Long term effects of more sensitive rate response PM settings

This issue emerged on a recent thread (See "HR dropping while on climbs") about rate response to support biking up hills. 

Link to thread:


Member frankmcw2 posted his suggested settings for Medtronic PMs to make the rate response settings more sensitive to movement. I'd previously (more than an year back) requested and got  that same pdf document from frankmcw2. I took them to my appointment with my EP and PM tech for review and had those settings changes done to my Medtronic PM.

One consequence of that change is that my HR goes raipdly upto 115 after taking ten steps (as designed). It took me a few weeks to get used to this higher rate but my body adapted.

I also check my (resting) blood pressure regularly and have noticed no upward trend wih the new settings. I've not done yet taken a BP reading while exercising - maybe I ought to get a treadmill stress test or wear some other ambulatory BP monitor while hiking or running.

Member crustyg was kind enough to comment on potential negative long term effects of the higher heart rate.

I invite discussion on this topic and I plan to  discuss this at length with my EP at my next appointment.

Thoughts? Questions?





A lot depends on how much time your heart is paced faster than normal

by crustyg - 2020-08-12 17:30:55

If you have normal SA pacing, your heart rate is quite low (whatever that is for you - 60-70BPM for seniors, perhaps 50 for the athletes), and spends overwhelmingly most of the time within 20-30BPM of that resting rate.  When you measure how many minutes per day your HR is well above this it's actually quite a small number.

The risk of deliberately making the PM's rate response algorithm overly sensitive is that your heart starts to spend 50-70% of each day at or above the mid-range of HRs that you have.  This is the territory where your heart muscle can run into problems.

I think most/all PM programming systems provide some indication of how much time is spent in each decade range of BPM - it's an easy to see overview of HR over time.  It's also a useful guide to how well the PM is operating for folk with SSS (too much to the left, and the RR isn't working well, too much to the right and it's indicative of over-pacing).  It's also a telltale for physical activity...

Medtronic adjustment to enhance pacing

by frankmcw2 - 2020-08-13 03:25:46

In my case, I spent over 2 years after PM implantation with my PM doing little more than maintaining my heart rate at the Lower Rate setting of 50 BPM at night. It was also effective during running, elevating my HR up to 150 to 160. However, for all other activities it was not pacing at all, because it was not responding to the lighter upper body movements of cycling, hiking and stair climbing. Therefore, I began much research and had many adjustments made to my PM. Finally, I was fortunate to find a Medtronic technician in Arizona who had worked with other athletes who had my same problem, which is Bradycardia & Chronotropic Incompetence. The adjustments he made cause the PM to more quickly elevate the HR so that I can now experience a higher HR for cycling, hiking up steep mountain slopes and even just climbing up a flight of stairs. The adjustments do not necessarily make the PM algorithm overly sensitive, but cause the PM to respond more quickly to upper body movements as needed. The elevated heart rates that are the result of PM pacing are no different than if I didn't have CI and performed the same movements. I travel a lot and have cardiologists in Seattle, Phoenix and Pensacola who have all reviewed my rate histograms on a quarterly basis. They have seen no problems from the adjustments that were made 3 years ago and have found no damage to my heart as a result. If anyone would like I can email a .pdf file that describes the Medtronic adjustment I am referring to. 

Some thoughts and questions

by Gemita - 2020-08-13 05:47:51

Hello ar_vin,

I too have a Medtronic pacemaker - Ensura DR SureScan EN1DR01 and it is working well enough to help with SSS (tachy/brady syndrome) and other troublesome symptoms.  I realise this thread may essentially be for cyclists but it is still nonetheless of interest.  

I am always looking to learn what my pacemaker can do for me and how any adjustments like rate response could affect my heart health in the future.  I was therefore interested to see your new post following both crustyg’s and frankmcw2’s comments in another thread.  I didn’t realise a Medtronic pacemaker could be so successfully fine tuned as Frank has discovered, or that this could come with some potential health risks as crustyg clearly points out.  

I could benefit from maintaining a more sustained higher heart rate during exertion.  Unlike many, my blood pressure which is historically low does not seem to respond to an increase in heart rate.  Instead my BP can be stubborn to rise and may even crash during a sudden increase in HR.   

May I suggest the following questions ar_vin might be useful although I apologise if I have not fully understood this complex subject ! 

At what level should my rate response ideally be set to protect my heart from any potential harmful effects of cumulative, sustained pacemaker over pacing while allowing me to reach and sustain a stronger, higher heart rate during exercise?  

Do we need to work with a doctor to determine our individual safe level or can our pacemaker be programmed/interrogated to give essential feedback for safe pacemaker adjustments to be made without exercise testing for example ? 

I believe there has to be a balance between what we want to do and what we can “safely” do without causing adverse effects.  I am aware that many endurance athletes are prone to heart enlargement from exercise. 

How does exercise induced cardiomyopathy differ from pacemaker induced cardiomyopathy or are they essentially the same?  Is there a difference in health outcomes between the two and can they both be reversed on cessation of heart rate stimulation ? 

How do we then safely achieve maximum HR during activity while at the same time maintain a relatively normal HR for the rest of the time ?   Are we able to determine what a sensible rate response setting would be for us individually to try to prevent any potential future complication of cardiomyopathy from pacemaker over pacing ?   

