Hypokalaemia ECG — RACP Adult Medicine MCQ

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EasyCardiologyHypokalaemia ECGRACP Adult Medicine

A 40-year-old woman presents with muscle weakness, constipation, and polyuria. Her ECG shows a prolonged QT interval, flattened T waves, and prominent U waves. What electrolyte abnormality is most likely?

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Correct answer: A — Hypokalaemia

Flattened T waves, prominent U waves, ST depression, and prolonged QT interval are the classic ECG changes of hypokalaemia. Severe hypokalaemia (<2.5 mmol/L) can cause life-threatening arrhythmias (torsades de pointes, VF). In contrast, hyperkalaemia causes peaked T waves, widened QRS, and loss of P waves. Causes of hypokalaemia include diuretics, GI losses, hyperaldosteronism, renal tubular acidosis, and hypomagnesaemia (which must be corrected to enable potassium correction).

Reference: eTG – 2025 – Cardiovascular; AMH – 2025 – Electrolyte Disorders