications

LGE extent is prognostic in several cardiomyopathies (informs ICD decision-making in some non-ischaemic cardiomyopathies)
Contraindications: some older pacemakers/ICDs (most modern devices are MRI-conditional), severe claustrophobia, incompatible implants
Increasingly used to risk-stratify (not just diagnose) cardiomyopathy, given fibrosis burden correlates with arrhythmic risk

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