Battery depletion

Dead battery

by AgentX86 - 2020-12-22 23:07:06

Hi Hairy,

Sure, it happens every time I leave the lights on overnight.  ;-)

Seriously, it can be a battery failure (there are recalls for such things) but it's more likely a bad lead causing it.  Either should be pretty easy to diagnose.  Ask!

Battery

by hairfairy - 2020-12-23 00:41:32

Agentx86 I have asked and they say the leads are fine , but I don't think so. They left so much slack in the leads that my pacemaker flips upside down when I roll over in my sleep and I have to lay a pillow next to me so I don't roll over and flip it. I have to manually flip it back over. That is bound to stress the leads and maybe cause fractures. I told them when it first started years ago and they just shrugged it off like no big deal. Well they are replacing it next month so hopefully it will be better after that. 

Battery depletion

by crustyg - 2020-12-23 05:14:08

As Agent says, battery depletion due to PM defects can happen (Boston Sci had a recall for this a while back).

The main reason for battery depletion is the amount of charge (literally the number of electrons) delivered in each pacing output.  And there are two reasons for this: 1) Poor contact between lead and heart muscle, 2) cracked or damaged lead(s).  Number 1 is much more common.

When your PM is setup (and, usually, as it self-calibrates) it determines what voltage and duration of voltage (pulse width) is required to 'capture' your heart - i.e. trigger a heartbeat.  For safety reasons, because leads and heart and lead=>heart muscle connection change over time, they usually set the PM to deliver 3*capture-voltage and a pulse-width that 'captures' at a high HR.  If capture is achieved at 0.6V 0.4ms then your PM will be set to 2.0V for 0.4ms output (usually the lowest voltage available for pacing).  If you need 4.0V for 0.8ms then your PM will be delivering a great deal more electrical charge for each pacing output and this drains the battery - there is a fixed amount of charge in any battery.  If your PM has to deliver this for each pacing lead, A & V, then that doubles the drain on the battery.  The actual number of pacing outputs delivered per day also has an effect, but per-24h period there isn't a lot of difference between pacing charges delivered between any two patients - some, but not a huge amount.

A cracked lead or one with damaged insulation can leak charge so the PM has to pump more into the PM end to achieve reliable pacing at the heart end.

This is why the EP-techs pay so much attention to voltages, pulse widths, lead impedances at PM checkups.  Lead impedance changes over time are probably the best way to monitor the changes at the lead=>heart muscle connection.  Sometimes scar tissue builds up here (doesn't conduct electricity very well), sometimes a lead is starting to work loose - fairly rare, and impedance changes can be a clue to damaged insulation, or even a cracked lead.

I *suspect* that you may be looking at a lead revision in the not-too-distant future.

what crusty said

by Tracey_E - 2020-12-23 08:44:04

I had a lead go bad and that's exactly how it happened, the lead needed to be turned up to get the signal through and my battery life plummeted. I got less than 3 years out of that battery. The thing was, my reps knew. They saw the problem and I knew what was happening and we had a discussion, several discussions actually, about how to handle it, whether to extract or add a new lead. 

Flip it over

by AgentX86 - 2020-12-23 13:23:04

This was said in an off hand way but it's important.  It likely has nothing to do with battery depletion but it's not right.  You should not be able to turn the PM over in its pocket.  Since it looks like you're due for a new PM anyway, make sure they address this.

If you get your pacing reports, it'll tell you what your lead impedances are, the capture voltage, and the pacing energy (and all sorts of other things).  Get this and go to the manufacturer's web site and download the PM manuals and you should be able to tell what's going on.