Saturday, February 24, 2024

ECG Blog #418 — A Single Lead Tells the Tale ...

The ECG in Figure-1 was obtained from a previously healthy man in his 40s — who presented to the ED (Emergency Department) with new-onset CP (Chest Pain) that awakened him from sleep.
  • ECG #1 was recorded ~90 minutes after the patient was awakened from sleep. He was still having CP

  • In view of this history — How would YOU interpret the ECG in Figure-1?
  • Does a single lead “tell the tale”?

Figure-1: The initial ECG in today's case. (To improve visualization — I've digitized the original ECG using PMcardio)

MY Thoughts on the ECG in Figure-1:
The important points about today’s history are: i) That the patient is a previously healthy man in his 40s; — ii) That the patient was awakened from sleep by new CP; — and, iii) That his CP was still ongoing 90 minutes after it began, at the time ECG #1 was recorded in the ED.
  • The ECG in Figure-1 shows normal sinus rhythm at ~75/minute — with normal intervals (PR-QRS-QTc) and axis — and no chamber enlargement.
Regarding Q-R-S-T Changes:
  • Q waves: There are no Q waves. There is a small-but-present initial positive deflection ( = r wave) in lead III (I don't count as "Q waves" the initial negative deflections we see in leads aVR and V1 — since it is normal to see Q waves in these leads).
  • R wave progression: There are good-sized R waves beginning in lead V2 — albeit there is slight delay in transition (with the R wave becoming taller than the S wave is deep only between leads V4-to-V5).

What About ST-T Wave Changes?
As we assess today's initial ECG for ST-T wave changes — It is important to remember that this patient was previously healthy — and — he was awakened from sleep by CP that was still present 90 minutes later (ie, at the time this initial ECG was recorded!).
  • As a result — We need to consider this patient to be in a higher-risk group for having an acute event. This point emphasizes that the burden of proof falls on us as medical providers to prove that this patient is not having an acute event, rather than the other way around!

We Need to Remember the Following:
  • Even with an acute event — the initial ECG may not necessarily show remarkable changes — and/or — ECG changes may be present, but subtle (and sometimes only recognized when compared to a prior baseline ECG on the patient — or when compared with serial ECG changes over time)
  • PEARL #1: Even with an ongoing, extensive acute MI — the initial high-sensitivity troponin may sometimes be normal.

  • PEARL #2: It is important to note and correlate the presence and relative severity of symptoms with each serial ECG that is done. This is because the course of an acute OMI ( = an acute MI that results from acute coronary Occlusion) — is not always predictable. Instead, even before treatment — there may be spontaneous reopening of the "culprit" vessel — which often can be recognized by reduced CP that occurs in association with improved ECG changes.
  • Spontaneous reopening of the "culprit" vessel may result in "pseudo-normalization" of ECG changes (IF the ECG is recorded "between" the stage of acute ST elevation — and the later stage of coronary reperfusion as ST elevation evolves into ST depression and T wave inversion)

  • KEY Clinical Point: This "pseudo-normalization" stage still mandates prompt cath with PCI, because what spontaneously reopens — may just as easily reocclude at any point in time if not prevented by PCI.


With the above caveats in mind — Take Another LOOK at today's initial ECG in Figure-1:
  • Which single lead in ECG #1 tells the tale? 

ANSWER (shown below):
I highlight the answer to the above "Challenge Question" in Figure-2:

Figure-2: I highlight the KEY lead in today's initial ECG.

Regarding ST-T Wave Changes in Figure-2:
As per the title of today's ECG Blog — one KEY lead "tells the tale".
  • ST-T wave changes in the limb leads show nonspecific ST-T wave flattening — but nothing that looks acute.
  • I've highlighted within the RED rectangle in Figure-2 the single lead ( = lead V3) that in a patient with new severe CP is clearly abnormal. While a slightly elevated, gently upsloping ST segment is common and normal in leads V2,V3 — there is definite straightening of the ST segment in this lead on the initial ECG — and the amount of ST elevation (seen with respect to the dotted RED line in this V3 lead) is excessive. This represents a hyperacute ST-T wave in lead V3 until proven otherwise! 

PEARL #3: To emphasize that lead V3 is the KEY lead in today’s initial ECG — without which I would not have diagnosed acute OMI. But since we know (for the reasons stated above) that in a patient with new CP, that the ST-T wave in lead V3 is hyperacute — I also interpreted the 2 neighboring leads in Figure-2 ( = leads V2 and V4) as abnormal and consistent with acute LAD OMI until proven otherwise:
  • Lead V2 — The amount of ST elevation in lead V2 is not necessarily excessive, given how common slight ST elevation is normally seen in anterior leads V2,V3. But in the context of lead V3 definitely showing a hyperacute ST-T wave — I thought there was a bit more “straightening” of the initial part of the ST segment in lead V2 that I would normally expect (at least in the 1st complex in this lead).
  • Lead V4 — While not necessarily abnormal if looked at as an isolated finding — I thought the amount of ST elevation in neighboring lead V4 to be a bit more than is usually expected in this lead. And, at least for the middle complex in this lead — there seemed to be a bit more-than-expected ST segment straightening.

