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Torsades de Pointes — EECC MCQ

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EasyArrhythmia & ElectrophysiologyTorsades de PointesEECC

A 55-year-old woman admitted with pneumonia is started on intravenous clarithromycin. She is also taking citalopram. On day 3, telemetry shows polymorphic VT with a twisting morphology that self-terminates after 15 seconds. The preceding rhythm strip shows QTc prolongation at 580 ms. Serum potassium is 3.1 mmol/L and magnesium is 0.6 mmol/L. What is the most appropriate immediate management?

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Correct answer: B — Intravenous magnesium sulphate 2 g bolus and aggressive electrolyte correction

This is torsades de pointes (TdP) — polymorphic VT in the context of acquired QT prolongation from multiple QT-prolonging drugs (clarithromycin + citalopram) compounded by hypokalaemia and hypomagnesaemia. First-line treatment is IV magnesium sulphate (2 g over 10-15 minutes, regardless of serum magnesium level) and correction of potassium to >4.5 mmol/L. The offending QT-prolonging drugs must be stopped immediately. Amiodarone is contraindicated as it further prolongs the QT interval. If TdP recurs, temporary overdrive pacing or isoprenaline infusion to increase heart rate (shortening the QT interval) should be considered. DC cardioversion is for sustained haemodynamically compromising episodes.

Reference: ESC (2022): Guidelines on Ventricular Arrhythmias and Prevention of Sudden Cardiac Death