Which statement about electrocardiogram findings in calcium disorders is true?

Which statement about electrocardiogram findings in calcium disorders is true?

• A. Hypocalcemia causes prolongation of the QT interval with inverted T waves.
• B. Hypocalcemia causes shortening of the QT interval with widened QRS.
• C. Hypercalcemia causes prolongation of the QT interval.
• D. Hypercalcemia causes shortening of the QT interval with prolongation of PR interval.

Answer: (A)

Calcium levels directly influence how long it takes ventricles to repolarize, which shows up as the QT interval on ECG. Low calcium (hypocalcemia) prolongs the QT interval because repolarization takes longer, especially the ST segment. This prolongation is the key ECG change and is the reason why hypocalcemia can predispose to torsades de pointes. High calcium (hypercalcemia) does the opposite, shortening the QT interval by speeding up repolarization; it does not prolong the QT. So the statement that hypocalcemia causes prolongation of the QT interval is correct. The note about inverted T waves isn’t a defining feature of hypocalcemia, and the other options misstate how calcium levels affect the QT and other intervals.

Calcium levels directly influence how long it takes ventricles to repolarize, which shows up as the QT interval on ECG. Low calcium (hypocalcemia) prolongs the QT interval because repolarization takes longer, especially the ST segment. This prolongation is the key ECG change and is the reason why hypocalcemia can predispose to torsades de pointes. High calcium (hypercalcemia) does the opposite, shortening the QT interval by speeding up repolarization; it does not prolong the QT.

So the statement that hypocalcemia causes prolongation of the QT interval is correct. The note about inverted T waves isn’t a defining feature of hypocalcemia, and the other options misstate how calcium levels affect the QT and other intervals.