Limb leads

Definition

The six leads that view the heart in the frontal (vertical) plane: the three standard limb leads of Einthoven (I, II and III), each recording the potential difference between a pair of limb electrodes, and the three augmented limb leads (aVR, aVL and aVF). All six come from the same right-arm, left-arm and left-leg electrodes, so together they contain only two independent signals; they are displayed on the hexaxial diagram used to determine the cardiac axis. The right leg electrode acts as an electronic reference that improves noise rejection and is not part of any lead.