This site is intended for healthcare professionals

Go to /sign-in page

You can view 5 more pages before signing in

ECG changes in high potassium

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

Hyperkalaemia causes a rapid reduction in resting membrane potential leading to increased cardiac depolarization, and muscle excitability which in turn causes EG changes (1).

ECG changes are usually progressive and may include:

  • tall, peaked (tented) T waves [T wave larger than R wave in more than 1 lead]
  • first degree heart block (prolonged PR interval) [>0.2 s];
  • flattened or absent P waves
  • ST-segment depression
  • S and T wave merging (sine wave pattern)
  • widened QRS [>0.12 s]
  • arrythmias including bradycardia, ventricular tachycardia or fibrillation
  • cardiac arrest (pulseless electrical activity [PEA], ventricular fibrillation/pulseless ventricular tachycardia [VF/VT], asystole) (2)

ECG changes with hyperkalaemia do not consistently follow a stepwise, dose-dependent pattern.

  • risk of arrhythmias increase with potassium values > 6.5 mmol/L and even small elevations in potassium above this concentration can lead to rapid progression from peaked T waves to ventricular fibrillation or asystole
  • the longer a patient has high potassium concentrations, the greater the risk of sudden deterioration (1)

Click here for an example ECG and further information


  • ECG finding are neither specific nor sensitive for detecting hyperkalaemia (3)


Related pages

Create an account to add page annotations

Add information to this page that would be handy to have on hand during a consultation, such as a web address or phone number. This information will always be displayed when you visit this page