I was given the ECG in Figure-1 — knowing only that the patient was a woman with "CP" (Chest Pain). Many of my colleagues interpreted this tracing as "normal".
- QUESTION: Do you agree? Explain your answer.
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Figure-1: The initial ECG in today's case. |
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MY Initial Thoughts on Today's Tracing:
On seeing the ECG in Figure-1 — I instantly knew that this tracing was not "normal". Instead, given the history of new CP — my instinct was that providers should activate the cath lab!
- Why do I say this?
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Looking Closer at ECG #1:
The rhythm for the ECG in Figure-1 — is sinus (despite the baseline artifact — We see upright P waves in lead II, with definite P waves showing a constant and normal PR interval in other leads).
- My "eye" was immediately drawn to lead V3 (within the RED rectangle in Figure-2). Normally, there should be slight, gently upsloping ST elevation in leads V2 and V3. Instead, there is obvious ST segment straightening, with slight shelf-like ST segment depression in this lead V3, that finishes with terminal positivity.
- This is the concept of pattern recognition. Similar to entities such as a Brugada pattern ECG, which the experienced "eye" should recognize within 2 seconds on seeing (as in ECG Blog #244) — the ECG "picture" within the RED rectangle in Figure-2 in a patient with new CP should prompt the diagnosis of acute posterior OMI until proven otherwise.
- To assist with "engraving" the ECG picture of acute posterior OMI in one's memory — use of the "Mirror" Test may be helpful (See ECG Blog #317).
- NOTE: Before deciding that the cath lab needs activation — I seek confirmation of my initial impression in other leads.
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Figure-2: I've labeled today's initial ECG. |
Confirmation of Posterior OMI from Other Leads:
My 2 favored ways for solidifying my initial impression of acute posterior OMI (with need to immediately activate the cath lab) are based on:
- i) Awareness that with posterior OMI — ST depression in the chest leads tends to be maximal in lead V2 and/or lead V3 and/or lead V4; — and,
- ii) Awareness that there is usually a common blood supply to the inferior and posterior walls of the left ventricle. As a result, if there is posterior OMI — then we'll often see limb lead evidence of either acute inferior OMI (if the "culprit" artery is the RCA) — or — of acute high-lateral OMI (if the "culprit" artery is a branch of the LCx).
Looking Closely in Figure-2 for posterior OMI confirmation:
- Support that there is an ongoing posterior OMI is forthcoming in Figure-2 — from similar ST segment straightening and depression with prominent terminal T wave positivity in leads V4 and V5, but not in lead V6 (as seen within the BLUE rectangle).
- PEARL #2: Unfortunately — leads V1 and V2 have almost certainly been placed too high on the chest because: i) There is an rSr' complex in lead V2, which is usually not seen as an isolated finding, especially in the absence of an rSr' in lead V1; — ii) There is significant terminal negativity of the P wave in lead V1; — and, iii) The QRST complex in leads V1 and V2 looks similar to the QRST in lead aVR (See ECG Blog #274 — for more on quick recognition of V1,V2 misplacement).
- The importance of quickly recognizing lead V1,V2 misplacement — is that this invalidates our diagnostic use of these leads for confirming posterior OMI (ie, lead V2 especially should show similar ST segment flattening and depression as we see in lead V3 when there is posterior OMI).
- Clinically: IF the diagnosis of acute posterior OMI was in doubt — I would immediately repeat the ECG on seeing the picture of leads V1,V2 that is present in Figure-2 (within the GREY dotted rectangle). That said — I don't feel that is necessary in today's case, since the ECG in Figure-2 is so clearly diagnostic of acute posterior OMI.
There is further support of posterior OMI from the limb leads:
- Although limb lead findings in Figure-2 are more subtle — they are nevertheless diagnostic. Despite the baseline artifact — we see: i) ST segment straightening in each of the inferior leads (BLUE arrows in leads II,III,aVF), with a hint of ST depression in III and aVF — and with prominent terminal T wave positivity in leads II and aVF; — and, ii) Straightening and slight elevation of the ST segment takeoff in high-lateral leads I and aVL.
- To Emphasize: In the absence of the chest lead findings that we see in Figure-2 — I would be less cerain about acute posterior OMI from the subtle ECG findings that I see in the limb leads. But given the history of new CP and the absolutely diagnostic findings of posterior OMI within the RED and BLUE rectangles of Figure-2 — I interpreted the overall ECG pattern in today's initial ECG as diagnostic of acute infero-lateral OMI.
PEARL #3: What about lead V6?
- At this point in our interpretation — We can go back and take another look at lead V6. As opposed to the chest leads V3,V4,V5 which all showed ST segment straightening with slight ST depression — lead V6 lacks this ST segment straightening. Instead — Doesn't the T wave in this lead look a bit "bulkier" than would usually be expected?
