Look for these possible events when examining a rhythm strip showing the activities of a DDD pacemaker:

• Intrinsic rhythm—No pacemaker activity occurs because none is needed.
• Intrinsic P wave followed by a ventricular pacemaker spike—The pacemaker is tracking the atrial rate and ensuring a ventricular response.
• Pacemaker spike before a P wave, then an intrinsic ventricular QRS complex—The atrial rate is falling below the lower rate limit, causing the atrial channel to fire. Normal conduction to the ventricles then ensues.
• Pacemaker spike before a P wave and a pacemaker spike before the QRS complex—No intrinsic activity above the lower rate limit occurs in either the atria or the ventricles.