Step 7b: Inspect QRS complexes for bundle branch block or fascicular block

In the normal heart, at the beginning of ventricular depolarization, the QRS axis is oriented to the right because of left-to-right depolarization of the septum. This produces a small R wave in lead V1. Immediately following septal depolarization, the left and right ventricles depolarize. The size of the left ventricle results in a predominantly leftward axis for the remainder of the QRS complex.