- Whereas I would probably not interpret the ST-T wave in lead V6 as abnormal if it was an isolated finding — in the context of our overall findings suggesting acute postero-lateral OMI — I interpreted the slight "bulkiness" of the ST-T wave in lead V6 as a hyperacute finding in further support of lateral OMI.
PEARL #4: It should be apparent from the above description of my "process" — that optimal clinical interpretation of ECGs is like "telling a story". The story makes sense when multiple pieces of the story "fit".
- In today's "story" — 3/12 pieces are diagnostic ( = leads V3,V4,V5 — that in today's patient with new CP, so strongly suggest acute posterior OMI).
- 6/12 additional pieces ( = leads I,II,III; aVL,aVF; V6) although much more subtle — do support the hypothesis of the first 3 pieces.
- Of the remaining 3/12 pieces — 2 of them are invalid ( = leads V1,V2 — which are placed too high on the chest).
- Isn't it difficult to negate our hypothesis when 9 of the 10 available leads to us all point to the same hypothesis?
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Putting It All Together:
In today's patient with new CP — the ECG picture of acute postero-lateral OMI usually suggests acute occlusion of a branch in the LCx (Left Circumflex) as the "culprit" artery.
- CASE Follow-Up: Cardiac cath revealed complete occlusion of the distal OM (Obtuse Marginal) branch of the LCx. Peak Troponin attained a value over 22,000 ng/mL.
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An ECG was obtained after PCI (Figure-3).
- How does the post-PCI ECG in Figure-3 — compare to today's initial tracing?
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Figure-3: Comparison of today's initial ECG — with the repeat ECG that was recorded after PCI. |
The Post-PCI ECG:
Lead-to-lead comparison in Figure-3 of today's initial ECG with the post-PCI tracing — shows obvious improvement (deflation of ST-T wave findings) in each of the 9 leads that I highlight above as supportive of my diagnosis of acute postero-lateral OMI.
- PEARL #5: The BEST way to hone your ECG interpretation skills for picking up the subtle findings that I highlight in today's case — is to follow the course of serial ECGs correlated to the course of events. Seeing the improvement after PCI in each of the 9 highlighted leads confirms the validity of the subtle abnormalities pointed out in Figure-1.
- NOTE: Leads V1,V2 remain suggestive of too high electrode lead placement (not uncommon with female patients).
Final Learning Point: To emphasize that while STEMI criteria never came close to being satisfied — 9/10 of the leads available to us in this patient with new CP decisively told us the answer within seconds of seeing the initial ECG.
- To delay prompt cath waiting for ST segments to rise or Troponins to come back would only serve to diminish the chance to save viable myocardium.
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Acknowledgment: My appreciation to David Didlake (USA) for allowing me to use this case and these tracings.
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ADDENDUM (7/11/2025):
- For More Material — regarding ECG interpretation of OMIs (that do not satisfy millimeter-based STEMI criteria).
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Figure-6: These are links found in the top menu on every page in this ECG Blog. They lead you to numerous posts with more on OMIs. |
- In "My ECG Podcasts" — Check out ECG Podcast #2 (ECG Errors that Lead to Missing Acute Coronary Occlusion).
- In 'My ECG Videos" — Check out near the top of that page VIDEOS from my MedAll ECG Talks, that review the ECG diagnosis of acute MI — and how to recognize acute OMIs when STEMI criteria are not met (reviewed in ECG Blog #406 — Blog #407 — Blog #408).
- Please NOTE — For each of the 6 MedAll videos at the top of the My ECG Videos page, IF you click on "More" in the description, you'll get a linked Contents that will allow you to jump to discussion of specific points (ie, at 5:29 in the 22-minute video for Blog #406 — you can jump to "You CAN recognize OMI without STEMI findings!" ).
P.S.: For a sobering, thought-provoking case discussed by cardiologist Dr. Willy Frick — with editorial Commentary by me at the bottom of the page (in the March 17, 2025 post) — Check out this case.
- As Dr. Frick and I highlight — not only is the current "STEMI paradigm" outdated — but in cases such as the one we describe, because providers waited until STEMI criteria were finally satisfied — cardiac cath and PCI were delayed for over 1 day.
- BUT — because the cath lab was activated within 1 hour of an ECG that finally fulfilled STEMI criteria — this case will go down in study registers as, "highly successful with rapid activation of the cath lab within 1 hour of the identification of a "STEMI". This erroneous interpretation of events totally ignores the clinical reality that this patient needlessly lost significant myocardium because the initial ECG (done >24 hours earlier) was clearly diagnostic of STEMI(-)/OMI(+) that was not acted on because providers were "stuck" on the STEMI protocol.
- The unfortunate result is generation of erroneous literature "support" suggesting validity of an outdated and no longer accurate paradigm.
- The Clinical Reality: Many acute coronary occlusions never develop ST elevation (or only develop ST elevation later in the course) — whereas attention to additional ECG criteria in the above references can enable us to identify acute OMI in many of these STEMI(-) cases.
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