# Shockable Rhythms



## Achromatic

I'm jumping the gun a little (I prefer to call it 'being prepared'), but I had a question that came up following doing the AHA CPR course last weekend (our dept actually uses it as a pre-req for EMT-B training, which the county does in-house, using results from the practical and written to determine placement in EMT training)... anyway:

Using an AED, it will analyze, and shock VF and VT rhythms.

Are these the only shockable rhythms? (I know they are the only ones the AED will shock.) I know(?) you can't shock asystole, much to the surprise of many TV hospital shows, but say your ALS upgrade arrives with 5/12 lead ECG and a manual defib, are there other rhythms that are shock candidates? A-fib? Bradycardia? SVT?

Not that I'll be doing these as BLT, I just like absorbing knowledge - any good web resource on the above?


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## Shishkabob

Vfib and pulseless Vtach are the only ones you can defib with an AED, but there are others you can "shock" with a monitor/defib depending on how you define it.

There's something called transcutaneous pacing, which basically acts as a pacemaker for the heart, telling it to beat.  You use it for things such as a bradycardia that causes shortness of breath / altered mental status / low BP.


Another way you can shock is cardioversion, which is essentially defibrillating, but on the peak of the R wave in the QRS complex.  







This is used for things such as symptomatic Vtach with a pulse, and SVT.  It's done on the peak of the R wave because if it's timed wrong, and falls on the downslope of the T wave, you can cause very bad things to happen.


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## Achromatic

Ahhh, I see. I'd heard of pacing, and I'd pretty much presumed it is what it is, so thanks for the clarification.

I'm guessing, too, that cardioversion is something you'd want to feel pretty confident at before attempting in a moving rig?


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## Shishkabob

Any time 

The newer monitors/defibs have a "Sync" button, where when you press it down, the computer automatically detects the R wave and discharges at the correct time.


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## Achromatic

Linuss said:


> Any time
> 
> The newer monitors/defibs have a "Sync" button, where when you press it down, the computer automatically detects the R wave and discharges at the correct time.



Ahhh, that would make sense


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## Shishkabob

Oh, thought I'd add something else:

A-fib technically CAN be shocked / medicated, but it more then likely won't.  The atria has been contracting wildly without actually pushing much blood, and because of such, clots can form in the atria.  If you shock them or push Diltiazem, and it works, it will end up pushing the formed clot and either causing a pulmonary embolism or a stroke.

The cut off, depending on who you're talking to / protocols, is 48 hours.


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## absolutesteve81

Don't forget SVT where you identify WPW (Wolff Parkinson White).  Adenosine would be a no-no therefore you would jump straight to Cardioversion


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## Akulahawk

The idea behind the synch cardioversion is to get the entire heart to depolarize simultaneously... This means that all the normal "pacemaker" nodes, any ectopic sites, and all other cells all depolarize... and then, the theory goes, the normal pacing sites take over normal cardiac conduction...

Sparking the patinent right on top of the T-wave results essentially in an "R on T" phenomenon... which can kick-off lethal arrythmias.

Sacramento never had adenosine in its arrythmias protocol... precisely for the reason that the narrow complex tachycardia (SVT) really is the WPW... and goes straight to electrical therapy for unstable patients. This stems from Sacrameto's history of being LALS... and in ways, Sacramento EMS is stuck in that LALS mentality. Allowing (and trusting) it's Paramedics to identify various types of SVT and VTach rhythms goes against the LALS mentality...

We'd have Cardizem, Procainamide, adenosine, and Amiodarone... and we have none of those...

But at least we have Versed... We used to only have Valium... then they added the Versed... and now they prefer using just the Versed. Probably better that the patient not remember the cardioversion...


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## Dominion

absolutesteve81 said:


> Don't forget SVT where you identify WPW (Wolff Parkinson White).  Adenosine would be a no-no therefore you would jump straight to Cardioversion



I'm curious about this, I've seen and heard different things.  I've heard the above from an instructor during our cardiology/ACLS sections.  I've seen other medics say it, I've seen cautions such as administer only if cardioversion is immediately available. I have also seen no cautions or warnings and have the "In presence of SVT, administer Adenocard unless patient is unstable or poor perfusion in which case perform immediate cardioversion."

