Certified EkG technician (CET) Practice Exam

What leads are created between the left arm and left leg?

1. Lead I

2. Lead II

3. Lead III

4. Lead aVF

The correct answer is: Lead III

In the context of electrocardiography, the leads created between the left arm and left leg specifically refer to bipolar lead II. This lead is derived by placing the positive electrode on the left leg and the negative electrode on the right arm. However, when discussing the connection between the left arm and left leg directly, it actually corresponds to Lead I, which measures the electrical potential between those two points. Understanding these leads is crucial for accurately interpreting ECG readings, as each lead provides unique information about the heart's electrical activity from different perspectives. Lead I, for example, provides insight into the lateral aspect of the heart. The other options represent different combinations or derivations of leads. While Lead II involves the left leg, it measures voltage change with respect to the right arm. Lead III measures voltage between the left leg and the left arm. Lead aVF is an augmented unipolar lead that records the potential at the left foot with respect to the midpoint of the potential between the right arm and left arm, not directly involving a connection exclusively between the left arm and left leg. Therefore, the key here is recognizing that although the question may lead you to consider Lead III as the answer due to the left arm and left leg context, the technical understanding indicates