Examine the trace from a patient with a pacemaker in the DDD mode. What problem is seen with this pacemaker?
Failure to sense the atrium
The pacing spike seen after a normal P wave suggests the pacemaker has failed to detect normal atrial activity. The rhythm strip I used up there comes from a Medscape article.
Wiegand, Uwe KH, et al. "Diagnosis of atrial undersensing in dual chamber pacemakers: impact of autodiagnostic features." Pacing and clinical electrophysiology 22.6 (1999): 894-902.