UNCONTROLLED WHEN PRINTED
Introduction

Reflection on the average direction of ventricular depolarisation during ventricular contractions – Provides indication of the heart’s direction and position of the electrical activities.

  • ‘Axis’ refers to electrical depolarisation direction (in degrees°)
  • Normal electrical pathway would be leftward then downward

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Method 1: ECG Leads
  • If aVF is unavailable – Lead II can be used but with extreme caution.
 Normal AxisRight Axis Deviation (RAD)Left Axis Deviation (LAD)Extreme Axis Deviation
Lead IPOSITIVE (+)NEGATIVE (-)POSITIVE (+)NEGATIVE (-)
Lead aVFPOSITIVE (+)POSITIVE (+)NEGATIVE (-)NEGATIVE (-)
Axis Angle 0 to +90° +90 to 180°0 to -90°-90 to 180°
Method 2: Hexaxial (Perpendicular) Reference System
  1. Look at the limb leads – Find smallest OR most equiphasic complex
  2. Using the degrees – Find this complex on the reference axis
  3. Trace to the centre then find perpendicular lead (right angle)
  4. Follow this lead back out to the axis quadrant

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Types of Devations
Normal Deviation:
  • Normal electrical activity is leading towards Lead I (most positive) & aVF hence the positive leads. aVR is in opposite direction of the impulse therefore is negative
Left Axis Deviation (LAD):
  • Depolarisation to the left side usually caused by conduction abnormalities.
Right Axis Deviation (RAD):
  • Depolarisation to the right side may be due to extra tissue mass (stronger signal) – May be normal in tall individuals.
Extreme Axis Deviation (EAD):
  • Rare event usually from electrode misplacement – Can be due to ventricular tachycardia (if rhythm is tachycardia with wide QRS complex).
Axis Deviations Causes
No Axis DeviationLeft Axis DeviationRight Axis Deviation
  • No conditions
  • Healthy heart
  • Inferior AMI
  • Left Anterior Hemiblock
  • LBBB
  • Wolf Parkinson White Syndrome
  • Obesity
  • Pregnancy
  • Pacemaker (or paced rhythm)
  • Pulmonary Hypertension
  • Pulmonary Embolism
  • Dextrocardia
  • Anterior / Lateral AMI
  • Valvular Lesions
  • Right Ventricle Hypertrophy
  • COPD

References

College of Pre-Hospital Care. (2015). 12-Lead ECG Analysis: Self-Directed Learning Package. Version 3. St John Ambulance Ltd.  

Curtis, K., & Ramsden, C. (2016). Emergency and trauma care for Nurses and Paramedics (2nd ed.). Elsevier Australia.

DeLaune, S. C., Ladner, P. K., McTier, L., Tollefson, J., & Lawrence, J. (2016). Australian and New Zealand fundamentals of nursing (1st ed.). Cengage Learning Australia Pty Limited.

ECG & ECHO Learning. (2020). Clinical ECG Interpretation. https://ecgwaves.com/topic/ecg-normal-p-wave-qrs-complex-st-segment-t-wave-j-point/

Life in the Fast Lane. (2020). ECG Library. https://litfl.com/ecg-library/

St John WA Ltd. (2017). Electrocardiography (ECG). Clinical Resources. https://clinical.stjohnwa.com.au/clinical-skills/assessment/vital-signs/electrocardiography-(ecg)

WikiEM. 2020. The Global Emergency Medicine Wiki. https://www.wikem.org

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Page contributors:

60825Thanh Bui, AP60825
Event Medic, Emergency Medical Technician &
Volunteer Development Officer

 

16790

Andrew Moffat, AP16790
Volunteer Training Manager & Volunteer Development Officer

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