Atrial-Sensing Pacemaker in AF

Report:

Atrial flutter/fibrillation 2

Dual-chamber pacemaker 3

Tachycardia up to 129/min due to atrial (over)sensing 5

Comment:

The pacemaker is programmed to follow – up to a set upper rate limit – atrial activity. This is really meant for sinus rhythm. With atrial tachyarrhythmias, the paced rate may become fast or irregular, as here. The atrial electrode is now only a liability, unless sinus rhythm can be restored and maintained. To report this as oversensing is meaningless, given the chaotic nature of atrial f waves.

As the amplitude of atrial activity is variable, some is not sensed: hence the two (doomed) attempts at AV sequential pacing. Again, this is not the same as undersensing in sinus rhythm.

Toward the end of the recording, the unit is appropriately inhibited by patient’s own conducted QRS complexes. He may not be pacemaker-dependent; the unit was probably implanted for sick sinus syndrome.

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