A 54 yo male with sudden chest pain. Computer says normal. Paramedic disagrees.

Announcement!

There is now an Android app for the 3- and 4-variable formulas. It is of course free (#FOAMed).  It was written by Yannick Schäfer (a medical student in France):
https://play.google.com/store/apps/details?id=com.SMITH490.ecg_smith

Remember there is also an iPhone app called "SubtleSTEMI"
https://itunes.apple.com/us/app/subtlestemi/id617146818?mt=8

Case

This was sent by a very astute paramedic.

A 54 year old male came to the door of the fire department because of sudden chest pain while working.  It was squeezing and substernal.

The medic recorded an immediate ECG:

What do you think?
There is ST elevation, but it looks exactly like normal ST elevation ("Early Repolarization"), right?
By the way, "Unconfirmed" means a human needs to overread it.

This medic wanted to be certain that this ST elevation with large T-waves was normal ST Elevation, and not a subtle LAD occlusion that only appears to be normal.

He recorded another 1 minute later:

Not much change.

The medic applied the LAD occlusion vs. early repol formula immediately.

1st ECG:
STE60V3 = 3.5
QTc = 390
QRSV2 = 19
RAV4 = 11

3-variable formula value = 23.61 (most accurate, but not most sensitive, cutpoint is 23.4)
4-variable formula value = 18.18 (most accurate, but not most sensitive, cutpoint is 18.2)

2nd ECG
STE60V3 = 3.5
QTc = 383
QRSV2 = 20.5
RAV4 = 10.5

3-variable formula value = 23.36 (lower)
4-variable formula value = 17.72 (lower)

The medic used the 3-variable formula and obtained values of 23.4 and 23.5 (positive)

He activated the cath lab from the field.

The cath team was ready when he arrived less than 5 minutes later.

Before going to cath, the patient had this ECG in the ED:

Not much change.
STE60V3 = 3.5
QTc = 450
QRSV2 = 19.5
RAV4 = 10
3-variable formula = 27.46 (very high)
4-variable formula = 21.49 (very high)

This last ECG obtains a much higher value because the computerized QTc measurement, at 450 ms, is much longer.  Even if we doubt the last QT measurement by the computer, and assume that it is much shorter, with a QTc a value of 400, both formula values remain very high.

The MDs in the department did not think it was an MI.

The patient went to cath within 5 minutes and had a 100% LAD thrombotic occlusion.

This was his ECG after stenting:

Now the EKG is normal (and the computer would agree!)
The ST elevation and tall T-waves are all resolved.
This would be how the patient's baseline ECG would have looked, if one had been available.

Outcome:
This reperfusion was so fast that the peak troponin was only 0.3 ng/mL.  There was no residual wall motion abnormality.  Symptom onset to balloon time was less than 30 minutes.

Learning Points
1. This shows how any individual patient's normal ST segments may have zero ST elevation.
2. Other individuals may have quite a bit of normal ST elevation.

Therefore, if there is any ST elevation, it is up to you (not the computer!) to determine if it is normal or ischemic.

The formulas are very helpful in this regard.

Again, the computer called the ECG "normal."  

I have argued that physicians should view these ECGs even if the computer interprets it as completely normal.  This is because the computer is so bad at finding subtle occlusions.  Physicians have argued that they don't have the time and that they will be no better at identifying these subtle cases than the computer will be.  

Well, a doctor might not see it, but a paramedic did.  Kudos!!

That is because the paramedic learned.  

I am sure that MDs can learn too!