A Male in his 50's with epigastric pain

This was sent by a recent residency graduate who works at a hospital without a cath lab.  As you might imagine, our graduates have learned to scrutinize ECGs for subtle findings:

This middle-aged male with a history of smoking and alcohol use who had not had medical contact in many years presented with sharp, severe, "indigestion" in his epigastrium.  Medics gave him nitro and aspirin without improvement.  He received more nitro and also a "GI cocktail" in the ED without improvement.

Here is his initial ECG:

There is subtle scooped ST depression in III and aVF, and subtle ST elevation in aVL  (and also I).  The T-wave in aVL is very large compared to the QRS.  There is also a "down-up" (reverse biphasic) T-wave in V2.  This finding is very suspicious for posterior MI.
Since lateral and posterior MI are in one vascular territory (the circumflex), these findings are highly suspicious for circumflex occlusion.

Remember that circumflex occlusion results in diagnostic ST elevation (1 mm in two consecutive leads) in only about 50% of cases.  The lateral wall is often referred to as being "electrocardiographicaly silent".

Part of the reason for this is that the QRS axis is often perpendicular to lead aVL, so there is often very little QRS voltage in aVL: when there is low QRS voltage, there is also low T-wave voltage.  So one must rely an subtle findings that do not reach 1 mm if one is to make the diagnosis.

Often the findings of ST elevation in aVL are best seen in the reciprocal ST depression in inferior leads.

Here is another case for contrast, in which ST elevation in aVL with reciprocal ST depression in lead III is a false positive:

 

http://hqmeded-ecg.blogspot.com/2011/12/subtle-lateral-st-elevation-false.html

This was a false positive cath lab activation.
Here there is a lot of voltage in aVL, so you can't blame subtle ST elevation on lack of QRS voltage. 

Case continued:

The physician was worried about all these findings but was reluctant to activate.  The first troponin I returned at 0.031 ng/mL (less than 99% cutoff of 0.32).

At one hour, with the patient still in pain, he repeated the ECG:

There are some subtle changes: mostly a more upright T-wave in III and V2

The physician started a nitro drip and heparin and consulted a cardiologist at a referral institution.

The patient's pain increased while waiting for transport and another ECG was recorded:

No significant change

Just after leaving, the second troponin I returned at 0.90 ng/mL (positive).  The physician called the referral hospital to recommend immediate cath given a now objective diagnosis of NonSTEMI and with pain refractory to medical therapy.

On arrival, he did not go immediately to the cath lab.

Later that night he did go.  The circumstances surrounding that delayed decision are uncertain.

He had a 100% mid circumflex occlusion with otherwise clean coronaries.  It was stented.

I do not have the peak troponin or echo results.

Learning points:

1. Many occlusions do not reach 1 mm of ST Elevation.  These NonSTEMIs with occlusion can be recognized and need immediate cath lab activation.

2. The ACC/AHA recommends immediate cath for patients with ACS who have uncontrolled symptoms.