Which leads are considered bipolar leads?

Bipolar leads in an electrocardiogram (ECG) use two electrodes to measure the electrical potential difference between them. Leads I, II, and III are identified as bipolar leads because each lead is formed by comparing the electrical activity from two distinct limb electrodes.

For instance:

• Lead I compares the potential between the left arm and the right arm.

• Lead II compares the potential between the left leg and the right arm.

• Lead III compares the potential between the left leg and the left arm.

This set of leads is crucial for assessing the heart's electrical activity in multiple directions, providing vital information about the heart's rhythm and function as seen in the frontal plane.

In contrast, the other options contain leads that do not fit the definition of bipolar leads. Unipolar leads, such as aVL, aVR, and aVF, measure the electrical activity from a single point (the limb electrode) to a theoretical point of reference, which is not included in the bipolar lead classification. Similarly, V1, V2, and V3, which are precordial leads, also measure the electrical activity from one point to a reference point rather than between two electrodes. Moreover, the combination presented in the fourth option does not