Certified Cardiovascular Technician Practice Exam

In Lead II of a 12-lead ECG, where is the positive electrode placed?

1. Right arm

2. Left leg

3. Left arm

4. Right leg

The correct answer is: Left leg

In a 12-lead ECG, Lead II is one of the limb leads, which records the electrical activity of the heart and provides important information regarding its function. For Lead II specifically, the positive electrode is placed on the left leg. This setup allows the ECG to measure the electrical potential difference between the left leg and the right arm, effectively capturing the heart's electrical activity as it travels in a specific direction – from the right atrium towards the left ventricle. The placement of the positive electrode on the left leg is significant due to the anatomical position of the heart, which is tilted towards the left side of the body. This orientation improves the detection of electrical signals generating from the heart, providing a clear and accurate representation of the heart's electrical axis. In contrast, the other options involve placements that would not provide the same optimal view of the heart’s performance. The right arm, for instance, is used as the negative reference electrode in this lead configuration. The left arm, while involved in other lead configurations, does not serve as the positive electrode in Lead II. The right leg also has its designated role, typically as a grounding or indifferent electrode. Thus, placing the positive electrode on the left leg is critical for obtaining accurate and representative