Tuesday, May 26, 2020

A middle-aged male with chest pain

A 40-something male presented with chest pressure.

Here is his triage ECG:
What do you think?


















The triage physician suspected that this was a false positive due to benign normal variant ST Elevation (Often called "Early Repolarization," though many are trying to get away from that terminology for this morphology)

When I saw the ECG I immediately thought that this was not STEMI.

I applied the Early Repol/LAD occlusion formula.
See this post for explanation and references:

12 Example Cases of Use of 3- and 4-variable formulas to differentiate normal STE from subtle LAD occlusion


Remember it can only be applied when NONE of these are present:
1. Presence of a straight or convex ST segment in just ONE of V2-V6
2. STE of at least 5 mm in one lead of V2-V4
3. ANY ST depression in ANY lead, reciprocal or not
4. Any T-wave inversion
5. Any Q-wave in V2-V4
6. Any terminal QRS distortion (absence of both an S-wave and J-wave (notch) in either V2 or V3
If any of these are present, it is NOT normal variant, and so the formula should not be applied.


ST Elevation at 60 ms after the J-point in lead V3 = 4 mm
R-wave amplitude in V4 = 20 mm
QRS amplitude in V2 = 10 mm
Computerized QTc was 365 ms (this is the feature of this ECG which is most potent -- it is a very short QTc for acute MI.  In our series of subtle LAD occlusions, the mean QTc was 420 ms, vs. 390 for normal variant STE) 

Formula value = 16.36 (most accurate cutpoint is 18.2; a value below 17.0 is 97% sensitive and a value above 19.0 is 97% specific.

I generally give this warning:  
--Use the formula to help you make the diagnosis of LAD occlusion when you did not suspect it.  
--Do NOT use the formula to dissuade you from the diagnosis of LAD occlusion.

I was already convinced by looking at the ECG that this was a false positive, so the formula value reassured me.

Then I went to look for a previous ECG, and found one:

Almost exactly the same


History revealed that the symptoms had been going on constantly all day, so an initial troponin would be positive if this was a true positive ST elevation.

The first trop returned undetectable, as did the 2nd trop.

We discharged the patient with "atypical chest pain."
___________________________

Ken wrote below about all the features that make this unlikely to be an acute MI.
However, what he wrote are features specific to acute MI, but not sensitive.  These features do NOT make acute MI unlikely by themselves, they make is less likely.

In our series of 355 consecutive LAD occlusions, 143 had none of the features that Ken discusses:

LAD occlusions were excluded from the study if they had any of the following:
1. Presence of a straight or convex ST segment in just ONE of V2-V6. (There must be concavity)
2. STE of at least 5 mm in one lead of V2-V4
3. ANY ST depression in ANY lead, reciprocal or not
4. Any T-wave inversion
5. Any Q-wave in V2-V4
6. Any terminal QRS distortion (absence of both an S-wave and J-wave (notch) in either V2 or V3


So when you apply the formula, it must be ONLY to ECGs that have NONE of the above.

If they have any ONE of the above, then you must assume that it is LAD occlusion because normal variant STE in V2-V4 has NONE of them.

Finally, we looked at degree of upward concavity in V2-V4 and it did not add ANY additional value to the multivariable formula.  It does have univariate value, but does not help at all if you are already using the formula, which is far better.  In other words, unless there is a straight or convex ST segment, in which case you must assume it is not normal, the SHAPE of the ST Segment has no further added value over the formula, except insofar as it makes you recognize normal variant more easily.



===================================
MY Comment by KEN GRAUER, MD (5/26/2020):
===================================
While contemplating My Comment for this case — I decided to concentrate on ST segment elevation SHAPE. So, I looked through previous cases I commented on for Dr. Smith’s ECG Blog — and I came across My Comment in the June 7, 2019 post, in which the points I’m about to make on today’s case are virtually identical to what I wrote in that 2019 case. Clearly, this is an “ECG Theme” that repeats itself.
  • For clarity — I again show the initial ECG in the ED for today’s case (Figure-1).

