One of the most important diagnostic dilemmas in ECG interpretation entails assessment of a regular WCT ( = Wide-Complex Tachycardia) rhythm. The tracing presented here provides an excellent example of this.

I agree with the points made in Dawn’s discussion. I’ll simply add a few additional comments that serve to amplify the approach I previously suggested in the 3/19/2015 ECG Guru Instructor Collection Tracing:

Although we do not know the age of the patient in this case, nor whether this patient has a history of underlying heart disease — we DO know that this man was clearly symptomatic (palpitations with light-headedness and near-syncope). Thus, regardless of whether the rhythm is ventricular or supraventricular in etiology — immediate cardioversion is indicated — and, after conversion to sinus rhythm — full evaluation with consideration of EP (ElectroPhysiology) referral is in order.

The literature suggests that the statistical likelihood that a regular WCT rhythm without sign of sinus P waves is VT is at least 80%. Several features in this case increase those odds. As Dawn mentioned, QRS morphology in leads V1, I and V6 is consistent with a RBBB pattern. However, the entirely negative QS complex in leads V2-thru-V5 is unlike any normal RBBB pattern. In addition — the QRS complex in lead II is all negative — and, the QRS is all positive in lead aVR. Therefore, QRS morphology is highly suggestive that this rhythm is VT.

It is of interest that a number of leads on this tracing suggest the presence of atrial activity. This is perhaps best seen in the long lead II rhytm strip at the bottom of the tracing. That said, if the extra notching seen near the beginning of the T wave does reflect atrial activity — this does not help in distinction between VT vs SVT (SupraVentricular Tachycardia). That’s because there is no AV dissociation. Instead, the RP’ interval (ie, distance from the QRS until the notch in the T wave that follows) remains the same. Both VT and reentry SVT rhythms may transmit back to the atria with 1:1 VA (ie, retrograde) conduction.

Finally — the very fast ventricular rate of ~240/minute is worthy of comment. Both VT and SVT rhythms may conduct this fast, as can AVRT (Atrio-Ventricular Reentry Tachycardia) in which the reentry SVT rhythm travels anterograde (ie, down in the forward direction utilizing an accessory pathway). Of interest, EP cardiologists have noted that as an SVT rhythm attains these very fast ventricular rates — aberrant conduction sometimes fails to resemble the QRS morphology of a typical conduction defect. That’s because of much greater dispersion of refractory periods within the conduction fascicles at these very fast rates. That said — QRS morphology in this example is so atypical, that my strong hunch remains that this rhythm is Venricular Tachycardia until proven otherwise in the EP lab. But, because of this very-rapid-rate phenomenon and, resemblance in leads I, V1, V6 of a RBBB-pattern — IF this patient was hemodynamically stable, my initial intervention would probably be a trial of IV Adenosine prior to cardiovesion. Unfortunately, no follow-up on this case is available.

Dawn...

Thanks for another challenging wide complex tachycardia.

At first glance, we always tend to lean toward VT as the cause of a wide complex tachycardia. And with good reason: 1) if we knew nothing at all about this patient other than he/she had a wide complex tachycardia and we assumed it was VT, we would be correct 80% of the time. 2) If we knew that the patient had a history of heart disease (MI, angina, CHF, cardiomyopathy) and presented with this ECG and we assumed it was VT, we'd be correct 95% of the time! So it is not without some academic support that we tend to "want" to diagnose VT. And there is also a reassuring psychological boost for the person treating the patient: once we resolve that it is VT we can go ahead and treat the patient which usually means a dose of some "Edison medicine" rather than an IV antidysrhythmic medicine. Besides, generally whatever will treat VT will also treat SVT with aberrancy.

However, there are times when the diagnosis just doesn't want to conform to our preconceptions. Take this ECG, for instance...

When I use the Brugada criteria to analyze it, here's what I see...

