Cardiology Teaching Package
A Beginners Guide to Normal Heart Function, Sinus Rhythm & Common Cardiac Arrhythmias
Unipolar Leads
But, wait a minute. That gives us nine wires and it is a 12-lead ECG. Where are the other 3?
Well, so far we have nine wires. They all look directly at the heart with tunnel vision. They only give information based on what is immediately in front of them. These nine wires are known as "unipolar leads".
The three active peripheral leads are AVr, AVL, and AVf.
The "AV" stands for "Augmented Vector". The last letter refers to position, which are as follows:
| Label | Meaning of label | Position of lead on body |
|---|---|---|
| AVr | Augmented vector right | Right wrist |
| AVL | Augmented vector left | Left wrist |
| AVf | Augmented vector foot | Left foot |
These 3 leads create a triangle with the heart in the middle, as below. The lines into the centre indicate the line of sight of these leads.
Image: Line of site of the unipolar leads
