Hypothermia

Hypothermia overview

Hypothermia is defined as a core body temperature of < 35 °C [degrees centigrade]

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

ECG Changes in Hypothermia

Hypothermia may produce the following ECG abnormalities:

  • Bradyarrhythmias (see below)
  • Osborne Waves (= J waves)
  • Prolonged PR, QRS and QT intervals
  • Shivering artefact
  • Ventricular ectopics
  • Cardiac arrest due to VT, VF or asystole

Bradyarrhythmias

Patients with hypothermia may manifest a variety of bradyarrhythmias, including:

  • Sinus bradycardia (may be marked)
  • Atrial fibrillation with slow ventricular response
  • Slow junctional rhythms
  • Varying degrees of AV block (1st-3rd)

Example ECGs
Example 1
ECG Hypothermia sinus bradycardia 1

Example 2
ECG Hypothermia slow atrial fibrillation AF

Example 3
ECG Hypothermia 3
  • ECG with the classic features of hypothermia: bradycardia, Osborn waves and shivering artefact.

Osborn Waves

The Osborn wave (J wave) is a positive deflection at the J point (negative in aVR and V1).

  • It is usually most prominent in the precordial leads.
  • The height of the Osborn wave is roughly proportional to the degree of hypothermia.

Example 4
ECG Subtle Osborn wave J wave hypothermia
  • Subtle J waves in mild hypothermia [Temp: 32.5°C (90.5°F)]
  • The height of the J wave is roughly proportional to the degree of hypothermia

Example 5
J waves Osborn Wave hypothermia temp 30°C
J waves in moderate hypothermia. [Temp: 30°C (86°F)]

Example 6
J waves Osborn Wave hypothermia temp 30°C
J waves in moderate hypothermia. [Temp: 28°C (82.4°F)]

Example 7
Osborn wave temp 26 hypothermia

QT Prolongation
Example 8
ECG Hypothermia long QT shivering artifact

Shivering Artefact
  • Shivering artefact is seen as a “fuzziness” of the ECG baseline.
  • It is not specific to hypothermia and may be seen with other conditions associated with tremor (e.g. Parkinson’s disease).
Example 9
ECG hypothermia shiver artefact bradycardia long QT
  • Shivering artefact in a patient with hypothermia (note also the Osborn waves, bradycardia, prolonged QT)


References

Advanced Reading

Online

Textbooks


LITFL Further Reading

ECG LIBRARY 700

ECG LIBRARY

Electrocardiogram

Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

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