Prolonged QT interval predisposes to torsades de pointes. Which electrolyte disturbance commonly causes prolonged QT?

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Multiple Choice

Prolonged QT interval predisposes to torsades de pointes. Which electrolyte disturbance commonly causes prolonged QT?

Prolonged QT reflects longer ventricular repolarization, and electrolyte levels shape the duration of the cardiac action potential, especially the plateau phase. Calcium drives much of the plateau; when extracellular calcium is low, the plateau is prolonged, extending the overall action potential duration and the QT interval. This longer repolarization provides a substrate for torsades de pointes, a dangerous form of polymorphic ventricular tachycardia. Among the options, low calcium is the classic cause of QT prolongation, so hypocalcemia best fits. Hyperkalemia and hypercalcemia tend to shorten the QT, while low potassium can also prolong QT but is less specifically tied to this classic association here.

Prolonged QT reflects longer ventricular repolarization, and electrolyte levels shape the duration of the cardiac action potential, especially the plateau phase. Calcium drives much of the plateau; when extracellular calcium is low, the plateau is prolonged, extending the overall action potential duration and the QT interval. This longer repolarization provides a substrate for torsades de pointes, a dangerous form of polymorphic ventricular tachycardia.

Among the options, low calcium is the classic cause of QT prolongation, so hypocalcemia best fits. Hyperkalemia and hypercalcemia tend to shorten the QT, while low potassium can also prolong QT but is less specifically tied to this classic association here.

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