understanding how my PM works

I received my PM in January due to Complete Heart Block. Within days, after my wound check, I left for an extended vacation/recoup in Florida. When I got back in March they adjusted my PM and I had an MRI. I really still, even after extensive research don't' know exactly how this PM works. Excuse my ignorance but with Covid-19 I never get to talk to my Cardiologist, just staff. What kind of information do I need to figure out exactly what my PM is doing? The MRI found Cardiac Sarcoidosis but I haven't been able to get further testing yet. I am in a holding pattern as is everyone I assume.


5 Comments

how it works

by Tracey_E - 2020-05-20 16:34:35

If you have heart block, odds are you pace ventricular most if not all of the time.

How well did they explain what heart block is? The atria is the brains, it reads the oxygen level in our blood and raises/lowers our heart rate accordingly. The ventricles are the brawn, they make the strong beat we feel as our pulse. The SA node in the atria tells the AV node in the ventricles when to beat. Well, it's supposed to. With av block that signal doesn't get through either all or some of the time so the ventricles go too slowly, either missing some beats or beating at random. Complete, or 3rd degree block, means the signal never gets through on its own. Odds are high you pace 100% ventricle if this is the case. Many of us here do. 

The pacer is the watch dog. The atrial lead mostly just sits there. If our rate drops too much,it'll kick in and make it go faster. That's the lower limit. 60 is a common setting for that. But with av block this rate is often normal and the pacer doesn't do much for the atria. The ventricular lead will watch for the atria to beat. It'll give the venticles a fraction of a second to keep up. If it doesn't, it'll send a miniscule signal that mimicks what the heart should have done on its own. The heart responds by contracting (beating). 

The pacer can only go as fast as it's programmed to go. That's our upper limit. Sometimes they start it out too low and it needs to be raised. Example, you go for a run and your atrial rate gets to 150 on its own, but the pacer is set at 120, so even paced the ventricles won't be able to keep up with the atria because the atria is going faster than the  ventricular lead is programmed to go. In this case they can raise the upper limit.

Questions I would ask:

what is your upper limit. 

what is your lower limit

what percentage do you pace atrial

what percentage do you pace ventricle

what is your expected battery life. Keep in mind this is a wild guess at this point based on the current settings. Change the settings and the number will change. The closer we get to replacement, the more accurate it is. But it's nice to have a general idea.

what is your ejection fraction. That's how they measure how efficiently the heart is pumping. The pacer can make it go faster but it can't make it more efficient so they like to keep an eye on that number. This comes from the echo or mri, not pacing report.

Does that help?

How things work

by AgentX86 - 2020-05-20 19:29:10

If the only reason that you have a pacemaker is heart block, your pacemaker functions pretty much like a jumper wire.  A heart block is a disconnect of the electrical signals from the top of the heart (atria) to the bottom (ventricals).  The pacemaker senses the electrical signal from the sinus node (SI node) in the right atrium, waits an appropriate time, then initiates a pulse to the ventricals so they constrict, pumping the blood to the rest of the body. That's the bottom line, of course it's a little more complicated than that but, again, if the only problem is a complete heart block, that's about all it does.

As far as questions to ask...  I'd ask for more information about your condition and if there is an underlying reason for the block (that might get worse).  As noted above, your "Left Ventrical Ejection Fraction" (or LVEF) is important and something you should follow.  It should be in the 50-60% range, meaning that about half the blood in the left ventrical (the pump to the body) is pumped with each contraction.  This is good.  Either higher or lower isn't so good.  As long as you're in this range, don't worry about it but watch for it trending down.  Lower isn't an emergency but it gets more important.  35% and lower is bad and lower is more bad.  Just something to watch.  Pacemakers can make this happen but it's usually reversable if it does.