Dr. Smith gave “the Answer” to today’s case above — namely, that the ECG in Figure-1 is unlikely to indicate acute coronary syndrome.
  • QUESTION: In addition to a very low (totally normal) value in Dr. Smith’s Formula — WHAT are the ECG findings that suggested to me that ECG #1 was less likely to indicate acute OMI?

Figure-1: The initial ECG in the ED for today’s case (See text).



My THOUGHTS on ECG #1: There is a significant amount of artifact, especially in the limb leads.
  • PEARL #1 — While the amount of artifact in this tracing is not enough to prevent accurate interpretation of this ECG — knowing how to quickly determine which extremity is the cause of the artifact (due to tremor, a faulty lead connection/inadequate skin contact, etc.) is helpful, because this may expedite correction, which may be important when artifact does impede interpretation. In ECG #1 — baseline artifact is most prominent in leads I, II and aVR in the limb leads, with significantly less baseline disturbance in the chest leads. This suggests that the right arm is most likely the source of this artifact. (NOTE: For a quick primer on how to recognize which extremity is the cause of artifact — Please SEE the 1st bullet in Observation #2 in My Comment for the September 27, 2019 post in Dr. Smith’s ECG blog).

Returning to my Descriptive Analysis of ECG #1:
  • The rhythm in ECG #1 is sinus at ~60/minute. All intervals (PR/QRS/QTc) are normal. The frontal plane axis is normal at about +15 degrees. There is no chamber enlargement.

Regarding Q-R-S-T Changes:
  • There are narrow septal Q waves in leads I and aVL.
  • Transition (ie, R Wave Progression) occurs early — as the R wave becomes taller than the S wave is deep as soon as between leads V1-to-V2.
  • Regarding ST-T Wave Changes — The limb leads look fairly unremarkable. Although difficult to be certain due to the baseline artifact — there appears to be slight, concave-up ST elevation in leads I and aVL (and possibly also in lead II— without any reciprocal ST depression in the inferior leads. The ST-T wave in lead III is flat. This does not look acute.
  • There is definite J-point ST elevation in each of the chest leads. The amount of ST elevation is minimal in V6 — and maximal in leads V1, V2, V3 (up to 2-3 mm). The shape of ST elevation seen is consistently concave-up (similar to the shape of the gently curved RED lines in these leads — seen in Figure-2).
  • There is prominent J-point notching in leads V4, V5, V6 (BLUE arrows).

Figure-2: I’ve labeled key ECG findings seen in ECG #1 (See text).



Clinical IMPRESSION: WHY I thought the above findings in ECG #1 were less likely to be acute:
  • DISCLAIMER: No set of ECG features is perfect for ruling out acute OMI on the basis of a single ECG. Clearly, additional assessment will often be needed in the patient who presents with new symptoms — which is the situation for today's case (ie, the 40-something man in today's case did present with "chest pressure" which apparently was new). As a result — additional evaluation would be advised (ie, more history; comparison with a baseline ECG; serial tracings; stat Echo; troponin, etc.) — before comfort could be attained that no acute ischemic event is ongoing. THAT SAID — I thought the sum total of ECG findings in today’s case suggested that acute cath lab activation would not be indicated on the basis of this initial ECG! 
  • NOTE: My rationale below is based on qualitative findings. I did not use Dr. Smith's multivariate formula in my decision-making process.

