Sunday, March 15, 2015

Chest Pain: What do you see on the ECG?

I saw this ECG, knowing only that there was a chief complaint of chest pain:
What do you see?

I thought: "This looks like it could be an acute inferior MI."   This is because of the extremely subtle ST elevation in lead III, Q-wave in lead III, biphasic T-wave in aVF, and reciprocal subtle ST depression in aVL.

I went to find the providers because I thought this ECG is so subtle that it could easily be missed by anyone.

Here was the history:

A male in his 40s was eating a heavy meal when he developed "sharp" midsternal non-radiating chest pain of 10/10 severity.  Then he vomited and his pain decreased to 1/10.   About 20 hours later, his pain remained 1/10 and he presented to the ED because a friend suggested he should.  Exam was normal.

His pain resolved with both a nitro and an antacid.

Indeed, the ECG had been read as "no evidence of ischemia" by several providers.

After pain resolution, another ECG was recorded:
ST elevation and Depression is almost completely resolved. The probability of MI is increased.

The interpretation remained "no evidence of ischemia."

His initial troponin returned elevated at 0.746 ng/mL (99% cutoff, 0.030).  

He was appropriately treated for NonSTEMI.  He remained pain free, so no emergent cath was necessary.  10 hours later, this ECG was recorded:
Significant evolution of deeper T-wave inversion is present in inferior leads, diagnostic of inferior NonSTEMI.

The angiogram showed a 95% mid-RCA lesion that was stented.


There are many NonSTEMIs that truly have normal or non-diagnostic ECGs, but there are also many that are read as negative when they are at least highly suggestive of ischemia.

In this case, the initial troponin was positive and the diagnosis therefore should not be in doubt.  

Which begs the question: Would more accurate interpretation of the ECG add any value?

I believe the answer is yes.

1. If recognized, it can heighten your suspicion of NonSTEMI and help prevent a missed MI.  The troponin might be negative (not in this case) and you might send such a patient home.  It has happened!  And unstable angina still exists, despite rumors of its demise.

2. If immediately recognized, it can speed the evaluation and disposition.  This patient, even if he had had a negative initial troponin, should not be admitted to "observation," but rather should be an inpatient.  You can order that inpatient bed right away.

3. Immediate recognition facilitates more rapid use of nitro, a P2Y12 inhibitor, and use of anti-thrombotics such as heparin.

4. In a patient with ongoing, refractory chest pain, such an ECG tells you that it is most likely ACS and puts you on notice that more rapid angiography may be necessary if symptoms cannot be resolved medically.

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