Left Axis Deviation

Left Axis Deviation

Definition

• QRS axis between -30 and -90 degrees

Left axis deviation: -30 to -90 degrees

How to recognise left axis deviation

• QRS is positive (dominant R wave) in leads I and aVL
• QRS is negative (dominant S wave) in leads II and aVF

Left Axis Deviation: leads I and aVL are positive; leads II and aVF are negative

Causes

• Left anterior fascicular block
• Left bundle branch block
• Left ventricular hypertrophy
• Inferior MI
• Ventricular ectopy
• Paced rhythm
• Wolff-Parkinson White syndrome

Acknowledgements

• Axis diagram reproduced from David C Chung’s ‘ECG: A Pictorial Primer’.

Related Topics

• Right axis deviation

Further Reading

• ECG BASICS – Waves, Intervals, Segments and Clinical Interpretation
• ECG CLINICAL CASES – Your favourite ECG’s placed in clinical context with a challenging Q&A approach
• ECG and Cardiology Eponymous Syndromes – Cheats guide to eponymous emancipation
• ECG Reference Sites on the WEB – the best of the rest

Author Credits

References

• Mattu A, Brady W. ECGs for the Emergency Physician 2, BMJ Books 2008.
• Wagner, GS. Marriott’s Practical Electrocardiography (11th edition), Lippincott Williams & Wilkins 2007.