Observation

Suspected Problem

Possible Normal Pacer Function
Pacing artifacts delivered in the middle of normal ORS complexes
 Pacemaker undersensing Pseudofusion

Unexplained pauses after sensed but
not paced complexes

Pacemaker oversensing

Hysteresis

Pacer rate less than lower rate, which occurs at night

Pacemaker oversensing at night

Different sleep rate/lower rate
Rapid pacing rates Pacemaker oversensing of EMI in atrial channel or other atria events causing upper rate tracking
Pacemaker-mediated tachycardia 		Scanning hysteresis/rate drop response causing an increased "intervention"
pacing rate for vasovagal episodes
Activation of rate-response sensors
Upper rate tracking of unsuspected
atrial tachyarrhythmia or sinus tachycardia
Pacer reset due to EMI or low battery
Pacer that mode switched due to atria
tachyarrhythmia
DDD pacer operating in VVI mode

Malfunction of pacer

 Pacer reset due to EMI or low battery
Pacer that mode switched due to atria tachyarrhythmia
ABBREVIATION: EMI = electromagnetic interference.

Table 9
Suspected Malfunction Occurring During Normal Pacer Function

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