<Dd> V W = 1 3 (R A + L A + L L) (\ displaystyle V_ (W) = (\ frac (1) (3)) (RA + LA + LL)) </Dd> <P> In a 12 - lead ECG, all leads except the limb leads are unipolar (aVR, aVL, aVF, V, V, V, V, V, and V). The measurement of a voltage requires two contacts and so, electrically, the unipolar leads are measured from the common lead (negative) and the unipolar lead (positive). This averaging for the common lead and the abstract unipolar lead concept makes for a more challenging understanding and is complicated by sloppy usage of "lead" and "electrode". </P> <P> Leads I, II and III are called the limb leads . The electrodes that form these signals are located on the limbs--one on each arm and one on the left leg . The limb leads form the points of what is known as Einthoven's triangle . </P> <Ul> <Li> Lead I is the voltage between the (positive) left arm (LA) electrode and right arm (RA) electrode: </Li> </Ul>

Where are leads 1 2 and 3 placed