  • To EMPHASIZE: If not for lead V3 — I would not have interpreted leads V2 and V4 as necessarily abnormal. This is especially true in view of: i) The surprisingly good R wave progression that we see in ECG #1 — with an R wave of already 7-8 mm by lead V2 (whereas there is commonly “loss of R wave” in anterior leads with acute LAD OMI); and, ii) The complete lack of abnormality in the remaining chest leads ( = leads V1,V5,V6). It is lead V3 that "tells the tale"!

PEARL #4: As stated earlier — an initial ECG will not always be diagnostic. The KEY is to appreciate that in most patients — the process of an acutely evolving coronary occlusion is dynamic — sometimes showing dramatic changes in as short a period as between 5-10 minutes (See ECG Blog 115 for a case in which such dramatic ST-T wave changes occurred in just 8 minutes!).
  • The Take-Home Message from today's case is clear — IF you are at all uncertain about whether your patient with CP is or is not acutely evolving an OMI — Repeat the ECG soon and often — until you can confidently answer this question!

Today's CASE Continues: 
Given any uncertainty you might have as to whether today's patient was evolving an acute OMI — the initial ECG should have been repeated within 15-20 minutes.
  • The ECG was only repeated 80 minutes later. To facilitate comparison in Figure-3 — I have put these first 2 ECGs together. What do YOU see?

Figure-3: To facilitate comparison — I've put the first 2 tracings in today's case together. What has changed? (To improve visualization — I've digitized the original ECG using PMcardio).

Comparison between ECG #1 and ECG #2:
The BEST way to compare serial ECGs — is to put them side-by-side, as I have done in Figure-3.
  • Given our concern regarding lead V3 in ECG #1 — I began assessment of ECG #2 by looking at this lead, and at its neighboring leads.
  • Compared to ECG #1 — there is now unmistakeable straightening of the ST segment takeoff in lead V3 of ECG #2, with reduced T wave amplitude.
  • Lead V4 in ECG #2 — is now unmistakeably elevated (with straightened ST segment takeoff).
  • Each of the remaining chest leads also show differences. There is subtle-but-real ST elevation now in leads V1, V2 and V5 — and some ST depression in lead V6 than was not previously present. 

  • Limb lead changes in ECG #2 are subtle — but in the context of the above noted chest lead changes, I believe the slightly increased inferior lead T wave amplitude and ST-T wave flattening in lead aVL is real.

  • PEARL #5: Did YOU Notice the loss of R wave amplitude in ECG #2? There is now a QS pattern in lead V2, with noticeably reduced R wave amplitude in leads V2-thru-V5 compared to ECG #1. 

 If there was doubt about the diagnosis from ECG #1 — the repeat ECG in Figure-3 is now clearly diagnostic of acute LAD OMI because: i) Dynamic ST-T wave changes are seen in virtually all leads compared to the initial tracing — including progressive ST elevation in leads V2-thru-V5; and, ii) Loss of R wave amplitude in these chest leads.
  • The Important LESSON: Given the history of new-onset severe CP — acute LAD OMI can be diagnosed (or at least strongly suspected) from the initial ECG in today's case. But even if there was uncertainty about ECG #1 — definitive diagnosis could have been made much sooner by repeating this initial tracing within 10-15 minutes (instead of waiting 80 minutes).

CASE Conclusion: 
The diagnosis of acute LAD OMI was made once the repeat ECG in Figure-3 was obtained. Given unavailability of cardiac catheterization — Streptokinase was administered.
  • ECG #3 was recorded after completion of Streptokinase infusion — in association with clinical improvement. What do YOU see?

Figure-4: Comparison of ECG #2 — with ECG #3, recorded after completion of Streptokinase. (To improve visualization — I've digitized the original ECG using PMcardio).

Regarding the Post-Streptokinase ECG in Figure-3:
Streptokinase infusion was effective!
  • Other than slight residual ST elevation in leads V1,V2 — ST elevation in other chest leads has essentially resolved!
  • Although there has been loss of R wave amplitude compared to the initial ECG — there has been no further loss of R wave amplitude since ECG #2.
  • There is now terminal T wave inversion — that begins in lead V2, and extends through to lead V6. In association with clinical improvement of this patient — ECG #3 now shows reperfusion T waves consistent with effective thrombolytic infusion.

Acknowledgment: My appreciation to Kianseng Ng (from Malaysia) for the case and this tracing.

Related ECG Blog Posts to Today’s Case:

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

  • ECG Blog #193 — Reviews the basics for predicting the "culprit" artery (as well as reviewing why the term "STEMI" — should be replaced by "OMI" = Occlusion-based MI).

  • 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.

  • ECG Blog #294 — Reviews how to tell IF the "culprit" artery has reperfused.
  • 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 #400 — Reviews the concept of "dynamic" ST-T wave changes.

  • ECG Blog #337 — A "NSTEMI" that was really an ongoing OMI of uncertain duration (presenting with inferior lead reperfusion T waves).


  1. Thank you for your wonderfull blog. I have one question. Is it a T wave in v4 a little bit broad than normal.Thanks for your answer. I wish all the best.

    1. Thank you for your comment Marko! As I mention above in my discussion — lead V4 in does look abnormal. That said, the KEY point is that it is lead V3 that we KNOW is abnormal in a patient with new CP — and whereas by itself lead V4 might not catch attention — in the context of KNOWING that V3 is abnormal, we can better appreciate that the much more subtle findings in lead V4 are most probably part of the same process!