A junctional rhythm occurs when the electrical activation ... which is normally upright in lead II and biphasic in lead V1. Often, the P wave is inverted in lead II, if it can be seen at all.

This results in an inverted P wave in lead II (normally upright in sinus rhythm) and an upright P wave in aVR (normally inverted in sinus rhythm). Depending on the exact location of the pacemaker ...