Thursday, March 17, 2022

ECG Blog #291 (84b) - Errors in ECG (Part-2)


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This is Part-2 on Common Errors in ECG Interpretation. Today's Audio Pearl (below) focuses on problems I've observed in recognizing acute coronary occlusion (ie, an "OMI") with need for prompt cath despite the absence of enough ST elevation to satisfy millimeter-criteria for a STEMI.
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The ECG shown in Figure-1 was obtained from a man with chest pain.  
  • Despite not satisfying millimeter-based criteria for a STEMI — Why should the cath lab be activated?
  • HOW MANY of the 12 leads in this tracing are in support your answer? 

Figure-1: ECG obtained from a man with chest pain (See ECG Blog #272 for the complete case on this patient).

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NOTE: Some readers may prefer at this point to listen to the 6:00 minute ECG Audio PEARL before reading My Thoughts regarding the ECG in Figure-1. Feel free at any time to refer to My Thoughts on this tracing (that appear below ECG MP-84b).

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Today’s ECG Media PEARL #84b (6:00 minutes Audio) — Reviews my observations in this Part-2 of some Common Errors in ECG Interpretation (special attention to Errors in 12-lead Interpretation)(Part 1 was in ECG Blog #290)



ANSWER:
My purpose in reshowing the ECG in Figure-1 (that I initially presented in ECG Blog #272) — is that it highlights a number of often-ignored diagnostic ECG findings of acute coronary occlusion. As emphasized in today's Audio Pearl — Failure to recognize an acute OMI ( = Occlusion-based MI) because millimeter-based STEMI criteria are not yet evident is a potentially lethal error.
  • The rhythm in Figure-1 is sinus at ~70/minute. All intervals and the axis are normal. There is no chamber enlargement. Overall QRS amplitude is reduced.
  • In a patient with new chest painT-waves in leads V2-thru-V6 must be interpreted as "hyperacute" until proven otherwise. The 3 leads that are most abnormal in this tracing are leads V3, V4 and V5. In each of these leads — T waves tower over the small-amplitude R waves. Not only are these T waves much taller than the R waves — but these T waves are clearly "fatter"-at-their-peak and wider-at-their-base than one would expect, given the size of the R waves (and QRS complex) in these respective leads.
  • By the concept of "patterns of neighboring leads" — Since the ST-T waves in leads V3, V4 and V5 are so obviously abnormal — the somewhat less obvious ST-T wave changes in neighboring leads V2 and V6 are also almost certainly abnormal.
  • In lead V6 — although the T wave is not taller than the R wave — this T wave in lead V6 is still much taller-than-one-would-expect given small size of the R wave in this lead.
  • Height of the T wave in lead V2 is not as pronounced as T wave amplitude in lead V3. However, the ST segment "takeoff" is unusually straight (ie, parallel to the slanted RED line in lead V2 of Figure-2). In addition, considering how small the r wave is in lead V2 (ie, 2 mm) — the T wave in this lead is once again "hypervoluminous" (ie, clearly with a much wider than-it-should-be base). I would therefore interpret leads V2 and V6 as also being "hyperacute".
  • ST-T wave changes in lead V1 are subtle — but nevertheless "real". Normally in this lead — there is no more than minimal ST elevation. Although the T wave in lead V1 may normally be inverted (PURPLE arrow in Figure-2) — the shape of the ST segment in this lead (ie, coved or "frowny"-configuration, as schematically shown by the curved RED arc) — in association with the ST elevation seen (with respect to the dotted RED line in lead V1 — showing the PR segment baseline) is not a normal finding (especially given obvious ST-T wave abnormalities in the 5 other chest leads)!

Figure-2: I've labeled some of the abnormal ST-T wave changes that were seen in Figure-1.


Regarding ST-T wave Changes in the Limb Leads:

  • The ST-T waves in leads IIIII and aVF are all clearly abnormal. ST segments in each of these inferior leads are "scooped", with suggestion of slight ST depression. That said — the most remarkable finding is the terminal T wave positivity in each of these 3 inferior leads (upward-pointing BLUE arrows in Figure-2 — with the most prominent terminally positive T wave being seen in lead II)
  • Depending on the clinical situation (and the stage of evolution during an acute cardiac event) — this finding of terminal T wave positivity, in association with ST flattening or depression — is clearly abnormal, and may represent the beginning of reperfusion changes (ie, the mirror-image of inverting T waves in leads which manifested ST elevation).
  • Without the benefit of a prior (baseline) ECG for comparison — I was uncertain if the ST-T waves in leads I and aVL were abnormal. I thought the apearance of the QRST complex in lead aVR was unremarkable.


