The QRS complex shown on the page 3.1.3 and repeated here can be displayed as a series of spatial vectors in the frontal plane just as was done for the normal QRS complex.
The initial portion of the QRS complex, representing septal depolarization, i.e. the small Q in leads I,II and aVF, and the small R in aVR is directed to the right and slightly superiorly. Its vector has an axis of approximately +210 degrees.
The main portion of the QRS complex is equally positive in leads I and II and negative in aVR. Its vector has an axis of approximately +30 degrees.
The terminal part of the QRS complex, i.e. the S waves in leads I, II and aVL and the R’ in aVR has a spatial vecto with an axis of approximately +180 degrees. These individual vectors can be enclosed in a vector loop.