Ischaemic, Infarction, and Other ECG Abnormalities; Common Cardiac Conditions
Ischaemic, Infarction, and Other ECG Abnormalities
This domain tests recognition of ST-T changes and their territorial meaning. Ischaemia often alters ST segments and T waves; infarction can produce Q waves and ST elevation.
Core rules
- ST elevation in contiguous leads suggests acute injury; ST depression and T inversion suggest ischaemia but are less specific.
- Localisation: II, III and aVF indicate inferior; V1-V4 anterior; I, aVL, V5 and V6 lateral; V1-V2 septal.
- Reciprocal ST depression may appear opposite the injured territory, supporting the diagnosis.
- Other patterns: hyperkalaemia gives tall peaked T waves; pericarditis often causes diffuse ST elevation and PR depression; pulmonary embolism may show sinus tachycardia and right-heart strain.
Worked example
A tracing shows ST elevation in II, III and aVF with reciprocal ST depression in I and aVL. Reasoning: II, III and aVF face the inferior wall, while I and aVL face the lateral wall. The pattern therefore points to inferior injury, not anterior injury, and the reciprocal change strengthens the interpretation.
Traps that cost marks
Do not diagnose STEMI from a single lead; contiguous leads are needed. Early repolarisation and LVH can mimic ST elevation. An old Q wave may not indicate a new infarct. Pericarditis often produces diffuse rather than territorial changes. Always match ECG findings to symptoms and clinical assessment.