Sunday, June 9, 2019

A patient with chest pain that is resolving. Computer interprets ED ECG as completely Normal.

I posted this case a long time ago, before I started ranting about ECGs that are called completely normal by the computer.

A 60-something with chest pain arrived to the ED by ambulance with resolving chest pain.  Here is his ED ECG:

The computer interpretation was:
"Normal ECG"
What do you think?


























This ECG is NOT normal.  The T-waves in V2-V4 are very large in proportion to the QRS.   They are suspicious for hyperacute T-waves. There is low QRS amplitude.   

This points out another interesting phenomenon: hyperacute T-wave occur "on the way up" (before ST elevation, as the ST is on its way up) but also "on the way down" (when there is reperfusion, either spontaneous or by therapy): the ST segments may normalize before the T-wave normalizes, so that there are residual hyperacute T-waves.

Can you trust a computer interpretation of "normal?" 

Clearly not!  Here are 24 examples of critical ECGs that were called "normal" by the computer.


  1. Hughes KE et al. Safety of Computer Interpretation of Normal Triage Electrocardiograms. Acad Emerg Med 2017; 24(1): 120 – 24. PMID: 27519772
This study, discussed on Salim Rezaie's fine site REBEL EM, implies you can trust the computer interpretation of "normal." (http://rebelem.com/triage-ecgs-reducing-interruptions-busy-ed/)

We recently wrote an editorial debunking this study: 
Litell, John M., H. Pendell Meyers, and Stephen W. Smith. 2019. “Emergency Physicians Should Be Shown All Triage ECGs, Even Those with a Computer Interpretation of ‘Normal.’” Journal of Electrocardiology 54 (March): 79–81. https://doi.org/10.1016/j.jelectrocard.2019.03.003.

What to do?

Recording serial ECGs would be useful.  The chest pain is resolving, so if these are resolving hyperacute T-waves, then followup ECGs should show their size diminishing.

However, when I saw this patient, I knew that he had come by ambulance, so I knew there must be a prehospital ECG recorded somewhere and went to look for it. 

I found it. 

Here it is:
Need I say more?
Yes, I'll say more: see the computer interpretation:
"Normal variant ST elevation, consider early (repolarization)"
Why the medics did not see it, I'm not sure. 



The cath lab was activated, as it should be with transient STEMI

See this case of transient STEMI:

Spontaneous Reperfusion and Re-occlusion - My Bad Thinking Contributes to a Death.


Angiogram: There was 80% obstruction of the LAD with a large thrombus and TIMI-2 flow; the thrombus was suctioned out.

All serial troponins were undetectable!  (Remember this the next time you think you have ruled out a patient without looking at all the ECGs)

Comment:
Had we not seen those subtle hyperacute T-waves, and then sought out the prehospital ECG, the patient would have ruled out, with one of three outcomes:

1. Subsequent thrombus propagation with re-occlusion, recurrent chest pain and diagnosis made (although perhaps late and perhaps only after an adverse outcome)

2. Undergone stress test with uncertain results.

3. Been discharged to home with potential disastrous outcome.


Learning Points

1.  Computer algorithms that make the diagnosis of "normal" are usually correct, but is usually good enough?

2. Computer algorithms are completely unreliable at diagnosing STEMI, with both poor sensitivity and poor specificity.  Here are two recent articles confirming this:

    a. The Comparison of Physician to Computer Interpreted Electrocardiograms on ST-elevation Myocardial Infarction Door-to-balloon Times.
    b. Electrocardiographic diagnosis of ST segment elevation myocardial infarction: An evaluation of three automated interpretation algorithms

3.  Always look for the prehospital ECG

4.  Hyperacute T-waves occur not only shortly after onset of chest pain (as the ST segment is about to rise, or "on the way up"), but also shortly after reperfusion (as the ST segment is resolving after reperfusion or "on the way down").

5.  With very brief occlusions, troponins may all be negative.  What would high sensitivity troponins have shown?  We don't know.




