Electrocardiography 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.
Abnormal heart rhythms and inadequate blood flow to the heart muscle may occur only briefly or unpredictably. To detect such problems, doctors may use continuous ambulatory electrocardiography, in which the ECG is recorded continuously for 24 hours while the person engages in normal daily activities.