What generally happens to P waves during a junctional rhythm?

In junctional rhythms, the P waves are often absent or inverted due to the unique mechanism of impulse generation in the heart. Junctional rhythms originate from the atrioventricular (AV) junction, which is located near the area where the atrium connects to the ventricle. In this region, impulses may originate from the junctional tissue rather than the sinoatrial (SA) node, which is the heart's primary pacemaker.

When the impulse arises from the AV junction, it can occur before atrial depolarization is complete, resulting in a P wave that is either absent altogether or inverted in lead II, as the electrical activity in the atria may be activated in a retrograde manner (from the junction towards the atria). This reflects that the normal sequence of atrial depolarization is altered in junctional rhythms as compared to normal sinus rhythm.

Thus, the observation that P waves may be absent or inverted is a distinctive characteristic of junctional rhythms, confirming that the correct answer is indeed that P waves may be absent or inverted.