Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

- Rogue Medic

Rhythm Interpretation and Inattentional Blindness

A Comment on Rhythm Interpretation has the following comment from Brandon Oto of EMS Basics.

Thanks for the response, Rogue! Public shaming, eh? That’ll teach me to skim a strip on the way to work. 🙂

Sorry, Brandon. This was not intended as shaming.

What I believe is shameful is the way we educate people to not think. We educate people to just follow simple rules, so that they don’t have to think. Because thinking is fallible and fallibility is bad. As if these simple rules are somehow not fallible.

We are turning medics into 911 bureaucrats. I’m from the bureaucracy and I’m here to help.

This started with my post stating that medics should be required to think. This keeps coming back to the same place.

We need to have medics think. We need to have medics understand what they are doing.

The problem is that the way we have been taught in medic school is the way you are presenting this. This is what we have been told by experts is the right way to approach arrhythmias.

On the other hand, shaming-wise, rather than acknowledge the rhythm interpretation hole you have dug yourself into, you have continued to dig. So, how do we get out of this hole?

Okay, here is all that I really meant. In the lack of clear P-wave association, considering the rate becomes a potentially relevant factor to consider in your interpretation. Undoubtedly the “typical” ranges are mutable, and sinus can be as slow as the Nile or as fast as greased lightning, but that just says it’s not a perfect indicator, and nothing is perfect. It’s just one piece of the puzzle.

A lack of clear P Wave association would make it much less clear that this would be sinus tachycardia.

That is one of the reasons I chose this strip, even though it is from a dog. It does have clear P Waves that have a consistent PR Interval.

We do not see the P Waves and do not see that there is a consistent PR Interval because of inattentional blindness.[1]

Once we see that fast rate, how many of us see the P Waves?

We have been trained to look for signs that the patient is unstable. We have been trained to react aggressively to these signs of instability.

We should be taught to look for ways to disconfirm what we think we see.

If this is an unstable and shockable tachycardia, what should not be here?

A good blood pressure?

An awake and alert and oriented patient with only minor complaints?

P Waves with a consistent PR Interval?

An onset of A Fib (Atrial Fibrillation) with no current anticoagulation, but symptoms beginning a few days ago, or earlier?

A patient wearing body paint that contains a lot of metal – and other things that would interfere with, or divert the cardioverting current? We tend to obsess over the possibility of and exaggerate the potential for a problem, because we have been given simple rules, but without the information to make good decisions. Or maybe we have just asked if this going to be on the test.

How many people read this post, or just skipped to the strip, saw a very fast rate, and ignored the clear P Waves and the clear consistent PR Interval?

I think that most did. Especially those not familiar with my blog. You are brave enough to comment on this, while the rest will say, He doesn’t know what he’s talking about, and perhaps go on to shock and kill patients by shocking rhythms that should not be shocked. Some of them may even be doctors.

What I meant by my examples was — supposing I tell you nothing else, but I tell you there’s a rate of 300. Construct a differential based on that alone. Will sinus tach be at the top? Probably not. Probably at the bottom. (There’s a neat strip of 1:1 flutter at 300 I saw recently — baby, of course…)


Shouldn’t we go through all of the rhythm assessment steps before deciding that it is too fast not to be shocked?

Cardioversion is supposed to cause temporary asystole. If we are going to cause asystole, even temporarily, it is a good idea to have a really good idea of what we are stopping before we stop it.

This isn’t as good of a waysign as finding, or finding the clear lack of, obvious associated P waves! But my whole point is that at certain rates, and in certain rhythms, and in certain situations (i.e. bouncing down the road, or in my case, skimming on my Droid…), P wave associate is not always clear, and that’s why a bigger picture can be helpful.

The bigger picture should be even more discouraging for those who want to shock this.

Rhythms that need to be shocked right away are almost always for symptoms that had a sudden onset.

Sinus tachycardia is a response to something that is happening to the body – fever, stress, pain, hypovolemia, being Toto, et cetera. This is generally something that is not a sudden onset, although a trauma, such as a broken leg can produce a sudden onset for a couple of the reasons listed.

On my ancient G1 phone, I can clearly see the P waves, even without glasses. However, I don’t expect to treat something based on what I see on my phone.

I’m also not entirely sure whether sinus tachycardia is really something that needs to be “ruled in.” Is this something we need to “catch”? To me, if you’re not certain, ST is more of a diagnosis of exclusion. If things are unclear, you don’t say “welp, just sinus tach” unless you’ve ruled out everything else.

That is not what I wrote. 🙄

I wrote that we should fully assess the rhythm, which includes looking for P Waves, and a consistent PR Interval.

We should not see a fast rate, stop thinking, and start shocking.

And if you screw up and shock it, what’s the worst case?

Asystole is expected.

Asystole should be temporary.

The worst case is if the shocking does what we want it to do.


The worst case is if we get rid of the sinus rhythm. 😯


The sinus node is behaving appropriately. Sinus tachycardia is good.

Sinus tachycardia is definitely better than any of the alternatives.

