These leads have one positive and one negative electrode, making them what type of leads?

• A. Bipolar leads
• B. Unipolar leads
• C. Central terminal leads
• D. Standard limb leads

Answer: (A)

Leads are defined by how many electrodes and how the reference is used. When a lead uses two electrodes—one positive and one negative—it measures the difference in electrical potential between those two points. That setup is what we call a bipolar lead. The standard limb leads are the classic examples of bipolar leads, since each is formed by a pair of limb electrodes and reflects the voltage difference between them (for instance, one lead compares the left arm and right arm, another compares the left leg to the right arm, and so on).

In contrast, unipolar leads use a single active electrode and a distant reference created from a composite of electrode potentials (like the Wilson central terminal), which is why those are described as unipolar (augmented limb leads and chest leads). So the description of one positive and one negative electrode aligns with bipolar leads.