Saturday, October 21, 2023

ECG Blog #400 — Is this a NSTEMI?

The ECG in Figure-1 is from an older man with known coronary disease — who presents to the ED (Emergency Department) with new CP (Chest Pain) over the past several days. Troponin is pending.

  • In view of this history — How would you interpret the ECG in Figure-1?
  • Should the cath lab be activated?

Figure-1: The initial ECG in today's case.

MY Thoughts on the ECG in Figure-1:
Unfortunately — there is significant baseline artifact in today’s initial ECG (especially in the limb leads). That said — this artifact does not prevent accurate assessment because despite the thick, limb lead baseline undulations — overall QRST wave morphology remains consistent throughout the tracing.
  • The rhythm is sinus at ~75/minute. Intervals (PR, QRS, QTc) and the frontal plane axis are normal (about 0 degrees, given the isoelectric QRS in lead aVF). There is no chamber enlargement.

  • Regarding Q-R-S-T Wave Changes: There are no Q waves — and R wave progression is normal (with appropriate R wave amplitude in the anterior leads — and appropriate transition, in that the R wave becomes taller than the S wave is deep by lead V4).

Assessment of ST-T Waves in Figure-1:

In a patient with new CP — this is an extremely worrisome ECG!

  • There is J-point ST depression — with sharply angled downsloping ST segments in multiple leads. These depressed ST segments end with terminal T wave positivity in leads II,aVF; and in leads V2-thru-V6.

  • There is ST elevation in lead aVR > V1 (dotted RED lines in leads in Figure-2). The ST segment is flat in lead III.

  • IMPRESSION: Even without the benefit of a prior ECG for comparison in this patient with known coronary disease — the above noted ST-T wave changes in Figure-2 look acute. In this patient with new CP — the cath lab should be activated!

PEARL #1: Although seeing an elevated Troponin would provide additional support for immediate cardiac catheterization — the clinical reality is that the initial Troponin reading will not always be elevated in patients with acute coronary occlusion (See March 24, 2023 post in Dr. Smith's ECG Blog).

  • Since the initial Troponin will not always be elevated in patients with acute OMI ( = acute Occlusion-based MI) — an initial normal high-sensitivity Troponin should not be used to rule out acute OMI in patients with new CP and an abnormal ECG
  • Therefore — waiting until Troponin becomes elevated wastes precious time (and risks loss of valuable myocardium). Given the history in today's case and the ECG shown in Figure-2 — The cath lab should be immediately activated!

Figure-2: I've labeled some findings from Figure-1.

PEARL #2: As noted above — ECG #1 is remarkable for the presence of diffuse ST depression (in more than 7 leads!) — with ST elevation in lead aVR (as well as in lead V1). This ECG pattern suggests Diffuse Subendocardial Ischemia (DSI) — and should immediately prompt the following differential Diagnosis:
  • Severe Coronary Disease (due to LMain, proximal LAD, and/or severe 2- or 3-vessel disease) — which in the right clinical context may indicate ACS (Acute Coronary Syndrome).
  • Subendocardial Ischemia from another Cause (ie, sustained tachyarrhythmia; cardiac arrest; shock or profound hypotension; GI bleeding; anemia; "sick patient", etc.).

To EMPHASIZE: This pattern of diffuse Subendocardial Ischemia does not suggest acute coronary occlusion (ie, it is not the pattern of an acute MI). Instead — it suggests ischemia due to the above differential diagnosis!
  • That said, in today's patient, who presents with new CP and the ECG shown in Figure-2 — severe coronary disease with potential need for acute reperfusion should be assumed until proven otherwise.

PEARL #3: In today's initial ECG — Did YOU notice the negative U waves in leads V3 and V4? (BLUE arrows in Figure-2)
  • Having looked for negative U waves in patients with chest pain over a period of decades — I'll emphasize that this is not a common finding. That said, when you do see inverted U waves (as we do in ECG #1) — this is a significant marker of severe ischemia (Duque-Gonzálex et al — Cardiovascular Metal Sci 32(4), 2021).

Today's CASE Continues:
The worrisome findings in ECG #1 were recognized.
  • The initial Troponin came back significantly elevated. However while waiting for this initial Troponin value to come back — the patient reported that his CP had greatly decreased, and was almost gone. A repeat ECG (shown in Figure-3) was obtained at this time.

  • Based on near resolution of the patient's CP and the improvement on the repeat ECG (as seen in Figure-3— the diagnosis of NSTEMI (Non-ST-Elevation MI) was made. The call for immediate cath lab activation was cancelled.

  • Do YOU agree with the above management decisions?
  • Why or why not?

Figure-3: Comparison of the repeat and initial ECGs in today's case.

MY Thoughts on Seeing the Repeat ECG:
Lead-to-lead comparison in Figure-3 of the initial ECG in today's case — with the repeat ECG (done after the patient's CP had almost resolved) — shows marked improvement.
  • ST-T waves in ECG #2 are now uniformly flat — with virtually no ST elevation or depression.

