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Long QT — RCPSC IM MCQ

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ModerateCardiologyLong QTRCPSC IM

A 24-year-old woman has syncope while dancing. ECG shows QTc 520 ms. Potassium is 3.3 mmol/L and magnesium is low. Her medications include citalopram and clarithromycin for sinusitis. There is no structural heart disease on echocardiography. What is the most likely cause?

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Correct answer: D — Acquired long QT from QT-prolonging drugs with electrolyte depletion

Marked QT prolongation with hypokalemia, hypomagnesemia and two QT-prolonging drugs suggests acquired long QT syndrome, increasing risk for torsades de pointes. Correct electrolytes and stop offending drugs.

Reference: Canadian Cardiovascular Society prolonged QT clinical practice update