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

- Rogue Medic

The Three Flavors of VT.

 

Why is VT (Ventricular Tachycardia) so complicated?

It isn’t really much different from the other rate related arrhythmias.

Rate related?

The heart rate is the problem, not the arrhythmia.

But there are 3 different treatments for VT and none of the other rate related arrhythmias have that many different treatments.

The AHA simplified the rest of the tachycardias and bradycardia.

Please explain.

With an SVT we have stable, unstable, and pulseless – we just don’t have that written explicitly in the algorithms.

But there is no pulseless SVT treatment.

Are we claiming that a rhythm that usually produces a rate much faster than VT cannot produce pulselessness?

What does the rate have to do with it? It’s the rhythm, and VT is just really bad! I don’t know why they even pretend that there is such a thing as stable VT. VT is a lethal rhythm. Everyone knows that.

VT does look worse than SVT.

It is ugly.

We’ve been told how bad VT is.

We have to learn somehow.

We spend a lot of time on the perfect antidote for VT.

That amiodarone is great stuff!

No, it isn’t, but let’s go over the rhythm differences first. What causes the VT to be so bad?

Well, it wants to be VF (Ventricular Fibrillation).

The heart does produce its own electrical activity, but it does not think, so it doesn’t want anything.

How long do we expect someone to stay in VT?

Until the VT spontaneously resolves, or until the VT becomes unstable, or until the VT resolves with treatment, or maybe for hours or days without becoming unstable.

Days? Impossible.
 

All patients had recurrent spontaneous episodes of ventricular tachycardia that were typically sustained for minutes to days.[1]

 

This is from 1978, so we can see that very long periods of VT are nothing new.

But VT does not have an atrial kick.

Do we even know what an atrial kick is?

The atria help the heart beat.

Yes, the atria help to fill the ventricles. They help to push more blood into the ventricles than would enter otherwise. This stretches the heart muscle and allows it to contract more forcefully. When someone is trying to add force to a muscular contraction one effective method is to wind up, as a pitcher does. The muscles are stretched out and when they contract more force is produced. This is what the heart is getting from the atria. When the atria are not coordinated with the ventricles, or are not contracting at all, this extra force is lost and the heart has to work harder to fill up and harder to contract.

Right. VT gets rid of that extra force, so the heart has to work harder to produce the same circulation.

And SVT does not?

Hmmm.

With an SVT, the sinus node is not in charge, so coordination between any atrial contractions and the ventricular contractions is not going to happen. The electrical activity in the atria may also be preventing the atria from contracting.

So, what is the difference between SVT and VT.

Well, the causes are different. VT is often caused by a heart attack in older people, so the heart is naturally weaker. The medications are quite a bit different, too.

And you mentioned that VT spontaneously resolves?

VT probably goes away on its own more often than it does with any of our treatments. Just because we started giving something to the patient does not mean that the treatment is the reason the patient’s condition improved.

OK, what are the 3 flavors of SVT?

The same as the flavors of VT – stable, unstable, and PEA (Pulseless Electrical Activity).

But PEA and pulseless VT are entirely different.

Pulseless VT is just one type of PEA. VF is a PEA with electrical activity that is disorganized. We would not expect it to produce a pulse. Since rapid defibrillation is critical for treatment of VF, it is treated differently from PEA. Pulseless VT is treated the same as VF, so the two are lumped together in one algorithm. SVT can be fast enough to produce a pulseless condition. Bradycardias can be slow enough to produce a pulseless condition. Since pulseless bradycardias are treated pretty much the same way as asystole, they are lumped together with asystole. This makes treatment easier to remember.

So, what do we do for a pulseless SVT?

What do we do for an unstable SVT?

Cardiovert.

The same as for an unstable VT, so what do you think we should do for a pulseless SVT?

Defibrillate?

Sure. If we are comfortable enough with cardioversion that using the cardioverter will not delay the shock, go ahead and cardiovert. Since pulseless SVT is not something we will see often, we may want to keep it simple and defibrillate as if it were VF.

But the drugs are different.

Yes, but that is a topic for another post. And there are really 6 flavors of VT. Polymorphic VT is treated differently from monomorphic VT.

That sounds like another post, too.

Of course.

Footnotes:

[1] Recurrent sustained ventricular tachycardia. 1. Mechanisms.
Josephson ME, Horowitz LN, Farshidi A, Kastor JA.
Circulation. 1978 Mar;57(3):431-40.
PMID: 624152 [PubMed – indexed for MEDLINE]

Free Full Text Download in PDF format from Circulation.

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Comments

  1. RM,Sorry, this has nothing to do with the post, but I’ve just started reading, and am very impressed – very intelligent writing. I wondered if you might find the time to give me your views on my latest blogpost over at Space To RantIt would be greatly appreciatedChris

  2. LOL – You got me way too excited when I misread the title of your post as the three flavors of VD… made me think of my fav online store. A Sense of HumorMy mom about had a coronary when I told her I wanted herpes for my birthday Herpes VirusLOL

  3. Chris, thank you. I will visit.

  4. Laura,Don’t be silly. There are far more than 3 flavors of VD.As for Herpes for your birthday, that is not all that bizarre. I checked the link to the little Herpes “doll?” and that is not what I expected.Some children actually want to get chicken pox (Herpes zoster) out of the way, so they can participate in things that their parents keep them from because of their concern about the children contracting chicken pox. Less of a concern now with the Varivax.There are actually far more than 3 flavors of Herpes. Maybe I need to do a post on Chlamydia vs Syphilis for favorite VD, but that would be tasteless.

  5. Very Informative Kind sir. Touched on more than I think we thought about in my cardiology section. That or I might have fallen asleep. A few times.

  6. It’s inda interesting (and off topic), but I never had chicken pox as a child. My father never contracted it, either. It’s kinda strange. I wonder if my children will inherit an immunity without immunization. And why are parents immunizing their children nowadays against chicken pox anyways? Back when I was a child, parents would have chicken pox parties (yeah…a la South Park)…I went to many, but never got chicken pox.I have to say that my favorite VD (on that site anyways) has to be herpes. I guess chlamydia or syphyllis could be yours…:o)

  7. If you never had chicken pox and the rest of your family never had it, then maybe you have a natural immunity.”Varicella, or chickenpox, is usually a benign, self-limited, primary infection that affects approximately 4 million children per year in the United States. Varicella also accounts for significant morbidity (4000 hospitalizations per year) and mortality (50-100 deaths per year) in otherwise healthy children; moreover, the annual cost of chickenpox has been estimated at $400 million in medical costs and lost wages in the past. Universal immunization against varicella was first recommended in 1995 and has lead to a reduction in varicella related hospitalizations and hospital related charges for children and adults in the United States.”This is a link to the eMedicine article on chicken pox50 – 100 deaths is not a large number compared to most risks, so we tend to not realize that they happen. As far as the VDs go. You don’t choose different ones – you share them, silly. Why can’t I have the popular VDs?:-)

  8. LOL – if I had a popular VD, I would share it with you! (unless it was the cute little herpes guy, then you’d have to buy your own!);o)

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