Wide complex SVT versus VT

[jdiekhof]

Is there any tips on fast recognition of wide complex SVT versus VT? When there is just a few beats of this arrythmia I feel this is difficult to distinguish at times.

[BBFRN, BSN, PhD]

It depends on any other abnormal beats present. If the episode was preceded by a premature atrial beat, then it was most likely SVT. If it was preceded by a premature ventricular beat, then it was most likely VT. If there is a BBB, then it was most likely a wide complex SVT, as well. That's the short answer, in the absence of other variables (WPW, etc).

[ghillbert, MSN, NP]

There is lots of info about SVT with aberrancy -v VT in both the literature and books. You must look at the patient's history to get an idea whether there was a pre-existing BBB, or recent MI etc. You should assume and treat as VT if unsure.

A few ways to distinguish/things to assess for presence of VT:

- regular

- axis (VT usually has a left or indeterminate axis)

- QRS duration > 160 ms

- concordance in the precordial leads

- fusion beats at the onset of the arrhythmia

- AV dissociation

- slurring or notching on the downslope of the S wave in V1-2

[OptimusPrime]

jdiekhof said:

Is there any tips on fast recognition of wide complex SVT versus VT? When there is just a few beats of this arrythmia I feel this is difficult to distinguish at times.

Look to see if the deflection of the QRS complex reverses. If you have an atrial rhythm, you will almost always have a positively deflected QRS complex (minus QS waves). With VT, the pathway of the current reverses, going from the apex towards the base of the heart, hence a negative QRS deflection.

[hypocaffeinemia, BSN, RN]

OptimusPrime said:

Look to see if the deflection of the QRS complex reverses. If you have an atrial rhythm, you will almost always have a positively deflected QRS complex (minus QS waves). With VT, the pathway of the current reverses, going from the apex towards the base of the heart, hence a negative QRS deflection.

This totally depends on what lead you're looking at and their history.

For instance, you'd usually have a negative deflection on your anterior leads (V1, V2).

Also, even though you might think aVF would be a good indicator of general waveform polarity as it runs nearly vertical (in a normal patient, a ventricular rhythm would cause a negative deflection in aVF as the current is largely running the opposite direction), if before the dysrhythmia they had a left anterior hemiblock, the inferior leads might have started off negative.

What we usually do in such situations at my hospital is trial adenosine if there isn't any history of WPW. If the waveform doesn't respond to adenosine, it may be ventricular. Either way, if the patient's vitals stay stable we'd likely start an amiodarone drip and/or prepare for electrical cardioversion. Of course, if they go unstable prepare to treat via ACLS.

Edit to add: Something I see a lot that gets misclassified: patients with baseline atrial fib with rapid ventricular rates often exhibit wide complex aberrantly conducted beats that looks somewhat similar to v-tach. It's called "Ashman phenomenon" and are to the best of my knowledge benign.

[OptimusPrime]

methylene said:

This totally depends on what lead you're looking at and their history.

For instance, you'd usually have a negative deflection on your anterior leads (V1, V2).

Also, even though you might think aVF would be a good indicator of general waveform polarity as it runs nearly vertical (in a normal patient, a ventricular rhythm would cause a negative deflection in aVF as the current is largely running the opposite direction), if before the dysrhythmia they had a left anterior hemiblock, the inferior leads might have started off negative.

What we usually do in such situations at my hospital is trial adenosine if there isn't any history of WPW. If the waveform doesn't respond to adenosine, it may be ventricular. Either way, if the patient's vitals stay stable we'd likely start an amiodarone drip and/or prepare for electrical cardioversion. Of course, if they go unstable prepare to treat via ACLS.

Edit to add: Something I see a lot that gets misclassified: patients with baseline atrial fib with rapid ventricular rates often exhibit wide complex aberrantly conducted beats that looks somewhat similar to v-tach. It's called "Ashman phenomenon" and are to the best of my knowledge benign.

I agree, if looking at a 12 lead. But, pt's on the bedside monitor usually don't have a continous 12 lead, so we are stuck looking at one, maybe two leads.

Same goes for axis, no 12 lead, no way to determine axis.

[nursej22, MSN, RN]

I agree with the other posters, look at the preceding beats plus did the deflection change.

A quick way to determine axis withut a complete 12 lead (we can change the leads seen on our monitors so if this reoccurs maybe you can catch it): Look at leads I and AVF.

both leads point up-normal axis

Leads point at each other "right together" = right axis

Leads point apart "left apart" =left axis

Both point down "no man's land" indeterminate= probably VT.

but ultimately, look at the patient:

Assymptomatic=you got time to think,

symptomatic=get some help,

non-responsive=lets the sparks fly!

.

[hypocaffeinemia, BSN, RN]

OptimusPrime said:

I agree, if looking at a 12 lead. But, pt's on the bedside monitor usually don't have a continous 12 lead, so we are stuck looking at one, maybe two leads.

Same goes for axis, no 12 lead, no way to determine axis.

You can determine axis with some certainty using leads I and aVF-- no 12 lead required.

[OptimusPrime]

Ahhh, good points. I always forget about axis if Im not looking at a 12 lead. Oh well, thanks for the reminder.

[ghillbert, MSN, NP]

methylene said:

What we usually do in such situations at my hospital is trial adenosine if there isn't any history of WPW. If the waveform doesn't respond to adenosine, it may be ventricular.

Just be aware there have been reports in the literature of adenosine-induced VF in patients with stable WCT that turned out to be VT.

[hypocaffeinemia, BSN, RN]

ghillbert said:

Just be aware there have been reports in the literature of adenosine-induced VF in patients with stable WCT that turned out to be VT.

Yup. However, there's also reports in the literature of adenosine-responsive VT, so what is one to do?

(link)

[Babs0512]

According to ACLS protocol, a wide complex tachycardia, if unable to tell the difference, should be assumed V-tac. First, does the patient have a pulse or is he pulseless. Stable or unstable, I've seen patients in V-tac awake and totally stable with the rest of their vital signs, obviously, we need to interviene, but we must do so differently than pulselessness.

Basically, treat the patient, not the monitor. Adenosine can be used for SVT, someone said "if it doesn't work, then it's v-tac"" that's not necessarily true. Amnioderone works on all tachy arrhythmias - just a thought.

But again, treat the patient, not the monitor.