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

Online

Textbooks


LITFL Further Reading

ECG LIBRARY 700

ECG LIBRARY

Electrocardiogram

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) 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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