Differentiating AVNRT from really regular Af + use of adenosine

[triemal04]

Thanks mike

This issue for us i guess is the "is it AVNRT or Af" when your looking at rates in excess of 200 and the rate is regular but not metronomically regular (as in the rate will have slight variation over a period of time, say a minute) as a true AV nodal re entrant should be, and i cant see any reason why you would not manage them as SVT as the insanely short half life makes it relatively safe if it is in fact atrial fib. Indeed i have seen several time in hospital of patients who are unsuccessfully beta blocked given adenosine as an almost diagnostic test of sorts.

But for us atrial fib is an absolute contraindication for adenosine, and i cant seem to find any supporting evidence of that, so the issue of is this SVT or really fast and regular atrial fib that much more of an issue for us.

At that point, with such a high rate you really don't have a choice but to call it an SVT instead of rapid afib/flutter or AVNRT (or anything else). So...give the adenosine. I don't know anything about your QA/QI process or interactions with the recieving docs, but I can't imagine them having an issue with you giving adenosine in that situation. Just have a copy of your 12-lead and rhythm strip from before the conversion for them and for your chart.

If nobody ever mentioned it before, aflutter can often be right at 150 (give or take a few beats) without any real discernable p-waves OR flutter waves. Something to keep in mind if you see a rate that just sits at 150.

If you were to determine after the initial dose that it's afib/flutter, then obviously you wouldn't give more. But up to that point, I wouldn't worry about it.

Keep in mind there are some meds that adenosine doesn't interact well with (tegretol and persantine are two, though any in those classes will as well) and some rhythms that you absolutely shouldn't give adenosine to (though none are narrow complex so don't worry).

Anyway, it's a great drug. Good deal that you guys are getting it.

Hmmm I'm not sure on that one. We use adenosine ONLY for SVT. You have to be 100% certain it is SVT. Otherwise for all other compromised tachydysrythmia's it's an amiodarone infusion and/or electric cardioversion for significant compromise. I'd be pretty wary of making a guess with any cardiac drug, but adenosine can be pretty nasty so personally I'd err on the side of caution and not go down that line unless certain it was SVT or consulted with clinical and got their view on the rhythm.

Not really. There are times when it shouldn't be given, but most of the issues that it creates will happen when it never should have been used in the first place. Give it appropriately and, while not 100% free of anything but transient side-effects (not much is) it's pretty benign.

[mikeymedic1984]

You forgot to mention a critical piece to the puzzle, "is the patient stable or not" ? Although your EKG class taught you the basic rhythms, if you ever work in an ICU or for a company that interprets holter monitor reports you will find that there are all kinds of "inbetween" rhythms that 10 cardiologists would interpret differently. Sometimes, the smart thing is to just start an IV and monitor the patient, especially if you have an ETA to the ER of less than 20-30, when you encounter a weird rhythm. The "irregularly irregular" definition of Afib still guides my choice.

[BushyFromOz]

Thanks for the feedback guys.

Patient was stable but had the most "calssic: Iischaemic cardiac chest pain symptoms, i finally found one with retrosternal, heavy radiating to L arm and neck for the first time in 5 years and slightly hypotensive but not not crook enough to be in the sync cardiovert guideline.

Spoke to the ER doc afterwards, he basically said "when i cant figure it out, i beta block first" which is an answer I suppose.

The clinical department basically said that that adenosine for this patient given the story and the "in between" ecg is the correct course of action.

The Atrial Fib as a contraintidication appears to be more about making sure some dont try and use it on decompensated rapid Af instead of syncing them.

As it turned out, we wanted this guy on the stretcher instead of propped on the kitchen stool like he was, and he valsalva'd himself while we were doing that.

Thanks al

[triemal04]

Figures that's how it goes. There's always some...not angst, but extra concern maybe...when introducing a new drug/procedure/piece of equipment. It takes time to iron out all the kinks and get everyone up to speed and comfortable with it's use.

You're right about the afib contraindication; I've seen some prolonged periods of asystole/atrial activity only when I've mistakenly given adenosine to afib/flutter (usually flutter), but I've also seen that when I've given it to an AVNRT. It's not that adenosine will kill them, it's just that it won't fix the problem and other drugs will.

[Jaymazing]

Hmmm I'm not sure on that one. We use adenosine ONLY for SVT. You have to be 100% certain it is SVT. Otherwise for all other compromised tachydysrythmia's it's an amiodarone infusion and/or electric cardioversion for significant compromise. I'd be pretty wary of making a guess with any cardiac drug, but adenosine can be pretty nasty so personally I'd err on the side of caution and not go down that line unless certain it was SVT or consulted with clinical and got their view on the rhythm.

Nobody can be 100% certain of a rhythm Dx at that rate in a prehospital setting. End of story. So I guess you're never giving Adenosine. Which is a shame, because it's a good drug for most tachyrhythmias.

If you're going off the rate that the monitor gives, bare in mind that the depicted rate will vary occasionally based on irrelevant artifact (such as patient/vehicle movement), and determination of rate should more likely be based on hands on palpation and R-to-R measurements (use the small box method if it's that fast).

It seems to me that your medical director is opposed to the use of adenosine...Sucks for you, man. The only time I can think of A-FIB being a contraindication for Adeno is if it's in the presence of WPW or LGL syndrome, which are both incredibly rare, and it's likely that if they have either of those conditions that they'll be able to tell you.

Remember though; consider your causes, and is your patient stable....

