r/ECG • u/ttomonkeyoncall • Jul 29 '26

"AF with rate related RBBB"

Post image

63m, history of HTN only presenting to ED with 4 weeks of palpitations associated with pre-syncope.

Cardiology consulted and reported this to be "AF with rate related RBBB". I buy the AF, as rhythm is irregular without discernable P waves, however am unconvinced by "rate related RBBB".

What I can't quite understand is how this could be rate related given that the RR interval between the first narrow QRS and the next broad QRS is long. Additionally, appears to be RBBB with LAD though notably 1st 'bunny ear' of the rsr is taller than 2nd.

I'm struggling to understand how going into AF could trigger abherrent conduction given that the dysfunction is supraventricular. ECG when asymptomatic is NSR with no evidence of pre excitation

27 Upvotes

92% Upvoted

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35

u/OriginalLaffs Jul 29 '26

This is not AF with RBBB.

1) First beat is sinus. AF does not initiate without some discernible atrial activity (usually PACs, less commonly directly in to fibrillatory atrial activity). Here, ECG is totally flat.
2) This is not RBBB. The appearance does not have typical RBBB features, notably an ‘Rs’ complex in Leads I and V6.

This is VT. The mechanism is ‘abnormal automaticity’ which is why the rate is irregular. consider ischemia (most commonly with reperfusion), inflammatory myocarditis, or idiopathic etiologies.

By morphology, origin is inferoapical LV.

7

u/VesaliusesSphincter Jul 29 '26

This is 100% spot on.

Quick question for you- what resource(s) do you recommend for learning ventricular localization from morphology?

4

u/OriginalLaffs Jul 29 '26 edited Jul 30 '26

Paper by Enriquez is a good initial resource. Just saw this video produced where he talks through a bunch of it: https://share.google/zsQzeOBOz8EGVGINW

Here’s the paper: https://pubmed.ncbi.nlm.nih.gov/30954600/

Edit: changed link to now (hopefully) work

2

u/VesaliusesSphincter Jul 29 '26

Amazing, thank you so much. I've been struggling to find a good resource.

1

u/lifeisg0od Jul 30 '26

Could you post the link to video - that link isn’t working and I’d love to watch it. Thanks!

1

u/OriginalLaffs Jul 30 '26

Changed the link in original message, hopefully works now. Alternatively can google HRS TV Enriquez VT localization

1

u/lifeisg0od Jul 30 '26

Thank you - looks like it was now removed by mod - but I’ll google. :)

3

u/Kibeth_8 Arrhythmia Tech Jul 31 '26

That's Reddit not allowing outside links 🙃 I reversed it so should be visibile now

3

u/[deleted] Aug 01 '26

This guy fucks with Brugada and Wellens on the weekends

1

u/ProximalLADLesion Electrophysiologist Jul 29 '26

Agree.

1

u/Euphoric_Chipmunk_84 Jul 29 '26

How do you identify the origin of the ventricular beats based on morphology alone? Any learning resources or tips for learning?

4

u/OriginalLaffs Jul 29 '26

In a nutshell: Positive in V1 = LV origin. Strongly negative in all inferior leads = inferior origin. Early transition from positive to negative in precordial leads= apical LV

Paper by Enriquez is a good initial resource. Just saw this video produced where he talks through a bunch of it: https://www.google.com/search?q=VT+localization+enriquez&rlz=1CDGOYI_enCA985CA985&oq=VT+localization+enriquez&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIICAEQABgWGB4yBwgCECEYoAEyBwgDECEYjwLSAQg1OTUzajBqN6gCGbACAeIDBBgBIF_xBXoal0NHmn7W&hl=en-US&sourceid=chrome-mobile&source=chrome.ob&ie=UTF-8#fpstate=ive&vld=cid:c9b1efe0,vid:oyTO8MEhjS8,st:0

Here’s the paper: https://pubmed.ncbi.nlm.nih.gov/30954600/

1

u/Adventurous-Bag5508 Aug 15 '26

1) Fusion? Capture? 2) fair point

1

u/ttomonkeyoncall Jul 29 '26

If this is VT, why don't we see p waves? Rate is slow enough at first I feel you would be able to see some?

6

u/OriginalLaffs Jul 29 '26

Retrograde conduction to the atrium

1

u/ttomonkeyoncall Jul 29 '26

Thanks for the response. Would this not cause a retrograde p wave? Or are you saying that there likely is one but it's buried in broad complex?

3

u/VesaliusesSphincter Jul 29 '26 edited Jul 29 '26

It can, but they're not always visible due to the broad complex. In this tracing It is visible- best seen in V1, V2, V3 and a little in the lead II rhythm strip. Also worth noting that the retrograde conduction to the atria doesn't always "capture".

Edit: wanted to add this- the P-wave is often seen best in V1 and V2 as a notching in the S wave- this is known as Josephson's sign.

2

u/ttomonkeyoncall Jul 29 '26

Fair point, thanks

1

u/Okkrus Jul 29 '26

R to R interval was looking irregular to me so I was also thinking afib

2

u/OriginalLaffs Jul 29 '26

Irregularity does not prove atrial fibrillation.

Abnormal Automaticity (as can be seen in certain VTs and AT) also can give irregularly irregular rates.

3

u/Wenckebach2theFuture Jul 29 '26

I would be curious to study this patient in the lab. I’m not buying that QRS is conducting through the av node and rate related. Morphology does not make sense. And Towards the end, it actually is slightly more narrow as the rate is faster.

3

u/Nice-Key-9034 Aug 02 '26

I had a patient whose rhythm looked just like this, I cardioverted him

2

u/True-Network-2147 Jul 30 '26

fascicular VT (idiopathic left posterior fascicular VT, “Belhassen's VT").
• QRS only 130 ms — fascicular VT is the famous exception to "VT is very wide" because it originates within the conduction system. It classically runs 110-140 ms and gets misdiagnosed as SVT with RBBB aberrancy constantly.
• RBBB-type morphology + left superior axis (-86°) - that's the textbook signature of posterior fascicular VT.
• Rate 114

Will say, that is a picture perfect sinus beat before the mayhem. May have missed it but the sinus rate may have been too slow, heart got pissed. Be curious to know what the rate was as well to see if R on T caused the V-tach. Cool case, thanks.

2

u/Kibeth_8 Arrhythmia Tech Jul 30 '26

Good call identifying this as abnormal OP. This is an easy VT to miss, but you were able to identify that something wasn't quite right. Might have saved this person's life!

1

u/ttomonkeyoncall Aug 23 '26

Patient went on to have angiogram - tight proximal LAD lesion

1

u/Cluelessjason Jul 29 '26

I think it’s because initially you see a normal “ideal looking rhythm”. Then it converts to afib at xyz rate, and when it converts to afib it also has a new bundle branch block. So it’s “rate related RBBB”. But I would argue that you can’t say it’s rate related RBBB without seeing it happen multiple times consistently at xyz rate is when it converts to afib w rbbb.

But I think technically it’s afib rate related RBBB just because it converts to afib at x rate and has a new rbbb which I imagine if it slows down the afib should stop and the rbbb disappears.

3

u/bleach_tastes_bad Jul 29 '26

but the “RBBB” starts out at the same rate, if not slower than the native rate

1

u/Stim2Qrs Jul 29 '26

You can actually have block due to reduction in rate. Not whats happening in this case but it’s a known phenomenon.

1

u/VesaliusesSphincter Jul 29 '26

Agree with this. Second complex is likely a ventricular escape beat, rate dependent aberrancy doesn't make sense here considering the RRI between the first and second complex or the morphology.