Hypothermia is a medical emergency that occurs when your body loses heat faster than it can produce it, causing a dangerously low body temperature. 

Occurs when body temperature falls below 35 °C.  

Left untreated, hypothermia can lead to complete failure of the cardiovascular and respiratory system and eventually to death.

  • Mild hypothermia is 32-35 °C
  • Moderate hypothermia is 29-32 °C
  • Severe hypothermia is < 29 °C

 Clinical presentation 

  • excessive shivering, weak pulse, slowed breathing, slowed speech, clumsiness or lack of coordination, confusion or memory loss

ECG manifestation 

  • shivering artefact
  • bradyarrhythmia
  • prolonged PR interval, QRS and QT interval
  • Osborn waves (J waves) - a positive deflection at the J point (negative in aVR and V1), most prominent in inferior and precordial leads; the height is roughly proportional to the degree of hypothermia
  • ectopic activity -> atrial fibrillation 

If temperature below 30°C

  • ventricular fibrillation 

If temperature below 28°C 

  • cardiac arrest due to VT, VF or asystole

Picture 1 Osborn wave  


ECG 1A  Patient after CPR before targeted temperature management (only atrial fibrillation present) 


ECG 1B Patient during targeted temperature management (34° C) - slower rate of atrial fibrillation, ST elevations with incipient Osborn waves (II, III, aVF, V5-V6), prolonged QT interval.



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  4. Mareedu RK, Grandhe NP, Gangineni S, Quinn DL. Classic EKG changes of hypothermia. Clin Med Res. 2008;6(3-4):107-108. doi:10.3121/cmr.2008.809
  5. https://litfl.com/hypothermia-ecg-library/