ECGs for the MLA
In progress: Check back soon as I collect ECGs for you all
💡 ECGs for the MLA
Medical students should be able to recognise key ECG patterns in acute and chronic disease, linking them to underlying pathology and urgent management steps.
❤️ Acute Coronary Syndromes
- STEMI: Localised ST elevation in ≥2 contiguous leads ± reciprocal ST depression.
- NSTEMI/Unstable angina: ST depression, T-wave inversion, or normal ECG with symptoms.
- Hyperacute T waves: Earliest sign of MI, tall peaked T-waves before ST elevation.
- Old MI: Pathological Q waves (deep, >40 ms wide).
⚡ Arrhythmias
- Atrial fibrillation (AF): Irregularly irregular rhythm, absent P waves, fibrillatory baseline.
- Atrial flutter: Saw-tooth flutter waves, often with 2:1 block (ventricular rate ~150).
- Supraventricular tachycardia (SVT): Narrow complex tachycardia, regular, often no visible P waves.
- Ventricular tachycardia (VT): Broad complex tachycardia, regular, “capture/fusion” beats.
- Ventricular fibrillation (VF): Chaotic irregular waveform, no organised complexes — cardiac arrest rhythm.
- Torsades de pointes: Polymorphic VT with twisting QRS axis; associated with prolonged QT.
⏱️ Conduction Blocks
- First-degree AV block: PR >200 ms, every P followed by QRS.
- Second-degree AV block Mobitz I (Wenckebach): Progressive PR lengthening → dropped beat.
- Second-degree AV block Mobitz II: Intermittent dropped QRS with fixed PR — risk of complete block.
- Third-degree (complete) heart block: No relation between P waves and QRS; escape rhythm.
- Bundle branch blocks:
– LBBB: “WiLLiaM” — W in V1, M in V6.
– RBBB: “MaRRoW” — M in V1, W in V6.
🧪 Electrolyte & Drug Effects
- Hyperkalaemia: Tall tented T waves, flattened P waves, widened QRS → sine wave (pre-terminal).
- Hypokalaemia: U waves, flattened T waves, prolonged QT.
- Digoxin effect: Down-sloping ST depression (“reverse tick”), flattened T waves.
🩺 Other Must-Know Patterns
- Pericarditis: Widespread concave ST elevation + PR depression.
- STEMI mimics: LBBB, LVH strain pattern, pericarditis.
- Wolff–Parkinson–White (WPW): Short PR, delta wave, widened QRS.
- Long QT syndrome: QTc >440 ms (men) / >460 ms (women).
- Pulmonary embolism: S1Q3T3 pattern (rare, non-specific); sinus tachycardia most common finding.
⚠️ Red Flag ECGs in Exams
- STEMI → immediate reperfusion (PCI/thrombolysis).
- VT/VF → cardiac arrest protocols (defibrillation).
- Complete heart block with syncope → pacing needed.
- Hyperkalaemia with ECG changes → IV calcium, urgent treatment.
- Torsades de pointes → IV magnesium, stop QT-prolonging drugs.
📚 Teaching Pearls
- Always read ECGs systematically: Rate, Rhythm, Axis, Intervals, Morphology, ST/T changes.
- In MLA exams, you’re often asked: “What is the diagnosis?” or “What is the next step in management?”.
- Focus on life-threatening and common patterns, not rare syndromes.
