Is my Pacemaker Lying?

I was diagnosed with A-fib in 2004 and have an episode about every 1-2 months. My heart converts back to normal sinus rythm in about 12 hours. I am, and have always been, aware when an episode begins and when it ends.

My last two PM checks I was told that my A-fib is less than 2 percent. I mentioned that I had two episodes since my last check and was told that I hadn't had any. When I gave the dates of the episodes, the technician said "no" there was no A-fib activity.

I am now concerned that my PM isn't functioning properly since my A-fib episodes didn't show up on the PM reading.

Anyone had any similar experience?




by marylandpm - 2019-10-24 10:05:44

 My Pacemaker wasn’t showing me going into Afib but when  I was in the hospital with a EKG monitor the monitor showed me going into Afib when I got up to go to the bathroom. The Pacemaker didn’t register the  Afib. The doctor said the theashold was set to low on the Pacemaker. 

Pacemaker High Rate Threshold

by KonaLawrence - 2019-10-25 03:31:45

I have occassional Afib, but my pacemaker usually doesn't record it.  That's because the "Atrial High Rate Episode Dection Rate = 180". 

Since my Afib events are usually 120-150, the pacemaker doesn't record it.  I've asked about it and they say below 180 is not significant!  I think next time I go in for an interrogation I'll ask them to lower the "Dection Rate".


by Gemita - 2019-10-25 13:01:17

Hello Normalou,

Yes, I have had a similar experience in that if an arrhythmia like AF is not of a certain duration or speed, the pacemaker may be set up to ignore it.  This I believe gives a false picture of the true total burden of an arrhythmia.  I feel too my doctors are only interested in significant arrhythmia episodes.  

When I first started out, like many patients perhaps, my AF and other arrhythmias were closely monitored - from minor to major episodes.  Then when my doctors understood the extent of my problem, only significant episodes were recorded and reported on to my Electrophysiologist.  When I hit well over 200 + bpm, this triggered an immediate response for example.  But at 170 bpm there was less concern.  So you are right, you will be aware of many more episodes of AF than may be automatically recorded by your pacemaker.  A pacemaker can only do what it has been set up to do and our doctors will only want significant data retained.  Because of the unpredictable nature of AF, I do though wonder how an earth they can say with any accuracy what the "% time we are in AF is" if they are rejecting so many frequent short episodes and only basing their "% time in AF" on episodes say over a certain duration, or speed ?? 


you can't handle the truth

by ROBO Pop - 2019-10-25 18:17:59

Your pacemaker only answers questions it's won't lie

My device won't report any tachycardia or even fibrillation...because those functions are shut off. Doesn't mean they aren't happening just we chose not to monitor them.


by NormaLou - 2019-10-28 01:46:39

Thank you all for your feedback.

I had never given a thought that it could be my PM settings. The first two years after I had the PM it recorded all my A-fib episodes. Somewhere along the way the setting may have been changed. 

I will definitely ask about this at my next visit to my electrophysicolgist. 

Thank you again, I appreciate the information.

AFib %

by MrTech - 2019-12-01 11:25:26

Atrial fibrillation rate can be very irregular and fast up to about 350pm. The ventricular response (your Heart rate/pulse rate )will be considerably lower as your AV node (junction box between atrium and ventrical) won’t allow it. 

An atrial rate of 120bpm to 150bm is almost certainly not AF. The ventricular response to AF can easily reach 120-150bpm. 

Anyway, assuming one has an atrial and ventricular lead,  pacemakers normally have a default monitor of around >170bpm for AF/atrial tachycardias . As prev said, AF will be much quick than this. One shouldn’t have to lower this detection level to detect AF. 

If someone were having lots of symptomatic small (3-4 beats) runs of atrial ectopics, or an atrial ectopic every other beat for example, this would not be recorded and stored as it will not reach criteria as AF/atrial tachycardia. It would just be placed in the  ‘PAC volume’ stats where you can see how many ectopics you get. Depends on make and model of pacemaker. 

Its quite possible to see a 2% AF burden with 500k atrial ectopics for example. 

Its possibly someone could be feeling ectopics but this isn’t stored as AF by the device. And neither would these ectopics necessarily be AF either.

As mentioned previously, if the atrial sensing is not sensitive enough (Rarely - usually detection is fine) it may not detect all the beats and could think these are lots of 2-4 beat runs of Atrial ectopics and not label this as AF.  All things being equal, if AF has been successfully recorded previously, then this is usually  unlikely. Undersensing can underestimate % of AF but unlikely not to detect it at all. 

Pacemakers don’t lie. They respond to how they are programmed. 




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