Monday, March 2, 2015



  • Normal level of Potassium  is vital for regulating the normal electrical activity of the heart.
  • Increased extracellular potassium level  reduces myocardial excitability, with depression of both pacemaking and conducting tissues.
  • Progressively worsening hyperkalaemia leads to suppression of impulse generation by the SA node and reduced conduction by the AV node and His-Purkinje system, resulting in bradycardia and conduction blocks and ultimately cardiac arrest.


  • Hyperkalaemia is defined as a potassium level > 5.5 mEq/L
  • Moderate hyperkalaemia is a serum potassium > 6.0 mEq/L
  • Severe hyperkalaemia is a serum potassium > 7.0 mE/L
Watch this Video  :

Effects of hyperkalaemia on the ECG

Serum potassium > 5.5 mEq/L is associated with repolarization abnormalities:
  • Peaked T waves (usually the earliest sign of hyperkalaemia)
Serum potassium > 6.5 mEq/L is ASSOCIATED with progressive paralysis of the atria:
  • P wave widens and flattens
  • PR segment lengthens
  • P waves eventually disappear
Serum potassium > 7.0  mEq/L is ASSOCIATED with conduction abnormalities and bradycardia:
  • Prolonged QRS interval with bizarre QRS morphology
  • High-grade AV block with slow junctional and ventricular escape rhythms
  • Any kind of conduction block (bundle branch blocks, fascicular blocks)
  • Sinus bradycardia or slow AF
  • Development of a sine wave appearance (a pre-terminal rhythm)
Serum potassium level of > 9.0 mEq/L causes cardiac arrest due to:
  • Asystole
  • Ventricular fibrillation
  • PEA with bizarre, wide complex rhythm

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