Chronotropic Incompetence

When I first received a PM, like many others I received a diagnosis of CI alongside SND.  My consultant shared the 72hr holter monitor results with me which evidenced the low h/rates when my diary notes evidenced that I was at the gym.  My legs felt like lead on a running machine and RR and the pacemaker removed these symptoms. 

The CI diagnosis was then called into doubt after years of RR pacing on a sensitive setting, and so many people confirmed that it was no longer present, that I had to consider it seriously although it had simultaneously come to my attention (via a knowledgeable forum member) that chronotropic incompetence isn’t always well understood or clear cut.   (I think I posted about this a while ago).

Since I've been asked (in an indirect but fairly obvious manner) whether I understand what RR can do to the heart when it is used extensively / unnecessarily?  I don't!

My question is therefore a simple one :

Are there any detrimental effects from RR that has been used extensively in the absence of CI or with CI that has improved / gone away? 


RR for CI

by Tracey_E - 2024-03-19 17:13:49

The main detriment would be using up the battery faster. 

If they don't think you still have CI, ask them to turn it off for a bit and see how you do. 

Curious, if rate response is on a sensitive setting now, how do they know you don't need it? Can they tell that your rate is going up on its own without help? 


by Penguin - 2024-03-19 18:35:04

Thanks for your reply Tracey-E.  I meant detrimental effects on the heart itself rather than the PM battery. 

Just to correct a misunderstanding: RR was on a sensitive setting  (previous device) - now it's about average.  

I can't answer your question because I didn't ask the right questions at the time. I was more interested in how the dx of CI could disappear.  I've since done a bit of research and asked around, and it seems that CI isn't straightforward. I'm not trying to understand CI in any depth - I've accepted that this is well above my head - but I do want to understand what I'm dealing with in terms of continuing with RR, why others have hinted that previous high levels may have been detrimental and yes, how they can tell I'm not using it? I'm curious too. 

I was told that my heart is increasing it's rate on it's own - that was it!  I've had exercise testing but I'm not comfortable discussing the results on the open forum.

Chronotropic Incompetence

by Gemita - 2024-03-19 19:49:23

How can they tell if you are not using Rate Response?  They will know if you are exercising from your rate histograms.  For example, mine were flat before RR was turned on.  Having RR on and in use showed up immediately on my reports, although I think you are more active, so you probably didn't have completely flat histograms at any time.

The only detriment to your heart that I can see is that having RR on might mean you experience more in the way of rhythm disturbances, like spikes in heart rate if you suddenly exert yourself or turn suddenly while at rest particularly if settings are too sensitive  I certainly am getting more rhythm disturbances with RR turned on.  

Seeing the cardiologist tomorrow.  Cataract op has been postponed until 15 April which is disappointing, but it gives me chance to sort the heart out.  I will write tomorrow night or Thursday Penguin xx


Sinus node disease and beta blockers are the likely cause of my CI, neither of which can be eliminated.  It is so complex as we know.  The cardiovascular system is controlled and influenced by not only a unique intrinsic conduction system, but also by our autonomic nervous system and endocrine system.  There is a lot that can change on a day to day basis Penguin, so your Chronotropic Incompetence status may change or even resolve.  If you are able to exercise without symptoms, this would be a good sign that your settings and your own heart are performing well, but I don't think you are saying this, are you?


by Tracey_E - 2024-03-19 22:33:16

I have never heard that rate response, or any atrial pacing, is detrimental to the heart. RV pacing is the one that can have a long term effect on the heart because the ventricles can get out of sync. 

Tracey-E & Gemita

by Penguin - 2024-03-20 06:29:18

Tracey_E - That is what I heard too, and tbh I'm not that much the wiser now - but investigating currently.  Gemita is talking some sense in her post above yours - or so it seems to me!

Gemita - My own responses (via the ANS) to triggers like fear, anxiety, stress produced very high h/rates during the diagnostic period for CI sometimes during testing, but (fear / stress etc) didn't necessarily occur during holter monitoring.

As you point out exercise capacity is a tricky one for me to judge atm for reasons previously discussed. I used to get histograms showing the amounts of RR used and the % of atrial pacing accounted for by RR. Not so much now.  

