Wednesday, March 30, 2022

ECG Blog #294 — One Hour Later

The patient whose ECGs are shown in Figure-1 — was a 55-year old man who presented with new chest pain of ~2 hours duration. ECG #1 was obtained on arrival at the ED (Emergency Department). His symptoms continued — and an hour later, ECG #2 was obtained.

  • How would YOU interpret these 2 serial tracings?
  • "Culprit" artery? (Be as specific as you can.).
  • Was there any hint in ECG #1 that just 1 hour later we'd see the picture shown in ECG #2?

Figure-1: The first 2 ECGs in today's case, which were done just 1 hour apart (See text).


NOTE: Some readers may prefer at this point to listen to my 10-minute ECG Audio PEARL before reading My Thoughts regarding the ECG in Figure-1. Feel free at any time to review My Thoughts on ECG #1 (that appear below ECG MP-10).



Today’s ECG Media PEARL #10 (10 minutes Audio) — reviews the concept of why the term “OMI” ( = Occlusion-based MIshould replace the more familiar term STEMI — and — reviews the basics on how to predict the "culprit" artery.

MY Thoughts on the 2 ECGs in Figure-1:
I was sent the tracings in today's case — and I looked first at ECG #1. I saw sinus rhythm at ~65-70/minute — normal intervals (PR, QRS, QTc) and normal axis (about +20 degrees). No chamber enlargement.
  • Regarding Q-R-S-T Changes in ECG #1 — there were no Q waves — R wave progression was normal, with slightly delayed transition (the R does not become taller than the S wave is deep until between leads V4-to-V5).
  • The only ST-T wave findings of note are seen in the inferior leads. There is nonspecific ST-T wave flattening in lead aVF, and to a lesser extent in lead II. There is shallow, symmetric T wave inversion in lead III — but given that the QRS complex is predominantly negative in this lead, this is not necessarily an abnormal finding (especially given the absence of T wave inversion in the other 2 inferior leads).

  • BOTTOM LINE for ECG #1: There are some nonspecific ST-T wave abnormalities in the inferior leads — but I saw nothing to indicate what was soon to occur in ECG #2.

Regarding ECG #2:
Sinus rhythm is again present at a rate similar to that seen in ECG #1. Intervals and the axis are again normal. There is no chamber enlargement. BUT — the rest of the interpretation has dramatically changed in the space of an hour. Specific ECG findings that are now seen on ECG #2 include the following:
  • Marked ST elevation in each of the inferior leads (with ST elevation in lead III clearly greater than in lead II). Small q waves in leads II and aVF + a large, wide Q wave in lead III.

  • Marked reciprocal ST depression in high-lateral leads I and aVL (with shape of the ST-T wave in lead aVL being the mirror-image opposite picture from the shape of the ST elevation in lead III).
  • Marked shelf-like ST depression in leads V2, V3, V4 (ie, positive Mirror Test) — but virtually no ST depression at all in lead V1.

  • BOTTOM Line for ECG #2: In this patient with new chest pain — this ECG is diagnostic of an acute infero-postero STEMI, from acute proximal RCA  (Right Coronary Artery) occlusion

  • PEARL #1: In addition to acute infero-postero MI — acute RV (Right Ventricular) involvement is highly likely, given the absence of any ST depression in right-sided lead V1 in this tracing with such marked ST depression in neighboring leads V2,V3 (ie, ST elevation from RV MI in lead V1 is probably attenuated by what otherwise would have been ST depression in this lead from acute posterior MI). It is this acute RV involvement that for practical purposes localizes the site of acute coronary occlusion to the proximal RCA — because the LCx (Left Circumflex) coronary artery does not supply the RV wall (See ECG Blog #190for more on acute RV MI).

  • PEARL #2: It is sometimes quite humbling to see how quickly dramatic ECG signs of infarction may develop. The case I presented in ECG Blog #115 showed a similar dramatic evolution from subtle ST-T wave changes — to full-blown ST elevation in the space of only 8 minutes. The MESSAGE is clear: Serial ECGs can change extremely rapidly. IF concerned about an acutely evolving OMI (Occlusion-based MI), especially if the patient's chest pain is ongoing — ECGs may sometimes need to be repeated as often as every 10-20 minutes, until a definitive diagnosis is made.

Follow-Up to this Case:

The facility where this patient was seen did not have acute cardiac catheterization capability. The patient was instead immediately treated with thrombolytic therapy (Streptokinase). Chest pain resolved — and ECG #3 (shown in Figure-2) was obtained.


  • Was thrombolytic therapy successful? If so — HOW can you tell?
  • What would you expect subsequent ECGs to show?

Figure-2: Comparison of ECG #2 — with the ECG obtained following completion of Streptokinase.

