ECG changes seen in hypocalcemia: March 2010

Ans. B: Prolongation of ST segmentHypocalcemia causes prolongation of the ST segment and consequently of the QT interval, a change that is also produced by phenothiazines and tricyclic antidepressant drugs and by various diseases of the central nervous system. Increases in extracellular Ca2+ concentration enhance myocardial contractility. When large amounts of Ca2+ are infused into experimental animals, the hea relaxes less during diastole and eventually stops in systole (calcium rigor). However, in clinical conditions associated with hypercalcemia, the plasma calcium level is rarely if ever high enough to affect the hea.