An electrocardiogram (ECG or EKG, from the German “elektrokardiogramm”) is a medical test used to evaluate and diagnose possible cardiac problems. An ECG electrode is a device attached to the skin on certain parts of a patient’s body — generally the arms, legs, and chest — during an electrocardiogram procedure; it detects electrical impulses produced every time the heart beats. The number and placement of electrodes on the body can vary, but the function remains the same.
Every ECG electrode placed on the body is attached by a wire to an ECG machine. The electricity that an electrode detects is transmitted via this wire to the machine, which translates the results into wavy lines that the machine then records on a piece of paper. The ECG records in such great detail that the results can be used to diagnose a very broad range of heart conditions.
It is not painful to undergo an electrocardiogram. The procedure is usually over quickly, within five to 10 minutes. Very rarely, a patient may develop localized irritation because of the adhesive used to attach the electrodes to the skin, but there are no other risks associated with this procedure. An ECG is simply a recording device. There is no electricity passed through the body, so it will not interfere with electrical devices such as pacemakers, and it will not cause electrical shocks.
Electrodes come in a few different varieties, but the basis is the same. An ECG electrode is usually composed of a small metal plate surrounded by an adhesive pad, which is coated with conducting gel to help transmit the electrical signal. The wire that connects the ECG electrode to the ECG machine is clipped to the back of the electrode. Some electrodes are reusable, and other types are intended to be disposable after a single use.
ECGs are usually performed and interpreted by medical professionals, so the average person will not need to purchase his own electrodes. Some patients, however, such as those who can stay at home but need to be on a heart monitor for an extended period of time, may need periodically to replenish their supply of electrodes. For these patients, medical suppliers exist both online and off that can be used to purchase replacement electrodes. These patients should keep in mind that different types of ECG machines use different numbers, and sometimes different placement, of electrodes. These patients should make sure to get adequate instructions from their doctors to ensure accurate recordings.