Electrocardiography (ECG) is the process of recording the electrical activity of the heart over a period of time using electrodes placed on the skin. It is a quick, simple, painless procedure in which the heart’s electrical impulses are amplified and recorded.
This record, the electrocardiogram (also known as an ECG), provides information about the part of the heart that triggers each heartbeat (the pacemaker, called the sinoatrial or sinus node), the nerve conduction pathways of the heart, and the rate and rhythm of the heart. Sometimes, the ECG can show that the heart is enlarged (usually due to high blood pressure) or that the heart is not receiving enough oxygen due to a blockage in one of the blood vessels that supply the heart (the coronary arteries).
Usually, an ECG is obtained if a heart disorder is suspected. It is sometimes also obtained as part of a routine physical examination for middle-aged and older people, even if they have no evidence of a heart disorder. It can be used as a basis of comparison with later ECGs if a heart disorder develops.
To obtain an ECG, an examiner places electrodes (small round sensors that stick to the skin) on the person’s arms, legs, and chest. These electrodes do not contain needles and are painless. If thick hair is present, the areas to which the electrodes are applied may first be shaved. These electrodes measure the magnitude and direction of electrical currents in the heart during each heartbeat. The electrodes are connected by wires to a machine, which produces a record (tracing) for each electrode. Each tracing shows the electrical activity of the heart from different angles. The tracings constitute the ECG. ECG takes about 3 minutes and has no risks.