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.
Common causes of LAD include left ventricular hypertrophy, left anterior fascicular block (or hemiblock) and inferior myocardial infarction. 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, although some sources claim that LVH does not cause LAD.
See also