Dual chamber atrioventricular sequential pacing

Two pacemaker spikes are seen within each complex; there is an atrial spike (marked by red lines) and an associated P wave, followed by a ventricular spike (marked by green lines) and an associated paced QRS complex. The P wave morphology is variable, depending upon the location of the wire within the right atrium.

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.