Battery monitoring

Battery monitoring

by piglet22 - 2023-11-16 05:44:31

I can only speak for UK practice and for  my specific health trust.

The pacemaker battery (cell) is a lithium type, lithium iodide in my PM.

Lithium batteries have a stable discharge curve during most of their life with only small changes in early years.

Depending on use, sooner or later it reaches a point sometimes called a knee on the chart where the rate of discharge rises quite rapidly.

In theory, this can be at about 9 years.

Depending on how you are monitored, in person, remote, your team will know when that critical knee is being reached.

Be aware that this is not an exact science. We are talking about tens of millivolts changes at about 3 volts.

The voltage will be measured by the PM using a device called an ADC or Analogue to Digital Converter. Typical resolution is about one in 1024 or 3 mV in 3 volts, so reasonably accurate.

My clinic went from annual to 3-monthly face to face checks when they estimated less than 12 months was left before EOL (End of Life) and replacement would be due.

Unfortunately, all the monitoring was to no avail and the PM failed one January evening sitting at home.

Immediate symptoms were muscle twitching over the PM site which spread to my left arm.

After a night in A&E, the PM was replaced the next day with a comment from one of them "we had you on our radar"

Let's hope their radar doesn't check for incoming missiles.

So, it can and does go wrong.

I won't bore you with the details, but with about 15 months left on my PM, I've just found out that the already cut to the bone checkups are to be reduced further to the point that they will only contact me when the annual remote download results are not within normal ranges.

So now, not only do they not see you, but only call you when something is wrong.

With their track record, I'll be packing an overnight bag fairly soon.

Of course, your experience might be much better, but beware.

EOL

by Penguin - 2023-11-16 13:01:50

Hi Jane, 

I'm in the UK too and I'm pretty sure that our health systems do battery replacement differently. 

If you put EOL (End of Life) into the search box, quite a lot of posts come up from people in the US which describe what happened to them when they had their device replaced. 

In the UK, 12 months battery remaining seems to be the trigger. Mine was monitored monthly leading up to replacement (in person) as I had an old device with no monitoring. 

Battery life becomes unpredictable.  

At least 12 months before EOL

by LondonAndy - 2023-11-16 15:22:02

Another Brit, I'm afraid! And I agree with Penguin and Piglet22: in my case I am 100% paced, no remote monitoring, and normally annual checkups. It was at 8 years that they stepped up the frequency of testing to 6-monthly. I had two of those checks, and was told the next test would be in 3 months, but then instead of the check I got invited in for the replacement instead. 

It's important to remember that when the device gets to End of Life, there's still expected to be 3 months of operating but it will turn off advanced functions to save battery. But I notice on your profile you have had 5 devices, so you probably already know this? 

EOL/ERI

by Good Dog - 2023-11-16 16:17:02

Not another Brit here.....

I have noticed that you brits do things different, but not necessarily better than us here in the good ol U.S.A.

For pacemakers we have ERI = Electrive Replacement Indicator

or

EOL = End of life (3 months after ERI

They are different!

Dave

Battery life - Access to your files

by ANDREW75 - 2023-11-16 20:08:15

Hi Jane,

An Ex - Brit living in California USA.

Perhaps you could ask your doctor or the technician for the readout files.

Here in the USA, I believe you may be entitled to them. I have a Biotronik pacemaker, and they gave me the download in .pdf form. I took a memory stick to my last visit. My readout is for 13 days since the pacemaker installation. I am on a 3-month checkup also and intend asking every time I go.

I attach a link about your right to access that varies state to state. (Sorry you will have to google the link)

Medical Record Ownership and Access - American Academy of Ophthalmology (aao.org)

Extract:

“However, most physicians are comfortable with the concept that patients should be able to access their entire medical record upon request. Many EHRs now contain patient por­tals providing varying degrees of data access.”

I was able to see Expected ERI (Elected Replace Indicator) reads 10 Years 1 Month, and remaining capacity at 100%.

I am an engineer so having the .pdf files answers many questions for me, saving time for everyone and gives me the foresight to ask questions. 

I would imagine getting these files in the UK would be like pulling hen’s teeth!

Thanks!

by JaneJ - 2023-11-16 22:20:41

Thanks for all the helpful info!  Much appreciated!  The dr had said when the eri indicator goes off that the replacement can be scheduled at that time.  Sounds like things can be rather unpredictable as far as the timing with the battery.  I have the home monitor system, latitude, which has a battery status indicator.  Right now, is reading, "implanted battery status is good", "no action is required".  Will keep an eye out as time goes on.  Thanks again for all the helpful comments and knowledge.  Super grateful!

Different answers from pacemaker rep vs dr

by JaneJ - 2023-11-16 22:55:29

I forgot to add that when I asked the pacemaker rep how reliable the 1.5 years remaining quote on the battery, I got the answer "it is extremely reliable and you can almost count on it being in 1 1/2 years".  Then when my dr came in, I asked him the same question.  His answer "fairly reliable, give or take 1 year " 🤣🤣.  Wow...give or take one year doesn't exactly seem extremely reliable 🤣

Give or take

by piglet22 - 2023-11-18 05:41:10

I suspect that "give or take a year" was slightly off the cuff, but does reflect the uncertainty.

Battery behaviour isn't a precise science, but can be made to look like it when you look at a data sheet.

The real problem is that you are looking at past voltages, and extrapolating them using a theoretical curve.

The EOL part of the curve is very different to the early years and subject to small numbers being geared up and can quite easily be months out.

In my own case, the 3-monthly checks in clinic weren't good enough and they weren't cautious enough, or careful enough.

I'm entering the last year or two of this device's lifetime and having been bitten once, am going to be super careful.

My device does not have app facilities, so probably starting next June, I will be doing monthly downloads whether they like it or not.

There is another way to track your pacemaker

by okvol - 2023-12-15 22:36:08

Get a watch that monitors your heartbeat, with tracking on a smartphone app. Mine came up with a chart that showed a knee in the graph, where I dropped from 70bpm normal set rate to 65bpm which is "limp" mode. I sent the graph to my cardiologist, and got scheduled right away for replacment.