A prehospital ECG in a patient with chest pain. The paramedics tell me it is normal.

I was working at triage when the medics brought this patient who is 65 yo and has had chest pain for 12 hours.

They recorded a prehospital ECG at 2112 and said that it was “normal”.  It had already been crumpled up and put in the waste basket.  

So I uncrumpled it:

What do you think?

You need to click on it to enlarge it to view it well

I was suspicious for inferior and posterior OMI (Large T-wave in aVF, slight STE in lead III with inverted T-wave in aVL, and a slightly downsloping ST with negative T-wave in V2, and minimal STD in I, V5, and V6).  

However, this is very sublte and not diagnostic in my view.  But also very suspicious.

I recorded a triage ECG immediately on arrival at 2204, 52 minutes after the first (prehospital transport time was long):

What do you think?

I thought this was all but diagnostic, but still uncertain and I wanted to know what the Queen of Hearts thought:

If the Queen says OMI with high confidence and I am worried, then I am VERY worried.   

I took the patient to the critical care area and questioned him more on the way.  The pain had been intermittent until an hour before arrival, when he called 911.

We activated the cath lab.

Another ECG was recorded while awaiting the cath team:

Now there is STEMI

Here are the two ED ECGs, in median beat format (the "average" beat), overlayed on each other (orange first, blue second):

Let's look at that first (prehospital ECG) again:

Very subtle!

I wondered the next day what the Queen would have said:

OMI with high confidence!!

The first troponin I returned at 7 ng/L

The patient went for angiography and had RCA Occlusion (TIMI-0 flow).  

It was opened and stented.  

Peak trop was 7000 ng/L (since the intervention was so fast)!!

If the medics had had the Queen, the OMI would have been diagnosed 52 minutes earlier.  This was a weekend late evening, and so it took time the cath team to get in to the hospital.

A prehospital activation would have save a lot of time and would have been possible if the paramedics were using the Queen of Hearts PMCardio AI app.

Click here to sign up for Queen of Hearts Access

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MY Comment, by KEN GRAUER, MD (7/23/2024):

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Today's case illustrates the importance of attention to subtle serial ECG findings.

• For clarity in Figure-1 — I've put together the 3 tracings from today's case.

Figure-1: I've put together the 3 serial tracings from today's case. (To improve visualization — I've digitized the initial ECG using PMcardio).

The Initial ECG in Figure-1:

The patient in today's case is a 65-year old man with CP (Chest Pain) over the previous 12 hours before contacting EMS. As per Dr. Smith, although the initial ECG had been interpreted as "normal" — it is clearly suspicious for OMI.

• The rhythm in ECG #1 is sinus — with normal intervals; a normal (horizontal) frontal plane axis — and no chamber enlargement.
• It is hard to determine if there is a QS vs an rS in lead III. That said — even if this is a QS complex, an isolated Q wave in lead III is not necessarily abnormal. No other Q waves.
• R wave progression is normal — with transition (where the R wave becomes taller than the S wave is deep) occurring normally between leads V3-to-V4.

The subtleties in ECG #1 lie with assessment of ST-T wave changes:

• In a patient with new CP over the past 12 hours — my "eye" was immediately drawn to lead aVF (within the RED rectangle in ECG #1). Given tiny size of the QRS complex in this lead — the T wave in lead aVF is clearly hyperacute (This T wave towers over the tiny r wave in lead aVF — and could easily "swallow" the QRS within its borders).
• Although not quite as disproportionately enlarged as the T wave in lead aVF — the T wave in lead III looks "bulkier" than I'd expect for the QRS in this lead.
• In the context of the clearly abnormal ST-T waves in leads III and aVF — the inverted T wave in lead aVL is consistent with a reciprocal change (Whereas T wave inversion per se is not necessarily abnormal in lead aVL — the depth of the T wave seen here is disproportionately large compared to modest height of the R wave in aVL, that is nowhere near satisfying LVH criteria).
• In the context of abnormal leads III, aVL and aVF — the ST segment flattening with slight depression in lead I supports validity of the reciprocal change in aVL.
• Finally — there is nonspecific ST-T wave flattening across the chest leads. By itself — this finding would not be indicative of anything acute. But in the context of the above-noted limb lead findings suggestive of inferior OMI (with onset at some point over this patient's 12-hour history of CP) — the lack of upright T waves with slight upsloping ST elevation is consistent with posterior OMI, that so often accompanies inferior OMI.
• 
  
• BOTTOM Line: As per Dr. Smith — while not diagnostic, the above subtle findings in this patient with ongoing CP over a period of hours should be viewed as highly suspicious for infero-postero OMI until proven otherwise.

The Value of Serial Tracings:

Due to prolonged transport time — the repeat ECG was not obtained until 52 minutes later ( = ECG #2).

• KEY Point: Optimal comparison of serial tracings is achieved by looking lead-by-lead while holding both tracings right next to each other! If each of the tracings is looked at separately — it is all-too-easy to overlook subtle differences.
• So it is with comparison of ECG #1 and ECG #2 in today's case. Seeing both tracings next to each other (as we do in Figure-1) — I thought there is a subtle-but-real increase in hyperacuity in ECG #2 — in that ST segments are straighter, with T wave "volume" being slightly (but consistently) more in leads II,III,aVF and aVL.
• Although the slight changes in chest lead ST-T wave appearance in ECG #2 remain nonspecific — in this patient in whom we strongly suspect inferior OMI — there is no doubt that lack of the gently upsloping, slight J-point ST elevation that is normally seen in leads V2,V3 is absent.
• 
  
• BOTTOM Line: As per Dr. Smith — the cath lab should be activated.

The Final ECG:

The last ECG in today's case was recorded while awaiting cardiac catheterization.

• The heart rate in ECG #3 has increased — with a number of PACs.
• As per the dotted RED line — there is now clear ST elevation in lead III, as well as in the other inferior leads. This is countered by reciprocal ST-T wave changes, with an increase in the amount of J-point depression in lead aVL.
• Although difficult to assess because of artifact with baseline wander — there now appears to be ledge-like ST depression in lead V2, consistent with ongoing posterior OMI.
• 
  
• KEY Point: As per Dr. Smith — the serial ECG changes in today's first 2 tracings are extremely subtle, until frank ST elevation is finally seen in ECG #3. But in context with the worrisome history of new CP in this 65-year old man — these subtle ECG findings in ECGs #1 and #2 should be sufficient to recognize the need for prompt cath. 
• The BEST way to get good at recognizing these important early ECG clues — is to Go Back after you know the answer — to LOOK AGAIN at ECG #1 — then ECG #2 — and SEE how these initially subtle findings evolve into the obvious acute MI evident in ECG #3.