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ECG Disease Patterns

Hypokalaemia on ECG

February 15th, 2021


Potassium is important in maintaining membrane potentials, particularly in cardiac myocytes. 
Hypokalaemia, or a reduced serum potassium concentration of <3.5mmol/L, is associated with hyperpolarisation of cardiac myocytes. If severe, hypokalaemia causes abnormal ventricular automaticity which may result in ventricular arrhythmias.
  • Severity of Hypokalaemia

  • Mild - 3.0 - 3.5 mmol/L
  • Moderate - 2.5 - 3.0 mmol/L
  • Severe - <2.5 mmol/L
ECG changes are not typically seen until the potassium concentration is <3.0.
  • ECG Findings in Hypokalaemia

  • Moderate to Severe

  • PR prolongation
  • ST depression
  • T wave flattening or inversion
  • Prominent U wave (resulting in an apparent prolonged QT interval)
  • Life-Threatening

  • Torsade de pointes
  • Ventricular tachycardia
  • Ventricular fibrillation
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