A 50-something with no previous cardiac history and no risk factors presented to the ED with acute chest pain (pressure) that radiated to the left arm.
An ECG was immediately recorded:
There is ST depression in V1-V3. We showed that this is diagnostic of OMI (of the posterior wall).
Moreover, there is ST elevation in V6 (which is getting close to the location of posterior lead V7). Thre is also absence of S-wave in V6, which is not entirely abnormal, but is suggestive of OMI (when this finding is in V2 or V3 in the setting of STE in V2 or V3, we call this "terminal QRS distortion", and it rules out normal STE)
Later, it queried the PM Cardio AI bot ("Queen of Hearts," a deep neural network trained by Pendell and me), and its diagnosis was "OMI with High confidence"
Case continued
The faculty physician in triage was very suspicious of OMI and took the patient to the critical care area. Another very astute faculty physician immediately recognized that the ECG is diagnostic of posterior and lateral OMI, and activated the cath lab.
The cardiology fellow came to the ED. Another ECG was recorded as the patient's pain was improving.
The cardiology fellow was skeptical of the need for the cath lab, but he took the patient up.
The first troponin I returned at 34 ng/L (URL = 35 ng/L)
The HEART score (also HEART pathway) = 3 (But this is only if you were to think that the ECG is normal, as the computer does)
Cath report: Findings in left circumflex:
LCX: Large, but non-dominant. Supplies a very large OM1. There is no stenosis in the proximal LCX and OM1 but a small to medium sized mid LCX continuation supplying a left posterolateral artery (LPLA) has a 99% stenosis with TIMI II flow
(Flow was probably TIMI 0/1 during the initial ECG, but there was some spontaneous lysis and it partly opened to TIMI-2 flow (still insufficient, causing ongoing infarction).
It was stented with good results.
Formal Echo next morning:
The estimated left ventricular ejection fraction is 44%.
Regional wall motion abnormality-mid to basal infero-lateral.
Regional wall motion abnormality-basal anterolateral.
Peak hs troponin I over 36,000 ng/L (too high to measure, a VERY large infarction)
Learning Point:
1. There can be a VERY large infarct in a patient with a low HEART score and a "Normal" ECG.
2. If you do not recognize subtle OMI on the ECG, your patient may suffer large myocardial loss, or even die.
3. YOU must be the one to recognize it. Your cardiologist might not see it.
4. Our AI program from PM Cardio, trained by Pendell and me, is amazing and when it is FDA approved you will be able to use it to make this important and difficult decision to activate the cath lab.
===================================
MY Comment, by KEN GRAUER, MD (4/29/2023):
===================================
Today's case solidifies the need to add acute posterior OMI to the list of "Must Recognize" ECG patterns for emergency providers. As we've emphasized on many occasions — in a patient with new chest pain, ST depression that is maximal in one or more leads between V2-to-V4 is diagnostic of acute posterior OMI until proven otherwise! This is precisely the picture seen in the initial ECG in today's case ( = ECG #1 in Figure-1) — and — this ECG picture needs to be instantly recognized.
- More than just the finding of maximal ST depression in V2-to-V4 — is the shape of the depressed ST segment in these leads. Normally, there will often be 1-2 mm of gently upsloping ST elevation in anterior leads V2 and V3. If instead, in a patient with new chest pain — there is "shelf-like" ST depression, similar to the flattened, depressed ST segment seen in leads V2 and V3, but not beyond lead V4 (as is the case in ECG #1) — this should serve as an instant "tip-off" to posterior OMI.
- As a visual aid to facilitate recognition of the ST-T wave changes characteristic of acute posterior MI — I favor the Mirror Test (See My Comment at the bottom of the page in the September 21, 2022 post in Dr. Smith's ECG Blog). By simply flipping the ECG over, and holding it up to the light — the mirror-image of QRST complexes in one or more of the anterior leads is revealed — which provides insight to the ST-T wave appearance in the posterior LV wall.
- Doesn't the Mirror Test faciliate appreciation of the abnormal shape of the shelf-like ST depression in leads V2 and V3 in ECG #1? (within the RED rectangle showing this mirror-image in leads V2 and V3).
- As per Dr. Smith's discussion above — there are other abnormal findings in ECG #1 (ie, subtle-but-real ST elevation in lead V6, with a straightened, hyperacute-looking ST segment in this lead). In addition — there is subtle ST elevation in high-lateral leads I and aVL, with a Q wave in aVL that looks disproportionately wide. But even without these additional findings — the "Must Recognize" ECG pattern in this patient with new chest pain — is the unmistakeable shape of the ST depression in leads V2 and V3!
- "A picture is worth 1,000 words ... ". I've added links below to 10 cases of posterior OMI in Dr. Smith's ECG Blog — in which I illustrate application of the Mirror Test. There are many other examples throughout Dr. Smith's ECG Blog.
-USE%20copy.png) |
| Figure-1: Comparison between the 2 ECGs in today's case. |
- As noted by Dr. Smith — the repeat ECG in today's case is more subtle than the initial ECG. That said, if a patient with new chest pain presents with ECG #2 as the only tracing available — I would still be very suspicious of acute posterior OMI for similar reasons as described above for ECG #1. That is, instead of the small, normal amount of gently upsloping ST elevation in anterior leads — there is subtle-but-real "shelf-like" ST depression in leads V2 and V3. ST segment flattening persists in lead V4 — but is not present in lateral chest leads V5 and V6. While not by itself definitive — in a patient with new chest pain, the abnormal ST-T wave shape in leads V2,V3,V4 of ECG #2 should prompt timely repeat tracings, serial troponins, stat Echo — with high likelihood that OMI confirmation would soon be forthcoming.
- Lead-to-lead comparison between ECG #1 and ECG #2 in Figure-1 is valid — because QRS morphology, the frontal plane axis, and R wave progression are all virtually unchanged between these 2 tracings.
- In association with a reduction in chest pain — there is now beginning T wave inversion in lead III of ECG #2 — and, slight-but-real increase in T wave amplitude in both leads V2 and V3 of this repeat tracing. I interpreted these ST-T wave changes as subtle findings suggesting reperfusion T waves (which in the posterior wall distribution — manifests as increased T wave amplitude in anterior leads). Clinicallly — this would be consistent with the less-than-total coronary occlusion seen on cath.
=================================
Selected LINKS for More on the Mirror Test:
- ECG Blog #246 — Reviews the concept of the "Mirror Test" with a clinical example.
- The February 10, 2022 post in Dr. Smith's ECG Blog — My Comment (at the bottom of the page) illustrates the Mirror Test in a case with posterior reperfusion waves (ie, tall anterior T waves).
- The March 21, 2023 post —
- The January 23, 2023 post —
- The July 16, 2022 post —
- The May 3, 2022 post —
- The January 3, 2022 post —
- The October 11, 2020 post in
- The September 28, 2020 post in
- The September 21, 2020 post —
- The February 16, 2019 post —
No comments:
Post a Comment
DEAR READER: I have loved receiving your comments, but I am no longer able to moderate them. Since the vast majority are SPAM, I need to moderate them all. Therefore, comments will rarely be published any more. So Sorry.