Short QT Interval Hypercalcaemia — FRCA Final MCQ

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ModeratePreoperative AssessmentShort QT Interval HypercalcaemiaFRCA Final

A 55-year-old woman (ASA III) with end-stage renal failure is having a parathyroidectomy. Her pre-operative ECG shows a shortened QT interval. This is most likely due to:

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Correct answer: D — Hypercalcaemia

A shortened QT interval is characteristically caused by hypercalcaemia. In ESRF with secondary (or tertiary) hyperparathyroidism, PTH excess causes increased bone resorption and elevated serum calcium. Calcium accelerates cardiac repolarisation, shortening the ST segment and QT interval. Conversely, hypocalcaemia prolongs the QT interval. Other causes of short QT: digoxin toxicity and congenital short QT syndrome. At very high calcium levels (>3.5 mmol/L), cardiac arrhythmias and cardiac arrest may occur.

Reference: RCOA – 2023 – Final FRCA curriculum: electrolyte ECG effects; ESC – 2022 – Cardiac arrhythmia guidelines