Elevated RV capture

I was in the hospital for heart failure. I have a duel chamber pacemaker that was adjusted by the rep while I was in the hospital. Elevated RV capture changed to unipolar capture threshold of 1.8v@0.5 ms, Anyone know what that means?


Here goes

by crustyg - 2021-08-20 17:01:06

Most modern PM leads are configured as bipolar: each lead has two conductors and in bipolar mode the pacing pulse is provided between the tip and the outer ring electrode.  It sounds as though the voltage required to provide reliable pacing (==achieve capture of the heart's pacing) had become too high, which drains the PM's battery.

So this lead has been set to uni-polar mode, where the pacing output is between one of the two contacts at the heart end of the pacing lead (RV in this case) and the metal case (==can) of the PM.  This has allowed the rep to set the pacing voltage to 1.8V at 0.5ms pulse width which is close to ideal, therefore preserving battery life.  I expect your PM had reported increased impedance for the RV lead, either on the ring or the tip and has set the pacing to use the lead's lower impedance for uni-polar mode.  Chances are that one of the lead contacts to the heart muscle is being affected by scar tissue, or, much less likely, that one lead has partially fractured within the lead.

Drawback to uni-polar pacing: much bigger artefact on the ECG, and, *sometimes* a risk of stimulating muscles other than the heart - usually the diaphragm.  Bi-polar pacing: the activating pulse is only presented to the heart muscle, so eliminating the risk of affecting other muscles.

Hope that helps.


Elevated RV capture

by Jam - 2021-08-20 18:21:59

Should I be concerned with affecting other muscle?.if so should I bring this up to my EP at my next appointment?


by crustyg - 2021-08-21 04:43:40

You'll know soon enough if this pacing mode affects other muscles, it's not a common problem.

Try not to focus too much on possibilities that may never happen, and probably won't.  That way lies madness.

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