Riding down hill on bicycle

I am an avid cyclist and had a Boston Scientific PM installed in June, 2012. I have bradycardia which was causing me to pass out when my heart rate dropped too low (like at the breakfast table).

I am having problems with the feature that detects changes in breathing and/or activity level. I ride up and down hills and have no problem climbing up the hills. But after I have started downhill (just coasting for the most part--but going pretty fast and hitting a few bumps) the PM decides it needs to kick in and jumps my heart rate way up. This results in my getting very dizzy and having to stop until the heart rate drops. Yesterday the problem got so severe that I had to call my wife to pick me up.

I am interested in thoughts of others but am also interested in reading anything that explains specifics of how the PM detects condititons that make it decide to jack up my heart rate.

The technician adjusted the settings on my PM yesterday and I have not ridden yet to see if the problem is rectified.

6 Comments

Don. Is right

by IAN MC - 2012-08-03 01:08:13


... and I hope his suggestions work for you but some PMs are not very sophisticated when it comes to Rate Response. Cycling seems to confuse the system as you may be putting in plenty of effort but the accelerometer device in the PM doesn't recognise it e.g. when you're going uphill but as Pookie says the reverse applies at downhill speed with all the vibrations.

I believe that there are PMs which may help you and some of our engineer- whizzos will know more

Best of luck

Ian

Whooopsie!

by donr - 2012-08-03 01:08:19

I did not read all the question before answering.

The RR function is a small accelerometer - just like the ones in inertial navigation systems. It is a small mass that is fixed to the body of the PM by a spring (To simplify the functioning). The body of the PM starts shaking & the mass lags behind it because it is attached in a flexible manner. This lag is sensed & it generates a signal telling the PM to speed things up for the heart.

The point at which it switches on the heart is variable. Mine is set at some horrendous number because I really don't need it - my heart functions pretty well under increased load. It can also be turned off completely.

I know mine is set pretty darned high. On Wed we went to an Atlanta Braves Baseball game. I'm on crutches for the aftermath of having a bunion repaired, so we got a wheelchair. The ride in the wheelchair was across a plaza paved in paving bricks w/ beveled corners. I thought my teeth were going to be jarred out of my head I bounced so hard. I was surprised that my RR did not kick in, so it must really be set high! It was a short time before smarts overruled stupidity & I asked the pusher to slow down.

Don

Frank is the true expert on this little torture device.

Rate Response

by donr - 2012-08-03 01:08:48

Pookie, I think that is what is causing the problem. The RR feature of the PM senses the bumps as increased physical activity & boosts the HR thinking you are working harder,but the heart is not.

Easy tweak - either increase it or TURN IT OFF!

Don

RR

by mike thurston - 2012-08-03 02:08:41

I have the opposite problem. I struggle mightily going uphill and constantly tap on the PM to get it to speed up. Even then riding hills is hard but I have lots of heart damage, am totally ablated and in permanent a-fib. At the IMAX showing of the Dark Night a couple of days ago the incredible loud, low frequency sound was messing with my PM and I started having PVCs. I tapped on the PM increasing the rate and soon the PVCs were gone. Wierd but it works. Certainly frustrating to have to deal with all these issues.

Hi Oldbiker:)

by Pookie - 2012-08-03 12:08:19

Glad you found us.

I've been a member here for quite a few yrs and there are lots of avid cyclists on this site. Hopefully a few of them will see your post and comment.

The word that jumped out to me in your post was bumps. This might cause your pacemaker to start pacing you. For example: we have had a lot of members even tell us that they experience similar to what you describe when they are in a truck driving over bumpy roads.

I don't know much about Boston Scientific as I have a Medtronics pacemaker, but have you thought of calling them - their 1-800 # should be on your card. They might be able to help you.

Until then, hang tight until the cyclists here tune in. Check back from time to time.

Welcome to our club,
Pookie

Follow up

by oldbiker - 2012-08-04 09:08:33

Thanks for the responses.

Don (or Frank), do you know if it is possible to turn off the RR feature that senses a bumpy road (the road is in fact pretty smooth), yet leave on the feature that detects increased breathing?

I rode the same ride as the one ridden on Thursday (the first time since the technician changed my settings). The problems on the down hill were much less severe than on Thursday but I did notice my HR going up at inappropriate times, just not as high. And I did not have to stop even once.

The part of the detection system that I liked was that, on climbs, the PM would push my HR up to 170. Before the PM was installed, I could not get a HR higher than 135. The new adjustments to the PM included setting the breathing detector to "Passive" and the motion detector (accelerometer?) to "Medium". Both of those setting were less aggressive than prior to Thursday.

After the recent adjustment, my max HR on the climb was only 140. My question is whether or not I can have the setting changed to go back to allowing 170 on the climbs without risking the very nasty problem on the descent.

I have had one phone conversation with the Boston Scientific home office and don't want to become a pest by calling regularly. So if you know how this works, I can save my next call for something thats stumps all.

Thanks again

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