Question

With bipolar limb leads, which one is always positive? Negative?

a) Lead I is always positive, Lead II is always negative
b) Lead II is always positive, Lead III is always negative
c) Lead I is always positive, Lead III is always negative
d) Lead III is always positive, Lead I is always negative

Answer 1

Bipolar limb leads in ECG have standardized positive and negative electrodes, with none of the leads being 'always' positive or negative. The positivity or negativity refers to the electrode placement rather than the leads themselves.

Step-by-step explanation:

In the context of electrocardiography (ECG), bipolar limb leads refer to the leads that record the electrical activity of the heart between two limbs. There are three standard bipolar limb leads: Lead I, Lead II, and Lead III. For bipolar limb leads, the designation of positive and negative poles is standardized.

Lead I has the left arm as the positive electrode and the right arm as the negative electrode, Lead II has the left leg (or foot) as the positive electrode and the right arm as the negative electrode, and Lead III has the left leg as the positive electrode and the left arm as the negative electrode. Therefore, none of the options provided in the question are correct, as each lead has a positive and a negative electrode, but they are not 'always' positive or negative by themselves.