Which electrolyte abnormality is most associated with prolongation of the QT interval and predisposes to torsades de pointes?

Which electrolyte abnormality is most associated with prolongation of the QT interval and predisposes to torsades de pointes?

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

Answer: (B)

Magnesium helps stabilize cardiac cell membranes and regulate the ion channels that control repolarization. When magnesium is low, repolarization is slowed, lengthening the QT interval. A prolonged QT creates a substrate for early afterdepolarizations, which can trigger torsades de pointes, a dangerous type of polymorphic ventricular tachycardia. That’s why hypomagnesemia is the electrolyte abnormality most associated with QT prolongation and torsades. Clinically, magnesium is often given IV to treat or prevent torsades even if magnesium levels are not severely low, because magnesium helps stabilize the myocardium and suppress abnormal impulses. Hypermagnesemia tends to slow conduction and isn’t the typical driver of QT prolongation; hyperkalemia tends to affect conduction differently and can shorten the QT interval, while hypernatremia isn’t a primary factor in QT changes.

Magnesium helps stabilize cardiac cell membranes and regulate the ion channels that control repolarization. When magnesium is low, repolarization is slowed, lengthening the QT interval. A prolonged QT creates a substrate for early afterdepolarizations, which can trigger torsades de pointes, a dangerous type of polymorphic ventricular tachycardia. That’s why hypomagnesemia is the electrolyte abnormality most associated with QT prolongation and torsades. Clinically, magnesium is often given IV to treat or prevent torsades even if magnesium levels are not severely low, because magnesium helps stabilize the myocardium and suppress abnormal impulses. Hypermagnesemia tends to slow conduction and isn’t the typical driver of QT prolongation; hyperkalemia tends to affect conduction differently and can shorten the QT interval, while hypernatremia isn’t a primary factor in QT changes.