Which of the following statements about severe hypercalcemia and the QT interval is correct?

• A. QT interval unchanged
• B. Prolonged QT interval
• C. ST depression
• D. Shortened QT interval

Answer: (D)

The main idea is how calcium levels influence ventricular repolarization and the QT interval. Calcium governs the plateau phase of the ventricular action potential; when calcium is elevated, the plateau is shortened, leading to earlier repolarization. That makes the QT interval shorter on the ECG. So, in severe hypercalcemia, the QT interval is shortened because repolarization happens more quickly.

Think of it opposite to what happens with low calcium: hypocalcemia prolongs the QT by extending the plateau and delaying repolarization. ST depression isn’t a hallmark change for calcium abnormalities, and a QT interval that remains unchanged wouldn’t reflect the impact of severe hypercalcemia.