CCI Certified Cardiographic Technician (CCT) Practice Exam

Leads that are bipolar measure the electrical difference between two recording sites. The limb leads I, II, and III do just that by comparing different pairs of limbs: I compares the right arm and left arm, II compares the right arm and left leg, and III compares the left arm and left leg. Because each lead records the potential difference between two points, they are considered bipolar. The other leads are unipolar. Precordial chest leads V1 through V6 have a single positive electrode on the chest with a reference point derived from the Wilson central terminal, so they measure the heart’s activity relative to a central reference rather than between two limbs. The augmented limb leads aVR, aVL, and aVF also use a single limb electrode as the positive input and an augmented central reference, making them unipolar as well, though with signal amplification. So the correct set of bipolar leads is the limb leads I, II, and III.