Normal axis of hea is?

-30 to +90 REF: Harrison's Internal Medicine 17th edition chapter 221 The hea's electrical axis refers to the general direction of the hea's depolarization wavefront (or mean electrical vector) in the frontal plane. With a healthy conducting system the cardiac axis is related to where the major muscle bulk of the hea lies. Normally this is the left ventricle with some contribution from the right ventricle. It is usually oriented in a right shoulder to left leg direction, which corresponds to the left inferior quadrant of the hexaxial reference system, although -30deg to +90deg is considered to be normal