A 58-year-old woman on sotalol develops recurrent runs of polymorphic ventricular tachycardia with twisting QRS axis around the baseline, preceded by a QT interval of 560 ms. She is hemodynamically stable during short runs. What is the first-line intravenous therapy?

• A Intravenous amiodarone
• B Oral flecainide
• C Intravenous isoproterenol infusion as primary treatment
• D Intravenous magnesium sulfate ✓

Explanation

Torsades de pointes is polymorphic VT occurring with prolonged QT, classically precipitated by QT-prolonging drugs such as sotalol. Intravenous magnesium sulfate suppresses early afterdepolarizations and terminates the arrhythmia even when serum magnesium is normal, making it first-line. Isoproterenol is reserved for bradycardia-dependent torsades when magnesium fails. Amiodarone prolongs repolarization further and would worsen the QT, while flecainide has no role in acquired long QT.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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