Hypocalcaemia

• Ed Burns and Robert Buttner
• Jun 3, 2021

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ECG changes in Hypocalcaemia

• Hypocalcaemia causes QTc prolongation primarily by prolonging the ST segment
• The T wave is typically left unchanged
• Dysrhythmias are uncommon, although atrial fibrillation has been reported
• Torsades de pointes may occur, but is much less common than with hypokalaemia or hypomagnesaemia

Hypocalcaemia prolongs the ST segment causing QTc prolongation

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Hypocalcaemia Overview

• Normal serum corrected calcium = 2.2 – 2.6 mmol/L.
• Mild-moderate hypocalcaemia = 1.9 – 2.2 mmol/L.
• Severe hypocalcaemia = < 1.9 mmol/L.

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Causes of Hypocalcaemia

• Hypoparathyroidism
• Vitamin D deficiency
• Acute pancreatitis
• Hyperphosphataemia
• Hypomagnesaemia
• Diuretics (frusemide)
• Pseudohypoparathyroidism
• Congenital disorders (e.g. DiGeorge syndrome)
• Critical illness (e.g. sepsis)
• Factitious (e.g. EDTA blood tube contamination)

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Symptoms of Hypocalcaemia

• Neuromuscular excitability
• Carpopedal spasm
• Tetany
• Chvostek sign
• Trousseau sign
• Seizures

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ECG Examples

Example 1

Hypocalcaemia:

• QTc 500ms in a patient with hypoparathyroidism (post thyroidectomy) and serum corrected calcium of 1.40 mmol/L
• Reproduced from Nijjer et al. (2010)

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Example 2

Hypocalcaemia:

• QT prolongation in a patient with DiGeorge’s syndrome and serum calcium of 1.32 mmol/L
• Reproduced from Kar et al. (2005)

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Example 3

• Hypocalcaemia causing a long QTc (510ms)