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Left axis deviation

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

Left axis deviation (LAD) is a condition whereby 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]


Common causes of LAD include left ventricular hypertrophy, 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.

Left ventricular hypertrophy (LVH) is generally recognised as a cause of LAD,[2][3][4] although some sources claim that LVH does not cause LAD.[1][5]

See also


  1. ^ a b
  2. ^ a b Lilly, Leonard (2006). Pathophysiology of Heart Disease. Lippincott Williams and Wilkins. ISBN 978-0-7817-6321-9. 
  3. ^ a b 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. 
  4. ^
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