ECG Blog #468 — Aberrant or VT?

I was sent the ECG in Figure-1 — without the benefit of any clinical information.

QUESTIONS:

• What is the rhythm?
•      — How certain are you of your answer?

Figure-1: The ECG I was sent ... (To improve visualization — I've digitized the original ECG using PMcardio).

MY Thoughts on Making the Diagnosis:

Rather than a "Yes-No" answer (ie, Rather than saying the rhythm is VT vs SVT) — it is preferable to simply describe what you see.

• PEARL #1: There is a tendency for many providers to think only about 2 possible answers for the first question that I ask above — that is: i) That the rhythm is either VT (Ventricular Tachycardia); — or — ii) That the rhythm is an SVT (SupraVentricular Tachycardia) with aberrant conduction.
• This thinking is erroneous — because rather than the rhythm being either VT or an SVT with aberrant conduction, I think of a 3rd (very common) possibility, namely: iii) That the answer is a probability statement, in that we realize we can not be 100% certain what the etiology of the rhythm is, based on the single ECG that we have in front of us. In this case, depending on a series of factors (ie, the clinical history — frontal plane axis — QRS morphology, etc.) — we may only 30-to-50% confident, or perhaps 80-to-90% (but not 100%) confident of our diagnosis.
• PEARL #2: Thinking about our answer in terms of a probability statement is important for optimal treatment — since the clinical reality is that much of the time, we need to begin our treatment before we are 100% certain of the rhythm diagnosis. Awareness of our relative certainty about whether we are dealing with ischemic or idiopathic VT vs some form of SVT vs a WPW-related tachycardia — can guide us for deciding when to try vagal maneuvers, electrical cardioversion, or some form of medical therapy (ie, Adenosine, Amiodarone, Verapamil, ß-Blocker, or other).
• PEARL #3: As a result of the above 2 Pearls — rather than saying, "VT" or "SVT with aberrancy" — it is BEST to simply describe what you see. For example, in Figure-1 — the rhyhm is a regular WCT (Wide-Complex Tachycardia) at ~160/minute, without clear sign of atrial activity.

PEARL #4: I provide numerous links in the references below illustrating my approach to a series of WCT rhythms. That said — it is well to remember the literature-based Statistics, which suggest that even before you look at the ECG — about 80% of regular WCT rhythms without clear sign of atrial activity will turn out to be VT.

• This figure goes up to ~90% if the patient is an adult of a certain age (say, over 50-60 years old) — and if the patient has some form of underlying heart disease.
• Assessment of the frontal plane axis and QRS morphology can help in selected cases to further increase your probability estimate of the likely diagnosis (See my ADDENDUM below for my "user-friendly" approach to WCT diagnosis).

PEARL #5: Many providers limit their considerations to a differential between VT vs SVT with aberrancy. But as I show below in Figure-2 in my ADDENDUM — rather than aberrant conduction, the QRS complex may be wide in a supraventricular rhythm due to: i) Preexisting bundle branch block; — or, ii) Something else! (ie, a WPW-related tachyarrhythmia, hyperkalemia, some other toxicity).

PEARL #6: There are 2 insensitive (ie, uncommonly found) findings that I always look for when assessing WCT rhythms — because IF seen — you can approach 99% likelihood that the rhythm is VT:

• Finding #1: Is there AV Dissociation during the WCT rhythm? IF so — this is virtually diagnostic of VT. That said — most of the time, AV dissociation will not be seen unless the rate of VT is relatively slow. Therefore — the absence of AV dissociation is nondiagnostic. However, its presence may be confirmatory.
• NOTE: Many providers "think" they are seeing AV dissociation when in fact it is not present. Unless you can walk out regular underlying P waves through much (most) of the tracing — it is unlikely that AV dissociation is present (See ECG Blog #133 — and — ECG Blog #151 for examples of AV dissociation with VT).
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• Finding #2: Is there Concordance of the QRS in all chest leads? IF ever all QRS complexes in leads V1-thru-V6 are either all positive or all negative (ie, if there is "global positivity" or "global negativity" ) — this is virtually diagnostic of VT. That said — since the sensitivity of this finding is so low (probably less than 10% of cases) — the lack of chest lead concordance is not helpful.

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Back to Today's CASE:

As stated earlier — the rhythm in Figure-1 (that I reproduce again below) — is a regular WCT at ~160/minute without clear sign of P waves.

Figure-1: The ECG I was sent. No history.

MY Approach to Figure-1:

We do not have the benefit of any history in today's rhythm — so we do not know the age of this patient, nor whether there is any underlying heart disease. That said, by PEARL #4 — Statistical likelihood that the regular WCT in Figure-1 is VT is ~80% even before we look closer at the ECG.

• By the 3 Simple Rules (shown in Figure-3 in the Addendum below) — there is an "extreme" frontal plane axis, because the QRS is all negative in each of the inferior leads. This finding significantly increases statistical likelihood of VT!
• Also by the 3 Simple Rules — the wide QRS does not look like any known form of bundle branch block (ie, QRS morphology could be consistent with LBBB in the limb leads — but the all positive QRS in lead V1 looks more like RBBB, albeit none of the lateral leads have wide terminal S waves). Not resembling any known conduction defect makes VT more likely.
• Looking for AV dissociation — Although there are some intermittent undulations in the baseline, I do not see a regular underlying atrial rhythm. There is no sign of AV dissociation (but we know that most of the time with a faster VT — we will not see AV dissociation — so not seeing it here does not alter our prediction of the rhythm).
• PEARL #7: But there is global positivity (ie, QRS Concordance) in all 6 chest leads! Although the QRS in lead V6 is tiny — it is all positive! All other chest leads are decisively positive.

