Which lead is designated as the negative in a three lead system?

In a three-lead system, the white lead is typically designated as the negative electrode, which is placed on the right arm (RA). This lead serves as the reference point for the other leads in the system, allowing for the measurement of electrical activity of the heart from the other two leads relative to this negative reference.

The three-lead system often uses color coding to simplify the process of connecting the electrodes. The red lead (often associated with the left leg) is typically used as the positive electrode, and the black lead commonly corresponds to the left arm. Each of these colors plays a specific role in the functioning of the electrocardiogram (ECG) or electrocardiography setup, with the white lead being crucial for establishing a baseline from which heart activity can be accurately assessed.

This understanding of lead configuration is essential for anyone working with ECGs, as it informs the correct placement of leads to obtain accurate cardiovascular readings.