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The ST segment
The reader may be confused why I have inserted an image of a ̶w̶a̶n̶k̶e̶r̶t̶r̶o̶n̶ ̶3̶0̶0̶0̶ BMW, when this is an ECG teaching series.
The answer is pretty simple - they're pretty similar.
The ST segment is generally the loud and flashy part of the ECG which everyone get's fixated about.
It is unfortunately not a joke that a great deal of clinical ability when it comes to ECG interpretation is simply "Is it a STEMI?"
They are an absolute pain, and you cannot ignore them.
If you are unaware of their existance, that bodes ill for everyone involved.
It is rare that they are not brutally direct, and indeed they don't tend to give a damn about what else is doing on in your world that moment - they need priority, first and foremost.
They come in various shapes, sizes, ages, and have a habit of ruining your day at the worst possible moment.
The fact that you, the reader, have read this section and have no idea whether I'm referring to a BMW or a STEMI proves my point.
The ST segment
Physiologically, this is the period between ventricular depolarisation (the QRS complex) and ventricular repolarisation (the T wave)
It should therefore be isoelectric.
The term "isoelectric" is often bandied about like a football with very little understanding of what it actually means.
In a nutshell, to be isoelectric is to be where there is no electrical activity.
That means, by definition, it is the T-P segment.
Everything on an ECG is relative (depression, elevation) to this fixed mark.
Given this segment under normal circumstances should be isoelectric, in situations like the following:
We can calmly say that everything is working fine as far as the ST segment goes, and to therefore carry on. This would be filed under the category of "boring" in my world.
I dislike boring. I like things to be interesting. Which is why I signed up for EM - the best speciality in the world. It's the best, because there is precisely zero pressure. When you arrive on shift, it is a dumpster fire. When you leave, it is a dumpster fire. Everything you do can only be an improvement.
For those who prefer pictures, EM in the UK right now can be summarised as follows:
When it goes wrong
Given we now have our starting point, observe how there are distinct changes in the above ECG.
The ST segment, compared to the TP segment, is mis-behaving in all sorts of leads and demands immediate attention.
For brevity's sake, the author will not go into a multi-hour tirade into STEMI, NSTEMI/OMI here.
Instead, if the reader wishes to hear said multi-hour tirade, they may do so in Part 1 of my lecture series.
The J point
You will often find that when one refers to ST depression/elevation the term "J point" gets reference.
This is simply referencing the point between the QRS complex, and the ST segment.
The author will point out that the "J point" is like mandatory training. We know it exists, we know what it generally means, but we rarely pay it any heed. This is as demonstrated as follows.
Onto the T wave!
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