Electrocardiogram Augmented Limb Leads (Unipolar)
The three augmented unipolar leads, coupled with the three bipolar leads, constitute the six limb leads of the ECG. These leads record electrical activity along a single plane, termed the frontal plane relative to the heart. Using the axial reference system and these six leads, it is simple to define the direction of an electrical vector at any given instant in time. If a wave of depolarization is spreading from right-to-left along the 0° axis, then lead I will show the greatest positive amplitude. If the direction of the electrical vector for depolarization is directed downwards (+90°), then aVF will show the greatest positive deflection. If a wave of depolarization is moving from left-to-right at +150°, then aVL will show the greatest negative deflection according to the rules for ECG interpretation.
For a heart with a normal ECG and mean electrical axis of +60°, the augmented leads will appear as shown below: