Sinus pause

Sinus pause is the result of intermittent failure of sinus node impulse generation. This is manifest as a long RR cycle length (in this tracing P to P interval) which is longer than the RR interval of the underlying sinus rhythm. There is no relationship between the cycle length of the pause and that of the intrinsic sinus rhythm. The P-P interval for the beats before and after the pause are less than two times the underlying sinus P-P interval.

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.