Which electrolyte disturbance is characterized by prolonged QT interval on EKG?

The electrolyte disturbance characterized by a prolonged QT interval on EKG is hypocalcemia. This condition affects the myocardial action potentials, leading to changes in the duration of the cardiac cycle. A decreased serum calcium concentration can prolong the QT interval because calcium plays a critical role in the cardiac electrical conduction system, particularly in the cardiac repolarization phase.

When calcium levels drop, the repolarization of the cardiac muscle takes longer, which results in the well-known prolongation of the QT interval. Clinically, this can increase the risk of arrhythmias, including Torsades de Pointes, which is a specific type of polymorphic ventricular tachycardia that can occur in the setting of prolonged QT.

In contrast, hypercalcemia can lead to a shortened QT interval, while hypokalemia typically causes a variety of EKG changes, including U waves and may lead to a prolonged QT interval in extreme cases. Hyperkalemia primarily presents with characteristic changes such as peaked T waves and a widening QRS complex. Understanding these relationships can help in the identification and management of potential cardiac complications associated with electrolyte imbalances.