High Threshold

Hello. My son is 19 and has pacemaker that was just replaced four months ago (epicardial). Two weeks ago he said he felt dizzy then a half hour later he passed out completely. When his pacemaker was checked it showed multiple episodes of high threshold on the V lead. Dr. turned the threshold setting up to "5" and did a 48hr holter. The holter showed no failure to capture or a systole. He has been doing better with the threshold setting being turned to 5v but not 100% This is all just happening so not sure what they plan to do at this point as seems a bit scary to think what may happen next. Would very much appreciate any input. Thx much.

5 Comments

Thresholds of epicardial leads

by golden_snitch - 2013-07-23 06:07:03

Hi!

How long has he had this epicardial lead?

Unfortunately, epicardial leads tend to develop higher thresholds over the years, mostly due to scar tissue around the tip of the pacemaker lead. Especially the old epicardial leads have this problem; the newer steroid-eluting ones have a better performance.

Now, with the amplitude ("threshold setting") set at 5 V, the pacemaker's battery will drain faster because the pacemaker has to stimulate with a much higher voltage than usually. To compare: the amplitude of my ventricular, epicardial pacer lead is 1.5 V. So, sooner or later your son will need a new ventricular pacemaker lead, unless you opt for having the pacemaker unit replaced more often rather than having a new lead put in. But if the threshold has already risen, it's likely to rise even more resulting in a loss of capture again. The amplitude of a pacemaker is limited, so you cannot just keep increasing it. In my pacemaker the highest setting is 7.5V. So, if the threshold keeps rising, you'll sooner or later come to the point where the highest amplitude does no longer lead to effective stimulation.

I guess since your son is already 19 and still has an epicardial lead (or leads), there is a reason for not implanting transvenous (endocardial) leads instead. I know that in uni-ventricular hearts they don't implant endocardial leads at all, and I'm sure there are a couple of other congenital heart defects in which those leads cannot be implanted. If, however, there should not be any reason in your son's case, he could be switched to endocardial leads that are placed via venous access. That's the "normal" lead placement nearly all adults get. The surgery is less invasive than placing epicardial leads.

I'd be very interested to hear how the story continues since I have epicardial leads, too. Mine were implanted five years ago, and so far the thresholds are very good. My leads are Medtronic CapSure Epi leads.

Best wishes
Inga

hi there!

by colieamarie - 2013-07-24 01:07:21

hey, i'm nicole! i don't have much advice to give but i'm 19 as well. if your son ever wants to talk to someone who has a pacemaker as well and who is the same age as him i'm here!! i hope everything get better and i wish you both the best of luck! this is my facebook page.. https://www.facebook.com/goodbyebluesky38

High Thresholds

by Bowen6049 - 2013-07-24 02:07:01

Hi Nicole. I will give him your info. Thanks:)

High Thresholds

by Bowen6049 - 2013-07-24 02:07:48

Hi Inga. I want to say thank you so much for you response. Unfortunately the lead with the high thresholds is itself only four months old. He has epicardial because he is occluded on one side and MediPort on the other. This is his FIFTH V lead...seems to continually be an issue one way or another. The surgery four months ago was an eight and a half hour surgery to remove all the excess abandoned wires. At that time they also replaced both leads and generator (Medtronic). I am so disheartened that seems we already have an issue with the V lead. Not sure what the plan is yet with the cardiology team but seems they will need to do something.

Oh no :(

by golden_snitch - 2013-07-24 06:07:25

Hi!

Oh no, that's really odd that the ventricular leads keep going bad!

Maybe there is a muscle tissue reaction at tip of the lead much that is worse than the usual inflammation that happens whenever a new lead is put in? That's the only possible cause I could think of. Some people, especially younger ones, tend to develop extensive scar tissue. I'm one of those people, too, but fortunately not around the tip of my pacer leads. Not sure, but what I'd ask the doctors is, if there is anything one could do about reducing the inflammation when new leads are put in. The leads are already steroid-eluting to help with this, but maybe one can add a medication for the first couple of days or weeks? Or try a different lead model? Not sure, how many manufacturers actually offer epicardial pacemaker leads. Mine are by Medtronic.

Hope you'll get some answers soon!

Inga

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