1. Is there a LACK of RS complexes in ALL precordial leads? No. There are rS complexes in V5 and V6. The rSR' in V1 does NOT count as an RS complex according to the Brugadas.
2. In the precordial leads with RS complexes, is the "R to S nadir" time GREATER than 100 msec? No. No where near it. And please be aware that the Brugadas were insistent that an "R to S nadir" time EQUAL to 100 msec DID NOT QUALIFY for a "Yes" answer.
3. Is there evidence of AV dissociation? No, none that I can see. As Dr. Grauer pointed out, 1:1 retrograde conduction means nothing here. So now we move on to the "morphological criteria."
4. Morphological Criteria: This rhythm has a right bundle branch block pattern, so we will use the criteria specific for that. V1 has an rSR' morphology which is consistent with a normal RBBB morphology which favors SVT with aberrancy. Nothing more to look at in V1. V6 has an rS morphology which is NOT consistent with RBBB because the R/S ratio is < 1.0. It is, however, consistent with VT - except that it still means nothing toward diagnosing VT because BOTH Leads V1 and V6 must be consistent (i.e., BOTH would have to show complexes consistent with VT). None of the other criteria for V6 (QR or QS, monophasic R. triphasic QRS, R/S ratio > 1.0) that would help make the diagnosis are present. There is notching of the S waves in V2 and V3, but that is a LBBB pattern criteria and does not help us when a RBBB pattern is present. When we have gotten down to the morphological criteria for a RBBB pattern, the fact that there is a wide S wave in V6 means nothing; it is the R/S ratio that will make the determination.

Therefore, as much as this tracing looks like VT, if we adhere to the Brugada criteria, it is SVT with aberrant conduction.

In their landmark paper on the criteria and algorithm, the Brugadas include an ECG that is almost exactly the same as this one and they come to the same conclusion. Both ECGs appear to have a LAFB and LAFB can result in an R/S ratio < 1.0. They make no mention of fascicular blocks or fascicular tachycardias in their paper.

Also, I would like to point out that NO CRITERIA for distinguishing VT from SVT with aberrancy ever mention AGE. Don't let the fact that a patient is in his or her 20's dissuade you from a diagnosis of VT if the criteria fit.

Dawn, thanks again for a great learning ECG and a wonderful website.

     My thanks to Dr. Jones for making discussion of this tracing even more interesting than it already was! There are indeed many criteria in the literature for assessment of the regular wide-complex tachycardia (WCT). It is true, that if one adheres strictly to the Brugada algorithm that Dr. Jones refers to — that the answers to each of the 4 Steps in the Brugada approach are “No” — so that IF one adheres solely to this algorithm — then one would conclude that this rhythm is SVT.

That said, there are 12 leads on this 12-lead ECG — and 3 of these 12 leads would seem strongly suggestive of VT. The finding of an entirely upright, monophasic R wave in lead aVR is highly specific for VT. The finding of an all negative QRS complex in lead II in the setting of an otherwise indeterminate front plane axis during a regular WCT without P waves is also highly suggestive of VT. Finally, while true that leads V1 and V6 are not helpful in morphologic assessment of this WCT (as per Dr. Jones) — the all negative QRS in leads V2,V3,V4 (and almost all negative QRS in V5) are clearly neither suggestive nor consistent with RBBB aberration by any of the usual standards for making that diagnosis. I therefore would argue that on a morphologic basis — the WCT rhythm shown here is distinctly atypical for any form of conduction block, and therefore unlikely on morphologic grounds to be an aberrantly conducted SVT.

That said, EP cardiologists have observed in the laboratory that highly unusual QRS morphologies may be observed with aberrant conduction when the ventricular rate is extremely fast. The rate of 240/minute as seen here would seem to qualify for this phenomenon. BOTTOM LINE — Whether due to some morphologically atypical form of aberrant conduction or anterograde AVRT or VT — the clinically important points I hope Dr. Jones agrees with me on regarding this tracing are: i) that we cannot be 100% certain of the ECG diagnosis in this case; ii) that if the patient is hemodynamically unstable at the time of this tracing — that immediate electricity is indicated; iii) that if the patient was hemodynamically stable — that empiric treatment with Adenosine would be a reasonable initial option; and iv) that definitive diagnosis of the etiology of this arrhythmia might not be obtained until some later point after the patient has been converted out of this rhythm.

