Pacemaker battery life

My grandson had a pacemaker check in mid-February and was told he had 9 months of battery life plus the 3 month ERI time (total 12 months). They were looking at a pacemaker replacement toward the end of the year. We were doing 3 month pacemaker checks, until August, then going to monthly until time for the replacement.  We did a remote check in mid-May and was told the pacer went into the ERI time on April 10th, therefore he was already almost 2 months into the ERI.  What would make a pacemaker battery lose that much battery in so little time?  
Thank you!

4 Comments

Battery voltage against time isn't completely linear

by crustyg - 2021-06-17 18:39:20

Most battery curves of voltage against time show marked non-linearity towards exhaustion.

And there may be other factors (increased drain by the PM) increasing the rate of voltage decay.

If you want better answers you need to get access to the PM reports which will show pacing output voltage, pulse duration, percentage pacing etc. for then and now.  Every time the PM delivers a pacing pulse a little bit of electrical charge comes out of the battery, and it's stored charge that really matters - voltage is only an indicator of remaining charge.  So higher pacing voltage or longer pulses - or both - will drain the battery more quickly than it was being used before, hence the battery life will be much shorter than than it had been predicted.

You see the same on a car: estimated range will change (for any given amount of fuel) depending on whether you're cruising down a -1% slope with the wind behind you, or climbing up a 6% slope into a 25mph headwind.  But the change is more dramatic with a primary cell battery due to non-linearity.

Battery gas guage

by AgentX86 - 2021-06-17 23:34:31

It's impossible to know how much juice is really left in a battery.  The total taken out can be measured, fairly easily, but to know the remaining energy you'd have to know how much was there to begin with or have some other parameter that could be monitored.  Neither of these are accurate, so it's only a guess.  That's why the move in the interrogations near the EOL.  They don't know and need to watch it more closely.

sounds about right

by Tracey_E - 2021-06-18 10:07:01

I'm on my 5th. Some of them needed replaced right on schedule. Two were like your grandson, depleted quickly at the end. And one of them kept saying 3-6 months for a full year. It's a guess, it's not like a car that tells you how many miles to go. As long as it's in ERI, it's still fully functional and he won't feel any different. 

weeks not months

by dwelch - 2021-06-22 07:58:13

If the estimate is in weeks, then it is probably good enough to trust and basically it is time to schedule.  If the estimate is in months or years, then just ignore it it is bogus.  Very rough estimate.  I have had new pacers say I have like 5 years left on them.  This is one of the long term anxiety problems, worrying about battery life every visit.  It is time when it is time, cant predict usage any more than you can predict how long a tank of gas in your car is going to run out.  So you just dont worry about it. 

When you get into that home stretch where some places bump up the visits or checks (to cover that ERI window) that home stretch can be a year, it can be three years.  What you plan for is that MAYBE on this visit I will have to get one within a few weeks....MAYBE not.  You take it one visit at a time, and eventually it happens.

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