ECG Blog #325 — A 50s Woman with Chest Pain

HOW would you interpret the ECG in Figure-1 — IF told that this middle-aged woman was having chest discomfort?

• Should you activate the cath lab?

Figure-1: ECG obtained from a middle-aged woman with chest discomfort.

MY Thoughts on the ECG in Figure-1:

The rhythm is sinus at ~90/minute. All intervals (PR, QRS, QTc) and the frontal plane axis are normal. There is no chamber enlargement. 

Regarding Q-R-S-T Changes:

• There are no Q waves.
• R wave progression is normal. Transition (where the R wave becomes taller than the S wave is deep) — occurs normally between leads V3-to-V4. 

Regarding ST-T Wave Changes:

There is subtle-but-real ST elevation in lead aVL. The reason this is difficult to recognize — is that QRS amplitude in lead aVL is tiny. But the shape of the ST segment is unmistakeably coved and elevated above the baseline (Figure-2).

• The other lead showing ST elevation in Figure-1 is lead aVR.
• Otherwise — there is subtle-but-real ST depression in no less than 8/12 leads (ie, leads I,II,III,aVF; and in V3-thru-V6). 
• The amount of ST depression appears to be greatest in the inferior leads (II,III,aVF) — which clearly show straightening of the ST segment, as well as depression.
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• NOTE: Although there is no ST elevation in lead V2 — there is normally slight ST elevation in this lead. Therefore — the fact that the J-point is not at all elevated in lead V2 may indicate that there has been some depression from the usually slightly elevated ST-T wave baseline.

Figure-2: Magnified view of lead aVL from ECG #1 — showing that the ST segment is elevated in this lead.

Putting It All Together:

I've previously reviewed optimal use of lead aVL for predicting the "culprit" artery when there is ST elevation in this lead (See ECG Blog #324).

• When ST elevation is isolated to lead aVL — acute LCx (Left Circumflex) occlusion becomes a prime suspect as the "culprit" artery (especially involving occlusion of the 1st obtuse marginal branch).
• Alternatively — this could represent acute occlusion of the 1st or 2nd Diagonal, although this would seem less likely given the lack of ST elevation in lead V2. That said — the patient in ECG Blog #324 had ST elevation isolated to lead aVL (without any ST elevation in lead V2) — so exceptions do exist.
• Acute occlusion of the LAD would not be expected from seeing the ECG in Figure-1 — because there is no ST elevation in any of the chest leads.
• OR — "something else" may be going on (ie, prior infarction, an anatomic variant, an unusual pattern of collateral circulation).

What About the ST Depression in 8/12 Leads?

Recognition of the ECG pattern in which there is diffuse ST segment depression (usually present in at least 7-8 leads) + ST elevation in lead aVR (and sometimes in lead V1) — should immediately suggest 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 some other cause (ie, sustained tachyarrhythmia; cardiac arrest; shock/profound hypotension; GI bleeding; anemia; "sick patient", etc.).
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• To Emphasize: This pattern of diffuse subendocardial ischemia does not suggest acute coronary occlusion (ie, it is not the pattern of an acute MI) — but rather ischemia due to the above differential diagnosis!

BOTTOM Line: The history we were given — is that this middle-aged woman was having chest discomfort in association with the ECG shown in Figure-1. While possible that the subtle ST elevation isolated to lead aVL might represent acute occlusion of the LCx — this initial ECG is not definitive.

• What is definite — is that in this middle-aged patient with new chest pain, the presence of ST segment straightening, with at least some ST depression in 8/12 leads + ST elevation in lead aVR — should be interpreted as subendocardial ischemia until proven otherwise.
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• Additional investigation is indicated in today's patient to rule out an acute cardiac event (ie, repeat ECGs, serial troponins, Echo during chest pain — looking for a localized wall motion abnormality).
• Even if troponins are negative and no frank criteria for a STEMI are seen on follow-up ECGs — IF chest pain persists — then cardiac cath would be indicated to clarify the anatomy (See ECG Blog #193 — regarding the importance of recognizing OMI when STEMI criteria are lacking on ECG).

CASE Follow-Up:

Today's tracing was sent to me. I subsequently learned additional details about this case:

• The patient was a previously healthy, middle-aged woman without significant cardiac risk factors. She was initially seen in the ED for exertional chest pain and dyspnea that occurred several months prior to the ECG shown in Figure-1. Evaluation in the ED revealed ECGs similar to today's tracing — with normal serial troponins and no wall motion abnormality on Echo. No cardiac cath was recommended at that time.
• The patient overall did well for a period of several months — but then had another episode of exertional chest pain and dyspnea. Once again — troponin was negative and Echo showed no wall motion abnormality. The patient's symptoms resolved — and the ECG shown in Figure-1 was obtained at that time. Because of the recurrence of symptoms, and the diffuse ST depression on ECG — the decision was made to perform cardiac catheterization to clarify the anatomy. 
• The result of cardiac cath is shown in Figure-3.

QUESTION:

• Can you explain the cardiac cath findings shown in Figure-3 — on the basis of this patient's history and the ECG in Figure-1?

Figure-3: Cardiac cath films on today's patient — showing a high-grade stenosis of the mid-RCA (Right Coronary Artery). There was no significant disease elsewhere. Right Panel: PCI (Percutaneous Coronary Intervention) successfully restored flow.

MY Thoughts on this CASE:

I did not expect to see single-vessel disease in the RCA. This would not be expected to produce the subtle ST elevation isolated to lead aVL. When diffuse ST depression is the result of ischemia — it usually is indication of either multi-vessel disease — or LMain or a proximal LAD lesion.

• Troponins were negative — and Echo failed to reveal a localized wall motion abnormality on the 2 occasions that the patient was evaluated.
• Perhaps the patient had an inferior MI in the past? (ie, that spontaneously reperfused, but retained the high-grade mid-RCA stenosis that was seen on cath?).
• OR — Perhaps the high-grade mid-RCA lesion reduced coronary flow enough to produce the exertional angina episodes — but the Echo studies was not obtained during chest pain (ie, Echo is only valid for ruling out an acute cardiac event IF there is no wall motion abnormality and the Echo is obtained during an episode of chest pain).
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• BOTTOM Line: Although I cannot fully explain the cath results of today's patient in light of the history and ECG findings — the correct decision was made. This patient had exertional chest pain with an abnormal ECG that strongly suggested coronary disease. When troponins and Echo studies were unrevealing — cardiac cath was needed to define the anatomy.

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Acknowledgment: My appreciation to Nelson Nersisyan (from Yerevan, Armenia) 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 #320 — Reviews the typical ECG picture for recognizing the 1st or 2nd Diagonal as the "culprit" artery (ie, the "South African Flag" Sign).
• ECG Blog #324 — for another example of isolated ST elevation in lead aVL (here due to acute OMI of the 1st Diagonal).
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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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• ECG Blog #228 — Reviews the concept of "Silent" MI (including an Audio Pearl on this topic).
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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 reflrecting "Reperfusion" T-waves).
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• ECG Blog #258 — How to "Date" an Infarction based on the initial ECG.