Final answer:
Hypercalcemia can lead to an abbreviated QT interval and broadened T wave on an ECG, potentially affecting myocyte repolarization and possibly increasing the risk of cardiac dysfunction or arrest.
Step-by-step explanation:
Effect of Hypercalcemia on Myocyte Repolarization
Hypercalcemia, or high levels of calcium ions (Ca2+) in the blood, can significantly affect heart rate (HR) and contractility of the heart muscle, or myocytes. Increased levels of Ca2+ are associated with a shortened QT interval on an electrocardiogram (ECG) and a widened T wave. The QT interval represents the period from ventricular depolarization to repolarization, which includes ventricular systole. Excessive Ca2+ may even lead to cardiac arrest.
Calcium ions serve critical roles in cardiac muscle physiology by entering through slow calcium channels during the plateau phase of the action potential, contributing to the long refractory period necessary for efficient pumping of blood. They also bind to troponin in the protein complex involved in muscle contraction. When hypercalcemia occurs, the ability of the myocyte to repolarize properly after contraction could be compromised, which can impair cardiac function.