What type of lead is aVR classified as?

aVR is classified as both a unipolar lead and an augmented lead. It is one of the three augmented unipolar limb leads in the ECG system, which also includes aVL and aVF.

Unipolar leads are characterized by their single positive electrode and a reference point that is derived from a combination of the other electrodes. In the case of aVR, it has a positive electrode placed on the right arm, while the reference point is derived from the average potential of the left arm and left leg electrodes, making it unipolar.

As an augmented lead, aVR is specifically an augmentation of the unipolar lead system, which increases the amplitude of the electrical signals relative to the standard limb leads. The "augmented" classification refers to this amplification of the signal to improve the visual representation of cardiac activity.

In summary, aVR's classification as a unipolar lead stems from its structure of having one active electrode and a derived reference, while its status as an augmented lead highlights the enhancement of the signal for clearer interpretation.