Heart rate changes

I guess I don't understand how the PM works.  I am 100% paced due to bradycardia - rate was between 25-30 bpm.  So my PM is set for a rate of 60 bpm.  What makes my rate go above 60 when I exercise if the PM is set for 60?  This makes me think that my heart takes over the pacing when I require a rate greater than 60, but I thought my heart could no longer do the pacing.  What am I missing here?


Okay, thanks very much for the responses..  I was definitely in the dark regarding the Rate Response function.  That clears up a lot!  I just had my annual "inspection" by the technician.  I wish I had known about this before the exam - it would have generated some questions.  I guess they can wait until next year.


Pacemaker tech

by Theknotguy - 2019-01-10 23:04:42

Understanding how the pacemaker works can be very hard.  That's why they pay the EP the big bucks.  

Basically the pacemaker "watches" your heart rate.  It senses when you need increased activity and initiates a heart beat in the atria, then it watches  to see if the ventricles kick in a few milliseconds after the atrial beat.  For most of us, if the pacemaker sees your heart has initiated a beat, it just sits there and does nothing.  As soon as the atrial beat kicks off, the pacemaker starts a timer to see if the ventricles initiate their beat.  If they do within a  proscribed time, once again, the pacemaker sits there and does nothing.  Even though you are 100% paced, activity requiring an increased heart rate can  be monitored by the pacemaker.  Basically the pacemaker is running a constant timer and is waiting to initiate a heartbeat.  If a heartbeat is needed it will initiate one, otherwise it just sits there.  ICD's are different and I don't know enough about them to get into a discussion.  

The pacemaker keeps a running watch on your heart rate.  It uses an algorithm to time when your heartbeat is supposed to happen.  In the older models they weren't as responsive and there would sometimes be a lag between the time you really needed a heartbeat and when the heartbeat was initiated.  This lag was called chronotropic incompetence.  Obviously the pacemaker doesn't react as fast as your natural, organic heartbeat.  Right after I got my  pacemaker I went for cardio rehab because there would be a lag.  I had to learn how fast the pacemaker would start my heartbeat.  At first, it didn't start as fast as I would like and I'd run out of air.  I'd just stand there gasping .  Over time, my body has adjusted and I don't have as much trouble.  Oh, and my pacemaker has an accelerometer.  So it will sense if I start to move quickly and it will kick up my heart rate to adjust.  (If I'm riding in a bouncing truck it will sometimes fool my accelerometer into thinking I'm running and kick up my heart rate too.  Fun!)

Your pacemaker is an amazing piece of equipment.  In addition to keeping your heart going, it also keeps statistical information.  Mine keeps track of how many times it needed to initiate a heartbeat in the atria, how many times it needed to initiate a heartbeat in the ventricles, how many times I've been in afib, how long the afib lasted, and what kind of afib I had, and much more.  That information is recalled whenever they do a reading.  Your EP can then use that information to track how your heart is doing and if any changes are needed in your treatment.  Another number it keeps track of is how much it paces.  Supposedly yours is set to 100%.  My pacemaker paces at 80-90%.  You don't want to get hung up on how much you pace.  You can't do anything about it anyway.  You pace what you pace.  

Pacemakers are often set to high and low rates.  The usual low number is 60, although some people have that number adjusted.  Pacemakers can keep your heart in rhythm up to a high number.  Mind is set to 120.  So if I do exercise and my heart rate goes up to 120, the pacemaker can keep pacing up to that  level.  If my heart rate goes over 120, the pacemaker just sits there and watches.  It lets my natural, organic pacemaker take over at that point.  

The longer you live with the pacemaker the more you become accustomed to it.  After five years I'll go days without thinking about my pacemaker.  It just sits there and does its job.  At first it's really hard to just take that on faith, but as you live with it longer you'll relax and get accustomed to it.  

Hope this helps.  The pacemaker gives you that second chance at a good life.  

What makes my rate go above 60?

by Gotrhythm - 2019-01-11 15:24:09

Theknotguy's repsonse is accurate and thorough. Given your question, I'd like to clarify one point.

You asked, "What makes my rate go above 60?"

In addition to timing beats and supplying one as needed, as Theknotguy explained, your pacemaker has a function called Rate Response. Your heartrate increases when your pacer senses activity.

Basically, it senses vibration (some pacers sense vibration and breathing) and interprets that as increased activity, and raises your heart rate accordingly. Rate Response can be programmed to be more or less sensitive to vibration.

Getting the right (for you) RR settings can make a big difference in having a pacemaker that helps you return to your normal life and do the things you want to do.

One downside of RR is that the sensors sense all vibration. It might react to something like riding in a car on a bumpy road--which can be disconcerting.

One final point. You know your base rate is set at 60 bpm. Do you know what your maximum is? The Rate Response will not increase your heartrate past the set maximum. If your heartrate goes above the set maximum, your heart has done it on its own.


by zawodniak2 - 2019-01-13 12:27:45

Great explanation. Thanks for taking the time for the comments. 👍


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