Hypomagnesaemia Overview

  • Normal serum magnesium = 0.8 – 1.0 mmol/L.
  • Hypomagnesaemia = <0.8 mmol/L

ECG changes in Hypomagnesaemia

  • The primary ECG abnormality seen with hypomagnesaemia is a prolonged QTc.
  • Atrial and ventricular ectopy, atrial tachyarrhythmias and torsades de pointes are seen in the context of hypomagnesaemia, although whether this is a specific effect of low serum magnesium or due to concurrent hypokalaemia is uncertain.
  • Nevertheless, correction of serum magnesium to >1.0 mmol/L (with concurrent correction of serum potassium to >4.0 mmol/L) is often effective in suppressing ectopy and supraventricular tachyarrhythmias, while a rapid IV bolus of magnesium 2g is a standard emergency treatment for torsades de pointes.

Example ECG

ECG Hypomagnesemia prolonged QT

Hypomagnesaemia causing long QTc (510ms)

Related Topics

LITFL Further Reading

Advanced Reading




Emergency Medicine Specialist MBChB FRCEM FACEM. Medical Education, Cardiology and Web Based Resources | @jjlarkin78 | LinkedIn |

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