Biking and flatting out


I bike for @ an hour on a trainer. During the second half I would experience shortness of breath and my hr dropping into the upper 60's for just a brief period before climbing back up to the 120's. Toward the end it dropped into the 80's and stayed there for 8 minutes.

Admittedly, this is measured by a chest strap and bluetooth, but it seems pretty accurate. 

Should I be concerned or is this typical PM behavior?

I'm going to post the above to my cardio and electro. I have a Medtronic dual lead.

Thanks for any insight.



This is *probably* some programmed limit being reached

by crustyg - 2019-12-10 11:42:19

Is this typical behaviour?  Well it might be if you are hitting/reaching some programmed limit, or your HR (+/- any PVCs) is hitting some threshold that has been set to prevent PMT or an arrhythmia.

Is it normal/typical?  Not at all: I can cycle hard for 3h with my PM driving me to maxHR for most of that time.   I'm 10yr younger than you are, which helps.  I use the Garmin ANT+ chest strap which we've verified whilst using the Zoom wandless interrogation mode of my PM - matches beat for beat.  But it should, it's a good quality Lead I (in ECG terms) HR measurement.  Yours is probably reliable/correct too.

Is it *appropriate* - for you?  Not sure, you've not provided a lot of detail about your PM model/reason for you needing a PM etc.

Back to your EP tech/EP doc, I think.  They can do an interrogation, look for any events recorded in the PM log and you can discuss why this is happening and if there's an easy way to prevent it - because it's great that you exercise and everyone will want to encourage you to keep on doing it without feeling terrible for some of the time.


by Pacer2019 - 2019-12-10 12:35:22

Isn't 120 low if your are really hitting it hard ?  At max exertion 125 is about as high as mine gets and I feel I need more .


by DonNiederfrank - 2019-12-11 08:51:10

Thanks for the comments.

Picking up a 4-lead halter thingy today and will try to repeat the phenomenon tomorrow. I'll let you know what I find out.

My limit is 140 so that's why I was concerned.

My PM's a Medtronic dual lead and just put in the end of May. Works fine otherwise. I got it b/c I have partial 2:1 left bundle block which was dropping my hr into the 30s.

Crusty, 3 hrs! I =might= have 3 hr legs, but I've only got a 90 min. butt. :-)



motion and biking

by DonNiederfrank - 2019-12-12 13:02:52

Crusty, et al., have you had any luck flexing/extending your arms on the handlebars to simulate a jogging motion? I'm wondering if the issue is the relative motionless of my upper body on a trainer in the basement as opposed to biking outside or jogging (which I do not do).


by DonNiederfrank - 2019-12-16 09:31:01

I found this morning if I grab my bars and shake my upper body fast and hard enough I can get my HR up to 140, which solves the out of breath problem for a while. 

Going to ask that my Medtronic Azure be made more sensitive to motion...


Biking and flatting out

by darmaggi - 2019-12-24 18:43:53


This won't be any direct help to you, but I find I have a similar issue with my two lead Biotronic Eluna 8 DR-T, which is set on CLS, or closed loop stimulation which measures cardiac muscle contractility and electrical resistance. I believe the PM housing can send a signal to the heart, then the muscles resistance is measured by one or both leads.

Biotronic's marketing says this is supposed to be the best at rate adaptation.
Although, at times it seems as though I don't have a PM, because my rate will get stuck below 100.
I notice this the most when exercising at a steady state like biking or swimming.

I've got both a RBBB, and a 2nd degree AV block Mobitz type 2, and before I got the pacemaker my heart was responding more like what you describe in your first post, I'd be exercising at a BPM of around 140 and instantaneously it would get cut in half and drop to 70. At the outset of the issue, if I really backed off on the exertion level after noticing the drop, it would bounce back up to near the original BPM. Over several years it got worse, with both the triggering elevated BPM getting lower and lower, and then the suppressed rate also dropped with a similar ratio as the original experience.

