Is this a STEMI?!

A 73 years old male presented to ED with a few hours of chest pain that sounded cardiac in origin.

He was hemodynamically stable.

There were no old ECGs available in the records for comparison.

This was his ECG on the day,

Does this case fulfill the STEMI definition?

Will you activate Primary PCI for this patient?

Discussion:

This was a nice case that I am going to use to cover some basics for the beginners, to discuss some updates & to get the opinion from the advanced ECG interpreters from you guys about some stuff, so let's go.

Let's start with the criteria for activating primary PCI,

According to the latest version of the Advanced Life Support (ALS) manual 2021:

• ST elevation of 2 mm or more, in at least two contiguous leads, in the chest leads (V1-6), or

• ST elevation of 1 mm or more, in at least two contiguous leads, in the limb leads (I, II, III, aVL, aVF) in the presence of cardiac chest pain.

BUT,

According to the American College of Cardiology Foundation/AHA 2013 guidelines (still in use till now), they defined STEMI as:

• ST elevation of 1 mm or more, in at least two contiguous leads (except V2-V3), in the absence of LBBB or Left Ventricular Hypertrophy (LVH).

• Regarding ST elevation in V2-V3: - In males (<40 y.), it is 2.5 mm or more. - In males (>40 y.), it is 2 mm or more. - In females, 1.5 mm or more, regardless of their age.

The European Society of Cardiology (ESC) guidelines in 2017 (till now) & the 4th Universal Definition for Myocardial Infarction document follow the same American definition.

So, it is 1 mm anywhere except V2-3.

Let's start analyzing the ECG,

There is some ST elevation in our case in the inferior leads (II, III, aVF), but:

• Is it high enough to activate PPCI/bypass the local hospital for the paramedics to the nearest PCI center?

• Is it fulfilling the definition of STEMI?

Let's make things bigger,

"This lead II, < 1 mm of ST elevation"

"Lead III, about 1 mm of ST elevation, maybe less"

"Lead aVF, < 1 mm of ST elevation"

So far, the ECG doesn't fulfill the STEMI definition in any published guidelines.

How about the possibility of Posterior wall STEMI here?

I am sure that some of you must have suspected posterior wall involvement. The reason behind this is that they correctly noticed that we have the triad of posterior wall STEMI in V1-2 which is:

1) ST depression (early).

2) Upright T (early).

3) Tall R wave in V1-3 relative to the S wave (late).

Because I had the same concerns when I saw this patient, I asked for posterior leads ECG, & this is what we got.

When it comes to posterior leads, you only need 0.5 mm or more of ST elevation to activate PCI.

In this case, I could convince myself that there is some ST elevation in V8-9 (mainly V9), but to be honest, it is NOT > 0.5 mm.

So according to the ALS recommendations, the European guidelines, & the American guidelines, this patient does NOT fulfill the criteria to activate the Cath Lab.

BUT,

When it comes to interpreting ST elevation, I personally think that it should NOT be done in mm.

• The reason behind this is that the ST segment is part of the whole gain/voltage of the ECG, so if you have a high-voltage ECG, everything will be bigger/higher/more obvious.

• If you have a low-voltage ECG, any tiny ST change could be a considerable proportion of the complex height.

This is something that Dr. Stephen Smith talked about many times before, but I have never seen it written or considered clearly in any guidelines I came across (please correct me if I am wrong).

If you apply this to our ECG, you will find that although the ST elevation is not high enough per the guidelines to activate PCI, it is actually a significant proportion of the complex height (about 40-50 %) in some leads.

So, based on the above, the decision for the case was to activate PPCI.

While the patient was on the way to CCU, the Troponin level came back & it was >23000 (our normal is <20).

The Outcome:

• The PPCI showed a complete occlusion of the right coronary artery (RCA) & the patient had successful stenting with a good outcome.

The Learning Points:

1. Criteria to activate PCI varies from one place to another, so what you think is NOT a STEMI in your country may be a STEMI in a different country.

2. Don't interpret the ST elevation in mm when it comes to STEMI, but always correlate the ST elevation to the complex height to get a better interpretation.

3. Be very careful with any minimal ST elevation in a low-voltage ECG.

Thank you.