A person with abnormal heart functions may have to take an EKG through an EKG machine. To ensure transmission between the body and the device, ECG electrodes are required. There are different sizes and shapes of electrodes. Classified according to a color code, these must be positioned on the patient in a very precise way for a good recording and not to distort the patient’s ECG.

The ECG, or electrocardiography, consists of recording the electrical activity of the heart by means of ten ECG electrodes, identified in different colors. These are affixed to the patient and directly connected to a recorder, called an EKG machine. They serve as a conductive element capable of picking up electrical signals from the heart and transmitting them to this recorder. The respective positions of these electrodes are essential for a good recording and not to distort the patient’s ECG.

The various signals picked up and transmitted by the ECG electrodes are then presented in the form of a plot on graph paper, called an electrocardiogram. The doctor interprets this trace taking into account the shape, frequency and amplitude of each signal as well as the conduction duration of the electrical signals.

ECG electrodes are used to pick up electrical signals from the heart and transmit them to the electrocardiograph. This examination is necessary if there are signs of abnormalities in the functioning of the heart or in the event of heart diseases such as:

• heart rhythm disturbances, with irregular beats;
• a heart attack ;
• pericarditis, which is inflammation of the pericardium, the membrane covering the heart;
• pulmonary embolism;
• abnormal shortness of breath during exertion, etc.

The use of the various ECG electrodes, associated with the electrocardiograph, makes it possible to perform this examination at rest or during a stress test. The latter consists in making the patient perform an intense physical effort, on a bicycle or a treadmill, in order to increase the body’s oxygen needs and then measure the intense activity of the heart. In this case, numerous ECG electrodes are placed on the subject for the measurement of the electrocardiogram and the objective of this examination is to detect any abnormalities in cardiac activity. For athletes, the stress test can also represent a preliminary step in the creation of a specific training.

The standard position of the ECG electrodes is the same as that used since 1938. These standards were defined by the American cardiologist Frank Wilson. To do this, the electrodes can be divided into two groups: 6 electrodes on the torso and 4 electrodes on the limbs.

Arrangement of so-called precordial electrodes on the torso

• the red electrode at the right edge of the sternum, between the 4^st and 5^st côte ;
• the yellow electrode symmetrically opposite to the red, between the 4^st and 5^st côte ;
• the green electrode on 5^st side, between the yellow electrode and the brown electrode;
• the brown electrode between the 5^st and 6^st rib, left side;
• the black electrode between the brown electrode and the purple electrode;
• the purple electrode, at the same horizontal level as the brown electrode and the black electrode.

Arrangement of the electrodes on the 4 limbs, at the wrists and ankles

• (R) for Right: red in color, placed on the anterior face of the right wrist;
• (N) for Neutral: black to place on the inner part of the right ankle;
• (F) for Foot: green to be placed on the inside of the left ankle;
• (L) for Left: yellow to stick on the front part of the left wrist.

Precaution for use

• check the expiration date of the ECG electrodes before use;
• always keep them in a dry place, protected from light;
• shave the hairs of the areas where the electrodes will be stuck;
• clean the skin with alcohol or soap and water;
• spread a thin layer of conductive paste or wet the electrodes before positioning them;
• avoid the presence of metal near the electrodes;
• firmly clip the electrodes to the conductive wires;
• press firmly on the adhesive edges to ensure good adhesion of the electrodes;
• once the examination is complete, disconnect and remove the electrodes;
• remove excess conductive paste.

Whether rectangular or round, there are different models of ECG electrodes:

• disposable or reusable;
• suitable for exercise ECGs or ECGs of short, medium or long duration (up to 24 hours);
• pre-gelled;
• with suction cups, also called pear electrodes, made up of a metal dome associated with a pear to produce the vacuum necessary for the adhesion of the electrodes, favoring the installation of electrodes without prior shaving of the patient;
• pressure, equipped with a button to connect the electric cables: these electrodes also equip electrostimulation devices for the rehabilitation and muscle strengthening of patients;
• with pliers;
• with tab, usable with cables fitted with “crocodile” type clips;
• with jumper, designed for stress tests, usable with cables fitted with “banana” type plugs.