An electrocardiogram or ECG (also called an EKG) is a non-invasive, painless test that records the electrical activity of the heart. By analyzing this activity, cardiologists can determine if a patient is experiencing a heart rhythm disturbance.

An ECG exam requires the placement of conductive electrical leads on the patient's chest and back. These leads record the electrical impulses emitted by the heart. A computer converts the recorded information to waveforms that are displayed on a monitor and stored in a file that can be printed. The waveforms are divided into time segments so the rate of the heart's electrical impulses can be measured.