Rate response settings

After no settings changes after 90 day check up on my dual lead St Jude PM, I had a video appointment with my Cardiologist the next week.  He decided to tell the tech to raise my HR from 60 top 70 and make rate response more sensitive.  It seems my legs have more strength and I’m less fatigued.  But, one of the changes or the other has me wondering.  I was just riding in my golf cart not playing just watching...I followed my buddies foursome about 4 holes and it was on some really rough terrain.  I started getting a hollow, spasm feeling in my chest and all of a sudden head rush with ears stopping up pretty severely.  I left immediately and tried to go slow and not hit any more bumps.  I made it home and later that afternoon mowed grass on my lawn tractor..after a little mowing I was starting to have the same feeling so quit mowing.. would the move to 70 BPM or the more sensitive rate response be responsible.  I’ve been mowing For several months with no problems.  What should I tell the tech and docs.  Also could to sensitive rate response make me have a problem when I get up from my recliner.  Any input, especially from someone who understands rate response and BPM changes would be appreciated.

2 Comments

Rate response

by AgentX86 - 2020-08-23 19:01:12

This sounds like a classic side effect of rate response.  There are several "sensivity" settings and all are a trade-off between a more "natural" response to activity and an over-response.  The more sensitive to motion it's set, the better the natural response to things like bicycling or swimming but also more sensitive to other stimulous, like bumpy roads. The faster the response, the better it is going from zero to 60 (climbing stairs) but minor events can trigger a high pulse rate.  In the end, you have to decide what fits your lifestyle and feels better to you, within the abilities of your pacemaker. 

A healthy heart increases rate depending on the amount of CO2 in the blood. When your muscles work harder they trade O2 for CO2.  Your SI node detects the increased CO2 and responds, quckly, by increasing its rate to increase blood flow back to the muscles.  This is pretty finely tuned because there is a "negative feedback", which stabilizes the amount of CO2 in the blood.

Your pacemaker doesn't have this information so has to guess at the heart rate needed to supply the muscles.  It guesses by measuing your motion and, more or less, assuming that it's caused by your activity.  The adjustments attempt to balance minimum/maximum rates, sensitivity to motion, rate of increased rate, delay before rate starts increasing, and time it stays at the higher rate until it starts coming down.  Depending on your lifestyle, this can be a difficult, or impossible, balance.  To do everything you want to do, you may have to put up with some odd artifcts.

Rate response

by Radioman#1a - 2020-08-23 19:15:43

Thanks for the comment!  I am just trying to get my quality of life back.  I’ve been playing golf on the average of 3 to 4 days a week for 50 years.  The last 3 months I’ve sat pretty much in my recliner day and night. I’ve tried to walk and ride my recumbent bike too.  I just want to feel as good as I did before the PM.

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