Your point about heart rate variability provoked by (sensitive) RR and it's effect on atrial high rate episodes (AHREs) may hit the nail on the head.  This paper which mainly talks about the effect of RR on CRT patients and AHREs alludes to that, although I don't understand the detail or the CRT bias of the paper and how this might affect the findings.  The discussion section numbered 4.0-4.2. is the part that describes this.,rate%20(%3C68%20bpm).

Perhaps RR causes excessive heart rate variability when used on it's more sensitive settings at lower heart rates and perhaps this can lead to AHREs?  Guesswork of course. I'm sure that someone will know better than me. 

I agree with Tracy

by Good Dog - 2024-03-20 07:51:53

Please take this with a grain of salt, but my concern would be longer term as Tracy indicated. That would depend to a large extent on your lead placement and the duration of your QRS. If your chambers are not well in sync now, I would be concerned that it could negatively impact your EF over time. What do I know, but I think it is something to consider. However, the bottom-line is really how you feel. If you need RR on to have a better quality of life, then that may be the most important factor. As Gemita always says: It is all about how you feel. The PM is suppose to enable us. If you have it turned-on and there are detrimental effects you can always have it turned-off.

I am sure you will arrive at the best decision for yourself. I wish you the best!



Bad effects of too much RR

by crustyg - 2024-03-20 08:02:18

There are two obvious bad effects of excessive RR that come to mind.

1 Hypertension.  Beat to beat, BP is controlled by the force of each heartbeat (sympathetic and parasympathetic tone) and Heart Rate.  BP is really the rate of heart blood delivery balanced against the needs of the peripheral circulation (which opens up for exercise and tends to close down when resting).  If your RR is giving you a high HR from minor movement - standing up to visit the toilet - you will become hypertensive.  And this is really bad from the stroke risk.  Longer term, excessive BP tends to lead to atrial stretching => more ANP => kidneys dump sodium + water => BP tends to fall.  But ANP production is often impaired in folk with SS+CI (damaged atria is often the cause of SS).

2 Serious over-pacing can cause tachycardia induced cardiomyopathy: the heart muscle starts to stiffen up so that filling pressures go up.  This isn't good, and AFAIK, it's irreversible.  There's no chest pain, nothing to warn, except eventually ankle oedema and a positive sniff-test on abdo u/sound.  Typically only happens for those with lots of SVT or who have been in AFlut for many months. 

Depending on pacing mode and RV lead placement, excessive RR can also cause a lot of RV pacing - with the recognised risk of LV remodelling leading to reduced %LVEF which is usually (but not always) corrected by CRT.

For me (and this is where it becomes personal), I've always been wary of over-pacing through excessive RR.  Resting HR within 10months of PM implantation, 28BPM.  I'm athletic so a decent HR when I'm active is essential for me, but it can be overdone.

Talk about personal

by Good Dog - 2024-03-20 10:20:20


Frankly, after reading your well-articulated response, it made me very angry (certainly not at you), because it once again reinforces my belief than an ignorant and unthoughtful Pacer Tech caused my stroke last year. I am not looking to sue anyone, but an apology would at least have been nice when I brought it to his attention. Instead, he became indignant. After 35 + years of being paced and never having RR turned-on. This guy turns it on and doesn’t even tell me. I am not an athlete, did not want it on and did not need it! So with an EF of 40 and having a pulse that rarely left the 50’s for many years and almost never exceeded the mid to high 80’s I go for a walk and my rate spikes into the 130’s. I dealt with this for several weeks before it was finally turned-off. A month later, I had a stroke and they found a collection of soft plaque all on one side (of my left carotid) blocking 60% of it. When I rubbed my neck a piece broke-off and caused a stroke that impacted my vision. That was my experience with RR.

I am sorry for venting (and hijacking this thread), but your explanation brought to mind a real sore spot for me as it seems to clearly indicate in no uncertain terms what happened to me. I'll let it lay now and will not bring this up again. However, beware that this is the kind of thing that can happen if your care is put in the wrong hands.

Criteria for Rate Response

by SeenBetterDays - 2024-03-20 13:41:04

Good Dog - Your post is disturbing as this suggests that incorrect application of rate response could potentially have significant medical implications.  In your case, if your theory is correct, it has led to the movement of arterial plaque.  The change to settings should absolutely have been discussed with you first and I am astonished that no mention of this was made before this was done.  This is worrying and potentially has led you down a road which potentially you could have avoided.  I'm really sorry that you had such a difficult experience.  

