Left Axis Deviation (LAD)

Left Axis Deviation LAD

Left Axis Deviation = QRS axis less than -30°.

  • Normal Axis = QRS axis between -30° and +90°
  • Right Axis Deviation = QRS axis greater than +90°
  • Extreme Axis Deviation = QRS axis between -90° and 180° (AKA “Northwest Axis”)

Hexaxial Reference System

Haxaxial ECG AXIS Reference 2021
Hexaxial Reference System – relationship between QRS axis and frontal leads of the ECG.

How to recognise left axis deviation

Three Lead analysis
  • QRS is POSITIVE (dominant R wave) in Lead I
  • QRS is NEGATIVE (dominant S wave) in leads II, III and aVF
Lead I II aVF Hexaxial Evaluation LAD Pathological 2021

Example ECG of LAD
Left Anterior Fascicular Block (LAFB) Left axis LAD

Left Axis Deviation:

  • Leads I and aVL are positive; leads II and aVF are negative

Causes of LAD

Advanced Reading



LITFL Further Reading


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

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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