Can Heart Rate Actually Drop Below The Base Rate of a Pacemaker

The Heart Analyzer app on my iWatch (Series 5) reports daily occurrences of heart rate in the low to mid-40s even though the base rate on my pacemake (St Jude PM2240) is set for 50. Is this an artifact of the app or is it an indication that my pacemaker is not functioning properly?


It certainly feels like it !!

by Gemita - 2020-08-24 10:12:11

I had this conversation with my doctors some time ago and they said my pacemaker would not allow the minimum set rate to fall lower.  They suggested the problem was ectopic beats which are not always picked up by home monitors because they are often too weak to be felt.  However, it certainly feels like my pulse is slow at times (in the mid 40s) when my minimum set rate is 70 bpm.  I expect I will be having this conversation again with my doctors in the near future for a further explanation.

I usually feel my neck pulse and count manually and I can get a more accurate reading but still quite difficult with ectopics or other arrhythmias present.  It would however be perfectly normal for our pacemakers to drop a few beats below the minimum I believe

Very Helpful ...Thanks

by rafimf - 2020-08-24 10:37:56

You are so kind to respond.  I will be reviewing this with my Dr's and hopefully a pacemaker expert ... will post back anything I might learn.

lower than the minimum

by Tracey_E - 2020-08-24 11:05:27

The pacer is set by the second, not by the minute. I'm going to use a minimum of 60bpm as an example because the math is easier- 1 beat per second. If your heart goes a second and doesn't beat the pacer will kick in and cause a beat. Over the course of a minute, this will be close to but not exactly 60. Ectopics, pvc and pac's can also throw off the count, the pacer counts them but the monitor misses them. Last, you can't always trust the watch. It's always good to bring it up with your doctor when anything seems off, but it's common to go a bit under the set minimum. 


by AgentX86 - 2020-08-24 21:48:56

This is the most likely cause.  It's pretty easy to tell if you're having PACs or PVCs.  If you feel your pulse (and count it), you might notice skipped beats.  These really aren't skipped rather are small because the heart hasn't had time to refill whan they occur.  As others have said, your pacemaker sees these ahd holds off for the next beat.  It's doing the right thing but your heart interrupts the cycle.

Your watch can't count these either so will read low.  A watch it's a very good measure in any case.  There are too many ways to fool them.

Thanks to All ...Good Stuff to Know

by rafimf - 2020-08-25 10:19:59

I appreciate all responses. They are quite an education. Relieved!

Pluse Oximeter

by marylandpm - 2020-08-25 21:29:42

  You could pick up a Pluse Oximeter at the drug store and check your oxygen level.   If its low then you know you have a problem. 

Pulse Oximeter 👌

by rafimf - 2020-08-25 23:47:46

97  ..... I'm good.  

That's Happened To Me Too

by Marybird - 2020-08-26 00:32:39

My pacemaker lower rate is set at 55, though it doesn't spend much time there. But there are times when I wear my old Garmin heart rate watch it will show the heart rate briefly drop into the 40's. I've also seen it do this with a pulse oximeter, and even once in the ER ( trip was for a broken wrist) on a heart monitor. It doesn't stay there long before it goes back up, and I attribute the drop ( speculating here) that it may be PVCs or arrhythmia hiccups, or possibly the pause before the pacer kicks in to see if the old ticker will work on its own?

I solved the problem by not wearing the watch.

Yes we could stop trying to capture what is happening but

by Gemita - 2020-08-27 04:22:31

in my opinion, I think the moral of this story is that if we are "symptomatic"  during recording/noticing a heart rate drop and if it stays there for any length of time, there may be a problem and it should be brought to the attention of our pacemaker team, particularly since pacemaker settings and medication can clearly affect heart rhythm.  

I am noticeably symptomatic during heart rate drops to the 40s bpm range and these lower rates - as confirmed both manually by finger on neck pulse and with a blood pressure monitor - may last for long periods before they return to my set lower limit of 70 bpm.  I certainly know/feel immediately when these falls in heart rate occur, as though my pacemaker is not supporting me during these periods, although I clearly have some complex arrhythmias running in the background at times.  On the whole though my pacemaker is doing a great job to sort out all the nonsense!!

You know you're wired when...

Your device makes you win at the slot machines.

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