Junctional premature complexes

Atrioventricular junctional premature beats (beats 2 and 4) are early ectopic beats which originate in or near the AV junction and have a QRS morphology that resembles the sinus complex. Although their timing and morphology are similar to that of an atrial premature beat, there is no P wave present before the 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.