Page 7 - EKG STUDY GUIDE

Figure 2: Conduction System of the Heart

Fundamentals of electrocardiogram

Limb Leads:
Consist of three bipolar leads and three augmented leads. These leads record electrical potentials
in the frontal plane.

Electrodes are usually applied just above the wrists or upper arms and ankles although the
electrical potential recorded will be the same no matter where electrode is placed in the extremity

Bipolar Standard Leads

Electrodes are applied to the left arm (LA), the right arm (RA) and the left leg (LL). Leads are
then applied to their respective electrodes. Electrode and lead are also applied to the right leg
which acts as a ground (or reference lead) and has no role in production of the
electrocardiogram.

Lead I = the left arm is positive and the right arm is negative.
(LA – RA)
Lead II = the left leg is positive and the right arm is negative.
(LL – RA)
Lead III = the left leg is positive and the left arm is negative.
(LL – LA)

National Healthcareer Association EKG Study Guide (Ea) 9