Junctional escape rhythm

Escape junctional beat or rhythm occurs when there is failure of impulse generation from the sinus node or atrial myocardium. The 4th and 5th beats of this tracing are junctional beats that are not preceeded by a P wave and occur after a pause that is longer than the underlying sinus cycle length.

The normal P wave in sinus rhythm is slightly notched since activation of the right atrium precedes that of the left atrium. The P wave is upright in a positive direction in leads I and II. A P wave with a uniform morphology precedes each QRS complex. The rate is between 60 and 100 beats per minute and the cycle length is uniform between sequential P waves and QRS complexes. In addition, the P wave morphology and PR intervals are identical from beat to beat.