Narrow complex tachycardias – Part III

Documenting the heart’s response to adenosine

Let’s look at some different cases where adenosine was used. Rather than give you all the details about the age, gender, chief complaint, and vital signs, I’m just going to show you the rhythm strips.

Right now I’m only concerned with how the heart behaves during the administration adenosine.

The PRINT button is your friend!

Case #1

These strips were given to me by the same paramedic who did such a wonderful job in Part II. For some reason, with this patient, he didn’t bother obtaining a 12-lead ECG prior to giving the adenosine.

He did, however, remember to press the PRINT button prior to giving the drug.

The following five rhythm strips are continuous.


Case #2

I pulled these strips from the archives of the LP12. The paramedic in charge of the call suddenly remembered to hit the PRINT button after he gave the adenosine.

Better late than never!


There was reportedly no change in the heart rhythm after the adenosine. The paramedic in charge stated that the post-adenosine heart rhythm looked identical to the initial rhythm.

Case #3

The paramedics in this case actually did capture 12-lead ECGs of the pre and post-adenosine heart rhythms. However, I’m only going to post the strips of the initial rhythm and the heart’s behavior during the administration of the drug.

Case #4

I pulled this case from the archives of the LP12. The treating paramedic did not capture a 12-lead ECG. He also didn’t push the PRINT button until the several seconds after the administration of adenosine.


So what do you think?

Take a look at these cases and ask yourself some questions.

How are they the same?

How are they different?

Assuming that the patient was symptomatic but hemodynamically stable, was adenosine indicated?

Does the behavior of the heart during the administration of adenosine give you any information as to the mechanism of the tachycardia?

Based on what you see, would you give adenosine again?

Would you switch to another drug?

Look carefully!

Looking forward to hearing your comments.

If you have rhythm strips laying around that were taken during the administration of adenosine, please scan them and email them to me at ems12lead@gmail.com.

I’m also interesting in any and all rhythm strips of attempted transcutaneous pacing (TCP)!

See also:

Narrow complex tachycardias Part I

Narrow complex tachycardias Part II

Narrow complex tachycardias Part III

12 Comments

  • akroeze says:

    Ok, I'll bite and take the first stab at it.Case 1:Irregularly irregular with no clearly defined p-waves and a narrow QRS therefore I would call it a-fib with rapid response.Post-adenosine you can see a very erratic baseline. Are these fib waves from the atria or just artifact? Hard to say. Looks like you have ventricular escape beats in there. Then it seems to resume an a-fib pattern.I would monitor this patient closely and if they became hemodynamically unstable then cardiovert.Case 2:Seems quite regular. Narrow complex. No identifiable p-waves and when you mentally remove the QRS you could argue that there is a saw-tooth pattern underneath there. Looking at just the first strip I would call it Atrial Flutter with 2:1 conduction.Post-adenosine the patient almost seems to be in a sinus tachycardia with a second degree type 2 with 6:1 conduction. I'm not sure if that terminoligy is the correct way to word it? Then there is a couplet and we don't know what happens after that.Makes me less sure that it was Atrial Flutter in the first place, perhaps it was a sinus tach after all? I think adenosine is probably not contraindicated here as we don't know for sure and adenosine can sometimes be a useful diagnostic aid. Could argue for an if the patient is stable monitor and transport situation. It goes without saying that a 12 lead may change everything.Case 3:To the eyeball this one seems to be quite regular and narrow complex. No p-waves. Now that I look again, could we say that the rounded part at the end of the QRS is still part of it? Or is it part of the ST segment? My thought now is that I would say it is part of the QRS since we have a normal looking ST after that. Now I'm thinking that this might actually be a wide complex rhythm, which we would presume is Vtach until proven otherwise.In this case a 12 lead would be HUGELY helpful. IF all I have is this rhythm strip I want to be cautious and treat it as v-tach. If they are stable I won't do anything. If they are symptomatic I treat it as vtach which to me is lidocaine. If they are hemodynamically unstable I treat it with therapeutic electrocution.This is an interesting one and I'm wondering if I'm falling into the trap of seeing things that aren't there.Aaaaaaaand, adenosine slowed it down. So it probably wasn't ventricular and I have shown myself a fool. Oh well, I'll leave the above there anyway so that perhaps others can show me the errors of my thought process.Case 4:Wow…. that's, interesting. The rate is about 220/230ish I would say. Regular and the only thing I can say is that it is narrow and there are no identifiable p-waves. Adenosine would be reasonable here. Interestingly I can see electrical alternans…. one of those things the textbook says you see with very high rates like that.Am I imagining it or are those flutter waves post-adenosine? Hard to tell with this strip.Ok, I've thrown my thought processes out there and what I would do. I'm hoping someone will correct me where I am mistaken.