The cause of the sinus tachycardia is what we should be treating. You gave them some unneeded electricity, which is not great, and very embarrassing, but not the end of the world, and now you know.

Unless it is the end of the patient’s world.

Image credit.[2]

Cardioversion to V Fib (Ventricular Fibrillation), which responded to defibrillation, but we should try to avoid going from having pulses to not having pulse when there is no possible benefit for the patient.

And how much sedative are we giving to this patient who meets our unstable criteria?

If the patient has a blood pressure of 70/50, but the patient is awake and alert, what are we going to give to the patient to decrease the pain? Cardioversion pain is expected to be severe. The kind of pain that is enough to make a patient say, I would rather die than have that done again.

This is not the way to make things better.

It’ll delay finding and correcting the cause of the tachycardia,

What if you just keep shocking the sinus tachycardia until it stops coming back?

Why should we expect that you will switch to looking for the cause of sinus tachycardia, when you do not believe it is sinus tachycardia?

but I submit this is a less time-sensitive goal than correcting a life-threatening arrhythmia (i.e. VT).

If we think this is V Tach (Ventricular Tachycardia), why are we going to look for the cause of the sinus tachycardia?

This is where the inattentional blindness figures into things. We did not fully assess the rhythm to begin with.

We decided that the rhythm is life threatening and needs to be shocked right away.

We start with stopping the heart.

We follow the cardioversion, or V Tach, protocols.

Where does it state that after shocking V Tach unsuccessfully at 50 joules, then shocking at 100 joules, then shocking at 200 joules, then shocking at 300 joules, then shocking at 360 joules, we should look for the cause of the sinus tachycardia?

Once we start down the wrong path, it becomes very difficult to recognize that we are on the wrong path.

The time to recognize that the rhythm is not V Tach is before we start shocking the rhythm to get rid of the rhythm.


V Tach is generally a stable rhythm that probably goes away on its own much more often than it goes away because of anything we do.


How long has the V Tach existed before we showed up?

If the V Tach begins while we are there, has it been coming and going on its own before we got there?

Once we start to have tunnel vision, we seem to keep going until we reach the light at the other end. It is painful, and then some, if that light is an oncoming train.

If we have just resuscitated someone, but gave epinephrine before we realized that we had ROSC (Return Of Spontaneous Circulation), is there any other rhythm that we should expect, but sinus tachycardia. We can argue about which is more toxic to the heart, epinephrine or cocaine, but we will not be able to tell the difference by the way the heart is racing in response to either drug. We do not want to shock this rhythm, even if the rate is over 200.

The sinus node is our friend.

Sinus tachycardia is just our friend stressed out from having a bad day.

We should not electrocute our friends for becoming stressed out.

Consider the informed consent.

I don’t know what your rhythm is, but rather than do a proper assessment of the rhythm, I am going to turn your chest into a living high amperage electrical circuit.

Then you will be dead.

Then I am hoping that this death will only be temporary and that your heart’s sinus node will kick back in. I have my lucky rabbit’s foot, my fingers crossed, and everything.

And if we do not sedate the patient appropriately, we should at least give the patient this gentle warning.


If you are a masochist, you are going to love this!


Rabbit’s foot? Rabbit tachycardia? Rabbit sinus tachycardia? Imagine how much faster Rabbitachycardia must be than poodle tachycardia.

Not getting caught up in the tunnel vision/inattentional blindness is the best way to avoid this vicious circle of wrong treatment.

For those who want to make fun of Brandon for this, how many of you really would not have looked at this rhythm and not recognized it as sinus tachycardia?

Read the rest of what Brandon writes at EMS Basics and learn from the many things that Brandon writes about so well. I make plenty of errors of my own. This is not about who is right, but about how we treat our patients.

We should not be rushing to shock patients without considering the reasons to not shock.


[1] Inattentional blindness
Web site

[2] Images in cardiology. Ventricular fibrillation provoked by cardioversion and asynchronous pacing.
Bõhm A, Székely A, Préda I.
Heart. 2000 Apr;83(4):424. No abstract available.
PMID: 10722542 [PubMed – indexed for MEDLINE]

Link to Page with Free Full Text PDF Download



  1. Rogue,

    We’re talking past each other a bit, and I think we’re in agreement on most points. I agree that a rhythm should be fully interpreted in all its particulars, and that our providers should be trained to do this. I agree that shocking sinus tachycardia is not advisable (indeed, I lean towards your camp that shocking anything stable may not be advisable).

    In particular, as you state, “A lack of clear P Wave association would make it much less clear that this would be sinus tachycardia.” That’s the scenario I was imagining, because with many tachycardias, that’s what you’ve got — not clear P waves, as we have here, but a rapid mess. And I know you would agree that, in general, the rate is an important part of any interpretation — otherwise we wouldn’t even be able to call this a “tachycardia”! But obviously nobody’s thought processes should *stop* at that point, and there your point is well made and I agree.

    Thanks for the talk!


  1. […] it will be the last in this series, for a while, Brandon Oto of EMS Basics wrote this comment to Rhythm Interpretation and Inattentional Blindness. […]

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