In accelerated junctional rhythm, what is the characteristic of the P wave?

In accelerated junctional rhythm, the P wave is typically absent or inverted due to the location of the ectopic focus in the junctional area (the region between the atria and ventricles). In this rhythm, the impulses originate from the AV junction rather than the sinoatrial (SA) node. As a result, the atria may either not depolarize in response to the junctional electrical activity (leading to an absent P wave) or they may depolarize in such a way that the P wave appears inverted, as the atrial depolarization occurs in the opposite direction from that during normal sinus rhythm. This inversion is caused by the depolarization starting from the junctional tissue and propagating backward to the atria.

The presence and appearance of P waves in various rhythms provide critical information necessary for accurate diagnosis, with absent or inverted P waves in accelerated junctional rhythms being a key characteristic.