This term is associated with Electrocardiographic (ECG) recording.
The term “lead” relates to the point in space received in result of placing of electrodes in pre-defined points in the body around the heart.
The standard ECG includes 12 leads, i.e. 12 points in space that “look”, each one from its perspective, at the electrical activity of the heart. Each lead records the activity that it “observes”.
As a general rule, when a lead identifies electrical activity approaching it, a rising graph is recorded and when the activity is drawing away, a descending graph is drawn.
The knowledge of the location of the leads in space and of the pathways of the electrical activity flow in the heart helps to decipher the ECG and to identify pathology.