Tuesday, September 5, 2023

Computer: "Normal ECG," TIMI-3 flow at angiography: Does this ECG manifest Occlusion MI?

A 60-something awoke with 10/10 crushing chest pain.  He walked in to triage.

Here is the ECG:

Computer interpretation:  Normal ECG

Interventionalist after doing PCI:

To me, this first ECG is diagnostic of inferior OMI.

I sent this ECG to the Queen of Hearts (PMcardio OMI), and here is the verdict:


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.

The cath lab was activated.

The patient's pain began to spontaneously resolve, so another ECG was recorded at 22 minutes after the first:

Computer interpretation:  Normal ECG

Interventionalist after doing PCI: Normal ECG

This is still diagnostic of inferior OMI.  

If this were the patient's first ECG, I would activate the cath lab.

Here is the Queen's interpretation:

She thinks this is OMI also. She does not know that this is the same patient.  We have not taught her serial ECGs yet.

The patient's pain completely resolved, and a 3rd ECG was recorded just before transport to the cath lab, at 45 minutes after the first:

Computer interpretation:  Normal ECG

Interventionalist after doing PCI: Normal ECG

Smith interpretation: diagnostic of reperfusing or reperfused inferior OMI.


The Queen got this one wrong, but we are teaching her reperfusion too.

What would I expect the angiogram to show?  

I would expect TIMI-3 flow (normal flow, no persistent ischemia) with a culprit in the RCA (or possibly Circumflex).  I would expect that a stent would be placed.

The angiogram showed an open artery with 95% stenosis and thrombosis and it was stented.

Quiz: What percent of full blown STEMI have an open artery with normal flow at angiogram?

------20% (and another 15% have TIMI-1 or TIMI-2 flow)
------Only 65% have full 100% occlusion with no flow

So the very fact that the artery was open says nothing about what the state of the artery when the patient presented with 10/10 chest pain, and had an ECG which is diagnostic of OMI but is not a STEMI.

First hs troponin I was 41 ng/L
Peak hs troponin I was 440 ng/L

In our studies of OMI ECGs, this would have been a false positive because if there is TIMI-3 flow, we require a "very high" troponin, which for hs troponin I is usually greater than 5000 ng/L.  Yet this is not truly a false positive.  Because of spontaneous reperfusion, the injury was not great and even a full occlusion would get classified as a false positive.

Formal echo:

--Normal left ventricular systolic function with estimated ejection fraction of 60%.

--Regional wall motion abnormality- hypokinesis of the mid to basal inferior and inferolateral segments.

Normal ECG by Conventional Algorithm in the presence of acute Occlusion MI

This is all too common.

Imagine this:

The 3rd ECG is the first ECG.  Because the computer said "normal", you don't get notified.  But the patient's chest pain continues and so you order a 2nd ECG (ECG 2 here).  It also is interpreted as "normal" and the patient's chest pain is now 10/10 and so you are really diligent and order a 3rd ECG.  It too is "normal" and you decide that this is not OMI or STEMI and you just decide to get troponins.  In the meantime, a lot of myocardium is lost.

I have over 40 cases of OMI here that were "normal" by the conventional algorithm.  They were not just "Nonspecific ST-T abnormality" which at least would tell the physician that the ECG is not normal.  They were interpreted as completely NORMAL!!

Jesse McLaren et al. (including Pendell and Smith) just published this article:

Emergency department Code STEMI patients with initial ECG labeled ‘normal’ by computer interpretation: a 7-year retrospective review

Among 394 True positive cath lab activations, 16 (4.1%) had computer "normal" ECGs.


MY Comment, by KEN GRAUER, MD (9/5/2023):


When I first saw today’s initial tracing — I thought, “Too much Artifact!”. That said — both Dr. Smith and QOH (Queen OHeartsimmediately interpreted this tracing as “diagnostic of OMI” .

  • For clarity, and to facilitate taking another LOOK — I’ve reproduced the initial tracing from today's case in Figure-1.

  • NOTE: QOH interpreted today’s initial tracing without the benefit of including the history of “new-onset 10/10 crushing chest pain”. Awareness of this history immediately (and dramatically) increases the likelihood than any ECG findings (even when subtle) may indicate an acute event. So despite the artifact — and even without any history — this initial ECG has to be interpreted as an acute event until proven otherwise.

Take another LOOK at today’s initial ECG in Figure-1
  • WHAT are the specific ECG findings in this initial tracing that say, "acute OMI until you can prove otherwise?".

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

WHY is the ECG in Figure-1 Diagnostic of Acute OMI?
Despite the marked baseline artifact (especially in the limb leads) — we can see that the rhythm in Figure-1 is sinus (with upright P waves in each of the chest leads confirming sinus rhythm with a fixed and normal PR interval).
  • All intervals (PR, QRS duration, QTc) and the frontal plane axis are normal.
  • There is no chamber enlargement.

The KEY abnormal Limb lead findings include the following:
  • The inferior leads show a large (and relatively wideQ wave in lead III. There clearly is ST elevation in lead III, and probably also in lead aVF (and possibly also in lead II). Considering the tiny QRS amplitude in these inferior leads — the relative amount of ST elevation is significant. All doubt should be removed about the significance of these ST-T wave changes in leads III and aVF because of the markedly abnormal terminal T wave inversion that is clearly seen in lead III.
  • Final confirmation of the significance of these acute inferior lead ECG changes — is forthcoming from the mirror-image opposite reciprocal ST-T wave appearance in lead aVL (ie, There is no doubt that the flat ST depression with proportionately large terminal upright T wave indicates an acute reciprocal change in this lead aVL).

As is so commonly the case, when there are changes of acute inferior OMI — there will often also be changes in the Chest leads consistent with acute posterior OMI.
  • KEY Point: The chest lead changes of acute posterior OMI are so subtle in this initial ECG — that unless you are looking for them, they could be EASY to overlook!
  • Normally there should be at least a small amount (ie, 1-2 mm) of gentle upsloping ST elevation in anterior leads V2 and V3. This is absent in today’s initial ECG. Instead, there is even some ST segment flattening in lead V2 — which in the context of diagnostic ECG findings of acute inferior OMI in the limb leads — is diagnostic of acute infero-postero OMI in this initial tracing!


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