Makindo Medical Notes

🫀 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

• Radiopaedia: Cardiac MRI
• AHA: Clinical Indications for CMR