Rapid Change in Battery Life from June until Present

👋🏼 hi

by Lavender - 2023-10-15 09:55:43

Yep my battery is running down faster than expected. Mine is because of lead that's using up more voltage. The pacemaker is working fine but instead of using its former .05 volt it's burning 3.1 volts. It's not harmful to me but the battery will deplete sooner. 
 

The cardiologist isn't sure why it's happening but said when the time comes for pacemaker replacement, the lead may also be replaced. 

Battery life estimate

by Selwyn - 2023-10-15 11:07:47

My experience is that as you get to the lower end of your battery life the estimates get more irregular. I was going back every 6 months, then 3 months - there was a lot of variability. 

I do have a slight impedance problem in the ventricular lead.  Anything that uses up current ( such as increased impedence, a faster rate, a higher theshold, not having a night setting,  biventricular, triventricular pacing, will deplete the battery more.

estimates

by Tracey_E - 2023-10-15 14:08:49

As Selwyn said, as we get closer to the end, the estimate gets more accurate. That's not really considered a huge jump, esp with 4 months between the estimates. Battery life is always an estimate and every time they change the settings, it can change again. 

I'm on my 5th. I've had it say a year for a full year. I've had it say 6-12 months in August, then in October it was already in elective replacement mode. Frustrating, but perfectly normal and not an indication that something is wrong. 

If this is your first replacement, know that it's super easy. Most of the pain the first time was creating the pocket. Most of the restrictions the first time were new leads. Second (and third and fourth and fifth lol) are often just the incision to heal. 

Very similar experience

by JaneJ - 2023-10-16 01:11:13

I recently with my last check remote check noticed that the battery went down by an entire year within 3-4 months.  I was quite surprised, as my pacing percentages remained about the same, as well as all my settings and no significant changes with impedance.  I went from 2.5 years in March to 1.5 years in July.  I have a check coming up very soon, so will be interesting to see what it's at now.  I didn't realize near the end of your battery, that it is not as predicable with the time left.  Did the dr ever tell you why you had the significant drain of the battery?  Mine has been pretty consistent up to this point, as far as how quickly it goes down.

Battery (cell) lifetime)

by piglet22 - 2023-10-16 08:16:42

Predicting battery or cell lifetime from existing or past data is a pretty imprecise business.

There are too many factors involved for lifetime to be much more than a guide.

All batteries are different. I use the term battery and cell. A battery is made up from individual cells. A car battery of nominal 12-volts, has six cells of roughly 2-volts each. An AA "battery" is really a single cell with an output of 1.5-volts.

I've no idea exactly what's inside a pacemaker, but it's likely to be a lithium cell and depending on the chemistry, it can be from 3.0 to 3.6 volts.

Processors that run the pacemaker can run at all sorts of voltages from as low as 1.2-volts to 5-volts and the trend is to lower operating voltages.

I'll call them all batteries for simplicity.

One of the characteristics of batteries, re-chargeable and non-rechargeable, is that they have a discharge or use graph against voltage output. Lithium batteries have a good fairly constant output voltage throughout their life and a fairly sharp drop at end of life.

When you get into the starting to drop off region, it gets very unpredictable.

My present Medtronic PM has a specification of 9.2 years lifetime and that puts replacement at January 2025.

Other factors come into play like temperature and usage. Body temperature is higher than ambient for a lot of the time and this can speed up discharge. Data transmissions use more current. Hopefully all these are taken into consideration.

The processor or a more specialized chip will quite accurately measure the voltage in real time, but an equation will do the predicting.

So, the short answer is to be aware of battery voltage but be cautious with predicted lifetimes. With one exception. A very sudden change in voltage either way needs looking at.

From personal experience, battery lifetimes do go wrong.

I had the first pacemaker fail on low battery despite being on 3-monthly checks. Mine went into mode change one evening at home with muscle twitching and completely spoiled my plans. The PM was replaced the next day and an apologetic clinical physiologist popped into the ward and said "we had you on our radar". That's what you get when you push a battery nearly two years longer than it's expected lifetime.

Jane

by Tracey_E - 2023-10-16 09:30:36

It's just the opposite- early on the estimates are not so accurate. As we get closer to the end, the numbers get more accurate. But they are still rarely spot on! And every time they change the setting, the estimate will recalculate based on the new settings. It's frustratingly unpredictable. 

Batteries

by Selwyn - 2023-10-16 17:29:52

Just to help piglet22 and others: The power of a PM is a Lithium Iodine battery. This occupies about half the PM case space. The rest is semiconductors, reed switches, accelerometer, capacitors, micro chips etc.  Apparently, the battery life is limited by increased resistance as Lithium Iodide builds up.  Lithium releases electrons at the anode. At the cathode the iodine combines to produce lithium Iodide.

For ICD the battery is lithium silver vanadium oxide, I believe.  This has the ability to deliver a rapid charge. Lithium-manganese dioxide and the hybrid lithium-silver vanadium oxide/carbon mono-fluoride laminate have also been used.

 see:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1502062/

to learn more.

Thanks Selwyn

by piglet22 - 2023-10-17 06:51:25

I have had several chest X-rays and have been able to study the pacemaker in quite fine detail down to chip level.

I can't remember which of the two Medtronic pacemakers was clearest, but it was in two halves, I'm guessing a plastic or X-ray transparent part of the case and an opaque half.

In the main electronics half, it was easy at some magnification to see individual chips, count the legs etc. Also see in some detail the leads and connectors. Loops in the leads for movement and the position of lead tips in the chambers.

The ventricular lead seems to be flipped back on itself with a tight bend which is not a great thing to do with what I presume is a coaxial lead.

As for the battery, there are many lithium chemistries and the exact type used will be closely tailored to the requirements, constant steady drain, or recovery from burst loads like ICD charging or Bluetooth transmissions.

Tracey

by piglet22 - 2023-10-17 07:20:09

The important part of predicting lifetimes over quite long periods is the discharge curve of the battery/cell.

All batteries have characteristic curves with a lot of influences like temperature and self-discharge.

Almost certainly, the pacemaker will have the data for the curve loaded into the controller and the equation for predicting lifetime will be constantly updated as more and more data comes in over the lifetime.

I do predictions on a daily basis using polynomials and linear regression to see how sensors around the house are following real life.

Medically, I record and track blood glucose and have done for over 10-years.

The results are somewhat erratic going from normal to diabetic.

The surgery looks at annual blood tests and puts me on a diabetic awareness course and has me down as pre-diabetic.

My results, once monthly, show that despite the erratic curve, the important bit, the trend, is only slowly increasing at a rate that is insignificant and if it follows that trendline, it won't hit full type 2 diabetes for a very long time.

As a result, they now have me down as non-diabetic hyperglycemic.

Going back to battery predictions, the mid-range of the battery life is probably the easiest to calculate as the slope of voltage against length of discharge (in years) is only slowly changing.

It's where you hit the period before end of battery life and the curve begins to go negative.

You can get largish changes in voltage over short periods, the rate of change is higher than in the mid-range.

That makes predictions more difficult. Unfortunately, I had firsthand experience of what happens when the cardiology team relies too much on data points 3-months apart.

This was in F2F clinic days and hopefully as real-time monitoring gets better, those sort of incidents become rare.