Dr. Smith's ECG Blog: October 2024

Tuesday, October 1, 2024

VT in a Sick Patient? Paired with 2 old cases (see them at the bottom)

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MY Comment, by KEN GRAUER, MD (8/30/2024):

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I was sent the ECG shown in Figure-1 — knowing only that the patient was being seen in the ED (Emergency Department).

How would you interpret this tracing?

Figure-1: The initial ECG in today's case.

MY Initial Thoughts:

In my experience — all-too-many emergency providers fail to appreciate the potential contribution that a brief (1-to-2 line) history may convey when interpreting arrhythmias. Common things are common — so knowing what you are looking for (as is often suggested by the history) — may help you to find the answer. Not initially knowing the history in today's case — I considered the following:

The ECG in Figure-1 — shows a regular WCT (Wide-Complex Tachycardia), at ~150/minute — with some uncertainty about atrial activity.
QRS morphology in the chest leads is consistent with RBBB conduction (rsR' in lead V1 — and the presence of a wide terminal S wave in lead V6). This suggested a supraventricular etiology.
BUT — the unusual frontal plane axis (ie, with predominant negativity in both leads I and II) was not consistent with any form of hemiblock. This instead suggested the possibility of fascicular VT?
A distinct, rounded upright deflection in lead II (RED arrows in Figure-2) — clearly suggested atrial activity (? sinus P waves?) — but the finding of a regular tachycardia at a ventricular rate close to 150/minute with uncertainty about atrial activity — should always suggest the possibility of AFlutter with 2:1 AV conduction (and one might convince oneself of such 2:1 AV activity by the deflections under the BLUE arrows in Figure-2).
And — Are those upright deflections under the RED arrows in lead II truly sinus P waves? (when the usual negative P wave deflection of sinus tachycardia is nowhere to be found in lead V1)?

What do YOU think?

Figure-2: How have I labeled the initial tracing?

The ANSWER:

At this point in the case — I was provided with 2 additional pieces of information:

#1 Informational: It turns out that the patient in today's case was critically ill with multisystem problems. Synchronized cardioversion @200J was attempted twice on the rhythm in ECG #1 — but this had no effect on the rhythm.
#2 Informational: I was provided with a repeat ECG on this patient — which was recorded a bit after ECG #1, still in the ED (Bottom tracing in Figure-3).

QUESTIONS:

How does the #1 informational point that gives us a brief relevant history (including the effect of a treatment intervention) — help to increase our diagnostic certainty about today's rhythm?
After seeing ECG #2 — Can you explain: i) Why no negative P wave was seen in lead V1 of ECG #1? — and, ii) Why the frontal plane axis was so unusual in the initial ECG (ie, with predominant negativity in both leads I and II in ECG #1)?

Figure-3: Comparison between the 2 tracings in today's case.

ANSWERS:

Common things are common. While of course possible for the rhythm in ECG #1 to be either AFlutter or fascicular VT — sinus tachycardia immediately becomes a much more likely possibility once we know that this patient is critically ill with multisystem disease.
Proof that the rhythm all along was sinus tachycardia will almost certainly be found in review of serial telemetry tracings — because there will almost always be gradual (progressive) increase or decrease in the sinus tach heart rate as the patient's clinical condition gets better or worse.
AFlutter especially — but also monomorphic VT — are both responsive rhythms to synchronized cardioversion. The fact that two 200J cardioversion attempts failed to change the rhythm essentially rules out both AFlutter and VT. This essentially rules in sinus tachycardia. (If the BLUE arrows in Figure-3 were truly flutter waves — then we should be able to see more precise 2:1 activity in other leads, but we do not).
The reason that no negative sinus P wave is seen in ECG #1 — is that we learn from ECG #2 that the sinus P wave of today's patient is positive in lead V1 (the RED arrow in lead V1 of ECG #2).
Instead — the RED arrow in lead II of ECG #2 highlights the upright sinus P wave in this lead — that is in retrospect, similar in both shape and in PR interval to the upright sinus P wave deflections that were seen in virtually all 12 leads in ECG #1!
Finally — The reason for the unusual frontal plane axis in ECG #1 — is simply that this patient's apparent baseline tracing (which I presume is like ECG #2) — shows marked right axis (predominantly negative QRS in lead I of ECG #2).
Note that the RBBB pattern seen in ECG #1 is not present in the baseline tracing — so with the tachycardia, this patient developed rate-related RBBB aberration. This rate-related aberrancy pattern resolves as the rate of this patient's sinus tachycardia is slowing (as it is in ECG #2).

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A Final Retrospective Look at the Initial ECG:

Among the most helpful tips for me toward improving my ability in arrhythmia interpretation — has been to retrospectively take another look at those tracings about which I was initially less than 100% certain.

Although I suspected the deflections under the RED arrows in lead II of Figure-2 were sinus P waves — I initially considered other possibilities.
In retrospect — the fact that these deflections are actually seen in no less than 10 of the 12 leads at the same point in the cardiac cycle is virtually definitive for sinus tachycardia!

To demonstrate this — We take advantage of the simultaneous recording of the long lead V1 rhythm strip with each of the 4 groups of 3 leads — as shown in Figure-4.

I drew the vertical RED timeline in Figure-4 — to correspond to what looks to be the beginning of the P wave in lead II. Note where this vertical RED line passes in simultaneously-recorded leads I, III — and especially in the long lead V1 rhythm strip (where this RED line corresponds to the point just before a tiny positive deflection in this V1 lead).
I then drew in the vertical BLUE timeline — to correspond to what looks to be the end of the P wave in lead II. Doing so defines a biphasic (tiny positive — then tiny negative) P wave in lead V1, which is consistent with the sinus P wave morphology that is commonly seen in lead V1.
I then carried over the point in the long lead V1 that corresponds to the beginning of the tiny positive deflection in this lead — extending a dotted PURPLE line upward through the corresponding point in the other 9 simultaneously-recorded leads. Doing so identifies the precise beginning point of the small positive deflection that we see in all leads except aVR and aVL.
Neither VT nor AFlutter will so consistently show the onset of a small, upright deflection at the identical distance before the next QRS complex in 10 of 12 leads. In Retrospect: This finding could have allowed me to be certain these positive deflections that are seen in 10 of 12 leads are P waves — and that the rhythm was sinus tachycardia.

Figure-4: I’ve added vertical timelines that correspond to P wave activity in 10 of the 12 leads.

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— My appreciation to Sam Ghali (@EM_RESUS) for his contribution of today's case.

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Final Diagnosis:

Sinus Tachycardia with Right Bundle Branch Block.

No evidence of OMI.

Other Cases of Sinus Tach with Wide Complex due to RBBB.

These were catastrophically missed (EM cath lab activation cancelled both times by the interventionalist)

Here is a case of Sinus with RBBB and LAFB that was diagnosed correctly by the emergency physicians as acute STEMI. The interventionalist was convinced it was VT without acute OMI. So he would not cath the patient. The patient died of cardiogenic shock:

Go to the post to see the full explanation.