What is the proper answer?  Per protocol?  My nursing drug reference, flip book, state protocols, epocrates, and drug packet do not even mention WPW.


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## futuremedic

Linuss said:


> Oh, thought I'd add something else:
> 
> A-fib technically CAN be shocked / medicated, but it more then likely won't.  The atria has been contracting wildly without actually pushing much blood, and because of such, clots can form in the atria.  If you shock them or push Diltiazem, and it works, it will end up pushing the formed clot and either causing a pulmonary embolism or a stroke.
> 
> The cut off, depending on who you're talking to / protocols, is 48 hours.





You mean can be cardioverted??? It is not a shockable rhythm, you only want to cardiovert if it is less than 48 hours or the patient is unstable.


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## HotelCo

futuremedic said:


> You mean can be cardioverted??? It is not a shockable rhythm, you only want to cardiovert if it is less than 48 hours or the patient is unstable.



And the chances of cardioverting in the field (if the patient is stable and AFib is less than 48 hours) is slim to none.


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## Dominion

Thanks guys in chat, question answered and understood


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## Shishkabob

futuremedic said:


> You mean can be cardioverted??? It is not a shockable rhythm, you only want to cardiovert if it is less than 48 hours or the patient is unstable.



No, I meant shocked, as in the slang for sending electricity through someone, be it pacing, cardioverting, or defibrillating.  

And besides the fact that cardioverting already basically IS defibrillating, with minor differences (well... a few hundred joules minor   )


Shock, bake, cook, fry, electrify.  Whichever you want to use


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## MrBrown

defibrillation is unsyncronised cardioversion; what we refer to as "cardioversion" is technically syncronised defibrillation at lower energy levels


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## Melclin

I don't know why you blokes get so caught up in the difference between cardioversion and defib and shocking and so on. 

Cardioversion just means converting the rhythm whether its synchronized or unsynchonised, chemical or electrical. Defibbing a person in VF is cardio version, just as giving a glass of ice water to a person who pops into A-fib is cardioversion. Usually when using the term cardioversion, most people are referring (medics anyway) to electrical synchronised cardioversion. But it doesn't strictly mean that.

And as you say linuss "shocking" is slang. It can refer to anything you want it too.


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## Melclin

Damn it brown. You beat me to the punch.


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## futuremedic

Linuss said:


> No, I meant shocked, as in the slang for sending electricity through someone, be it pacing, cardioverting, or defibrillating.
> 
> And besides the fact that cardioverting already basically IS defibrillating, with minor differences (well... a few hundred joules minor   )
> 
> 
> Shock, bake, cook, fry, electrify.  Whichever you want to use



Try using your slang when you are testing for the registry and see how well that goes. There is a difference in joules as well as making sure that it is synchorinized at the proper time so you don't knock the patient into asystole.


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## Melclin

futuremedic said:


> Try using your slang when you are testing for the registry and see how well that goes. There is a difference in joules as well as making sure that it is synchorinized at the proper time so you don't knock the patient into asystole.



Really? Here I was thinking when Linuss said A-fib was a shockable rhythm that I should go and give 360 to the next old lady I find in a nice stable long term A-fib. 

Linus you really shouldn't use slang like that, especially not on a forum where we all know what you mean... just in case the national registry starts testing people based on casual conversations.


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## futuremedic

Melclin said:


> Really? Here I was thinking when Linuss said A-fib was a shockable rhythm that I should go and give 360 to the next old lady I find in a nice stable long term A-fib.
> 
> Linus you really shouldn't use slang like that, especially not on a forum where we all know what you mean... just in case the national registry starts testing people based on casual conversations.



You may understand it but the next person might not.


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## Shishkabob

futuremedic said:


> Try using your slang when you are testing for the registry and see how well that goes. There is a difference in joules as well as making sure that it is synchorinized at the proper time so you don't knock the patient into asystole.



