pulse width

i recently underwent a lead revision .at my first interrogation the pulse width was increased to 0.6. what would have happened to cause them to need to increase it. thanks for any answer you might have as I'm a newbie and trying to understand. g

4 Comments

Nothing to worry about

by PacerRep - 2012-09-11 01:09:29

Pulse width and Amplitude adjustments are common especially in new implants. FDA mandates reccomended safety margins that we adhere to when at all possible. The pulse width is just the length of time each pacing pulse is delivered. The longer the pulse width (to a certain point defined as Rheobase) the more energy being delivered.

To simplify. Your heart needs X amount of energy to make it squeeze. We must set the output of the device for each pacing pulse to X multiplied by 2. This can be accomplished by adjusting the Amplitude (voltage) or the Pulse Width.

After a new implant you have a period where the energy it takes to make your heart squeeze gets a little chaotic, eventually it settles down. So don't sweat it, your technician is just doing their job correctly. It doesn't effect the way the device functions at all or how you will feel, its all just walking between the lines

pulse width

by hairfairy - 2012-09-12 11:09:15

Thanks pacerrep for bringing it down to my level. I get it now .Sort of .........lol. just kidding........I do get it!! !!

asfasfasf

by boxxed - 2012-09-18 06:09:16

It's also used to conserve battery life as well. There's a formula involved, but typically...

The longer the pulse width, the less voltage needed to "capture" the tissue and force a contraction with the pacing stimulus sent from the device.

The shorter the pulse width, the higher the voltage needed.

So people do try to lower the pulse width by throwing pulse width out a bit and trying to lower the voltage to get a lower number that still respects the 2:1 safety margin. The 2:1 safety margin is to be confident that you will consistently and reliably pace AND capture (the heart contracts) even when accounting for changes in threshold (threshold being the LEAST amount of energy delivered that will still CONSISTENTLY cause a contraction)

asfasf

by boxxed - 2012-09-18 06:09:53

So people do try to lower the programmed outputs by throwing pulse width out a bit and trying to lower the voltage to get a lower number that still respects the 2:1 safety margin. The 2:1 safety margin is to be confident that you will consistently and reliably pace AND capture (the heart contracts) even when accounting for changes in threshold (threshold being the LEAST amount of energy delivered that will still CONSISTENTLY cause a contraction.

(Made a correction in first sentence)

Now these types of tweaks may or may not matter to you. If you are AsVs 99% of the time and the device is there for the 1% you truly need pacing and have syncopal episodes, battery might not be saved too much.

But if you're a CHB patient with close to 100% VP, efficiently but SAFELY adjusting outputs can add some serious mileage to your device

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