Which electrolyte disturbance is most commonly associated with torsades de pointes?

• A. Hypermagnesemia
• B. Hypokalemia
• C. Hyperkalemia
• D. Hypomagnesemia

Answer: (D)

The key idea is that torsades de pointes is a form of polymorphic ventricular tachycardia that occurs with prolonged QT and is strongly promoted by magnesium deficiency. Low magnesium prolongs repolarization and promotes early afterdepolarizations, increasing dispersion of repolarization across the myocardium. Magnesium also helps regulate calcium influx and stabilizes the cell membrane, so when magnesium is low, the myocardium becomes more prone to the abnormal, twisting rhythm characteristic of torsades. Because of this stabilizing effect, intravenous magnesium sulfate is the treatment for torsades even if magnesium levels are not severely low, underscoring the central role of magnesium in preventing and correcting this arrhythmia. While other electrolyte disturbances like low potassium can contribute by prolonging the QT, magnesium deficiency is the most strongly associated and most actionable factor in this scenario.