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
Marked sinus bradycardia (30bpm) secondary to hypothermia

Example 2
ECG Hypothermia slow atrial fibrillation AF
Atrial fibrillation with slow ventricular response due to hypothermia

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
Marked J waves in severe hypothermia [Temp: 26°C (78.8°F)]

QT Prolongation

Example 8
ECG Hypothermia long QT shivering artifact
Prolonged QTc (620ms) due to severe hypothermia

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)

Related Topics


References

  • Slovis C, Jenkins R. ABC of clinical electrocardiography: Conditions not primarily affecting the heart. BMJ. 2002 Jun 1;324(7349):1320-3. [PMC1123277]

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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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