Hypothermia is defined as a core body temperature of < 35 degrees centigrade
- Mild hypothermia is 32-35 degrees
- Moderate hypothermia is 29-32 degrees
- Severe hypothermia is < 29 degrees
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
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)
- Marked sinus bradycardia (30bpm) secondary to hypothermia
- Atrial fibrillation with slow ventricular response due to hypothermia
- ECG with the classic features of hypothermia: bradycardia, Osborn waves and shivering artefact.
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.
- 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
- J waves in moderate hypothermia. [Temp: 30°C (86°F)]
- J waves in moderate hypothermia. [Temp: 28°C (82.4°F)]
- Marked J waves in severe hypothermia [Temp: 26°C (78.8°F)]
- Prolonged QTc (620ms) due to severe hypothermia
- 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).
- Shivering artefact in a patient with hypothermia (note also the Osborn waves, bradycardia, prolonged QT)
- Slovis C, Jenkins R. ABC of clinical electrocardiography: Conditions not primarily affecting the heart. BMJ. 2002 Jun 1;324(7349):1320-3. [PMC1123277]
LITFL Further Reading
- ECG Library Basics – Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis – ECG interpretation in clinical context
- ECG Exigency and Cardiovascular Curveball – ECG Clinical Cases
- 100 ECG Quiz – Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS – the best of the rest
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric
- Wagner GS. Marriott’s Practical Electrocardiography 12e
- Chan TC. ECG in Emergency Medicine and Acute Care
- Rawshani A. Clinical ECG Interpretation
- Mattu A. ECG’s for the Emergency Physician
- Hampton JR. The ECG In Practice, 6e