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
ECG-QT-changes-Hypocalcaemia-Hypercalcaemia 2
Hypocalcaemia prolongs the ST segment causing QTc prolongation

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.

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)

Symptoms of Hypocalcaemia
  • Neuromuscular excitability
  • Carpopedal spasm
  • Tetany
  • Chvostek sign
  • Trousseau sign
  • Seizures

ECG Examples
Example 1
ECG Hypocalcaemia QTc 500


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

Example 2
ECG Hypocalcemia long QT


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

Example 3
  • Hypocalcaemia causing a long QTc (510ms)


Advanced Reading



LITFL Further Reading


Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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