The rest of the pacemaker stuff probably isn't that important as long as your only issue is the heart block. The more complicated pacemaker functions only come into play when there are other electrical issues.  Learning more about pacemakers is probably a good idea but I don't think it's critical in your case.

understanding how my PM works

by terricrowe26 - 2020-05-21 15:13:14

Thank you both, greatly appreciated. I also bought the book Pacemakers made easy, The pacemaker manual. I am sure anyone I have been dealing with for doctors has told me all this, but how am I to understand? It's like talking to my daughter who is a Marine! she talks in acronyms! Anyway, you both have helped greatly and the book has too. I have Complete Heart Block because of Sarcoidosis I guess. Now I need the petscan to determine if it is getting worse, in remission, or anywhere else in my body. 

acronyms and big words

by Tracey_E - 2020-05-21 16:09:14

It's overwhelming at first! And to make it even more fun, everything has multiple names so one doctor may call it one thing while another calls it something else. 

I was 5 when I was diagnosed with heart block. My cardiologist explained it that the top of my heart didn't talk to the bottom of my heart. I've got a better understanding of it now, but that still pretty much covers it! I was fortunate to get an amazing rep when I got my first pacer (1994), he and my doctor both get that I really want to understand and be informed. A lot of patients do not want to even try to understand, so I think some of them make the assumption that's most patients and stop explaining. Be sure they know you are not one of those patients! Once they know, I've never once had one refuse to slow down and explain things to me. 

Good luck with the PET. Fingers crossed it's good news. 

easy to see

by dwelch - 2020-05-23 05:55:20

Like others here I also have complete heart block.  I think the descriptions above are fine if you understand them.  In addition to what was mentioned heart block is really easy to see on an ecg. you can google it and find some examples, granted they are going to have all the big words.  Well if you have complete, third degree, block then well you can see it all the time in the ecg, if it is not all the time then perhaps not depends on how often, and as mentioned as your doc or staff or whomever you can reach.  If you google it and look at some images the big spikes are the ventricles, there are little bumps those are the atria

https://ekg.academy/learn-ekg?courseid=316&seq=7

practice strip third tab over (or fourth tab both show it)

you should have a one to one match instead the upper and lower run at their own rates independently.

As describeda above most of the job the pacemaker is doing for us (heart block patients) is listening for the atrial beat, and then making sure there is a ventrical beat in that period.  So listen on the top and drive the bottom of the heart.  If you look at even that strip or others if you use google, you can understand why we are often considered 100% paced?   That does not mean we are 100% dependent in anyway, one of the tests that they do if/when you get to go back in is essentially turn off this functionality and watch for your natural rythm, the tech will likely be capturing the ecg of your heart during this time and you can either ask the tech or ask the doc to show you that stirp and point out the heart block (if you have it bad enough that it is all the time or is showing up during that test).

I have had pacers for 32 years, was born with heart block for the first time one tech was training another and happened to do exactly this, take the strip and show her in detail this is the heart block see how this and that...I had seen it when I was a teen and first diagnosed with the problem, that doc explained it to me/us (my parents) at the time. (there was no nurse/tech in that office the doc came in put the pads on ran the ecg did the whole thing, long before computers were in the office and questions about your meds and all the stuff we deal with now).  

If/when you get to go in next for an interrogation ask for your copy of the report, it will generally be a summary and not include the ecg waveforms, but it should include information about your device and settings like upper and lower rates which is another function that almost all of us have.  for us moste of the time it listens to the atria and drives the ventricles but if the atria are foing to fast or two slow it will drive them as well to keep them within a range of beats per minite.

You may be experiencing difficulting sleeping not just from the pain of surgery but my sleeping rate was in the 30s, resting rate in the 40s back when I got my pacer and I think they started me off with a minimum of 60 so it was hard to sleep at first.

If you have to have a pacemaker worthy problem, heart block is one of the better ones to have, easy to fix with a pacer.  Not difficult to understand what it is doing once shown.  if you still have questions dont hesitate to ask, one or all of us will answer.

Good luck, be safe. 

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