Ventriculophasic sinus arrhythmia

A ventriculophasic sinus arrhythmia is characterized by episodic or permanent failure of conduction throught the atrioventricular (AV) node. In contrast to the typical second or third degree AV block, the PP intervals are not constant; the two P waves surrounding a QRS complex have a shortened interval or occur at a faster rate when compared to two P waves that occur sequentially without an intervening QRS complex.

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.