We've tried different programming modes and sensitivity settings, and believe the CLS is the best for my active lifestyle, but it's not as responsive as I would like so we continue to try and dial it in.
Most recently we've turned off the resting rate control, which is a function that can elevate your rate when you're not more active. We did that because the resting rate control has a ceiling of 50 over base rate setting. My PM is set at 40bpm floor and 160 ceiling. It now can have a tendency toward tachycardia from time to time when I'm not exercising, but it still sometimes seems to get stuck on the low end. For instance I was on a stationary bike the other day and my BPM actually went down to 37, which is odd since my lowest setting is 40. So much for a drop dead rate.

I can't do what you do in terms of upper body movement to stimulate the PM, so no matter how much I bang on my chest it doesn't wake up the accelerometer. I keep hoping I can find something specific I can do to elevate my rate every time before I jump on my bike.

Even though we don't have the same PM, I'm responding because of the similar issue of a dropping rate while exercising, which makes me think it's an issue specific to my PM and programming mode or your PM and programming mode, but must be something elemental that the PMs are not picking up on.

Last note on weird BPM artifacts . . . if I can do something to get my HR elevated to 120 or above before I jump on my bike I can usually keep it elevated for the duration, unless I get stopped somewhere when it has time to drop down to 90, and then it can often get stuck there. If successfully getting my rate elevated, and keeping it there for the duration of a typical 2 hour ride, my rate may hit the high 150's with an average in the 130's, which makes me feel like superman, but of course it's the opposite if the PM gets stuck below 100.

At the end of the day, I'm guessing that even though we have different types of PMs on different programming modes, we can suffer similar rate suppressed issues, and I believe it may have something to do with the relative steady state exertion level and the relative lack of upper body movement when on a bike. The second part of that equation shouldn't effect my PM since the accelerometer isn't used as a primary source of feedback.

I'm continuing to do research on my own, and present the Biotronik techs with theories, and new settings to try, because even though I'm on CLS programming there are still many settings that can be changed within the principal mode.

If I ever come across a definitive answer for why the PMs zone out and let the rate drop I'll let you know.


Rate suppression on the bike

by DonNiederfrank - 2019-12-25 11:40:28

Thanks, Mark.

My understanding of my device is that it is accelerometer responsive. I tried  shaking my pec muscle to see if that helped, and when I told my tech her eyes got big and she said Don't do that! We don't want to have to reinsert those leads! lol

She told me my PM was responsive to back-and-forth rather than up/down or sideways. I'm working on how to keep my HR up without any unnatural movements. So far I'm working ok in the 120s. But it seems my Yahoo Tckr is not accurate in the upper ranges. If I understood the tech correctly my 2:1 block kicks in when my HR goes above 160. She set it to 176, but I still experienced a drop into the high 60s yesterday on the trainer. (I live in Wisconsin so I'm in the basment until spring). My Tckr showed 129 before dropping to 62 for 20 sec. before climbing back up. I'm getting a Polar L10 for Christmas. :-)

Do you use any online or offline apps?  


p.s. If you'd like to continue this conversation via email, my address is



by PacedNRunning - 2019-12-31 20:24:20

That info is incorrect and it's why you are seeing 2:1 block at 120 and not your max set of 160. There is a calculation for TARP which is set by 2 settings. If it's not calculated right you will 2:1 Block before you hit your max. Example, my max is 185 and 2:1 block At 220. But I Wenckebach 185-220. I rarely get to 180 so I have no issues. My rep made a mistake of setting me to low in the beginning. 


by DonNiederfrank - 2020-01-01 12:59:48


Thanks. I need some interpretation. What info is incorrect? What is TARP?

This morning I rode for 90 minutes and experienced shortness of breath and HR drops at 37, 43, 51 and 58 during the first hour and then 8 times during the last half hour.

No sprints, no hill climbs. I consistently have no problems for the first half hour or so. I'm wondering if I settle in to too little mobility.

Anyway, going to keep asking questions.

Thanks again for your input.

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