. Would it be beneficial to use rate control meds to protect us from any long term over pacing, or can we adjust pacemaker settings alone to try to achieve a "safe" level?  

Although rate control meds may make it harder for us to exercise, if our heart rate and BP tend to increase with pacing, should we use rate control meds as a preventative measure against developing cardiomyopathy ?  A difficult balancing act.

Being an arrhythmia patient I am mindful of the fact that a sudden burst of energy leading to an increase in my heart rate can be a strong trigger for my arrhythmias, so exercise and/or the pacemaker suddenly pushing up my heart rate could cause problems. 

Frank I would appreciate a pdf of your settings even though I am currently not cycling.  Thank you.

Hope you have a very helpful meeting with your EP ar_vin and get some reassuring answers. Would be interested to hear the outcome at some stage


Perhaps I'm being overly cautious

by crustyg - 2020-08-13 11:24:01

There's no known treatment for the cardiomyopathy caused by prolonged tachycardia - as long as we're clear that we're not talking about the LV remodelling of prolonged RV-apical pacing.

I suspect that I'm being overly cautious: the (previously) common causes of this problem result in tachycardia for most/all hours of the day (although not necessarily always at the same high rate).  It's seen in SVTs, AFib/AFlut (where the AV-node conduction ratio can vary from something like 7 or 8:1 all the way down to 1:1 (which is more hazardous due to SCD than some future heart muscle problem), folk with *lots* of PVCs and repeated runs of VT, and it used to be seen in some patients who were overpaced - often during the night as well as during the day.

Being aware of the potential problem and actively looking for it in terms of reviewing HR over time is probably all that's needed.

Getting an accelerometer-only PM tuned to provide an effective HR for SSS/CI patients who like to road cycle is great, and a neat solution to the problem.

I've learned something new.


by ar_vin - 2020-08-13 13:33:11

This discussion started on a bike thread but I'm almost exclusively a trail runner, hiker and backpacker. Most of my outdoor activities consist of going up and down big hills: coastal California hills as welll as hills (mountains) in the Sierra Nevada.

Before I was first symptomatic of bradycardia (and diagnosed within a week) I routinely hiked, ran and backpacked up some big hills without issue. Shortly after diagnosis my bradycardia was accompanied by chronotropic incompetence; this meant I just struggled to walk up a hill that I previously could jog up with little effort,

This continued to be the state of affairs even after my PM implant. I started to dig into the PM manuals and researching here on the club. I was very fortunate to come across frankmcw2's very helpful posts and requested the pdf document from him.

Biking uphill and walking up steep hills share the same issue; not rapid enough movement for the accelerometer-only PM to pace accordingly.

I'll respond to the questions raised in a separate post and will post my EP's feedback when I do see him on this same thread.



Medtronic setting considerations

by frankmcw2 - 2020-08-17 00:09:02

To begin this comment I will say that the purpose of my suggested settings change is to increase the pacing of a Medtronic PM so that those attempting exercise will enjoy a high enough heart rate to be able to exercise. There have been many posts on this blog stating that the PM was not delivering that goal. The result has been such symptoms as running out of breath, weak legs from blood that is not fully oxygenated, and even fainting spells. The reason for this is that the initial PM settings after surgery are designed to accommodate the majority of patients who are not attempting significant exercise. The purpose of the settings I am suggesting is to enable the PM to elevate the heart rate enough to fully enjoy exercising again. Many patients, such as myself, have no heart issues other than the hearts natural electrical system not being able to read our blood chemistry well enough to naturally elevate our heart rate when needed, (called Chronotropic Incompetence). Gemita, I can't speak to other issues such as Atrial Fibrillation nor Tachycardia. I do believe that the settings changes I refer to will not create "over pacing" any more than natural heart pacing due to exercise. You also mentioned the possible hazard of developing Cardiomyopathy from "over pacing" but I have not seen any evidence of that being the case. When past endurance athletes, such as myself, develop SSS, Bradycardia and Chronotropic Incompetence it does not mean that we are suffering from Cardiomyopathy. Our hearts electrical systems are no longer doing the job, but it does not indicate Cardiomyopathy and damaged heart muscle. You can present the suggested settings to your cardiologist/technician and see if the adjustments work for you. Send me an email at paulafrankmcw@gmail.com and I will reply with the .pdf attached. Since you are not climbing 13,000' peaks (such as ar_vin and I do) you may want to modify the suggested Average Daily Living rate from 115 down to 110. (This would have the PM easily ramping up your heart rate to 110 bpm when lightly exercising.) At the same time have the ADL rate set to 15 instead of 10. (This will cause the PM to count out 15 "steps" before it begins ramping up your heart rate, instead of just 10 counts.) Make sure the other settings are exactly as described in the .pdf. You can immediately test the settings in the clinic to see if you like it. If there was any hint of tachycardia you could reprogram back to original settings. Every patient is different, so experimentation is the only way to find a good balance.

You know you're wired when...

Microwave ovens make you spark.

Member Quotes

My pacemaker is the best thing that every happened to me, had I not got it I would not be here today.