Choose from below:

EKG Leads and Angle / Standard Leads / Augmented Leads / Precordial Leads

EKG Leads and Corresponding Angle

EKG Standard Leads
There are three of these leads which are usually designated as I, II and III.
They are all bipolar (i.e., they detect a change in electric potential between two points) and detect an electrical potential change in the frontal plane.

Lead I is between the right arm and left arm electrodes, the left arm being positive. Lead II is between the right arm and left leg electrodes, the left leg being positive. Lead III is between the left arm and left leg electrodes, the left leg again being positive.

A diagrammatic representation of these three leads is termed Einthoven's triangle (shown in blue below), after the Dutch doctor who first described the relationship. The central source of electrical potential in the triangle is the heart.

EKG Augmented Limb Leads

The same three leads that form the standard leads also form the three unipolar leads known as the augmented leads. These three leads are referred to as aVR (right arm), aVL (left arm) and aVF (left leg) and also record a change in electric potential in the frontal plane. These leads are unipolar in that they measure the electric potential at one point with respect to a null point (one which doesn't register any significant variation in electric potential during contraction of the heart).

This null point is obtained for each lead by adding the potential from the other two leads. For example, in lead aVR, the electric potential of the right arm is compared to a null point which is obtained by adding together the potential of lead aVL and lead aVF.

EKG Precordial Leads

These six unipolar leads, each in a different position on the chest, record the electric potential changes in the heart in a cross sectional plane. Each lead records the electrical variations that occur directly under the electrode.

Combined Planes and Corresponding angle