THANKS to Dr. Jones for his stimulating discussion. We invite additional comments from others!

Thanks Dr. Jones! I do think we agree — and glad we could use our perspectives to amplify the discussion. 

After reading over all the comments (including my own) several times and reading quite a few similar discussions on other blogs and websites, I noticed something:

In the medical field - though this could apply as well to science in general or even business and political decisions - we tend to make decisions and THEN seek support for what we have already decided. I am referring to experienced physicians, nurses, PA-Cs and paramedics who carefully and thoughtfully look at an ECG, for instance, like the one with the wide-complex tachycardia posted on this site and, realizing that an immediate and confident diagnosis is not going to be obvious, then turn to one of a number of criteria and/or algorithms to try to distinguish a true ventricular tachycardia from the other diagnostic possibilities.

In fact, let's look at this ECG specifically. We are going to assume that the patient is very stable hemodynamically and well-oriented since otherwise there is only one decision to make: "How many joules?" There are a number of criteria and algorithms that can be used. All have some merit but none are 100% reliable. That is usually the situation no matter what the medical, scientific or business problem may be.

Let's say your impression is that the patient has a ventricular tachycardia. You then use Criteria/Algorithm A to see if it distinguishes between VT or "other dysrhythmia." Let's say it tells you that it is not VT. What do you do now? Do you accept that diagnosis or do you use Criteria/Algorithm B? Let's say that Criteria/Algorithm B diagnoses VT. What do you do now?

Even if Criteria/Algorithm B has a higher probability of being correct (let's say it is correct 75% of the time) and Criteria/Algorithm A has a 65% probability, neither really answers the question "Is this VT?" Each also has a probability of being wrong and while the one with a greater probability of being correct is the better choice if one HAS to choose, once having chosen one should still be less than 100% confident of having achieved the correct diagnosis - even though the proper decision was made given the circumstances.

My point is that whether we feel we know the diagnosis or not, before using any criteria or algorithm we have already decided what our diagnosis is going to be. If the first algorithm doesn't produce the result we expect, we tend to move on to another algorithm until we find one that DOES support our diagnosis and at that point we are suddenly "justified" in recording our diagnosis and acting upon it. Had one simply acted on one's first impression, the likelihood that the same treatment plan would have been arrived at much earlier is extremely high (I certainly have done no studies on this but I would surmise it to be very high!). Most people who feel that a patient has a VT are not going to accept an algorithmic diagnosis of SVT - they will keep looking for a justification for diagnosing VT when they've had the diagnosis and the justification all along. I maintain that anyone whose first impression of a rhythm is VT is NOT likely to accept an algorithmic decision of SVT. It's probably best to go ahead and treat - which may include a trial of adenosine before cardioversion (remember: our patient is very stable hemodynamically).

I suppose "Jones's Perplexium" is that we tend to make our decisions first and then seek support for them by running more tests or utilizing more algorithms. Our thought processes should be characterized by an inverted triangle with a large amount of information eventually being reduced down to a diagnosis or decision when instead, it is too often just the opposite: a diagnosis or decision followed by a lot of data (often selected with a bias) in order to justify the diagnosis. The simplest way to understand this is to ask yourself: "If I looked at a wide complex tachycardia and felt that it could be VT, would I stop at using just one algorithm if the algorithm diagnosed 'non-VT' or would I continue with another algorithm?" If you are going to keep looking until you get the answer you "want," then why waste time looking at all?

The wide complex tachycardia here satisfied two different criteria with two very different outcomes. The bottom line is that although no one interpreting this ECG felt totally confident of a diagnosis, in the real world a decision would still have to be made and treatment rendered. And while a definitive answer may only come via a trip to the EP lab, that isn't going to happen in real life.

Jones's Perplexium does not apply when one IS completely confident of the diagnosis and consequently has no need for algorithms or extensive testing.

I would like very much to hear other's thoughts on the process of decision-making. I'm not talking about the merits of specific WCT algorithms, but the way we approach our decision-making.