Dual channel oversensing of what?


66-year old patient implanted with a two-chamber pacemaker (Sorin Kora 100 DR) in 2014.

Interrogation revealed 1% ventricular pacing, stable threshold, sensitivity and impedance of both leads.

There was one episode of an atrial mode switch, which occured a few months earlier.

Does anybody have an idea what is causing the oversensing?

Physician advice: 

Trace category:



It looks like external atrial pacing that is visible on both channels (hight amplitude? Unipolar?)

Patient did not recall anything special that day. So no external atrial pacing.

We sent the EGM to Livanova (Paris)..

I would think about placement of electrodes and atrial rhythm origin: Is the ventricular electrode placed properly in RV? It looks like CS signal... but at the same time shows the atrial iEGM a dual signal too. It could be theoretically a double counting of sinus signal/atrial focus due to a two "pathways" between sinusnode/atrial focus and atrial electrode. At the same time a far-field sense of "this second atrial signal" in RV electrode. 



Sylvain Ploux's picture

Hi Marc,

The PM senses correctly the atrial signal around 3mV, and the V signal around 8mV. A supernumerary signals is present in between, on both channels. This signal is not as sharp as the near-field ones.

Physiologically there should be nothing in between the atrial and ventricular activation. I would go for a hardware issue (Minute Ventilation algorithm or so). Let see what Livanova says about it.

Nice brain teaser!