Pulse Width calculation explanation?

At my checkup yesterday, the tech lowered my voltage and also changed my pulse width from .4ms to .1ms. (I didn't understand, at that time, threshold voltage so didn't ask her what it was and what my new voltage ended up being) I came home and read, and I understand how she figured what to lower the voltage to, as in the safety margin and how to determine the threshold, but how do techs come up with the pulse width? Can anyone explain that in easy to understand terms for me? Do voltage and pulse width go hand in hand so whatever number voltage landed at, the corresponding pulse width was plugged in? I am 100 percent paced in left ventricle and the changes were made to this lead. .1ms seems like a mighty short time to initiate a heart beat from the pulse width. I know my medtronic was at .4ms out of the box and as far as I know has been at this for 2.5 years. I went into the appointment feeling great and was surprised when the tech said she was making changes. Maybe the battery life looked bad. But at any rate, why the pulse width change? Thanks so much for any information.

5 Comments

editing my last comment

by L5 - 2014-08-09 01:08:41

My last comment is badly written after I read it back so I guess I should clarify that I just want the LBBB to stay gone (my left ventricle in control is a terribly incorrect statement). So I am sure my pulse width is absolutely fine. I agree the techs are awesome. I just see a different one every time and they often start the conversation with, I wonder why the last tech did this....? So I've learned to try and ask what they are doing and understand what is changing. But because I knew nothing about voltage or pulse width I really couldn't understand why the changes were being made or how they related to one another. And since I am doing so well I overly worried at any changes happening.

That said I would like to include the old thread I read through that explained voltage and threshold so well in case it helps anyone out: http://www.pacemakerclub.com/public/jpage/1/p/story/a/storypage/sid/25196/content.do

And thank you again, Inga!



L5

by kmom - 2014-08-09 08:08:11

How much did the book cost?? When I looked up the book on google they wanted 65 bucks for an e book?? Was that right?? Or did I get wrong info??

kmom

by L5 - 2014-08-09 09:08:29

I read the part I needed on the google books website. I didn't purchase the book. I do think it is as expensive as you say, though it looks pretty informative and good. I just read the part regarding how to determine voltage and pulse width which was available for me to read free. I think I googled pulse width and that google books page came up with the book chapter already loaded for me. Sorry for the misunderstanding. My whole post read back to me as confusing. I'm the worst when trying to reply to things from my phone.

Pulse width

by golden_snitch - 2014-08-09 11:08:03

Hi!

Yes, the tech probably just wants to save battery life. A pulse width of 0.1ms does seem low, but she has for sure checked whether it's - together with the voltage - still enough to provide effective stimulation. You are 100% paced in the ventricle, so if this programming wasn't effective, you'd know right away. As long as she has programmed the voltage with a good safety margin, you should be fine.

There is an old thread regarding this topic at:
http://www.pacemakerclub.com/public/jpage/1/p/story/a/storypage/sid/24989/content.do

I'm totally in favor for interacting with the techs, asking questions, and trying to understand how a pacemaker works. But I think we sometimes tend to question a little bit too much. After all, most of the techs do know what they are doing ;-)

Inga

Just found another good explanation:

At implant, it is standard to fix the pulse width at 0.5 ms and reduce the voltage until the lowest voltage that maintains consistent pacing-which is the pacing threshold (Fig. 16h). One can fix the pulse width at any value, however (usually between 0.3 and 1.0 ms), and calculate a voltage threshold. Similarly, one can fix the voltage at a certain value and reduce the pulse width to the lowest value that maintains consistent pacing, which would also define the pacing threshold. Either method is acceptable to define a pacing threshold.

Source: http://www.rjmatthewsmd.com/Definitions/permanent_pacing.htm

Thanks!

by L5 - 2014-08-09 12:08:01

Your explanation is so helpful! I found a google book that helped too called The Nuts and Bolts of Cardiac Pacing and read the section on voltage and pulse width. I have pacing 100 percent of time due to LBBB so I am not sure I would notice. I had no idea the LBBB was there before the pacemaker. I assume it would just show up at my next checkup that my heart was over riding the pacemaker sometimes and maybe they would adjust it at that time. In my case the device was fitted to correct the LBBB as it was determined to be a contributor to why I developed cardiomyopathy. So that is why I am nervous, because I don't want my left vent to ever be in control. And I've seen heart improvement and am feeling awesome. I still may call on Monday, now that I have an idea of what the tech was trying to explain to me when she was doing it, and ask her more about my pulse width setting. Thank you again, so much!

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