Chest leads are unipolar leads. They are made up of an exploring electrode (either V1-V6 or more), which is positive and a negative electrode which is connected to an indifferent constant electrode at the Wilson Central terminal. The exploring electrode’s position is changed with V1, V2, etc placed at different places on the chest.
Chest leads pick up the electrical activity of the heart that is directed in a horizontal plane (also called transverse plane).