So, it turns out that the - by convention over the years, the EKG has come to have 12 different leads.
That is 12 different points that are looking at the wave of depolarization going down through the heart.
And the earliest ones from Einthoven were so-called leads I, II and III.
So, these leads are all designated by the points on a compass, 0 to 360 degrees.
Lead I is over here and it's looking in at the heart from the left point - like the left arm in.
And that is designated as zero degree. Lead II is looking from here; that's +60 degrees.
And lead III is looking from here; that's +120 degrees.
Well over the years, there have been additional leads added, and that these are the so-called augmented leads.
Leads aVR, aVL and aVF. Lead aVF is looking from straight down below; that's +90 degrees.
aVL is looking from -30; that's up here.
And aVR is looking from +210 from right over here on the right arm.
These are all looking in a frontal plane just as if we were a flat plane of - that the body was standing in.
So here we see again the leads I said before, the Einthoven leads.
Lead I coming in from the left arm; that's zero degree. Lead II, +60 degrees coming from here.
And lead III, 120 degrees plus.
We also have leads that are cutting the heart right down in a section just as if it were right through the body like this.
Those leads are placed on the chest out here.
Here's lead I, lead II, III and IV starting at the right sternal border and working around to the axilla.
And they give you views of the depolarization wave in a plane
and that's V1, 2, 3, 4, 5 and 6.
And all of these leads, well, the ones we said before, lead I, II and III, aVR, aVL and aVF, V1, 2, 3, 4, 5 and 6
are all printed out on a piece of paper or appear on a computer screen for interpretation.