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In what looks like 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.

Rogue,

We’re talking past each other a bit, and I think we’re in agreement on most points.

Probably, but I think that there are a lot of important points that we are covering that are not well covered in paramedic school or in continuing education classes, such as ACLS (Advanced Cardiac Life Support) or PALS (Pediatric Advanced Life Support).

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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).

What good reason would we ever have to shock sinus tachycardia, when we know that the sinus node is already controlling the rhythm? If we knock the sinus node out, then we have to hope for a junctional rhythm or a ventricular rhythm. these will not be better than a sinus rhythm, even if the sinus rhythm is ridiculously fast.

As for shocking something that is stable, what would be the reason?

ACLS and PALS do not encourage this outside of the hospital.

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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.

If there are no visible P Waves, or if the P waves are visible, but dissociated from the QRS complexes, then we should presume that it is not sinus tachycardia, unless there is some other good reason for believing the tachycardia is sinus.

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”!

Yes, the rate is important, but not for determining if the rhythm is sinus.

The rate is important for helping to determine if the patient is unstable due to the rhythm. An otherwise healthy 20 year old patient with a rate of 220 can be expected to be very symptomatic due to the rate. If the patient is unstable, it may be presumed that the rate is the cause. Still this rate does not tell me anything about whether the rhythm is sinus, junctional, atrial, ventricular, or some combination of these.

Nothing.

Tom Bouthillet posted a comment stating that he likes using the formula 220 – age (in years) for the maximum heart rate to determine if the rhythm is sinus. I disagree, but feel that the formula may be helpful in determining whether an unstable patient is unstable due to the rate.

A 50 year old patient with a heart rate of 152 is below the maximum calculated heart rate. I should work on maximizing oxygenation and intravascular volume, rather than rushing to cardiovert. I should strongly consider other possible causes of the symptoms, rather than focus on the heart rate.

Is someone amped up on Red Bull, or caffeine, or cocaine, or amphetamines, or even repeated injections of epinephrine for refractory asthma going to benefit from cardioversion or for treatment of the cause of the rapid heart rate?

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Look at both of these rhythms. Both were labeled as SVT.

Image credit.^[1]

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Image credit.^[2]

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One of them would receive my typical SVT (SupreVentricular Tachycardia) treatment, which begins with a vagal maneuver (slow large bore catheter insertion to provide a route for an adenosine bolus to be slammed in as quickly as possible without blowing the vein. Then there are the other vagal maneuvers available. Some of these may slow the rate to the point where I can see P Waves, or to the point where I can see that there are not P Waves. Another choice is to run the printer at double speed (50 mm/second) or to pull the paper through the printer faster to simulate a faster print speed. These may help to make P Waves visible.

Rather than cardioversion, I will use adenosine for SVT. It works almost as quickly and is much less painful for the awake unstable patient.

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Image credit.^[2]

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For ventricular rhythms, medication is essentially a waste of time, but all I can do is call command for permission to not give lidocaine or amiodarone.

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But obviously nobody’s thought processes should *stop* at that point, and there your point is well made and I agree.

On that we completely agree.

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Thanks for the talk!

It is always a good exercise to debate someone with a different approach to patient care.

Tom Bouthillet and I occasionally debate this kind of stuff, too.

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Footnotes:

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^[1] Archivo:SVT Lead II.JPG
Wikipedia Spanish
Image

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^[2]Atrioventricular Re-entrant Tachycardia
Thumbnail Guide to Congenital Heart Disease
Article

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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?

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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]

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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.

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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…)

But

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.

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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.

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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.

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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.

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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.

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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.

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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.

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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?

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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.

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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.

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Footnotes:

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^[1] Inattentional blindness
TheInvisibleGorilla.com
Web site

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^[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

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In the comments to Comment on ALS is Oxygen, IV, Monitor, and Transport – Part I, there is this from Brandon Oto of EMS Basics.

My apologies for skimming, Rogue. On closer look I see the P waves. I do hold, though, that at certain rates, when atrial activity is obscured as it often is, it can be reasonable to make presumptive rhythm calls based largely on rate, or at least carefully considering it.

I agree that it is reasonable to shock an unstable tachycardia if I cannot identify P waves.

However, I see this as even more reason for a thinking medic.

Reading ECGs can be an art form. I have spent a lot of time working on learning to read rhythms while they are moving on the monitor. I think that this is a neglected part of paramedic education. Rhythm generators do have the ability to present rhythms in a testing format.

I press the test button. The rhythm is shown moving across the screen and I have to identify it using the various buttons. I also have to identify any ectopy. While this is not perfect, it allows for a lot of practice. The weird stuff that we may only see on Tom’s blog EMS 12 Lead will be some of what will come up in the testing.

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Looking at unusual rhythms is not important for being able to recognize these unusual rhythms. That is just memorization, which is not the way to get medics to think.

Looking at unusual rhythms is important for learning how to approach rhythm analysis. One of the most important parts of rhythm analysis is getting comfortable with a method that includes all of the essentials.

P Waves?

PR Interval?

P-to-P Interval?

QRS Complex width?

QT Interval?

R-to-R Interval?

Rate?

Axis?

