Upper rate limit

Hello all

Question on upper rate limit. For someone with a pacemaker (Medtronic), is the upper rate limit in effect their maximum heart rate? Secondly, does rate response allow the heart rate to exceed this limit? I ask because I think my limit is set at 150 but when jogging, it goes up to 170 (readings from chest strap monitor). Cycling is of course a whole different story, settling at 80-85 regardless of terrain or effort.


4 Comments

Maximum permitted HR

by crustyg - 2019-10-09 13:22:16

Hi: with your current settings 150 is intended to be the maximum HR that your PM will drive you up to as part of the adaptive rate response.  This is likely to be too low for someone of your age and activity level.  Many of us have something more like 50/160, but it depends entirely on what is sensible for you, and your negotiating skills.

Depending on why you have ended up with a PM, then no, it's certainly possible for you to achieve a higher maximum HR than your PM has been programmed to.  Athletes with recurrent arrhythmias can often trigger runs of an atrial tachycardia (usually not very important, but a warning sign along the road to Afib), OR you may be getting runs of VTach - not so great and potentially quite serious if sustained.  Some PMs can be programmed to try and overpace your atria to reduce your ventricular rate (which is what your chest strap measures) in certain situations, but in general PMs are limited to increasing HR and drugs such as beta-blockers reduce the episodes of high HR.

If you're a cylist, then you probably have the wrong PM fitted.  AFAIK, BostonSci are still the only manufacturer with a working Minute Ventilation feature which allows adaptive response when the body is working hard but the upper body is fairly still, so the usual accelerometer (XL) value doesn't feed into the rate response algorithm.  If others know differently, please sing out!  I'm a keen cyclist and my PM will drive me to 160bpm on a road bike on smooth roads.  Mountain biking is usually easier as there's a lot of input to the XL, so perhaps you just need the response factor to be adjusted upwards.

Search for posts on Exercise and Sports - this is a common topic.

WOGEDA

by IAN MC - 2019-10-09 15:52:01

I always get confused when people talk about upper limits, maximum rates etc. There are 3 different " maximum heart rates " :-

i)   Maximum Tracking Rate :  This is the quickest the pacemaker will pace the ventricles in response to atrial activity. As an example , if you suddenly developed atrial flutter at 300bpm and every signal was passed down to your lower chamber then you would end up with a ventricular rate of 300 and this could be life-threatening. So the maximum tracking rate is a safety feature.  The importance of this is different for AV block and Sick Sinus Syndrome. You don't say why you have a PM

ii)  Maximum Rate Response Sensor Rate :  If you are one of the 50% or so of people who have Rate Response switched on then it will only drive your heart-rate so high in response to exercise.  This setting is often   slightly lower than the Maximum Tracking Rate but not always.

iii) Age-Related Maximum Heart Rate :  This is the maximum heart-rate which you should allow to safely reach when you are exercising. A common formula for this is 220 minus your age but this concept needs lots of  qualification depending on your fitness, drugs that you take, whether or not you have a pacemaker, underlying medical conditions etc.

So which upper setting are you talking about and why do you have a pacemaker ?

CRUSTY :  You ask whether Boston Scientific is the only manufacturer with minute ventilation as  well as accelerometer. Until fairly recently there was an Italian-based  company, SORIN which offfered both sensors. We used to get posts in the PM club from Sorin-implantees They had a name change and became LISANOVA  for  a time and more recently their PM business was absorbed into the Shanghai-based company ,MICROPORT.

Microport have a growing presence in the US and Europe and I do in fact have a cyclist-friend who has a dual-sensor Microport pacemaker. ( fitted in China  ! )

Cheers

Ian

Thanks for the update

by crustyg - 2019-10-09 18:47:58

I appreciate the feedback, Ian.  Any patents that Guidant took out on MV would have expired some time ago (Guidant was purchased by BSC and split with Abbott, I think), but often actually exploiting a patent requires considerable experience of the details - the trade secrets - which weren't disclosed in the patent.  I had thought that someone would be working to deliver this, but it's not trivial to make it work reliably,

Thanks

by wogeda - 2019-10-10 04:06:33

Thanks for the responses - they are really helpful. 

@IANMC - By maximum heart rate, I'm referring to the 3rd category in your list (Age-related max rate). By upper rate limit, I'm referring to the 2nd category (max RR sensor rate). I got the pacemaker after undergoing a catheter ablation that damaged the AV node.

@CRUSTY - The pacemaker is not due for replacement for a couple more years and even then, I'm not sure there's much variety in my corner of the world (Eastern Africa), either in terms of the brand or expertise in those. I may have to stick with Medtronic and go the adjustments route. 

Thanks

William

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