Left axis deviation

In electrocardiography, left axis deviation (LAD) is a condition wherein the mean electrical axis of ventricular contraction of the heart lies in a frontal plane direction between −30° and −90°. This is reflected by a QRS complex positive in lead I and negative in leads aVF and II.[1]

The hexaxial reference system is a diagram that is used to determine the heart's electrical axis in the frontal plane.


Common causes of LAD include left anterior fascicular block (or hemiblock) and inferior myocardial infarction.[2][3] Less commonly LAD may be a normal variant, particularly in obese or stocky individuals, or it may be associated with Wolff–Parkinson–White syndrome or an ostium primum atrial septal defect.

See also


  1. Jenkins, Dean (1996). "The electrical axis at a glance". www.ecglibrary.com. Retrieved 2016-11-12.
  2. Lilly, Leonard (2006). Pathophysiology of Heart Disease. Lippincott Williams and Wilkins. ISBN 978-0-7817-6321-9.
  3. Kasper D, Braunwald E, Fauci A, Hauser S, Longo D, Jameson J (2005). Harrison's Principles of Internal Medicine (16th ed.). McGraw-Hill. p. 1314. ISBN 0-07-147760-8.

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