Cardiac MRI ❤️
🫀 About
- Cardiac MRI (CMR) is a non-invasive imaging technique that provides high-resolution structural and functional information using magnetic resonance technology.
- ECG gating (synchronisation with the R-wave) is used to freeze cardiac motion, allowing clear images at different phases of the cardiac cycle.
- CMR combines anatomical, functional, and tissue-characterisation imaging in one study - it is now the gold standard for RV volumes and tissue fibrosis assessment.
🎯 Indications
- Infiltrative cardiomyopathies 🧩: Amyloidosis, sarcoidosis (LGE pattern helps differentiate from ischaemic scars).
- Pericardial disease 📏: Constriction vs restriction, pericardial thickness, effusions.
- Cardiomyopathies 🫀: Dilated, hypertrophic, restrictive, arrhythmogenic RV dysplasia.
- Ischaemia & Infarction ❤️🔥: Myocardial viability, perfusion, scar burden (guides revascularisation).
- Congenital heart disease 👶: Shunts, complex anatomy, repaired TOF follow-up.
- Valvular disease 🔄: Quantification of regurgitant volumes & flow (e.g. in AR or PR).
- Cardiac masses/tumours 🎭: Tissue characterisation (thrombus vs tumour).
- Ventricular function 💪: EF, stroke volume, wall motion - especially for right ventricle where echo is limited.
⚠️ Contraindications
- Pacemakers/ICDs: Only MRI-conditional devices are safe - always check compatibility.
- Metallic implants 🧲: Some aneurysm clips, cochlear implants, or older valves may move/heat.
- Claustrophobia 😰: May require sedation.
- Severe CKD 🧪: Gadolinium can rarely cause nephrogenic systemic fibrosis (avoid if eGFR <30 unless essential).
🎥 Advanced Techniques
- Late Gadolinium Enhancement (LGE) 🌟: Ischaemic scars (subendocardial/transmural) vs non-ischaemic (mid-wall/patchy).
- Stress CMR 🏃: Adenosine or dobutamine perfusion imaging for ischaemia.
- T1/T2 mapping 🎨: Quantitative tissue characterisation → oedema (T2↑), fibrosis/amyloid (T1↑), iron overload (T1↓).
- 4D Flow MRI 🌊: Tracks complex blood flow through heart and great vessels.
💡 Advantages
- No ionising radiation 🚫☢️.
- Unmatched tissue contrast - detects fibrosis, oedema, infiltration.
- Gold standard for RV and biventricular volumes, function, and mass.
- Single comprehensive test → anatomy + function + perfusion + tissue health.
- Complements echo (real-time, bedside) and CT (fast, coronary anatomy).
📝 Exam tip: Ischaemic cardiomyopathy shows subendocardial/transmural LGE in a vascular distribution. Non-ischaemic cardiomyopathy shows mid-wall or patchy LGE.
📚 References