PEARL #2 — ECG Findings that reduce the likelihood of an acute process in ECG #1 include the following:
  • Lack of any reciprocal ST depression! While true that a significant percentage of acute anterior MIs do not manifest reciprocal ST depression in the inferior leads (especially when there is mid-to-distal rather than proximal LAD occlusion) — the ST elevation seen in ECG #1 begins in lead V1! As a result — I would normally expect to see at least some reciprocal inferior lead ST depression if there was acute proximal LAD OMI.
  • The shape of the ST elevation that we see in the chest leads is uniformly concave-up (similar to the shape of the gently curved RED lines in these leads). While this upward-concavity (ie, smiley”-configuration) shape by itself does not rule out the possibility of acute ischemia — this type of ST segment shaping is often seen in repolarization variants. In contrast — straightening of the ST segment and/or ST segment coving (ie, frowny”-configuration) shape is much more commonly associated with acute ischemic heart disease.
  • There is prominent J-point notching in leads V4, V5, V6 (BLUE arrows). Especially when seen in multiple leads in association with benign-appearing (ie, concave-up) ST elevation — this type of J-point notching often occurs with repolarization variants.
  • The 2 q waves noted in this tracing are small and narrow — and, they are seen in lateral leads I and aVL. Normal “septal” q waves (attributable to the normal left-to-right initial vector of septal activation) may commonly be seen in any of the lateral leads (I, aVL; V4,V5,V6) — so the appearance of these q waves that are seen in ECG #1 is perfectly consistent with these being normal “septal” q waves.
  • A normal (if not relatively short) QTc interval. I estimate the QTc to be ~370 msec — which clearly is on the shorter side of the normal QTc range. In contrast — acute MI is often associated with QTc prolongation.
  • Prominent R wave forces in the chest leads. Acute anterior OMI often manifests reduced anterior R wave amplitude. The opposite is present here — as the R wave becomes tall and predominates as early as in lead V2.
  • Finally — There is a lack of localization! Counting the slight ST elevation in leads I, II and aVL — no less than 9 out of 12 leads in ECG #1 manifest ST elevation. Acute ischemic heart disease is far more likely to localize — instead of manifesting a consistent concave-up shape for the ST-T waves that we see here in 9 of the 12 leads in this tracing.

BOTTOM Line: I’ll repeat my “disclaimer” that I wrote above:
  • DISCLAIMER: No set of ECG features is perfect for ruling out acute OMI on the basis of a single ECG. Additional assessment may be needed before full comfort can be attained that no acute ischemic event is ongoing. Even if the ECG is unremarkable — sometimes cardiac cath will still be indicated to rule out an acute process. THAT SAID — I thought the overall picture, based on the combination of findings in ECG #1 was less likely to represent acute ischemic heart disease.
  • For additional practice in applying these concepts — Please CHECK OUT the June 7, 2019 post on Dr. Smith’s ECG Blog.

Our THANKS to Dr. Smith for presenting this case.


6 comments:

  1. Hi there. Is there not a terminal distortion in V3?

    ReplyDelete
  2. @ PM — T-QRS-D (Terminal QRS Distortion) is defined by Dr. Smith as the absence of both a J-wave and an S-wave in either lead V2 or lead V3. I believe the last part of the QRS in lead V3 does reach the baseline — therefore there IS an S wave in this lead. Since there is no J-wave in lead V3 — there is not T-QRS-D.

    ReplyDelete
  3. thank you very much for this intersting case. Your comments are very insightful even for an experienced clinician.
    One Question regarding the T waves (V2;V3)in this case: they seem rather large, the area under the curve ist large, so wouldnt you consider These t waves as hyperacute ??
    Thank you for your help

    ReplyDelete
    Replies
    1. Your question is an excellent one — and it is for the very reason you suggest that I emphasize in my “Disclaimer” (right under my Clinical Impression) that some additional evaluation (How much depending on the comfort level of the clinical who is “there” on the scene!) — but some additional evaluation would be needed because the T wave appearance you mention is not one I’d be 100% certain was benign. That said — as I mentioned in My Comment, I thought it was the SUM TOTAL of the ECG findings I described in this case that suggested there was a very good chance these ECG findings were not acute.

      Delete
  4. You describe ECG #2 as, "Not exactly the same [as ECG #1], but pretty close." Close might be an understatement since you've accidentally posted the same ECG twice! Otherwise, great case and discussion, as always.

    ReplyDelete
    Replies
    1. Thanks, Vince! I fixed it. It still looks almost exactly the same. In fact, unless you look extremely closely, you might still think it is the same ECG.

      Delete

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