I did already state those differences and infaxt one was in the post you just quoted. 

" (well... a few hundred joules minor)"

and besides, depending on protocols, the only energy setting that's different is the first one at 100j on a monophasic system.  After that, it's the normal 200,300,360 (if you follow AHA)


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## Brandon O

While on the topic, here's a question for the band:

What would happen if a defibrillation shock were given to a healthy, perfusing normal sinus rhythm?


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## Shishkabob

You'd Have a case of CPR on your hands.


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## Jinx

Not to mention one sore and pissed off pt. when they came to again... ^_^


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## Brandon O

So what are we talking about here -- you'd lose a pulse with the first shock, then just restore it with another?

The reason this is a little confusing is because of the seeming conflict between two things we're taught --

1. Electricity through the heart (e.g. an accidental shock) can cause cardiac arrest, which is a problem

2. Defibrillation (i.e. electricity through the heart), when all goes well, causes the heart to stop beating and then spontaneously reset into a functioning rhythm

Why would the latter "reset" not occur after a shock to a normal rhythm?


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## Jinx

It may happen that way but you could also shock them in to another rhythm. Also when you defib someone who is in VF/VT to "reset" the heart, it doesn't guarantee their heart will start again in a normal sinus rhythm and quite often it doesn't?


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## Akulahawk

Brandon Oto said:


> So what are we talking about here -- you'd lose a pulse with the first shock, then just restore it with another?
> 
> The reason this is a little confusing is because of the seeming conflict between two things we're taught --
> 
> 1. Electricity through the heart (e.g. an accidental shock) can cause cardiac arrest, which is a problem
> 
> 2. Defibrillation (i.e. electricity through the heart), when all goes well, causes the heart to stop beating and then spontaneously reset into a functioning rhythm
> 
> Why would the latter "reset" not occur after a shock to a normal rhythm?


 The problem with #1 is the possibility that you deliver electricity right on the T wave and you can put the heart right into VTach or VFib... both can be lethal arrythmias. If you delivery that shock just about any other time in the conduction cycle, all you do is cause the heart to depolarize or remain depolarized a little while longer. Normally the SA node will pick back up without too much of a problem... but it's that essentially R on T that you REALLY want to avoid.


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## Brandon O

Ahhh, thanks Akula.

So even in the case of an untimed shock through a healthy heart (oops, that cable was live?), arrest will only occur if you're unlucky enough that it hits you right during the T wave? Otherwise, no problem? (Although I guess with high enough voltage you might see significant trauma to the tissues anyway.)


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## Akulahawk

Brandon Oto said:


> Ahhh, thanks Akula.
> 
> So even in the case of an untimed shock through a healthy heart (oops, that cable was live?), arrest will only occur if you're unlucky enough that it hits you right during the T wave? Otherwise, no problem? (Although I guess with high enough voltage you might see significant trauma to the tissues anyway.)


 If you receive the shock that passed through the cardiac muscle basically beween the R wave and the 1st half of the T wave (absolute refractory period) you won't see another depolarization event... the cells can't fire again. It's at the beginning of the relative refractory period that you'd see that problem...

As to the other problem... it's not so much the voltage that causes tissue damage... it's the current. Think in terms of Watts... The higher voltage allows the energy to penetrate skin... but it's the amps that do the damage. The result is a pretty high wattage running through the body. You'll see the damage where the current flowed through the body...


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## Brandon O

How about if the shock lasts longer than a single cycle -- such as an accidental electrocution over a few seconds? Then are we sure to see an arrhythmia?


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## Akulahawk

Brandon Oto said:


> How about if the shock lasts longer than a single cycle -- such as an accidental electrocution over a few seconds? Then are we sure to see an arrhythmia?


 I would figure that the arrythmia would be one of 3... asystole, VTach, or VFib... in that scenario... assuming, of course, that the current passes through the heart in it's course from source to ground, and that the current seen by the heart is sufficient to cause depolarization. If it does, you'd see myocardial tetany until the current stops going through the body.


