Proportionality is a major element in the ECG Diagnosis of OMI.

 This middle aged patient presented with chest pain:

What do you think?

There is VERY low voltage.  There is some ST Elevation, but it is MINIMAL.  But look how small the QRS is!!

Let's stretch out the QRS vertically so it is not so tiny:

On upper left is the original.  

On the right are the precordial leads stretched vertically, so that the QRS is not tiny.  Now you can see the STE and Hyperacute T-wave better.

I published, and Emre Aslanger externally validated, the 4-Variable formula for differentiating the ST Elevation of LAD OMI from Normal ST Elevation.  

It is derived/validated/designed to correct for small amplitude (low voltage) QRS, by including R-wave amplitude in V4 and total QRS amplitude in V2.

This is the result for this ECG, from MDcalc.com:

The most accurate cutpoint is 18.2.  

A value above 18.2 (LAD OMI) vs. below (Normal variant) is about 88% sensitive and specific for LAD OMI.  

A value above 19 is about 97% specific for LAD OMI.

Version 1 of the Queen of Hearts AI app was taught by our subjective impression of OMI vs. Not OMI, and we (Pendell and I) always take proportionality into account.

So we taught the Queen on cases with very low voltage that were OMI.

And she learned it well:

She is not highly confident, but she does diagnose OMI.

Outcome:

100% LAD Occlusion

Here the Queen explains why:

The dark blue tells us that she is looking especially at the QRS in V3 and the T-wave in V2 and V3.

Here is a similar case from Pendell:

This ECG was handed over at triage. See how the Queen of Hearts AI does with these explainability images.

The Queen of Hearts PM Cardio App is now available in the European Union (CE approved) the App Store and on Google Play.  For Americans, you need to wait for the FDA.  But in the meantime:

YOU HAVE THE OPPORTUNITY TO GET EARLY ACCESS TO THE PM Cardio AI BOT!!  (THE PM CARDIO OMI AI APP)

If you want this bot to help you make the early diagnosis of OMI and save your patient and his/her myocardium, you can sign up to get an early beta version of the bot here.  It is not yet available, but this is your way to get on the list.

https://share-eu1.hsforms.com/18cAH0ZK0RoiVG3RjC5dYdwfyfsg

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MY Comment, by KEN GRAUER, MD (12/13/2023):

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As per Dr. Smith — the KEY concept in today's case is proportionality. That said — the ST-T wave in lead V2 looks to be small only if viewed in the context of its absolute height, as one of 12 leads in the initial ECG shown above in today's post.

• For clarity in Figure-1 — I've reproduced this initial tracing, and have added a magnified view below it of lead V2.

 

Today's CASE:

We have only been provided with limited information about the patient in today's case — namely, that the patient is a middle-aged adult who presented with CP (Chest Pain).

• It should be readily apparent from the magnified view of lead V2 in Figure-1 — that in the context of new CP — the ST-T wave in lead V2 is hyperacute because: i) The T wave in this lead is disproportionately tall (clearly taller than the R wave in V2); — and, ii) This T wave is much "fatter"-at-its-peak and wider-at-its-base than would be expected given small amplitude of the QRS in this lead.
• 
  
• By the concept of "neighboring" leads — there should be little doubt that the ST-T wave in lead V3 is also hyperacute (equal in height to the R wave in lead V3 — with a disproportionately wide base).
• The next "neighboring" lead is lead V4 — which is even tinier than than the QRST complex in leads V2 and V3 — BUT — in proportion to the tiny QRS in lead V4 (and in the context of knowing that the ST-T waves in leads V2 and V3 are hyperacute) — I interpreted the T wave in lead V4 as "more voluminous" than I would expect. 
• 
  
• BOTTOM Line: In this middle-aged adult with new CP — this makes for 3 consecutive anterior leads (V2,V3,V4) with hyperacute T waves — suggesting acute LAD OMI until proven otherwise.

Additional ECG Findings in Today's CASE:

• TAKE another LOOK at today's initial tracing in Figure-1. In addition to the 3 consecutive hyperacute anterior T waves — What additional ECG findings do YOU see in Figure-2?

Figure-1: I've labeled the initial ECG in today's case — as well as enlarging the QRST complex in lead V2.

Additional ECG Findings:

There are a number of interesting additional findings in today's initial ECG:

• There appear to be large Q waves in leads III and aVF. If this is the case — this size of a Qr wave in lead III, as well as the seemingly wide Q in lead aVF — would seem to suggest prior inferior infarction at some point in the past. Knowing the patient has a history of coronary disease could be relevant to today's case — as it should add to our suspicion of a new acute event.
• 
  
• That said — Did YOU Note the changing morphology of the Q waves in lead aVF? (RED arrows). The 2nd QRS complex in this lead actually manifests an rSr' complex (BLUE arrow highlighting an initial positive deflection). Either this is attributable to poor digitalization of the tracing — OR poor quality of the original ECG — OR to a phenomenon that I periodically observe, which is that QRS morphology in leads III and aVF may sometimes be altered by respiration due to diaphragmatic movement that may affect these inferior leads and result in a coming-and-going of Q waves in these leads.
• 
  
• OR — Maybe there is LA-LL Lead Reversal ??? For technical reasons — P waves are not well visible in this tracing — BUT — the P wave in lead I appears to be larger than the P wave in lead II, which is often a tip-off to LA-LL Reversal (See My Comment in the November 19, 2020 and the May 24, 2022 posts in Dr. Smith's ECG Blog). 
• Reasons why I favor LA-LL Reversal are that the "real" lead III would then be inverted (resulting in an upright QRS in lead III) — and leads aVF and aVL would switch places. Thus, if there was LA-LL Reversal — this would eliminate the unusual-looking "Q waves" that we now see in leads III and aVF. Suboptimal quality of today's tracing renders it impossible to know if there is or is not LA-LL Reversal — BUT — Good to be aware of this consideration, since you would want to verify lead placement and immediately repeat the ECG given concern about an ongoing acute OMI. 

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LOW Voltage:

Finally, as per Dr. Smith — there is extremely Low Voltage in the chest leads! We periodically review cases with low voltage — which takes on special relevance given today's presentation of a patient with new CP!

• As review — I've copied the Table in Figure-2 from previous discussions of potential causes of Low Voltage (See My Comment in the October 15, 2023 — the November 12, 2020 — and the January 24, 2020 posts in Dr. Smith's ECG Blog).
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• The differential diagnosis for "low voltage" that is frequently put forth by many providers is often limited to COPD and/or pericardial effusion. As shown in Figure-2 — there are other entities to consider! Relevant potential causes of Low Voltage to consider in today's case include: i) Pericardial effusion; ii) Takotsubo cardiomyopathy; and, iii) A large acute (or recent) infarction, that may result in myocardial "stunning" 
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• Myocardial "Stunning" — has been described as a transient marked reduction in cardiac contractility, that occurs in response to a major acute insult. This phenomenon has been associated with cardiac arrest; after cardiac surgery; post-cardioversion following a sustained tachyarrhythmia; with certain types of acute cerebrovascular events (such as subarachnoid hemorrhage) — and, in association with large acute MI, which could potentially be the clinical scenario in today's case! 

 

Figure-2: Causes of Low Voltage (See text).