KEY Point: When assessing an ECG for the possibility of acute ischemic heart disease — the more leads that are abnormal, the greater the chance that the abnormalities you identify are realI find it helpful to start with a few leads that obviously show acutely abnormal ST-T wave findings — and then to apply the concept of "patterns of neighboring leads" as I look closely to identify more subtle findings in the remaining leads.

  • As described above regarding the ECG shown in Figure-2 — We have identified definite ST-T wave abnormalities in no less than 9/12 leads (ie, in leads II,III,aVF — and in all 6 chest leads). This provides strong support in favor of a recent (or still ongoing) cardiac event.


What then is the Error?

The errors that are all too commonly made in patients who present with ECGs similar to the one in today's case include the following:

  • Not appreciating what an "OMI" is — in which the ECG strongly suggests acute coronary occlusion despite not satisfying millimeter-based criteria for a STEMI.
  • Failure to recognize hyperacute ST-T waves in a patient with new symptoms.
  • Failure to appreciate that the more abnormal leads there are in a patient with new symptoms — the more likely it is that an acute cardiac event is ongoing.
  • Failure to appreciate that there are other indications for prompt cath — apart from the finding of a millimeter-specific STEMI on ECG (ie, prompt cath is indicated for ongoing chest pain with abnormal ECG findings that look acute).

 

Case CONCLUSION:

Cardiac cath was performed on the patient in today's case. Not surprisingly, this revealed total occlusion of the mid-LAD (Left Anterior Descending) coronary artery. Minor lesions were found in the LCx (Left Circumflex) and RCA (Right Coronary Artery).



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ADDENDUM (3/16/2022): 

For clarity in Figure-3 — I have again listed those ECG findings, that when seen in association with new cardiac symptoms — are among those that suggest acute OMI despite not satisfying the millimeter-based definition of a STEMI.


Figure-3: ECG findings to look for when your patient with new-onset cardiac symptoms does not manifest STEMI-criteria ST elevation on ECG. For more on this subject — SEE the September 3, 2020 post in Dr. Smith’s ECG Blog with 20-minute video talk by Dr. Meyers on The OMI Manifesto. For my clarifying Figure illustrating T-QRS-D (2nd bullet) — See My Comment at the bottom of the page in Dr. Smith’s November 14, 2019 post.




Additional Relevant Material to Today's Case:
  • See ECG Blog #185 — for review of the Systematic Ps, Qs, 3R Approach to rhythm interpretation.
  • See ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation.

  • See ECG Blog #193 — for Review of the term, "OMI" ( = Occlusion-based MI).
  • See ECG Blog #218 and ECG Blog #260 — for Review of WHEN a T-wave is Hyperacute.


  • See ECG Blog #204 and ECG Blog #282 — for Review of a user-friendly approach for the ECG Diagnosis of the Bundle Branch Blocks (RBBB/LBBB/IVCD) in a matter of seconds!

  • See ECG Blog #196 and ECG Blog #263 and ECG Blog #220 — for Review on assessing the regular WCT rhythm
  • See ECG Blog #197 and ECG Blog #278 — for Review of the Idiopathic VTs (ie, RVOT VT, Fascicular VT, others).

  • See ECG Blog #211 — for Review of why some beats conduct with Aberration.
  • See ECG Blog #42 — for Review of Criteria for distinguishing between VT vs SVT with Aberration or Preexisting BBB.

  • See ECG Blog #240 — for Review on the ECG assessment of the patient with a regular SVT rhythm (including distinction between the various types of SVT reentry).

  • See ECG Blog #214 — for Review of why I emphasize the phrase, "12 Leads are Better than One".

  • See ECG Blog #235 and ECG Blog #286 — for, "Some Simple Steps to Help Interpret Complex Rhythms".

  • For more on distinction between Low Atrial vs Junctional Rhythm — Please see My Comment at the BOTTOM of the page in the January 28, 2019 post in Dr. Smith's ECG Blog.
  • For more on the Emery Phenomenon — Please see My Comment at the BOTTOM of the page in the June 3, 2020 post in Dr. Smith's ECG Blog.


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