Final answer:
Hypocalcemia leads to an extended opening of slow calcium channels, prolonging the plateau phase and refractory period in cardiac muscle cells, which in turn increases the QT interval on an ECG.
Step-by-step explanation:
How can hypocalcemia cause an increase in the Q-T interval?
Hypocalcemia, characterized by abnormally low levels of calcium in the blood, can impact cardiac function significantly. Calcium ions are crucial for the proper physiological functioning of the heart, affecting heart rate (HR) and contractility. The QT interval on an electrocardiogram (ECG) represents the time it takes for the ventricles of the heart to depolarize and then repolarize, corresponding to the duration of ventricular systole. When there is a deficiency in calcium levels, the duration of the slow calcium channels' opening may be extended, leading to a prolongation of the plateau phase and absolute refractory period of the cardiac muscle cells. This results in an overall increase in the QT interval. Conversely, high levels of calcium ions (hypercalcemia) may cause a short QT interval and a widened T wave in the ECG.
In summary, the precise balance of electrolytes, including calcium, is necessary for maintaining the normal rhythm and electrical conductivity of the heart.