What is the initial management for torsades de pointes when magnesium therapy is not effective?

• A. Increase magnesium dose
• B. Overdrive pacing or isoproterenol infusion
• C. IV calcium infusion
• D. Defibrillation only

Answer: (B)

Torsades de pointes is driven by a prolonged QT interval that allows abnormal impulses to trigger a repeating, dangerous VT. After magnesium, the most effective next step is to raise the heart rate to shorten the QT and suppress the ectopic activity fueling the arrhythmia. That’s achieved best with overdrive pacing using a temporary pacemaker or with an IV isoproterenol infusion. Both approaches increase the rate, shorten the QT interval, and reduce the likelihood of the triggering afterdepolarizations continuing the tachycardia.

Calcium infusions aren’t routinely used to treat torsades and don’t address the rate problem, while immediate defibrillation is reserved for a patient who is pulseless or severely unstable. If the patient remains stable, pacing or isoproterenol is the preferred next move.