intermittent block variation with heart rate

Hi all,

hope you are all doing well.

I am interested getting a feel for the people who have intermittent heart block whether they know if in their experience it reduces with increased heart rate or decreases.

Looking through posts on here I get the impression that the majority of people seem to see their block increase with rising heart rate but I am keen to know if any others are on here actually see it reduce with increasing heart rate.


Intermittent heart block with variations

by Dixie Chick 65 - 2021-04-07 08:20:00

Good morning !  I have intermittent grade 2 and grade 3 Heart Block. I don’t understand your question because I’m not aware ( with a pacemaker in place) of when my block occurs, or when it doesn’t. By the way, I have the very same PM that you do. I do know that as of late January, 2021, my pacing percentages were RA 14.8% and RV .02%. 

I’ve had my PM since late May, 2020 and have had several adjustments and changes to my settings since that time. Prior to my PM I had several fainting and near fainting episodes as well as Bradycardia. I got the pacemaker with a diagnosis of complete Heart Block. Since that time my Dx has been revised to intermittent grade 2and grade 3 HB. I never feel any difference...I’m not aware of when it kicks in or when it doesn’t ! 

Maybe I am not understanding what you’re asking, but thought I’d explain my experience. From what I’ve read, intermittent heart block is pretty rare. And as we all know, once you have it, progression is inevitable.

Best to you,


Does it matter ??

by IAN MC - 2021-04-07 08:49:54

Maybe I'm missing something but why does it matter which heart-beats occur naturally and which are initiated by the pacemaker ??  If you knew whether, or not, your AV block increased when you exercise what difference would it make , as long as your PM takes care of it. ? Would it alter your attitude to exercise  ?

I have Sick Sinus Syndrome which is commonly intermittent and I never know what triggers off each individual heart beat.

Would knowing give me a better life in any way ???

as I said.... maybe I'm missing something !



by Tracey_E - 2021-04-07 09:18:14

I'm 3rd degree block and pace 99.99% of the time. One of the very few times I beat on my own is during intense exercise. It's just an interesting fact, but as Ian says, makes absolutely no difference in anything. 

During checkups and downloads

by quikjraw - 2021-04-07 09:28:03

Sorry I did mean during checkups and downloads whether people knew when their block was occuring - I understand histogram data can help show this.

Dixie Chick I also have a an intermittent mix of Wenkeback and 2:1 heart block with the addition of a very long PR interval but I am up at 80ish percent ventricular pacing.

Ian MC it may help me understand things more and also inform me when I go for the next checkup. I am not, per se, interested whether each individual beat is intrinsic or artificial, I more interested in the possibility that large proportions of my intrinsic beats do not happen because the pacemaker beats them to it when it does not strictly need to. 

The reason for this is long term potential problems, shorter battery life, and potentially less than adequate exercise capacity.


long term potential problems

by Tracey_E - 2021-04-07 10:29:03

How much we pace is a very small part of how long a battery lasts. More important are the extra features we use, position of the leads, condition of the leads, how much power it takes to make the heart beat, safety margins. Less pacing while working out is going to be negligible in overall battery life. 

Exercise capacity, in theory, is the same whether it's a paced or natural beat. I'm no cardiologist, but I would think the pacer kicking in sooner to keep the venricles in sync with the atria, rather than waiting for the heart to do it on its own, would be more efficient. When our rate is up and we are pushing hard,  you don't want a delay, you want that beat. 

In other words, no long term implications. 

Just going to point something out here. Everyone assumes we want the battery to last as long as possible, and yeah, that's a good goal, but replacing it is not a bad thing. Replacements are super easy and there are some benefits to replacement because we get the latest technology. I'm on #5 so telling you this from firsthand experience. And what you're talking about is negligible, like not even a few weeks difference. 

I have intermittent bundle branch blocks (mainly right, but occasionally on the left too)

by Gemita - 2021-04-07 11:27:47


Is your question about whether you feel your block could be controlled or even prevented from progressing by either an increase or decrease in your base rate?  I suspect you want to try to prevent any progress from occurring so that you are minimally right ventricular paced.

Although I have Sick Sinus Syndrome, I also have intermittent bundle branch blocks (predominantly on the right) and I can certainly tell you that these have reduced in frequency since I received my pacemaker.  I put this mainly down to the increased base rate.  I have documentary evidence to prove that my blocks have eased.  With a slower heart rate I was really struggling.  

exactly right

by quikjraw - 2021-04-07 11:55:28

yes I think you are right Therese, i will be pushing for this at my next meeting or treadmill session whichever comes first.

Long PR interval

by AgentX86 - 2021-04-07 14:01:38

A long PR interval (P = atrial depolarization, R = ventriclar depolarization) says that the AV node, His, and all that, is slow.  At a high heart rate, it's easy to see how the block would get worse.  At some point there is no time to get the R in there at all.  At that point beats are skipped.  I can imagine a Wenckebach or Mobitz-II but I'm not an EP.

As others have indicated, the only interest is curiousity. We know what is, and it's been fixed.

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