Escape junctional rhythm is usually regular with a narrow QRS, and rates of 35-60 beats per minute. It is due to an automatic focus in the AV junction that takes over with either slowing or failure of the sinus node (e.g., sinus arrest) or with AV block. Retrograde P’s at times are hidden in the QRS or may be obscured by the ST segment or T wave; when visible they are typically best seen in the inferior leads.
The following animation illustrates what we have just described.