An electrocardiogram, often referred to as an ECG or EKG, is a fairly common medical procedure that records information about the electrical conductivity of the heart. Electrodes, small metallic devices that receive electrical impulses, are placed in different areas of the body as EKG leads. The number of EKG leads may vary depending on how in depth the testing is, but typically 3, 5, or 12 leads are utilized.

The principles of the ECG existed before the invention of the machine. William Einthoven is most commonly credited with creating this electronic measure of the heart's contractivity. Beginning in 1903, measurements of heart rate, rhythm, and strength of contraction have all been made possible by the ECG.

The electrical activity that causes heart contraction is picked up through the strategic placement of leads in different locations around the body. These electrodes may be compared and contrasted to deduce electronic differences during the phases of contraction. The 12-electrode EKG leads are the most complex and telling, whereas the 5- and 3-lead EKGs are the middle and least conclusive, respectively.

The placement of the 12-lead EKG is usually done in four columns. The first column is composed of the limb EKG leads and are named leads I,II, and III. The second column of EKG leads are aVR, aVL, aFV, collectively termed the augmented limb leads. The third and fourth columns of 12-lead electrodes are placed on the chest and tagged as V1 through V6.

Although the EKG leads may be difficult to visualize based on their scientific descriptions, they may also be referenced in regards to bodily location. In this manner, the first three of the ten leads are the right, or RA. LA stands for left arm, and right leg can be abbreviated as RL. The LL is placed on the left leg, and V1 through V4 are placed down the ribs, with V5 and V6 located in proximity to the axillary, or armpit, line. After the leads are properly placed on adequately prepped skin, the EKG may be effectively performed.

Three-lead placement is performed on three different sides of the heart, usually one below and one to both the left and right of the heart. These may be placed, for example, of the left ankle and both wrists bilaterally. Comparably, all three leads may be placed on the torso, but they must be consistent with angles respective to one another. The five-lead version garnishes more information through greater lead placement, which yields more possible angle combinations.