  • Tom B says:

    akroeze – Excellent comments! Case 1: I agree with your assessment. If the rhythm is irregularly irregular, why give the adenosine in the first place?Your treatment plan sounds reasonable to me.Case 2: I agree that sinus tachycardia is a strong possibility here, possibly with 1AVB in the initial rhythm strip (hiding the P waves in the preceding T waves).Whatever it is, I think it's safe to say that adenosine is not interrupting the atrial rhythm. It's just inducing a temporary 3AVB at the level of the AV node.Would there be any point in doubling the dose of adenosine and trying again?Case 3: Very, very good eye! The last part of the QRS complex in leads II and III is sometimes referred to as a "pseudo S-wave" but it's actually an inverted P wave. Not an unusual finding with AVNRT.I do have a 12-lead ECG of this rhythm which I could post if you like, but let's assume that it's not wide enough to be VT (I don't think it's foolish to carefully consider all possibilities prior to giving an antiarrhythmic).Take another look at the rhythm during the administration of adenosine. What happens to the heart rhythm? How does it look? Case 4: I don't think you're imagining anything! I saw the same thing (i.e., flutter waves) in leads II and III! That being the case, is there any point in giving adenosine again?Tom

  • Abe says:

    case one is a rapid afib, i would not even waste any time with adeosine, if patient has decent BP I would go with cardizem, and if patient is on the hypotensive side then I would go with an amioderone drip,

  • akroeze says:

    "Case 1: I agree with your assessment. If the rhythm is irregularly irregular, why give the adenosine in the first place?"I agree, adenosine would not be indicated here. One thing I was taught to do before treating any kind of dysrhythmia is to turn on the QRS beep on the monitor. The ear is one of the best tools for determining regularity quickly."Case 2: I agree that sinus tachycardia is a strong possibility here, possibly with 1AVB in the initial rhythm strip (hiding the P waves in the preceding T waves)."Measuring it out there doesn't even necessarily need to be a 1st degree block, a normal PR interval could still result in a hidden p-wave in this case.I still maintain that it wouldn't be unreasonable to give a trial dose of adenosine as a diagnostic agent. Whether it be pre-hospital or in-hospital depends on the situation."Would there be any point in doubling the dose of adenosine and trying again?"Not really, no."Case 3: Very, very good eye! The last part of the QRS complex in leads II and III is sometimes referred to as a "pseudo S-wave" but it's actually an inverted P wave. Not an unusual finding with AVNRT."Something I've been meaning to read up on actually, as soon as I find where I packed my dysrhytmia book when I moved!"I do have a 12-lead ECG of this rhythm which I could post if you like"I'd be interested in seeing it, see how it may change the puzzle. Either on here or you can e-mail it to me."Take another look at the rhythm during the administration of adenosine. What happens to the heart rhythm? How does it look?"Initially there are some FLBs (funny looking beats) that are probably PVCs. Then we get what appears to be a sinus beat with aberrancy (I'm calling that a p-wave) and then a sinus bradycardia which becomes rapid again in the same rhythm as before.Second dose of adenosine seems to induce a transiet third degree block with a junctional escape that evolves into a sinus brad with first degree block and then reinitiates as a reentry rhythm."Case 4: I don't think you're imagining anything! I saw the same thing (i.e., flutter waves) in leads II and III!That being the case, is there any point in giving adenosine again?"If we are hanging our hat on a-flutter then no, there is little point in giving another dose of adenosine.

  • Tom B says:

    Abe – To be honest, I don't see much point in using Cardizem for AF w/RVR in the field.Usually when I see AF w/RVR it's associated with CHF and acute pulmonary edema. Typically when the SpO2 goes up, the RVR comes down.It seems to me that the total number of AF w/RVR cases who are "symptomatic" (requires qualification) but hemodynamically stable and symptom onset less than 48 hours are pretty small.I know a lot of people like to argue that Cardizem controls the rate but does not convert AF to SR. Well, based on my anecdotal experience that simply isn't true.If the patient is stable, what's the rush? Tom

  • Tom B says:

    akroeze – Good point with regard to Case 2. It appears as though the PR interval is WNL. In the initial rhythm strip, it appears to be part of the T wave.I would not give adenosine again to this patient.I'll send you the 12-lead ECG to Case 3 if I don't end up posting it here.As for Case 4, I feel pretty confident we can "hang our hat" on atrial flutter based on the appearance of flutter waves in leads II and III during the brief pause triggered by the adenosine.Tom

  • TOTWTYTR says:

    I think that Case #2 is the only one that really calls out for Adenosine. Of course, it can be hard to sort out regular from irregular at really rapid rates, so it's an understandable and for the most part harmless error. There was a time when it was in vogue to use Adenosine as a diagnostic tool because of it's short half life and purported lack of harmful side effects. Fortunately, those days are gone. It's a different ball game when the complex is wide and fast, as posted about on my blog a few days ago.

  • Tom B says:

    TOTWTYTR -I saw that blog post Looks like an interesting case, but I think I missed the original post!Tom

  • I always try valsalva's first. If the rhythm breaks and then returns I will start with Cardizem instead of Adenocard. If my first dose of adenosine breaks the rhythm and it returns, it is Cardizem time. If my first dose did not break the rhythm, I re-evaluate the rhythm and the procedure in which I administered (maybe too slow).

  • Also, in the case of atrial fib. The HR on the monitor may be a good indicator of irregularity. SVT is extremely regular, and a-fib even with an RVR should show an irregularity within the numeric HR. If not, adenosine will metabolize pretty quickly, right?

  • Tom B says:

    Adam – What do you mean by "breaks"? If the rhythm breaks paroxysmally, suggesting a reentrant mechanism, then I would proceed with the adenosine.If it breaks by slowing down the ventricular response because AV conduction was slowed down temporarily (revealing the rhythm to be atrial fib or flutter) then I could see going to diltiazem (although as I mentioned earlier I have my doubts about the need in the prehospital setting).Tom

  • Tom B says:

    Adam -Your point is well taken with regard to the irregularity. Usually it's 2:1 atrial flutter that's easly to mistake for a reentrant SVT.Tom

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