TPM... AAI vs VVI c tx of bradycardia

Dinith88 · Sep 9, 2005

I work on a cardiac surgery step-down floor. The other day I had an orientee and I was trying to explain to her modes AAI and VVI on temporary pacemakers. I explained to her that if she had a patient with bradycardia it is best to pace VVI or DDD. I also explained she would see atrial pacing on pts who underline NSR and the benefits of that atrial kick. >>>>>My question is this: My orientee asked, "Why can't you pace a pt with bradycardia in AAI mode". Well I guess you can, but why is it better to pace VVI vs AAI? Can someone explain in depth for me? Thanks! :)

If a pacer is in AAI, it 'watches' the atrium and paces the atria if need be.

The big issue is that in heart blocks the atria may be 'firing' at a normal or accelerated rate, and the ventricle would/could be slow or standing still at the same time. The pacer wouldn't fire as it would be 'sensing' a normal atrial rate, and the patients ventricles would remain slow/stopped.

Also, even if the atria were being paced (because of a slow atrial rate), in a heart block the ventricles still wouldn't fire because the impulse from atria dont get through to the ventricle. (and an atrial kick wont mean a thing if the ventricles arent moving)

VVI solves this problem because the venticles will fire regardless of what the atria are doing (heart block, slow AF, etc.).

I suppose in rare instances of symptomatic sinus brady, an AAI mode would work...i've just not seen that...VVI or DDD would is preferable and 'safer'.

RN12345656 · Sep 9, 2005

If a pacer is in AAI, it 'watches' the atrium and paces the atria if need be.
The big issue is that in heart blocks the atria may be 'firing' at a normal or accelerated rate, and the ventricle would/could be slow or standing still at the same time. The pacer wouldn't fire as it would be 'sensing' a normal atrial rate, and the patients ventricles would remain slow/stopped.
Also, even if the atria were being paced (because of a slow atrial rate), in a heart block the ventricles still wouldn't fire because the impulse from atria dont get through to the ventricle. (and an atrial kick wont mean a thing if the ventricles arent moving)
VVI solves this problem because the venticles will fire regardless of what the atria are doing (heart block, slow AF, etc.).
I suppose in rare instances of symptomatic sinus brady, an AAI mode would work...i've just not seen that...VVI or DDD would is preferable and 'safer'.

Dinith-

I understand what you are saying...my question is with just sinus bradycardia ( leaving out blocks). What is the rationale of why you use VVI for backup rather than AAI? I realize VVI should be used and is better, but why?

SEOBowhntr · Sep 9, 2005

NurseinVA,

Pacing becomes complex when you start throwing in blocks, vs. SR, vs. A-fib, vs. whatever can be thrown at you, I teach a class on Epicardial Pacing, and will try to attach my quick guide to a PM tonight when I go to work. AAI is actually in my opinion the first pacing method I would use in a basic SB when trying to get a little more Cardiac output, that way I will allow the ventricle to do it's job if an increase in rate is adequate for what our desired outcome is. In Epicardial pacing, remember that less is best, as the more mAMPs you put through those wires the more likely they are to start developing scar tissue and lose a bit of their conductivity. If AAI doesn't quite cut it, then I will upgrade to DDD, but rarely do I even use VVI, as a good conduction system needs both the atria and the ventricle. Most Post-Op pts. I've paced were either brady with poor output. Rarely have I had too many problems with heart blocks, and in those cases I am even more cautious as the last thing I want to do is shorten the life of my wires, when I really need a permanent pacer placed soon. More to come. Gotta run.

Doug

Dinith88 · Sep 9, 2005

NurseinVA,
Pacing becomes complex when you start throwing in blocks, vs. SR, vs. A-fib, vs. whatever can be thrown at you, I teach a class on Epicardial Pacing, and will try to attach my quick guide to a PM tonight when I go to work. AAI is actually in my opinion the first pacing method I would use in a basic SB when trying to get a little more Cardiac output, that way I will allow the ventricle to do it's job if an increase in rate is adequate for what our desired outcome is. In Epicardial pacing, remember that less is best, as the more mAMPs you put through those wires the more likely they are to start developing scar tissue and lose a bit of their conductivity. If AAI doesn't quite cut it, then I will upgrade to DDD, but rarely do I even use VVI, as a good conduction system needs both the atria and the ventricle. Most Post-Op pts. I've paced were either brady with poor output. Rarely have I had too many problems with heart blocks, and in those cases I am even more cautious as the last thing I want to do is shorten the life of my wires, when I really need a permanent pacer placed soon. More to come. Gotta run.
Doug

Hey doug, what do you mean by 'shorten the life of your wires'? I've never ever seen (or heard of) those things burning-out or otherwise going bad. Surely you mean something else, as they could certainly stay in place for an extended time before they rust-out?

