By definition, an electrocardiographic lead is the measurement of the electrical potential difference between two points on the body— that is, between two electrodes. Therefore, from a physical standpoint, every lead is necessarily bipolar: an electric field cannot be measured using a single electrode.

In the so-called bipolar leads (true or classical ones, such as leads I, II, and III), both electrodes actively and equally contribute to the measurement of the signal. In contrast, in the