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The S wave
The S wave represents the final phase of ventricular depolarisation.
It is defined as the first negative deflection after the R wave.
The reason for this is fairly simple.
Refer to the below image:
Due to the way the propagation wave works, it goes down the interventricular septum to start with, but then works its way back up the ventricle walls.
Because I am a simple EM doctor, i have therefore also grossly oversimplified the above. For example, the heart is a 3d object yet i have forced it to be a 2d one for explanations sake.
With this hopefully obvious caveat in mind, the reader can then see, if they follow the analogy of the anchor tips being the S wave direction, why this is in the opposite direction to the R wave.
One may wonder why we do not refer to "S wave progression", given the above.
The reason is that they are two sides of the same coin - for each lead, the S wave will be the mirror image of the underlying vector.
Therefore, if we take note of and acknowledge the R wave and all its glory, we will be commenting on the S wave by default.
This is similar to how when I apologise to my wife, I don't need to specify the how or why, because it goes unsaid and is irrelevant. It is inevitably related, and intricately linked, to the chosen subject matter and therefore addressing the subject matter alone will be sufficient to address the summation of issues.
Also, she knows how to shoot a gun.
I promise the two subjects are not related.
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