[triemal04]

Nobody can be 100% certain of a rhythm Dx at that rate in a prehospital setting. End of story. So I guess you're never giving Adenosine. Which is a shame, because it's a good drug for most tachyrhythmias.

Along that same train of thought, it's really worth remembering that "SVT" is really just a catchall phrase; a supraventricular tachycardia is just that- a tachycardic rhythm with an origin above the ventricles.

A sinus tach...rapid afib...rapid aflutter...multifocal atrial tachycardia...even junctional tachycardia's are all "SVT's."

This isn't to say that adenosine will work on all different types of SVT's, just that people toss the term around without thinking about what it actually means way to often.

This isn't a problem that only happens in New Zealand either.

The only time I can think of A-FIB being a contraindication for Adeno is if it's in the presence of WPW or LGL syndrome, which are both incredibly rare, and it's likely that if they have either of those conditions that they'll be able to tell you.

Probably, but not always. Though rare WPW is definetly something to think about when you find someone with new tachy arrhythmia and no history of the same. The higher the rate goes, the more you should be wondering about an accessory pathway. Granted, as you said WPW isn't in and of itself a contraindication, but it's still worth considering as a cause.

Anecdotally they only time in 11 years that I can remember seeing WPW in the field the patient didn't have a clue that they had it...

[Jaymazing]

Along that same train of thought, it's really worth remembering that "SVT" is really just a catchall phrase; a supraventricular tachycardia is just that- a tachycardic rhythm with an origin above the ventricles.

A sinus tach...rapid afib...rapid aflutter...multifocal atrial tachycardia...even junctional tachycardia's are all "SVT's."

This isn't to say that adenosine will work on all different types of SVT's, just that people toss the term around without thinking about what it actually means way to often.

This isn't a problem that only happens in New Zealand either.

I couldn't agree more; SVT is a catchall phrase. In many respects, I believe the phrase is used more as a safety blanket than it is a confident diagnosis. I've gone on a few tangents about this topic in this past, myself. I'll spare you my typical SVT lecture (also known as my NCT lecture), as I get the impression we'd agree on most of the key points.

Probably, but not always. Though rare WPW is definetly something to think about when you find someone with new tachy arrhythmia and no history of the same. The higher the rate goes, the more you should be wondering about an accessory pathway. Granted, as you said WPW isn't in and of itself a contraindication, but it's still worth considering as a cause.

Anecdotally they only time in 11 years that I can remember seeing WPW in the field the patient didn't have a clue that they had it...

This basically is repeating my statement made previous, in which I made mention of likelihoods, not certainties.

Speaking strictly statistically, most accessory pathway abnormalities are found early in life (what with advancements in education, understanding of electrophysiology, and newly available telehealth consultation technologies) following previous events. While not being impossible, it's getting more and more rare to both see these phenomenon, but also be the first to discover someone with this phenomenon. However, I digress, because statistics can only take you so far, and I'm pretty sure I'm preaching to the choir here anyways.

Plus it's hard to dissuade from the allure of anecdotal evidence, even among the most knowledgeable practitioners.

I'm a little jealous of anybody who's caught it in person

Edited June 19, 2013 by Jaymazing

[HarryM]

Nobody can be 100% certain of a rhythm Dx at that rate in a prehospital setting. End of story. So I guess you're never giving Adenosine. Which is a shame, because it's a good drug for most tachyrhythmias.

Possibly may never give it. I've always had good relief with a properly done valsalva or spontaneous reversion. Our guidelines are to only give adenosine for SVT only if there is compromise or a hx of SVT responsive to Adenosine. It's specifically differentiated from A.Fib in our guidelines which is treated with Amiodarone. I'm not going to be the person to give Adenosine to someone in A.Fib and then have to explain it in an audit. I can use all the medical research in the world to prove a case that it was worth a try with a funky rhythym, but at the end of the day our guidelines are written by an intensivist and we follow them. We can go outside them provided we can prove we were correct. But as you say, you can't prove you were correct in a pre-hospital setting.

If we revert the SVT with Adenosine we can leave the patient at home provided it's not their first SVT responsive to Adenosine.

[BushyFromOz]

No one advocating using it for A/Fib, the point of my question was to flesh out what clinicians would do in the event of a rhythm that is difficult to differentiate from AVNRT / AVRT or Atrial fib, not about figuring out if its worth trying on a "funky rhythm".

If i extrapolate you post out, if i am presented with said difficult rhythm and a decompensated patient, do i sit on my hands because i cant decide to revert it with adenosine or amiodarone, or, do i wait for them to declare themselves and either better or get worse, and if they do deteriorate and hope they sync cardiovert successfully?

Just putting it out there.

[Jaymazing]

Possibly may never give it. I've always had good relief with a properly done valsalva or spontaneous reversion. Our guidelines are to only give adenosine for SVT only if there is compromise or a hx of SVT responsive to Adenosine. It's specifically differentiated from A.Fib in our guidelines which is treated with Amiodarone. I'm not going to be the person to give Adenosine to someone in A.Fib and then have to explain it in an audit. I can use all the medical research in the world to prove a case that it was worth a try with a funky rhythym, but at the end of the day our guidelines are written by an intensivist and we follow them. We can go outside them provided we can prove we were correct. But as you say, you can't prove you were correct in a pre-hospital setting.

If we revert the SVT with Adenosine we can leave the patient at home provided it's not their first SVT responsive to Adenosine.

That's how I feel about it, too. And I don't advocate going against your medical control or protocols, by any stretch of the imagination. If you want to go against your medical director, become a doctor hahah

I'm also a big fan of BLS before ALS when considering Tx for tachydysrhythmia's