<P> A "lead" is not the same as an "electrode". Whereas an electrode is a conductive pad in contact with the body that makes an electrical circuit with the electrocardiograph, a lead is a connector to an electrode . Since leads can share the same electrode, a standard 12 - lead EKG happens to need only 10 electrodes (as listed in the table below). </P> <P> A lead is slightly more abstract and is the source of measurement of a vector . For the limb leads, they are "bipolar" and are the comparison between two electrodes . For the precordial leads, they are "unipolar" and compared to a common lead (commonly the Wilson's central terminal), as described below . </P> <P> Leads are broken down into three sets: limb; augmented limb; and precordial . The 12 - lead EKG has a total of three limb leads and three augmented limb leads arranged like spokes of a wheel in the coronal plane (vertical) and six precordial leads that lie on the perpendicular transverse plane (horizontal). </P> <P> In medical settings, the term leads is also sometimes used to refer to the electrodes themselves, although this is not technically a correct usage of the term, which complicates the understanding of difference between the two . </P>

The leads that make up a 12-lead ecg consist of
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