Left and right axis deviation

Schematic representation of the QRS complex in leads I and II in left and right axis deviation. The net QRS area is normally positive in leads I and II. An axis more negative than -30º is referred to as left axis deviation, which produces a negative net area in lead II with a positive QRS area in lead I. In comparison, an axis more positive than +100º is referred to as right axis deviation, which produces a negative net area in lead I (a left-right lead) with a positive QRS area in lead II.