A 58-year-old woman on sotalol develops recurrent polymorphic ventricular tachycardia with twisting QRS complexes around the baseline, with a baseline QTc of 520 ms. She has one self-terminating episode and one episode requiring DC cardioversion. Which intravenous drug is the first-line agent to prevent immediate recurrence?
- A Amiodarone
- B Magnesium sulfate ✓
- C Procainamide
- D Lidocaine
Correct answer: B. Magnesium sulfate
Explanation
Torsades de pointes with a prolonged QT is treated first with IV magnesium sulfate even when serum magnesium is normal; it suppresses early afterdepolarizations that trigger the arrhythmia. Amiodarone prolongs repolarization further and can worsen torsades, making it the wrong choice here. Lidocaine and procainamide have no role as first-line therapy; procainamide actually prolongs the QT interval.
Reference: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 12th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.