got confused again with how may pacemaker works during exercise

Background - recently reaching and staying at 175 bpm or so during very minimal intensity running. Before pacemaker at that heart rate I would have been nearly at my highest intesity of exercise. I have grade 2 heart block.

I spoke the technician today and he said rate response is not on, I was hoping it was on as this would  make things more simple.

My question is, if my atria starts to beat at say 150bpm does the software change the amount of time it waits for an intrisic ventricular beat compared to if it was beating at only 100bpm?



If I were you ..........

by IAN MC - 2021-02-09 12:11:58

It seems to me that when you had your PM installed ( I quote from your Bio ) you had :-

Heart block grade 1 and grade 2 (Mobitz II) with no other heart issues

For whatever reason , you seem to have now developed  " other heart issues "  i.e. some sort of inappropriate tachycardia   ........  possibly not related in any way to your PM !

If I were you , I would be seeing my cardiologist a.s.a p. to get a diagnosis and hopefully a solution.

For what it's worth I had similar symptoms as you are having when I was diagnosed with atrial flutter ..... but I am sure, there are many possible causes.

Best of luck


My thoughts

by Gemita - 2021-02-09 12:15:05

Dear John,

When you notice your high heart rate, may I ask “how you feel”?   What monitoring are you using to check your heart rate?  Did your technicians give any indication of what the cause might be, or indicate that it might be your heart still finding its feet and perhaps going into Sinus Tachycardia with exertion?  If you feel unwell when you hit these high heart rates, then I would be worried but if you reach them without difficulty and can maintain these higher heart rates for good periods of time, for the moment I would be reassured that no harm will come to you.

I would however ask your team whether an event monitor could be worn for 24 hours, when you can challenge yourself and trigger these high heart rates so that your clinic can analyse the data and come to a conclusion on what may be going on.  Alternatively they may wish to do another stress echo

Thanks both

by quikjraw - 2021-02-09 12:34:33

Hi Both

My first appointment with the cardiologist is on 24th February subject to the hospital strain at that time.

They did not think it was the pacemaker but I have sent them a download today at their request.

The whole run was recorded on my heart rate watch. It started quickly to rise to 165 in as little as a few minutes and then for at least half of the remainder of the run increased to and stayed at around 175bpm. I felt fine at all heart rate dropped relatively quickly when I got home.

I agree a monitor and or a treadmill test would be a good idea.

I will look up atrial flutter and see if that might explain what I am experiencing. If atrial flutter is occurring would this be picked up on the download?

Kind regards


An atrial tachy arrhythmia ?

by Gemita - 2021-02-09 13:30:39

Yes John if the parameters set up in your pacemaker for the recording of an atrial tachy arrhythmia, like Flutter are met;   that is if any atrial tachy arrhythmia is detected at a certain speed and for a certain duration, it will be recorded and reported on.  So if there is something going on, it will be seen.  It is extremely reassuring though that you are not symptomatic during your high heart rates, at least not for the moment, so this seems to me to be a very good sign indeed that your tachy symptoms will settle. 

I hope your download will give them some good information.  It should certainly show the spike in your heart rate and give them an idea whether this is an appropriate response to exercise.  Please let us know what they find.  I think I recall you were getting tachy symptoms a few months ago at rest also?

I certainly will

by quikjraw - 2021-02-09 15:43:50

Thanks Therese

I will definitely update following my appointment.

You are quite right I was getting prolonged episodes of about 100 to 120bpm and palpations after walks when I'd been sat down for some time.

They have not reappeared thankfully. No idea what was causing them.

All the best


HR monitor

by ar_vin - 2021-02-09 16:18:50

You're an experienced runner so you probably know a fair bit about HR monitors.

I'd suggest using a chest HR strap to get a good estimate of your heart rate (especially while running). The wrist, upper arm, finger pulse ox optical HR monitors are notoriously inaccurate for a range of reasons.

You certainly don't want to go chase down rabbit holes if your HR monitor is off. I'm not suggesting that's THE explanation of what you're seeing and feeling but it's worth ruling out.

Hope you figure things out sooner than later!



Timing the beats

by Gotrhythm - 2021-02-09 16:42:19

When it comes to answering your question re: pacemaker, I'll be the first to admit when it comes to the technical aspects of pacemaker function, I have a drop of knowledge in a vast ocean of ignorance. And although I have symptomatic Type 1 heart block requiring pacemaker intervention, I don't know much about Mobitz Type 2.

As I understand it, with heart block, the signal that arises in the atrium, does not make it all the way down the heart to the ventricles. What the pacemaker does is sense the activity in the atrium and then stimulate a contraction of the ventricles so that all parts of the heart beat is coordinated.

There is a tiny lag between when the node fires in the atrium and the time the signal arrives in the ventricles. That's natural, and the pacemaker is programmed to take that into account, before it "decides" it's taking too long for the ventricles to react.

How it "decides" is a matter of fancy algorithms--a word I can't define much less explain the math. All I know is, depending on algorithms, it decides how long it should wait. Does it change between 100 and 150 bpm? Logically, I would say it does. But what's important to understand is that, with every single beat, in thousandths of a second, the pacemaker is re-doing its calculations. 

If you want to understand more, I suggest you consult Youtube. There are videos showing what's happening with every arrythmia and how the pacemaker copes. If one video doesn't help, there are 10 on the same subject done by other organizations.

Getting the settings right for the comparatively young and fit can be tricky. The more you understand about how your pacemaker works, the better questions you will be able to ask your doctor, and the better you'll understand the answers.


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