And i think a clarification is in order... A post open-heart patient (one with poor cardiac-output, etc) is a special case where you may desire the rate (in sinus brady) to speed-up in order to optimize it(the output/index).

I think the OP is referring to symptomatic bradycardia in patients who've not had open-heart but are requiring pacemakers. (or perhaps post cabg with symptomatic sinus bradycardia). By the time a patient reaches step-down/IMCU, cardiac output/index is not being monitored so a sinus bradycardia that's not symptomatic would unlikely be paced.

SEOBowhntr · Sep 9, 2005

Sorry, copy paste fails me on occasion. Boy, I bet that really through a monkey wrench in there, I will edit now to make this a little less confusing. Note that quote was not mine!!! :uhoh21: :smackingf

Alright, now continuing to answer your question Dinith.

I work on a cardiac surgery step-down floor. The other day I had an orientee and I was trying to explain to her modes AAI and VVI on temporary pacemakers.

She is talking about post-op patients, as you cannot select the chamber you desire to pace in any other sort of temporary pacer, unless you float the pacing lead in or out. But going on with that, I've taken care of a great many Post-CABG and valve repair patients who did indeed have wires go bad, usually around 7-10, but I've seen them last as long as 14 days in one occasion. In most open heart patients I've care for, even ones who already had a pacer, they will come out of OR with Epicardial pacing wires. Atrial and Ventricular. Often times the surgeon will not really know how he wants the patient paced, or what settings the pacer should be set up at and thats where our knowledge from both a cardiac, and surgical standpoint can mix and on many occasions, we are the ones who lead the doc to the right settings and get the patient optimized. Of all of the CTS surgeons I've dealt with, somewhere around 25-30, only a couple really knew what they were doing with epicardial pacing. Pacemakers are more a cardiologists specialty, and often times you may need the cardiologist to guide you if the pacemaker is giving you problems.

In referring to permanent pacemakers, the leads usually do not wear out, but they do on occasion break or dislodge.

Gotta run, time to go to work, will check in again later.

Doug

RN12345656 · Sep 10, 2005

Sorry, copy paste fails me on occasion. Boy, I bet that really through a monkey wrench in there, I will edit now to make this a little less confusing. Note that quote was not mine!!! :uhoh21: :smackingf
Alright, now continuing to answer your question Dinith.
She is talking about post-op patients, as you cannot select the chamber you desire to pace in any other sort of temporary pacer, unless you float the pacing lead in or out. But going on with that, I've taken care of a great many Post-CABG and valve repair patients who did indeed have wires go bad, usually around 7-10, but I've seen them last as long as 14 days in one occasion. In most open heart patients I've care for, even ones who already had a pacer, they will come out of OR with Epicardial pacing wires. Atrial and Ventricular. Often times the surgeon will not really know how he wants the patient paced, or what settings the pacer should be set up at and thats where our knowledge from both a cardiac, and surgical standpoint can mix and on many occasions, we are the ones who lead the doc to the right settings and get the patient optimized. Of all of the CTS surgeons I've dealt with, somewhere around 25-30, only a couple really knew what they were doing with epicardial pacing. Pacemakers are more a cardiologists specialty, and often times you may need the cardiologist to guide you if the pacemaker is giving you problems.
In referring to permanent pacemakers, the leads usually do not wear out, but they do on occasion break or dislodge.
Gotta run, time to go to work, will check in again later.
Doug

Yes...I am referring to post CABG/valve patients. I don't know what it is like at your institution, but we nurses at Sentara Heart use our own judgements when it comes to making changes with the tpm. If my patient has sinus bradycardia symptomatic or asymptomatic, which is the best mode to place my tpm in? We frequently place our pts on "backup" at 45 rather than 100% pace them. I have always been told to use VVI. Which is it? AAI or VVI? I realize it gets more complicated when we talk about blocks, but it seems to me you would want to pace them the same...and then Afib..how the heck can you atrial pace an Afibber...help me out here :)

SEOBowhntr · Sep 10, 2005

Actually, AAI or DDD would potentially be better, because you would be getting and improved atrial kick by pacing the atria, and should result in better ventricular filling and output.

