Hypothermia

ECG Changes in Hypothermia

Classification of hypothermia

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

Bradyarrhythmias

Bradycardia is a common finding in hypothermia. Patients may manifest a variety of bradyarrhythmias:

• 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

Example 2

Example 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

• 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

Example 6

Example 7

QT Prolongation

Example 8

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

• Shivering artefact in a patient with hypothermia (note also the Osborn waves, bradycardia, prolonged QT)

Related Topics

• Measurement of the QT interval
• The Osborn Wave

References

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

Advanced Reading

Online

• Wiesbauer F, Kühn P. ECG Mastery: Yellow Belt online course. Understand ECG basics. Medmastery
• Wiesbauer F, Kühn P. ECG Mastery: Blue Belt online course: Become an ECG expert. Medmastery
• Kühn P, Houghton A. ECG Mastery: Black Belt Workshop. Advanced ECG interpretation. Medmastery
• Rawshani A. Clinical ECG Interpretation ECG Waves
• Smith SW. Dr Smith’s ECG blog.

Textbooks

• Zimmerman FH. ECG Core Curriculum. 2023
• Mattu A, Berberian J, Brady WJ. Emergency ECGs: Case-Based Review and Interpretations, 2022
• Straus DG, Schocken DD. Marriott’s Practical Electrocardiography 13e, 2021
• Brady WJ, Lipinski MJ et al. Electrocardiogram in Clinical Medicine. 1e, 2020
• Mattu A, Tabas JA, Brady WJ. Electrocardiography in Emergency, Acute, and Critical Care. 2e, 2019
• Hampton J, Adlam D. The ECG Made Practical 7e, 2019
• Kühn P, Lang C, Wiesbauer F. ECG Mastery: The Simplest Way to Learn the ECG. 2015
• Grauer K. ECG Pocket Brain (Expanded) 6e, 2014
• Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric 6e, 2008
• Chan TC. ECG in Emergency Medicine and Acute Care 1e, 2004

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