The axis of the ECG is the major direction of the overall electrical activity of the heart. It can be normal, leftward (left axis deviation, or LAD), rightward (right axis deviation, or RAD ...

The ability to identify an abnormality on the 12-lead ECG, suggestive of underlying cardiac disease associated with sudden cardiac death (SCD), is based on a sound working knowledge of the normal ECG ...

In a “normal” electrocardiogram (ECG), the transition of the QRS axis in the precordial leads occurs between leads V 3 and V 4 (i.e., there is a dominant S in V 3 and a dominant R in V 4).

See the ECG basics section on determining axis for ... which is technically a normal QRS axis. To further distinguish normal from left axis deviation in this setting, look at lead II.

The goal of ECG interpretation in athletes is to classify the ECG as: (1) ‘normal’—no further evaluation needed ... pathological Q-waves, left axis deviation and conduction delays and findings ...