BOTTOM Line: Even without knowing the patient's age or the history in today's case — I'd estimate ~99% likelihood that the regular WCT rhythm in Figure-1 is VT because: i) There is an "extreme" frontal plane axis; ii) QRS morphology does not resemble any known form of conduction defect; — and, especially iii) Today's rhythm is one of the rare cases in which we do see QRS concordance (global positivity) in all 6 chest leads!

• About the only exception for which an SVT rhythm might produce the unusual QRS morphology that we see here in Figure-1 — would be in a patient with severe underlying heart disease, who during sinus rhythm has an identical QRS morphology as we see in Figure-1 as a result of previous infarction(s) and unusual conduction defects.
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• To Emphasize: My above discussion is in "slow motion". It literally took me no more than seconds to look at today's rhythm and know there was a 99+% likelihood that this was VT.
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• CASE Follow-Up: The patient was treated and converted to sinus rhythm. Today's rhythm was proven to be VT.

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Acknowledgment: My appreciation to Adem Ahmed (from Nouakchott, Mauritania) for the case and this tracing. 

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Additional Relevant ECG Blog Posts to Today’s Case:

• ECG Blog #185 — Reviews my System for Rhythm Interpretation — with use of the Ps, Qs & 3R Approach.
• ECG Blog #210 — Reviews the Every-Other-Beat (or Every-Third-Beat) Method for estimation of fast heart rates — and discusses another case of a regular WCT rhythm. 
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• ECG Blog #220 — Review of the approach to the regular WCT ( = Wide-Complex Tachycardia).
• ECG Blog #196 — Another Case with a regular WCT.
• ECG Blog #263 and Blog #283 — Blog #361 — Blog #384 — and Blog #460 — More WCT Rhythms ...
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• ECG Blog #197 — Reviews the concept of Idiopathic VT, of which Fascicular VT is one of the 2 most common types. 
• ECG Blog #346 — Reviews a case of LVOT VT (a less common idiopathic form of VT).
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• ECG Blog #204 — Reviews the ECG diagnosis of the Bundle Branch Blocks (RBBB/LBBB/IVCD). 
• ECG Blog #203 — Reviews ECG diagnosis of Axis and the Hemiblocks. For review of QRS morphology with the Bifascicular Blocks (RBBB/LAHB; RBBB/LPHB) — See the Video Pearl in this blog post.
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• ECG Blog #211 — WHY does Aberrant Conduction occur?
• ECG Blog #301 — Reviews a WCT that is SupraVentricular! (with LOTS on Aberrant Conduction).
• ECG Blog #445 and Blog #361 — Another regular WCT rhythm ...
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• ECG Blog #323 — Review of Fascicular VT.
• ECG Blog #38 and Blog #85 — Review of Fascicular VT.
• ECG Blog #278 — Another case of a regular WCT rhythm in a younger adult.
• ECG Blog #35 — Review of RVOT VT. 
• ECG Blog #42 — Criteria to distinguish VT vs Aberration.
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• ECG Blog #133 and ECG Blog #151— for examples in which AV dissociation confirmed the diagnosis of VT.
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• Working through a case of a regular WCT Rhythm in this 80-something woman — See My Comment in the May 5, 2020 post on Dr. Smith’s ECG Blog. 
• Another case of a regular WCT Rhythm in a 60-something woman — See My Comment at the bottom of the page in the April 15, 2020 post on Dr. Smith’s ECG Blog. 
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• Review of the Idiopathic VTs (ie, Fascicular VT; RVOT and LVOT VT) — See My Comment at the bottom of the page in the September 7, 2020 post on Dr. Smith’s ECG Blog.
• Review of a different kind of VT (Pleomorphic VT) — See My Comment in the June 1, 2020 post on Dr. Smith’s ECG Blog.

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ADDENDUM (2/8/2025):

• I've reproduced below from ECG Blog #361 — a number of helpful figures and my Audio Pearl on assessment of the regular WCT rhythm.

 

Figure-2 : My LIST #1 = Causes of a Regular WCT (Wide-Complex Tachycardia) of uncertain Etiology (ie, when there is no clear sign of sinus P waves).

Figure-3: Use of the "3-Simple Rules" for distinction between SVT vs VT.

Figure-4: Use of Lead V1 for assessing QRS morphology during a WCT rhythm.

—  —

ECG Media PEARL #13a (12:20 minutes Audio) — reviews “My Take” on assessing the regular WCT (Wide-Complex Tachycardia), when sinus P waves are absent — with tips for distinguishing between VT vs SVT with either preexisting BBB or aberrant conduction.

ECG Media PEARL #28 (4:45 minutes Video) — Reviews WHY some early beats and some SVT rhythms are conducted with Aberration (and why the most common form of aberrant conduction manifests RBBB morphology).

• CLICK HERE — to download a PDF of this 6-page file on Aberrant Conduction.