===================================
Comment by KEN GRAUER, MD (6/9/2019):
===================================
As per Dr. Smith — this “repeat case” is clearly worth repeating! I’ll add several thoughts to the important points highlighted by Dr. Smith. To do so — I’ve highlighted key findings of the initial ECG in this case — and contrast this with the normal ECG that Dr. Smith posted a few days earlier on June 7 (Figure-1).
Figure-1: The initial ECG in the ED from this case ( = ECG #1) — contrasted with chest leads in the normal ECG taken from our June 7 Case  (See text).
=====================

COMMENT on ECG #1: As always, the History is KEY to optimal ECG interpretation. The fact that this 60-something man presented with resolving (not ongoing! chest pain should clue us in to the fact even IF he has just had acute OMI, that ST segments may only be minimally (if at all) elevated. Instead, we are likely to see more of a reperfusion ST-wave picture — or as in this case, hyperacute T waveson the way down.

Dr. Smith speaks at length in answer to the question as to whether you can “trust” Computer Interpretation of an ECG as “normal”. I’ll address this issue by repeating what I wrote in MComment on March 11, 2019 to a case Dr. Smith posted.
  • In my opinion — it is not the fault of the computer that the diagnosis was missed. Instead — it is the fault of the provider who accepts the computer interpretation without independently interpreting the ECG before looking at what the computer said. My views may differ from others, in that as an Attending charged with overreading ECGs for numerous providers — I loved the computerized interpretation once I appreciated what the computer can and cannot do. That’s because the computer saved me LOTS of time (!) by speeding up my interpretation, when I would be confronted with a large stack of ECGs in front of me to interpret. But for anyone who has read less than many thousands of tracings — it is imperative not to even look at the computer interpretation until after YOU have independently interpreted the ECG yourself! Failure to follow this suggestion will most likely lead to overlooking a number of subtle acute MIs. NOTE: I expand on my approach to Optimal Use of Computerized ECG Reports — HERE —
====================
Back to ECG #in this Case: The reasons why I was immediately concerned about acute OMI on seeing ECG #1 were: iThe history of new-onset chest pain severe enough to summon EMS; iiThe hyperacute waves in the chest leads; andiiiThe fact that no less than 11 out of the 12 leads on this ECG (ie, all leads except aVR) are abnormal!
  • Clearly — iand iiare more than adequate for activating the cath lab — but, I think it important to get GOOD at recognizing ST-T wave abnormalities, even when they are not as flagrant as the hyperacute T waves in ECG #1.
  • Proportionality — is the KEY word for appreciating that the T waves in leads V2-thru-V4 are hyperacute in view of the history of recent chest pain. T waves tower over the QRS complex in leads V2 and V3 — and, T wave amplitude in lead V4 still exceeds QRS amplitude in this lead.
  • Neighboring Leads — is the KEY concept for appreciating that the T waves in leads V5 and V6 of ECG #1 are also hyperacute — since the Shape of these T waves is quite similar to T wave shape in leads V2-thru-V4. Even though T wave amplitude in leads V5 and V6 is less — their similar shape tells you this is part of the overall process. And, in the context of these T wave abnormalities in leads V2-thru-V6 — we can confidently say that the coved and slightly elevated ST segment in lead V1 is also abnormal!
  • R Wave Progression — is telling in ECG #1, because there is no more than a minimal r wave in leads V1 and V2 — and, the R waves that subsequently form remain quite small through to lead V6. Compare the amplitude of these chest lead R waves in ECG #1 — with the prehospital ECG (shown above— in which transition occurred by lead V2, with substantial R wave amplitude in the mid-chest leads. This loss of wave is clearly the result of the large anterior STEMI that this patient has just had.
  • SStraightening — is the KEY word for appreciating that there are ST-T wave abnormalities in no less than 11 of the 12 leads in ECG #1. First — Note the shape of the normal ST-T waves in the chest leads of the June 7 Case (BOTTOM in Figure-1— in which there is a gentle upsloping concavity to the ST segments, with imperceptible (smooth) transition between the end of the ST segment and the beginning of the T wave. Contrast this with distinct SSegment Straightening in leads I, II, aVL, aVF; and V2-thru-V6 (parallel RED lines in ECG #1). In addition, this ST straightening in leads V5,V6 manifests an abrupt angulation at the ST segment-T wave juncture.
  • Finally — there is the coved ST segment with shallow T wave inversion in lead III. By itself, in association with the predominantly negative QRS complex in this lead — this might not be an abnormal finding. But in the context of definite ST segment straightening in neighboring inferior leads II and aVF — the ST-T wave in lead III must be assumed as part of the overall picture.


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