There is no right order for these. Even the search for a PR Interval may be a part of an attempt to determine if what I am looking at are actually P Waves. This is not something that responds well to formulas that can be put into protocols. The important thing is to cover all of these in whatever way works. If I remember things one way, but you use a different order, there is nothing wrong with that.

All of this also requires a thorough understanding of the information that can be obtained from each of these. All of the intervals should be looked at for regularity.

Irregular = Arrhythmia (absence of a normal sinus rhythm or regular sinus rhythm).

Just because something is irregular does not make it unhealthy.

Athletes tend to have a lot of vagal tone, which is healthy. This healthy vagal tone leads to irregularity in the P-to-P Interval. As we breathe in, our heart rate will increase. As we breathe out, heart rate will decrease. With increasing intrathoracic pressure, such as when ventilating a patient by BVM (Bag Valve Mask), blood return to the heart will decrease. This is one of the reasons we keep decreasing the amount of ventilation we provide in cardiac arrest. Eventually, we will eliminate it from the first 5, 10, 15 minutes of CPR, but we have not accepted that, yet.

Anyway, the point of that diversion is to think about what we are doing.

An irregular sinus rhythm may be completely healthy.

A fast sinus rhythm may be completely healthy.

An arrhythmia may not be a sign of an heart problems, but purely a response to pathophysiology. Physiology is just a fancy word for the way the body works. Pathophysiology is a fancy word for the way the body works when something is wrong.

I chose this rhythm strip for one specific reason.

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Image source.

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Very fast, and I thought obvious, P Waves.

Part of the problem with looking at this is the way we are taught.

How many of us are told that faster than 150 is not sinus tachycardia?

Or that faster than the calculated maximum heart rate cannot be sinus tachycardia?

220 minus age = maximum heart rate.

An alternative is 200 minus half of the age = maximum heart rate.

This is nonsense, but if we hear it enough, we may subconsciously apply it to the way we interpret ECGs.

There are P Waves. I thought that the rate was about 220 – the maximum possible calculated heart rate for an infant according to the misinformation formula.

One of the reasons for using this was to get people to ignore this mythological formula. I had not even noticed paid attention to the information that is printed on the strip 50 mm/second. The paper is running through the printer at twice the normal speed of 25 mm/second (1 inch/second). Twice the print speed means that the rhythm is slowed down and spaced out to make it easier to identify things that may be harder to spot at the normal speed. Twice the print speed means that the heart rate is twice as fast as the normal box measurement method would come up with.

This rate is over 400. This is from a dog. I have never seen a human heart beat that quickly, but I have seen close to 300 in human infants.

What would you say if it were ~300? Still could be sinus? How about irreg. irreg. at ~275? How about very wide and regular at 220?

Funny that you should ask about a rate of around 300. The patients I have seen with close to that rate have been infants. Febrile, dehydrated, irritated, and/or in pain infants with sinus tachycardia.

This points out the primary point about sinus tachycardia.

 

Sinus tachycardia does not get better with cardioversion.

 

If the rate is so fast that you thing the synchronizer will not get capture, then you should defibrillate shockable rhythms, but sinus tachycardia is not a shockable rhythm.

 

Sinus tachycardia does not get better with defibrillation.

 

If judged to be sinus tachycardia, no specific drug treatment is required. Instead, therapy is directed toward identification and treatment of the underlying cause. When cardiac function is poor, cardiac output can be dependent on a rapid heart rate. In such compensatory tachycardias, stroke volume is limited, so “normalizing” the heart rate can be detrimental.^[1]

Sinus tachycardia is a symptom of something else. Sinus tachycardia is not a diagnosis.

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Still could be sinus?

Yes. Absolutely still could be sinus.

How do we determine if a rhythm is sinus?

There are P Waves.

There is a regular PR Interval for the sinus beats.

If there is ectopy, that means a sinus rhythm with _______ ectopic beats, but that is still a sinus rhythm.

P Waves with regular PR Intervals identify a sinus rhythm. Sinus tachycardia is a sinus rhythm.

 

The rate does not rule out a sinus rhythm.

 

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How about irreg. irreg. at ~275?

You are describing something very different from the strip I presented. 🙂

Irregularly irregular should be presumed to be A Fib (Atrial Fibrillation) – until proven otherwise. Why would I assume that something irregularly irregular is a sinus rhythm? Do you have a strip of this A Fib that you expect to be confused for a sinus rhythm? The strip I provided had clear P Waves with a regular PR Interval.

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How about very wide and regular at 220?

Are there P Waves?

Is there a regular PR Interval for these beats?

The presence of P Waves with an irregular PR Interval would be evidence of V Tach (Ventricular Tachycardia).

An irregular PR Interval would be evidence of dissociation and would probably lead to the conclusion that the rhythm is V Tach.

The wide complex is much less important than the PR Interval in determining if the rhythm is V Tach.

 

Sinus tachycardia is NOT treated with cardioversion.

 

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Sinus rhythm IS treated by treating the cause.

 

The cause of sinus tachycardia is not a lack of electricity.

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Footnotes:

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^[1] Sinus Tachycardia
2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science
Part 8: Adult Advanced Cardiovascular Life Support
Part 8.3: Management of Symptomatic Bradycardia and Tachycardia
Regular Narrow-Complex Tachycardia
Free Full Text from Circulation with links to Free Full Text PDF

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