What is the deflection direction of the right arm lead (aVR) in an ECG?

In an ECG, lead aVR specifically measures the electrical activity of the heart from the perspective of the right arm. It is designed to represent the potential difference between the right arm electrode and a combination of the left arm and left leg electrodes.

When we talk about the deflection direction of lead aVR, we must consider how the heart's electrical activity propagates relative to this lead. The heart's depolarization wave generally moves from the right atrium toward the left ventricle, which means that when observed from the right arm, this wave moves away from the positive electrode at the right arm. As a result, the aVR lead typically shows a negative deflection.

This negative deflection occurs because the primary movement of electrical activity is directed toward the left of the body (toward the left arm and left leg), leading to a reduction in voltage at the right arm electrode compared to the central average of the left arm and left leg. Thus, the deflection is typically negative, confirming that the answer provided is correct.