Which lead is formed between the right arm and left arm with the right arm as negative and the left arm as positive?

Which lead is formed between the right arm and left arm with the right arm as negative and the left arm as positive?

• A. Lead III
• B. Lead I
• C. Lead II
• D. aVL

Answer: (B)

Limb leads measure the electrical difference between two limb electrodes, and the sign convention sets which electrode is positive. When the left arm is the positive electrode and the right arm is the negative electrode, the lead records the potential of the left arm relative to the right arm (LA minus RA). This orientation views the heart along the frontal plane from right to left. So the described setup matches the lead that uses the left arm as positive and the right arm as negative, which is why it is the correct configuration. The other two-arm lead configurations involve different electrode pairings and directions, so they don’t match the given arrangement.

Limb leads measure the electrical difference between two limb electrodes, and the sign convention sets which electrode is positive. When the left arm is the positive electrode and the right arm is the negative electrode, the lead records the potential of the left arm relative to the right arm (LA minus RA). This orientation views the heart along the frontal plane from right to left. So the described setup matches the lead that uses the left arm as positive and the right arm as negative, which is why it is the correct configuration. The other two-arm lead configurations involve different electrode pairings and directions, so they don’t match the given arrangement.