Penguin, Good Dog has made me wonder what specific criteria are used for the application of rate response.  In Gemita's case it seems that flat heart rate histograms suggested that the heart needed this function but were there clear diagnostic criteria for you to have this function on a sensitive setting? Is it possible that the chronotropic incompetence is intermittent so at times this function was unnecessary and your heart could achieve the rates on its own?  My understanding is that the setting is either on or off so if the chronotropic incompetence is not present at all times this could create a problem.  My cardiomyopathy resulted from ventricular pacing but I am unsure of the implications of over pacing the atria.  This is a questions that a medical professional would need to answer.  Do you have the option to switch off rate response in a controlled environment and see how well your heart deals with exertion (maybe you have already tried this during your exercise testing?).  Hope you can find the answers you are seeking soon Penguin.  This is a difficult and complex subject and very tricky to navigate.

Sending you love and best wishes.

Rebecca x

It's not just about HR increases in response to activity

by crustyg - 2024-03-20 14:38:56

My one and only Bruce Protocol treadmill test I got from my resting HR (about 45BPM) to about 120BPM, which *might* have made an unthinking EP-doc decide that I didn't have CI.  However, the ECG running throughout showed the real issue.  From about 70BPM I was in a junctional rhythm - no SA-node drive => CI.  If I get really upset I can achieve about 125BPM from my AV-node (like the last 45min of a very long cycle post PM implantation but with no RR support).

My EP-doc suggested another Bruce Protocol for me recently.  He must have seen my face set, and quickly changed it to 'have a long workout on your bike.'  Smart guy.  For folk with CI, a Bruce Protocol treadmill test falls under 'Cruel and Unusual' punishment.  It's really unpleasant.

I don't think I've seen any formal CI definition, as it varies from patient to patient.  If you can't achieve a sensible maxHR for the activity you're doing, then leaving aside other considerations (==pathologies), you probably have CI.

Dave, Crusty & SeenbetterDays

by Penguin - 2024-03-20 17:19:56

Thank you for those responses. Crusty, your response answers the question and I realise that you know what you're talking about. I'll respond properly once I've digested what you're saying and how it might apply to me.  

Dave - please don't worry about hi-jacking the thread. Yes, I'm concerned about my own issues, but yours matter too. We all learn by hearing what happened to others and your story is no exception.  Please continue to ask Q's for your own benefit. I'm interested to hear the replies as I doubt that many of us were aware of atrial over pacing and how RR can increase VP.  

SeenBetterDays -  Yr Q. re: criteria for sensitive settings for RR.  I have no idea which criteria were used I'm afraid.  RR accounted for approx 1/3rd of my atrial pacing and v.pacing went up and up in the absence of any AV conduction issues. Atrial arrhythmia were eventually disclosed.  The VP was stopped using v.long AVDs - not at my request might I add - because I had no idea about the dangers of high VP, long AVDs or anything else at the time. I just knew that I began to feel terrible and my blood tests became concerning. The removal of VP improved things.

That's why I bang on about what can go wrong.  I think it's important that we are told about dangers in advance of their effects, rather than being left to work it out for ourselves when it may be too late or after damage has occurred. 

I can't really go into further detail online, but the over sensing which occurred a few months ago feels like it really was a very dangerous occurrence against this background.    


by Penguin - 2024-03-20 17:51:27

Well, that's what I call an answer! Thank you, although it was disturbing to read, there are elements which make a lot of sense. 

I don't want to go into further detail online, but wondered if you would mind explaining what might be found in an abdominal ultrasound to suggest any of the problems caused by too much RR and even tachycardia induced cardiomyopathy? 

Many thanks.

Penguin & SeenBetterDays

by Good Dog - 2024-03-20 19:23:21

Penguin: Your response was very gracious. Thank you!

SeenBetterDays: I have little doubt that my theory is correct. While I have to acknowledge that one can never be 100% certain, it is the only explanation that makes sense to me. Every Doc that looked at my CT remarked that they were amazed by it. All of my arteries were perfectly clear including my right carotid. The only place I had plaque was my left carotid and it was ulcerated. The surgeon that removed it for me said it had the consistency of toothpaste. My point is that it appeared that whatever plaque that existed elsewhere was transported to my left carotid. The only question is how any why. The sudden and unusual spikes in pulse and blood pressure are a plausible explanation.

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