  • IMPRESSION: The fact that the patient's CP has virtually resolved in association with the ECG "improvements" shown in Figure-3 — does not mean that this was a "NSTEMI". Instead, this change in ECG appearance (in this patient who presented with new CP that has now almost completely resolved) — is indication of "dynamic" ST-T wave changes!

When the 
ECG changes evolve in a way that corresponds to the coming and going of chest pain symptoms — this is important information. It tells us there is an active, ongoing process — and that prompt cath with acute reperfusion is likely to be needed regardless of whether or not the millimeter-definition of a STEMI has been satisfied.
  • The problem is — that the "culprit" artery may spontaneously open and close more than once during its process of arriving at a final result — so that even if ST elevation resolves in association with resolution of chest pain — this spontaneous reopening of the vessel, may just-as-easily be followed by spontaneous closure again — and this time, perhaps without spontaneous reopening.
  • It is this active evolution of ST-T wave changes that may occur with the coming and going of symptoms that we define as "dynamic" ECG changes. ST segments elevate with the onset of chest pain (signaling acute coronary occlusion) — and ST segments return toward their baseline, often followed by "reperfusion" changes of T wave inversion that signal reopening of the "culprit" vessel. The importance of recognizing these "dynamic" ECG changes — is that this indicates an unstable situation at risk of evolving further to permanent coronary occlusion.

  • Today's case differs from the above description — in that other than reciprocal leads aVR and V1 — there was no ST elevation on the initial ECG. This is not to say that there never was a period of ST elevation — but rather that no ST elevation was captured on the one ECG that was recorded during the time that the patient had CP.
  • That said, today's patient with known coronary disease — presented with new CP and a worrisome ECG picture of diffuse subendocardial ischemia — with "dynamic" ST-T wave changes in association with relief of CP. 

  • BOTTOM Line: Because the situation described above in today's case is clearly unstable — prompt cardiac cath was immediately indicated (and given the history — prompt cath was indicated as soon as the initial ECG was recorded). Given this situation — the anatomy needs to be defined to determine if acute reperfusion with PCI will be needed to prevent imminent coronary occlusion. 

  • Unfortunately, when cardiac cath is only performed days later — OMI confirmation is not always possible (as was the case for today's patient — such that the "final diagnosis" of NSTEMI is questionable, as is probably the case for many patients said to have had "NSTEMI" ...)


Acknowledgment: My appreciation to 張三毛 = JJ (from Taiwan) 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 #185 — Reviews the Ps, Qs, 3R Approach to Rhythm Interpretation.

  • ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation. 
  • ECG Blog #183 — Reviews the concept of deWinter T-Waves (with reproduction of the illustrative Figure from the original deWinter NEJM manuscript). 
  • ECG Blog #222 — Reviews the concept of Dynamic ST-T wave changes, in the context of a detailed clinical case. 
  • ECG Blog #260 — Reviews another case that illustrates the concept of "dynamic" ST-T wave changes.

  • ECG Blog #218 — Reviews HOW to define a T wave as being Hyperacute? 
  • ECG Blog #230 — Reviews HOW to compare Serial ECGs (ie, "Are you comparing Apples with Apples or Oranges?"). 

  • ECG Blog #193 — Reviews the concept of why the term “OMI” ( = Occlusion-based MI) should replace the more familiar term STEMI — and — reviews the basics on how to predict the "culpritartery.

  • ECG Blog #194 — Reviews how to tell IF the “culprit” (ie, acutely occluded) artery has reperfused using clinical and ECG data.

  • ECG Blog #115 — Shows an example of how drastically the ECG may change in as little as 8 minutes.

  • The January 9, 2019 post in Dr. Smith's ECG Blog (Please scroll down to the bottom of the page to see My Comment). This case is remarkable for the dynamic ST-T wave changes that are seen. It's helpful to appreciate: i) That acute ischemia/infarction is not the only potential cause of such changes (cardiac cath was normal); ii) That changes in heart rate, frontal plane axis and/or patient positioning can not always explain such changes; andiii) That entities such as repolariztion variants, LVH and/or acute myopericarditis may all contribute on occasion to produce an evolution of challenging dynamic ST-T wave changes on serial ECGs.

  • The August 22, 2020 post in Dr. Smith's ECG Blog — which illustrates another case of dynamic ST-T wave changes that resulted from a repolarization variant

  • The July 31, 2018 post in Dr. Smith's ECG Blog (Please scroll down to the bottom of the page to see My Comment). This case provides an excellent example of dynamic ST-T wave changes on serial tracings (that I illustrate in My Comment) in a patient with an ongoing acutely evolving infarction.


ADDENDUM (10/21/2023):

ECG Media PEARL #39a (4:50 minutes Audio) — Reviews the concept of Dynamic ST-T Wave Changes (and how this ECG finding can assist in determining if acute cardiac cath is indicated).

ECG Media PEARL #46a (6:35 minutes Audio) — Reviews HOW to compare Serial ECGs (ie, Are you comparing "Apples with Apples" — or — with Oranges?).


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