ECG Blog #317 — 80yo man-CP- The Culprit?

The ECG in Figure-1 — was obtained from an 80-year old man who presented to the ED (Emergency Department) with new-onset chest pain.

• How would YOU interpret the ECG in Figure-1?
• Is there a "culprit" artery?

Figure-1: The initial ECG obtained from an 80-year old man with new-onset chest pain.

MY Thoughts on the ECG in Figure-1:

Obviously — ECG #1 shows an acute STEMI, based the "eye-catching" ST elevation in leads V5,V6. That said — there are abnormal findings in virtually every lead! However, I thought the most interesting part of today’s case was contemplating the answer to my 2nd Question — namely, predicting the “culprit” artery.

• There is much baseline artifact in this initial ECG, especially in the limb leads. That said — we are still able to accurately interpret this tracing.
• The rhythm in ECG #1 looks to be a fairly regular sinus at ~85/minute. All intervals (PR, QRS, QTc) are normal.
• The frontal plane QRS axis is normal at +60 degrees.
• There is no chamber enlargement.

 

PEARL #1: Did YOU notice the Low Voltage in the limb leads? (ie, the QRS complex does not exceed 5 mm in any of the 6 limb leads).

• When contemplating the diagnosis of acute or recent infarction — it is important to remember that myocardial "stunning" from a large MI is one of the causes of acute low voltage (More on this subject in ECG Blog #262 and ECG Blog #272).

Regarding Q-R-S-T Changes:

• I'm uncertain if the small, fragmented QRS complex in lead aVL begins with a small q wave. I otherwise see no sign of Q waves in other leads.
• R wave progression is appropriate — with transition (where the R wave becomes taller than the S wave is deep) occurring normally between leads V2-to-V3. Of note — the R wave in lead V3 is surprisingly tall (ie, ~19 mm). This is relevant to today's case, but easy to overlook because of overlap with the very deep S wave in lead V2 (See RED and BLUE outlines of QRS complexes in these leads in Figure-2).

The most remarkable findings in ECG #1 relate to ST-T Wave Changes:

• As already mentioned — there is "eye-catching" coved ST elevation in lateral chest leads V5 and V6.
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• PEARL #2: There is also ST elevation in lead V4. While minimal in amount — we know this is real because: i) By the principle of "neighboring leads" — we know there is marked ST elevation in adacent lead V5, and the coved shape of the ST segment in lead V4 manifests similarity to that seen in lead V5; and, ii) There is ST depression in lead V3 that lies next to V4 — so even the small amount of J-point ST elevation seen in lead V4 is definitely real.
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• There is subtle-but-real ST elevation in 3 of the limb leads. This is perhaps best seen in lead I — but is also present in leads II and aVF (albeit not in leads III and aVL).
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• PEARL #3: Note how the presence of artifact complicates assessement of ST-T wave changes in the limb leads! For example — the shape of the ST-T wave changes from 1 beat-to-the-next for each of the 3 complexes in leads I,II,III and aVF. Some of these complexes clearly look more worrisome than others! When this common artifactual phenomenon occurs — I favor a "Gestalt" approach — in which you survey the "overall picture", realizing that our information is imperfect. In Figure-2 — my "Gestalt" is that there is subtle-but-real ST elevation in leads I, II and aVF.
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• Finally — there is marked ST depression in anterior leads V1,V2,V3. Note the shelf-like (flat) ST segment appearance in leads V2 and V3 — with terminal positivity in these leads! This appearance results in a positive “Mirror Test” — that in the context of the new chest pain experienced by the patient in today's case, is diagnostic of acute posterior MI (See Figure-2).

Figure-2: I've added the mirror-image of anterior leads V1,V2,V3 to Figure-1 — to illustrate how the initial ECG in today's case manifests a positive “Mirror Test”. As discussed in ECG Blog #193 (with many additional illustrative links to the Mirror Test provided below) — this test serves as my favorite visual aid to facilitate recognition of acute posterior MI. The mirror-image view of anterior leads provides insight to the perspective of what the posterior wall of the left ventricle sees. The shape of the ST depression seen in leads V1,V2,V3, when vertically flipped (as shown in the Mirror Test here to the right of ECG #1) — suggests deepening Q waves, a worrisome shape of ST elevation — and already deep T wave inversion in lead V2.

What Do YOU See in ECG-2?

Shortly after ECG #1 was recorded — the ECG was repeated with posterior leads (ie, leads V7,V8,V9) being substituted for leads V4,V5,V6 (See Figure-3).

QUESTIONS:

• Were posterior leads needed to make the diagnosis of acute posterior MI?
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• Extra Credit: What is the most useful finding in the repeat ECG that is shown in Figure-2?

Figure-3: Shortly after ECG #1 was recorded — a 2nd ECG was obtained with posterior leads (V7,V8,V9) being substituted for leads V4,V5,V6. Does this 2nd ECG help to clarify the clinical picture? If so — HOW specifically does it help?

PEARL #4: Posterior Leads Were Not Needed ...

In my experience over the years since 1983 (when I first published on the utility of the Mirror Test for recognizing acute posterior MI) — I have never seen an example of an ECG in which acute posterior MI diagnosed by posterior leads was not already evident in the standard 12 leads with use of the Mirror Test.

• QRST amplitudes with posterior leads are reduced compared to mirror-image anterior lead amplitudes — because assessment of electrical activity from posteriorly placed V7,V8,V9 electrodes has to traverse the thick back musculature before it can pick up the heart's electrical activity.
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• Isn't the mirror-image picture to the right of ECG #1 in Figure-2 more convincing than the lesser amount of ST deviation seen in leads V8 and V9 of Figure-3?
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• NOTE: I am not against those who prefer to obtain posterior leads because they feel this helps in their interpretation. I am simply saying that with minimal practice using the Mirror Test — that equal information is obtained faster without the need to apply additional leads. (Actually — more information is obtained — since there are times when the Mirror Test is positive despite negative posterior leads).

