What Do the EKG Leads Represent?

The leads in an electrocardiogram, or EKG, represent the electrical activity of your heart. Each electrode reads these electrical currents from the body's surface, creating a waveform, which provides a means of analyzing the polarization and depolarization of the heart.

Leads I-III

• A typical EKG will have 12 different leads. These are I, II, III, aVR, aVL, aVF, and V1 to V6--the combination of which show what is known as a P-QRS complex on the EKG strip.

  Lead I represents activity that is going from your right arm to your left arm, and lead II represents the same direction of activity on the legs. Lead III represents activity that is going from the left arm to the left leg.

Inferior Leads

• Leads II, III and aVF show electrical activity from the inferior wall of the heart. Leads I, aVL, V5 and V6 look at the electrical activity from the view of the lateral wall of the heart. V1 through V6 look at the anterior view of the heart and represent the anterior wall of the heart.

What Does aVR Represent?

• It is important to note that aVR is not typically needed for a diagnosis. Instead, it indicates if the leads of the EKG were placed accurately.

The Production of a Waveform

• The leads on an EKG produce a waveform, which is then printed on a strip to show the electrical activity of the heart at a particular moment, and are read to analyze the heart rate and irregularity in the beats, known as cardiac arrhythmias.

The QRS

• The P, QRS and T waveforms are the end result of the representation of electrical signals from the EKG leads. The form begins with a P wave, which represents atrial polarization through to the T wave, showing repolarization of the ventricles.