Inappropriate spikes on telemetry?

This 81-year old patient with a dual chamber pacemaker (implanted in 2015 for sick sinus syndrome) was admitted because of chest pain for which he will receive coronary angiography.

This strip of ECG telemetry was printed because it caught the attention of the attending nurse (see circles drawn on the stip).

What do you think is happening? Is it normal pacemaker behaviour? Which brand pacemaker is this?

Physician advice: 
Trace category: 

My take: junctional rhythm surpassing the atrial rate, resulting in intermitting cross talk with VSP. 

Thanks Dr. Lüker for the excellent take! But I don't think there is cross talk.

The junctional rhythm is indeed surpassing the atrial rate, resulting in ventricular sensed events (QRS-complexes) occuring during the safety window (within 110 ms after atrial pace) which triggers ventricular safety pacing.. This is normal MEdtronic pacemaker behaviour.

This is explained in more detail in this example:

Thanks Mark! Crosstalk was certainly the wrong terminology. What I meant was VSP because of safety window sensing ;) 

Naming the manufacturer was a tough one because the 110ms were hard to measure and I couldn't find a list of VSP intervals for all manufacturers (SJM 120ms? no VSP for Boston, Bio?, Sorin?). 


Sylvain Ploux's picture


I agree with Dr Lüker: how  do you expect us to mesure the AVD with such accuracy that we could differenciate Sorin 95ms, Bio 100ms, Medtronic 110ms or SJM 120ms??

Nice tracing!