Dinith88 · Sep 10, 2005

Yes...I am referring to post CABG/valve patients. I don't know what it is like at your institution, but we nurses at Sentara Heart use our own judgements when it comes to making changes with the tpm. If my patient has sinus bradycardia symptomatic or asymptomatic, which is the best mode to place my tpm in? We frequently place our pts on "backup" at 45 rather than 100% pace them. I have always been told to use VVI. Which is it? AAI or VVI? I realize it gets more complicated when we talk about blocks, but it seems to me you would want to pace them the same...and then Afib..how the heck can you atrial pace an Afibber...help me out here :)

It's actually less complicated when you're talking blocks. Simply because AAI wont/cant be used. DDD wont work in afib (you're right, cant pace a fibrillating atria). So..in blocks DDD would be bettter d/t atrial kick...in fib VVI because you cant get an atrial kick (or 'sense' a fibrillating atria) in a-fib.

And Doug...you need to look into using better wires. :) The idea of them 'going bad' (not including micro-dislodgement, etc.) is scarey and again is VERY VERY rare..at least where i'm at...

SEOBowhntr · Sep 10, 2005

It's actually less complicated when you're talking blocks. Simply because AAI wont/cant be used. DDD wont work in afib (you're right, cant pace a fibrillating atria). So..in blocks DDD would be bettter d/t atrial kick...in fib VVI because you cant get an atrial kick (or 'sense' a fibrillating atria) in a-fib.
And Doug...you need to look into using better wires. :) The idea of them 'going bad' (not including micro-dislodgement, etc.) is scarey and again is VERY VERY rare..at least where i'm at...

Dinith,

I've seen the wire problem in 3 separate hospitals, it's been going on since around 1996, if you need to use Epicardial wires past 1 wk, you probably really need a permanent pacer in the overall realm though, oft. times Dr.'s laziness or lack of action results in wires being overused.

As far as pacing A-Fib goes though, you can atrial pace A-fib, but you have to do a sensing threshold and to prevent tachycardia, you need to have your pacer set up with a PVARP, and so on and so forth, it CAN be done, but it's a little difficult to explain without putting a pacer in front of someone and showing them what I am doing. But trust me, on a dozen or more cases I have done it and increased cardiac output significantly, and I do teach how to do it in the class I teach.

Doug

ethelbsnrn · Sep 10, 2005

Dinith,
I've seen the wire problem in 3 separate hospitals, it's been going on since around 1996, if you need to use Epicardial wires past 1 wk, you probably really need a permanent pacer in the overall realm though, oft. times Dr.'s laziness or lack of action results in wires being overused.
As far as pacing A-Fib goes though, you can atrial pace A-fib, but you have to do a sensing threshold and to prevent tachycardia, you need to have your pacer set up with a PVARP, and so on and so forth, it CAN be done, but it's a little difficult to explain without putting a pacer in front of someone and showing them what I am doing. But trust me, on a dozen or more cases I have done it and increased cardiac output significantly, and I do teach how to do it in the class I teach.
Doug

It would be great if you teach us how you do it.....pacing an atrial fib. We don't use that procedure, we right away give cordorone or cardizem for a-fib. But, that would be nice to do while waiting for the doctor's orders to medicate.

Dinith88 · Sep 10, 2005

It would be great if you teach us how you do it.....pacing an atrial fib. We don't use that procedure, we right away give cordorone or cardizem for a-fib. But, that would be nice to do while waiting for the doctor's orders to medicate.

Doug, i agree with ethelbsnrn here...if you could explain this it would be helpful.

The ep-docs i work with have explained to me that because of the chaotic 'electrical-static' nature of a-fib you're unable to 'capture' an atrium with a pacemaker because the atria arent depolarizing/repolarizing in and orderly fashion. Because of this, when you attempt to pace an atrium that is 'fibrillating' the myocardial cells simply are unable to respond (again becAUSE they're all firing randomly).

It would be cool to understand how you do this, and would be a novel 'trick'.....but in the many yeARS i've used temporary pacers, i'v never even tried to atrial pace an a-fib.