Which of the following are classified as bipolar limb leads?

Which of the following are classified as bipolar limb leads?

• A. I, II, III
• B. V1, V2, V3
• C. IV, V, VI
• D. aVR, aVL, aVF

Answer: (A)

Bipolar limb leads are those derived from two electrodes placed on the body, allowing for a direct measurement of the electrical activity between them. In the context of the electrocardiogram, the leads I, II, and III are classified as bipolar limb leads because they are formed by comparing the voltage between the positive electrode at one limb with the negative electrode at another limb.

Lead I records the potential difference between the left arm (positive) and right arm (negative), lead II records the difference between the left leg (positive) and right arm (negative), and lead III measures the difference between the left leg (positive) and left arm (negative). These leads provide valuable information about the heart's electrical activity and are fundamental in diagnosing various cardiac conditions.

In contrast, unipolar leads—like those in the options that list V1, V2, and V3 or the augmented leads (aVR, aVL, aVF)—record the potential at one electrode against a neutral point in the body, not between two limb electrodes, which is why they do not fit into the classification of bipolar limb leads.