When promptly administered to appropriate patients — thrombolytic therapy can be extremely effective. Features of today's case that suggest a very favorable response to Streptokinase include the following:
  • The patient's chest pain resolved following use of thrombolytic therapy.
  • The dramatic inferior lead ST elevation has improved greatly. High lateral lead reciprocal ST depression in leads I and aVL has largely resolved.
  • ECG changes of acute posterior infarction (ie, shelf-like ST depression in leads V2,3,4) are no longer present. A more normal picture of shallow T wave inversion is now seen in lead V1.
  • Inferior lead Q waves have only minimally increased in size.


What to Expect in subsequent ECGs?
In addition to resolution of chest pain, with marked reduction in the amount of ST elevation and depression — reperfusion of the occluded coronary artery is typically marked by development of fairly deep T wave inversion in those leads that manifested ST elevation.
  • The opposite is seen with reperfusion of acute posterior OMI — with development of tall, peaked T waves in the anterior leads (instead of T wave inversion).
  • It would not be surprising to see transient AIVR (Accelerated IdioVentricular Rhythm) — as this is an extremely common reperfusion arrhythmia (See ECG Blog #194).
  • An example of reperfusion T wave changes can be seen in ECG Blog #268 . 

Acknowledgment: My appreciation to M Shah (from Srinagar, India) for the case and this tracing.



  • Included below are a series of links and other material relevant to detection of the “culprit” artery — and my thoughts for making the case to replace the term “STEMI” with “OMI”, in the hope of substantially increasing detection of acute coronary occlusion. 


Free PDF Downloads from relevant Sections in my ECG-2014-ePub:

  • PDF File: Overview on the Cardiac Circulation and the “Culprit” Artery in Acute MI —
  • PDF File: Posterior MI and the “Mirror Test” —


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.

Today’s ECG Media PEARL #11 (6 minutes Audio) — Reviews how to tell IF the “culprit” (ie, acutely occluded) artery has reperfused, using clinical and ECG criteria.


Relevant ECG Blog Posts to Today’s Post: 

  • ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation. 

  • ECG Blog #184  That magical inverse relationship between leads III and aVL.
  • ECG Blog #167 — More on that "magical" lead III-aVL relationship.
  • ECG Blog #183 — deWinter-like T waves.
  • ECG Blog #190 — How to recognize acute RV MI.
  • ECG Blog #56 — Posterior MI; Mirror Test
  • ECG Blog #80 — What's the Culprit Artery? + the Mirror Test.
  • ECG Blog #82 — What’s the Culprit Artery?
  • ECG Blog #162 — What’s the Culprit Artery?
  • ECG Blog #193 — Reviews a case with a probable dominant LCx culprit.
  • ECG Blog #194 — Reviews how to tell IF the "culprit" artery has reperfused (with an example of AIVR).

  • ECG Blog #230 — Reviews how to compare Serial ECGs.
  • ECG Blog #115 — Shows how dramatic ST-T changes can occur in as short as an 8-minute period.
  • ECG Blog #268 — Shows an example of reperfusion T waves.

  • ECG Blog #246 — Reviews the Mirror Test for diagnosis of Posterior MI (Also check out the Audio Pearl in this post).
  • ECG Blog #266 — How to distinguish between deWinter T waves vs reperfusion T waves with Posterior MI.

  • ECG Guru (9/3/2019) — See My Comment regarding acute occlusion of 1st or 2nd Diagonal Branch of the LAD.

  • The importance of the new OMI (vs the old STEMI) Paradigm — See My Comment in the July 31, 2020 post in Dr. Smith's ECG Blog.

  • Acute OMI that wasn’t accepted by the Attending — See My Comment at the bottom of the page in the November 21, 2020 post on Dr. Smith’s ECG Blog.
  • Another overlooked OMI (Cardiologist limited by STEMI Definition) — See My Comment at the bottom of the page in the September 21, 2020 post on Dr. Smith’s ECG Blog.
  • Recognizing hyperacute T waves — patterns of leads — an OMI (though not a STEMI) — See My Comment at the bottom of the page in the November 8, 2020 post on Dr. Smith's ECG Blog.
  • Recognizing T-QRS-D (Terminal QRS Distortion) as a sign of acute OMI — See My Comment at the bottom of the page in the November 14, 2019 post on Dr. Smith's ECG Blog.
  • LVH vs a Repolarization variant vs LAD OMI (and looks like Wellens' after reperfusion) — See My Comment at the bottom of the page in the October 23, 2020 post on Dr. Smith's ECG Blog.
  • Repolarization Variant vs Acute OMI (even repolarization variants may sometimes manifest "dynamic" ECG changes!) — See My Comment in the August 22, 2020 post on Dr. Smith's ECG Blog.
  • Diagnosis of an OMI from the initial ECG — Serial tracings with spontaneous reperfusion — then reocclusion! — See My Comment at the bottom of the page in the October 14, 2020 post on Dr. Smith's ECG Blog.
  • And for more on the Mirror Test — See My Comment at the bottom of the page in the September 21, 2020 post and, in the February 16, 2019 post on Dr. Smith's ECG Blog.


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