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## Ridryder911

Brandon Oto said:


> While on the topic, here's a question for the band:
> 
> What would happen if a defibrillation shock were given to a healthy, perfusing normal sinus rhythm?



http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=105x4640694

Some will remember of the idiot EMT that was playing around with the defib unit and shocked his partner killing her. He was convicted and now is serving prison time as her kids are without a mother. 

So yes, electricity in the hands of unqualified people is dangerous. 

R/r 911


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## Brandon O

Er... thanks Rid. I guess.


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## medic_texas

Ridryder911 said:


> http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=105x4640694
> 
> Some will remember of the idiot EMT that was playing around with the defib unit and shocked his partner killing her. He was convicted and now is serving prison time as her kids are without a mother.
> 
> So yes, electricity in the hands of unqualified people is dangerous.
> 
> R/r 911



This is why basics shouldn't play with the monitor.  I wonder how many joules he had it set to.  

Jackass


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## flhtci01

medic_texas said:


> This is why basics shouldn't play with the monitor.  I wonder how many joules he had it set to.
> 
> Jackass



*150   *http://www.courts.state.va.us/opinions/opnscvwp/1070091.pdf

but a lower charge may have had the same effect.


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## Lifeguards For Life

AED's shock vfib and vtach. other's can be shocked though


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## Lifeguards For Life

Brandon Oto said:


> While on the topic, here's a question for the band:
> 
> What would happen if a defibrillation shock were given to a healthy, perfusing normal sinus rhythm?



uhhh duh? bye bye healthy perfusing normal sinus rythm. hello cpr most likely


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## SurgeWSE

Dominion said:


> I'm curious about this, I've seen and heard different things.  I've heard the above from an instructor during our cardiology/ACLS sections.  I've seen other medics say it, I've seen cautions such as administer only if cardioversion is immediately available. I have also seen no cautions or warnings and have the "In presence of SVT, administer Adenocard unless patient is unstable or poor perfusion in which case perform immediate cardioversion."
> 
> What is the proper answer?  Per protocol?  My nursing drug reference, flip book, state protocols, epocrates, and drug packet do not even mention WPW.



The problem with giving any medication that slows AV conduction (specifically a Calcium blocker like Cardizem) to someone with WPW is that you risk a paradoxical increase in conduction through the accessory pathway (WPW is, by definition, an accessory pathway conduction).  When you slow the influx of calcium to the smooth muscle you cause vasidilation, the body then produces a sympathetic nervous response, which will follow the accessory pathway (which is the root of the original problem), thus increasing the rate of the tachycardia.

There is some controversy in using Adenocard for WPW in that any time you slow AV conduction while there is already an active accessory pathway, you make your accessory pathway all the more attractive.  My personal take is that if syncronized cardioversion is available (which it will likely be, considering you have your patient on a monitor to diagnose the WPW), use it.  If they patient isn't falling to pieces in front of your face (and is hemodynamically stable), give them an amnestic/anxiolytic first.



Linuss said:


> And besides the fact that cardioverting already basically IS defibrillating, with minor differences (well... a few hundred joules minor   )



Remember, all defibrillations are cardioversions, not all cardioversions are defibrillations.  Perhaps it's only a semantic difference, but it seems to be causing some confusion.  What we term defibrillation is simply "unsyncronized cardioversion" and what's being referred to in this thread as cardioversion is "syncronized cardioversion".  The number of joules is irrelevent.  I can defibrillate a 25kg child at 50j or syncronized cardiovert a rapid a-fib at 50j.  I can also defibrillate an adult at 200j or I can syncronized cardiovert them at 200j. One is a defibrillation, one is not.


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## fma08

Ridryder911 said:


> http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=105x4640694
> 
> Some will remember of the idiot EMT that was playing around with the defib unit and shocked his partner killing her. He was convicted and now is serving prison time as her kids are without a mother.
> 
> So yes, electricity in the hands of unqualified people is dangerous.
> 
> R/r 911



I especially like the "everybody plays on the job" quote at the end of the article... <_<


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