AXIS:

The axis of the heart is the major direction of overall electrical activity. It is measured in two different planes:  The coronal (vertical) plane and the transverse (horizontal) plane. The P wave axis and the QRS axis reflect electrical activity during depolarization. The T wave axis reflects electrical activity during ventricular repolarization.

CORONAL (VERTICAL) PLANE:

-Assess the P wave axis, the QRS axis, and the T wave axis.

-Normal Axes:

-P wave axis:          0 to +75 degrees.

-QRS axis:             -30 to +90 degrees.

-T wave axis:         0 to +90 degrees (within 45 degrees of the QRS axis).

-QRS Axis:

-Normal:                                                                        -30 to +90 degrees.

-Left axis deviation:                                                    -30 to -90 degrees.

-Right axis deviation:                                                +90 to +180 degrees.

-Superior axis (Extreme right axis) deviation:     -90 to -180 degrees.

TRANSVERSE (HORIZONTAL) PLANE:

-Referred to as Transition.

-Normal transition is in leads V3 and/or V4.

-Transition point before lead V3:

-Early transition (previously referred to as counterclockwise rotation).

-Transition point after lead V4:

-Late transition (previously referred to as clockwise rotation).