Einthoven's Triangle refers to an imaginary formation of three limb leads in electrocardiography formed by which points?

• A. The wrists and ankles
• B. The two shoulders and the pubis
• C. Chest leads V1-V6
• D. The head and neck

Answer: (B)

Einthoven's triangle is defined by the three limb electrodes placed on the limbs, forming a triangle around the heart. In standard practice, these points are on the right arm, left arm, and left leg (often at the wrists and ankles). The three limb leads measure the electrical potential between pairs of these points: between the arms, between one arm and the leg, and between the other arm and the leg. The chest leads V1 through V6 are placed on the chest and are not part of this triangle. Likewise, placements on the shoulders or pelvis aren’t used to form Einthoven’s triangle, and head/neck placements aren’t relevant to the limb-lead system.