Take Another LOOK: How Does ECG #2 Help in Today's Case?

Unfortunately — the 2nd ECG in today's case substituted leads V7,V8,V9 for leads V4,V5,V6. I would have been more interested in seeing what progression there was in leads V4,V5,V6 from ECG #1 (instead of seeing leads V7,V8,V9 which do not provide new information).

• BUT — Knowing that ECG #2 was obtained shortly after ECG #1 is important — because there is now increased ST elevation in lead I — new (and marked) ST elevation in lead aVL — and new (and marked) reciprocal ST depression in each of the inferior leads.
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• Putting It All Together: Given the history of new chest pain in association with the sequential ECG changes seen in ECG #1 and ECG #2 — there is active evolution of a large acute postero-lateral STEMI. As discussed in ECG Blog #193 — this type of distribution strongly suggests a dominant LCx (Left Circumflex) as the "culprit" artery.

CASE Follow-Up:

Cardiac cath confirmed the above ECG impression — showing acute proximal LCx occlusion (as shown in Panel A of Figure-4). 

• Panel B in Figure-4 shows the result of successful PCI — reestablishing perfusion in the "culprit" vessel.

Figure-4: Cath images pre- and post successful PCI.

Final QUESTIONS:

• In light of ECGs #1 and #2 — How would YOU interpret ECG #3, obtained the day after hospital admission? (Figure-5).
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• CHALLENGE: HOW MANY relevant ECG changes can you identify in ECG #3?

Figure-5: Comparison of the 3 ECGs obtained in today's case. What changes do you see in ECG #3, obtained the next day?

Final Thoughts on the 3 Serial ECGs:

There are a number of interesting findings in ECG #3, obtained the next day. These changes are best assessed in the context of ECGs #1 and #2, that were both recorded prior to PCI (Figure-5):

• ECG #3 shows marked evolutionary changes of the extensive postero-lateral STEMI, that now shows reperfusion T waves in these lateral leads (ie, in leads I,aVL; and in V4,V5,V6).
• There has been marked loss of QRS amplitude in each of the limb leads (compared to the already reduced limb lead amplitudes evident in ECGs #1 and #2). This is consistent with apparent loss of significant myocardium from this extensive infarction.
• There is no longer any R wave at all in lead V6 of ECG #3! Assuming this is not the result of lead placement error (which is unlikely given similar T wave inversion in both leads V5,V6) — the loss of R wave in lead V6 is one more indication of the extensive myocardial damage.
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• The frontal plane axis has been displaced rightward — and is now clearly indeterminate (ie, predominantly negative in both leads I and aVF). Whether this reflects development of LAHB (Left Anterior HemiBlock), with predominant negativity of the QRS in all inferior leads — or simply profound loss of QRS amplitude from the large infarction is uncertain.
• NOTE: The fact that the P wave in lead I of ECG #3 is positive — tells us that the reason for predominant negativity of the QRS in lead I is not LA-RA lead reversal. Instead, it reflects loss of QRS amplitude from extensive infarction.
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• There is now a predominant R wave (R>S) in lead V1 — that was not present in ECG #1. This is consistent with evolution of posterior infarction.
• The anterior lead ST depression evident on the initial ECG — has been replaced by positive T waves in each of these anterior leads! Note in particular how tall the positive T wave is in lead V1 of ECG #3. These are reperfusion T waves in the posterior wall of the left ventricle (which produce the mirror-image opposite picture of the deep, symmetric T wave inversion seen in leads V4,V5,V6 that reflects lateral wall reperfusion). 

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Acknowledgment: My appreciation to 林柏志 (from Taiwan) for the case and this tracing.

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Related ECG Blog Posts to Today’s Case:

• ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation.
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• ECG Blog #193 — illustrates use of the Mirror Test to facilitate recognition of acute Posterior MI. This blog post reviews the basics for predicting the "Culprit" Artery.
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• ECG Blog #285 — for another example of acute Posterior MI (with positive Mirror Test).
• ECG Blog #246 — for another example of acute Posterior MI (with positive Mirror Test).
• ECG Blog #80 — reviews prediction of the "culprit" artery (and provides another case illustrating the Mirror Test for diagnosis of acute Posterior MI).
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• ECG Blog #184 — illustrates the "magical" mirror-image opposite relationship with acute ischemia between lead III and lead aVL (featured in Audio Pearl #2 in this blog post). 
• ECG Blog #167 — another case of the "magical" mirror-image opposite relationship between lead III and lead aVL that confirmed acute OMI.
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• The September 21, 2020 post in Dr. Smith's ECG Blog — My Comment (at the bottom of the page) emphasizes utility of the Mirror Test for diagnosis of acute Posterior MI.
• The February 16, 2019 post in Dr. Smith's ECG Blog — My Comment (at the bottom of the page) emphasizes utility of the Mirror Test for diagnosis of acute Posterior MI. 
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• ECG Blog #271 — Reviews determination of the ST segment baseline (with discussion of the entity of diffuse Subendocardial Ischemia).
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• ECG Blog #266 — Reviews distinction between Posterior MI vs deWinter T waves (with anterior terminal T wave positivity reflecting "Reperfusion" T-waves).
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• ECG Blog #258 — How to "Date" an Infarction based on the initial ECG.
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• ECG Blog #262 — Potential significance of Low Voltage with acute MI.
• ECG Blog #272 — Significance of Low Voltage with acute MI.