Rate response question

Can anyone tell me the source of the rate response mechanism information? Is it from he electrical activity of the heart, the electrical activity of the rest of the body, the movement of the body (accelerations decelerations etc.) or none or all of these?

7 Comments

Rate response

by fishfighter - 2012-11-21 03:11:33

I find myself when riding on bumpy roads that my CRT-D will speed up my heart. I did ask about this and my doctors did tell me bouncing around will do that.

Mine is a St Jude. Don't know about others.

Rate Response

by SMITTY - 2012-11-21 06:11:42

Hello Ponch,

Here is part of an article on rate response that I collected last year. I don't know from where I got it. Maybe it will answer some of your question on RR.

"Some pacemakers automatically adjust the heart rate.”

"Some pacemakers can be equipped with a rate of activity response feature. This feature allows the pacemaker to pace faster during periods of physical exertion or stress. The body's metabolic activity increases with exercise and stress. Heightened metabolic activity in turn increases the need for more blood supply to muscles and other organs. Newer pacemakers with rate of activity response features can measure the body's metabolic activity (with sensors) and increase heartbeats by accelerating the pacing rate during exercise and stress. After exercise or stress, the pacing rate returns to the previously programmed setting.

Different rate of activity response pacemakers use various sensors to measure metabolic activity. One type of pacemaker contains a sensor that detects vibration related to activity. The pacing rate accelerates when the pacemaker senses increased vibration. Another type of pacemaker has a sensor that detects the rate of breathing. The pacing rate increases when a person breathes faster. Other types of pacemakers contain sensors that measure changes in body acidity, pressures inside the heart chambers, and body temperature, etc. Each of these sensors has its strengths and weaknesses. Because no one sensor method is perfect, some pacemakers now incorporate multiple sensors to more accurately gauge the body's metabolic activity."

Smitty

Rate Response Redux

by ebfox - 2012-11-21 08:11:24

Smitty's post is very good- just FYI, Medtronic PMs have the accelerometer (reacts to movement/ vibration). Boston Scientific PMs have an accelerometer plus a breathing monitor.

I had a Medtronic back in my PM days and my EP said if I was exerting and it wasn't keeping up, just slap my left chest like tarzan and the PM would raise the rate.

He also told me that the Boston Scientifics were better PMs for people who like to run, bike, or do any kind of regular cardio.

I know from my own experience, plus reading many posts on this website that getting RR adjusted for your own level of activity is frequently difficult. It is not unusual for your average PM tech to not necessarily know how to do it. You need to get on a treadmill with the pacer tech and let them tune it to your needs.

Best of luck,

EB

safsafasf

by boxxed - 2012-11-21 11:11:03

SJM and MDT use an accelerometer (SJM might also use a blended sensor but I don't think so. I know for a fact that MDT only uses accelerometer). Think of it like an iPhone or similar smart phones.

BSX and Sorin have both Accelerometer and Minute Ventillation. What Minute Ventillation does is check the transthoracic impedance (electrical resistance) in the chest area. What that means is that it checks the resistance of an electrical signal sent across the cavity, and that resistance can and will change depending on how you're breathing. So it essentially checks if you're breathing heavily or deeply.

So BSX and Sorin end up having blended sensors and alot more programming options (why ebfox mentioned that his/her EP said BSX may be better for certain circumstances). It's a rule of thumb that accelerometer picks up relevant readings and reacts FASTER while minute ventillation picks up relevant readings but reacts SLOWER. Both companies have algorithms in place to cross check and "hand off" diagnostic responsibilities back and forth.

Biotronik has a third function called CLS. Closed Loop Simulator. It's supposed to be (and I'm not too intimately familiar with it) a sensor that can actually read more than just motion and breathing. That it can detect in some part the sympathetic nervous response. That being, if you're watching a scary movie and the "fight or flight" autonomic response kicks in, CLS would be able to notice it.

All devices are tweakable to varying degrees with how sensitive all 3 sensors are in addition to how aggressively it reacts to increased activity. I am not sure why you're asking the original questions you asked, but I hope that clears up some for you.

asdasdas

by boxxed - 2012-11-21 11:11:49

Quick edit of above post (why doesn't this site have an edit function?1?!?!?)

Accelerometer - Reacts FASTER but assesses activity slightly less accurately

Minute Vent - Reacts SLOWER but assesses activity slightly more accurately over time.

Can I sneak another question in?

by ponch - 2012-11-22 05:11:56

First, thanks for the responses. They were very informative and just what I wanted.
So I take it that a Medtronics model D204DRM would have an accelerometer that is adjustable. Right?

Medtronic

by ebfox - 2012-11-23 10:11:35

I didn't have that exact model of Medtronic, but I believe the answer to your question is yes. There are several software adjustments- 1) how quickly the rate is increased when movement is sensed; 2) the amount of rate increase; 3) how long the heart rate stays increased when movement is not sensed (cooldown period).

There are other tweaks but if you can find a knowledgeable tech who will put you on a treadmill and adjust Rate Response while you exercise, he can tune it very closely to your individual needs.

Good luck,

EB

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