<prompt> QT depression is seen in ?HypokalaemiaHyperkalaemiaHypocalcaemiaHypercalcaemia  <response>: In vitro, hypokalemia not only prolongs the QT interval in the absence of drug but also potentiates drug block of ion channels that results in QT prolongation. Drugs i.e., certain antiarrhythmics and erythromycin and electrolyte disorders i.e., hypokalemia, hypocalcemia, hypomagnesemia can prolong the QT interval and predispose to torsades de pointes.Hypercalcemia can result in significant electrocardiographic changes, including bradycardia, AV block, and short QT interval; changes in serum calcium can be monitored by following the QT intervalHyperkalemia, or drugs such as flecainide tend to increase QRS duration. Conditions that prolong phase 2 use of amiodarone, hypocalcemia increase the QT interval.Hypocalcemia typically prolongs the QT interval ST portion, while hypercalcemia shortens it 