epicardial pacing

[MendedHeart]

Can someone please tell me a simple way to explain sensitivity settings on a temporary epicardial pacemaker?

[MunoRN, RN]

Think of sensing like a fence you can raise and lower. The pacemaker is on one side of the fence, and on the other are tall trees and shorter bushes. In the case of V-sensing you want to raise and lower the fence enough so that the pacemaker can see the trees (QRS's), but not the bushes (P waves, T waves).

When the pacemaker is attempting to pace when it shouldn't be based on it's settings it is under-sensing; it's not seeing the trees that should cause it to inhibit pacing impulses. In this case you need to make it more sensitive, you need to lower the fence enough so it can see the trees. This is where it gets confusing since to make it more sensitive you have to lower the sensitivity value, lower fence=more sensitive.

When the pacemaker is failing to attempt to pace even though it should be it is over-sensing. The fence is too low and it is seeing not only the trees, but also the bushes and maybe even the grass and as a result it doesn't see the need to pace, in this case you would decrease the sensitivity by raising the sensitivity number, raising the fence until you've hidden everything but the trees.

[MendedHeart]

Thank you very much, that is great!