ECG Blog #364 — VT in Need of Cardioversion?

The ECG in Figure-1 was obtained from a 60ish year old man on arrival to the ED (Emergency Department). The presenting complaint was chest pain — and the patient collapsed soon after arrival in the ED.

QUESTION:

A cardiologist interpreted the rhythm in Figure-1 as VT (Ventricular Tachycardia). 

• Do YOU agree with this cardiologist?

Figure-1: The initial ECG in today's case — obtained from a 60ish year old man who collapsed in the ED shortly after this tracing was recorded. (To improve visualization — I've digitized the original ECG using PMcardio).

MY Thoughts on the ECG in Figure-1:

There are a number of reasons why the ECG in Figure-1 is difficult to interpret:

• The rhythm is fast — and the QRS looks to be very wide. More than QRS widening — the shape of QRS complexes varies from one-beat-to-the-next (Seen best in the long lead II rhythm strip at the bottom of the tracing).
• The rhythm looks fairly regular — and atrial activity is absent. The finding of a fairly regular, wide tachycardia without clear sign of atrial activity (especially when seen in an acutely symptomatic patient) — should immediately prompt a diagnosis of VT until proven otherwise.

Rebuttal to the above Initial Diagnosis:

I initially thought that the rhythm in ECG #1 was likely to be VT. That said — I changed my mind after looking closer because of the following findings:

• The rhythm in the long lead II rhythm strip is not regular. Instead, close inspection reveals that there is slight-but-real R-R interval variation from 1 beat to the next. 
• The overall rate for the rhythm in Figure-1 is fast (ie, probably ~110-115/minute) — but not nearly as fast as expected with a hemodynamically significant VT (that almost always is at least 130/minute).
• There appears to be “Shark-Fin” ST elevation for beats #3,4,5,6 in the inferior leads — and for beats #8,9,10,11 and #15,16 in the long lead II rhythm strip.
• There is “shark-fin” ST depression in leads I, aVL and V2.
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• Putting These ECG Findings Together: I have described an irregularly irregular rhythm without P waves — at an overall rate of ~110/115/minute. These findings suggest that instead of VT — the rhythm in Figure-1 is AFib with a fairly rapid ventricular response. 
• This leaves us with having to explain why the QRS is wide. Since the rhythm is supraventricular (ie, AFib) — we can accurately assess QRS morphology. The upright R wave in lead V1 — together with the wide terminal S waves in lateral leads I and V6 — is consistent with RBBB (Right Bundle Branch Block). Predominant negativity of the QRS in lead I — with predominant positivity in the inferior leads suggests LPHB (Left Posterior HemiBlock). Thus, there appears to be bifascicular block (ie, RBBB/LPHB).
• That said — a significant component of the QRS widening that we see in Figure-1 is probably the result of “shark-fin” ST segment deviation (elevation and depression). Looking at the location of ST elevation (ie, in the inferior leads — and in V4,5,6) — and the location of ST depression (ie, in leads I,aVL; V1,V2) — this ECG picture suggests an ongoing acute infero-postero-lateral STEMI.

What is Shark Fin Morphology?

It's important to be aware of the pattern of "Shark Fin" ST segment elevation — in which the QRS complex looks wide, because it blends in with ST segments that show extreme ST elevation in multiple leads. As a result — the boundary between the end of the QRS complex and the ST segment becomes indistinguishable in those leads showing marked ST elevation or depression.

• "Shark Fin" ST segment elevation is most often a sign of severe transmural ischemia that results from acute coronary occlusion. Consideration of prompt cardiac cath is essential for clarifying the anatomy — since in many (most) cases, prognosis is likely to be poor unless there is prompt reperfusion. (For more on "Shark Fin" ST elevation — See the Audio Pearl in the ADDENDUM below — as well as ECG Blog #265 for an example of a case with even more dramatic "shark fin" ST elevation).
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• PEARL #1: The KEY for confirming that "Shark Fin" morphology is the cause of the striking ECG picture this produces — is to find 1 or 2 leads in which you can clearly define the limits (end point) of the QRS complex. The most helpful leads for doing this in today's case are leads II and III — in which in Figure-2, I've drawn in a RED line parallel to the heavy ECG grid line in simultaneously-recorded leads I,II,III. Note that I've extended this line down to the corresponding complex in the long lead II rhythm strip at the bottom of the tracing.
• The reason for continuing the RED line all the way down to the corresponding beat in the long lead II rhythm strip — is that this tells you where the QRS complex ends and the ST segment begins in the long lead II rhythm strip.
• Knowing this landmark for the complexes in the long lead II rhythm strip — allows us to draw in and extend upward the PURPLE lines parallel to the heavy ECG grid line in the other 3 sets of simultaneously-recorded leads (PURPLE lines in Figure-2).
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• CONCLUSION: The ECG in Figure-2 shows AFib with a fairly rapid ventricular response with "Shark Fin" ST elevation that is most marked for certain complexes in the inferior leads. Reciprocal "shark fin" ST depression is seen for certain complexes in leads I and aVL — and ST depression indicative of posterior infarction is seen in lead V2.

Figure-2: I've labeled the end point of the QRS complex selected leads to facilitate defining "shark fin" ST segment elevation or depression (See text).

CASE Follow-Up:

As noted in today’s case presentation — this patient presented with chest pain, and then collapsed soon after the ECG in Figure-1 was obtained. Cardiopulmonary resuscitation was promptly started — but was unsuccessful.

• Given the rapid rate of AFib — the new bifascicular block ( = RBBB/LPHB) — and the obvious extensive acute STEMI — it is unfortunate but not surprising that this patient could not be resuscitated.
• Given a lack of prior history — I don’t know if the AFib on ECG #1 is (or is not) a new finding. If this is a new finding — then it’s important to be aware of the adverse prognostic significance of seeing new AFib in association with acute MI.
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• Final PEARL: In my experience — it is not common that new AFib must urgently be cardioverted in the ED. That said — today’s case provides an exception to this generality, in that the patient is symptomatic (ie, with new chest pain) — the rate of the AFib is relatively rapid (almost all R-R intervals between 2-3 large boxes — therefore the overall heart rate is clearly over 100/minute) — and — the initial ECG shows a bifascicular block with an extensive ongoing STEMI. Even if providers initially thought that the rhythm was VT — prompt synchronized cardioversion might still be the treatment of choice for today's arrhythmia given the patient's instability in this clinical scenario. 

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Acknowledgment: My appreciation to 黄建成 and 罗莉莲 (from Malaysia) for the case and this tracing.

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ADDENDUM (2/19/2023):

• The Audio Pearl below reviews the concept of "shark fin" ST elevation. 

—  — 

ECG Media PEARL #73 (5:40 minutes Audio) — Reviews the concept of "Shark Fin" ST elevation and depression as a sign of extensive acute infarction.

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Additional Relevant ECG Blog Posts to Today’s Case:

• ECG Blog #185 — Reviews my System for Rhythm Interpretation, using the Ps, Qs & 3R Approach.
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• ECG Blog #265 — Reviews a case of Shark-Fin ST Elevation.