"Electrocardiogram" (ECG) is the English language version of the German word "elektrokardiogramm" (EKG). Both words refer to the same procedure, which is used to measure the electrical activity of the heart and diagnose heart problems. There is no difference between an ECG and EKG, except for the spelling. Both ECG and EKG are correct terms, however, in America the procedure is usually referred to as an EKG to distinguish it from the similar sounding abbreviation for the electroencephalogram (EEG), which measures brain electrical waves instead of heart electrical waves. Other countries besides America tend to more commonly use the abbreviation ECG, although this is not always the case.
The root word "electro" or "elektro" means electricity. "Cardio" or "kardio" is used to refer to the heart. "Gram" or "gramm" means writing. The procedure is called an ECG and EKG because it uses a device to measure the electric impulses produced by the heart, and then record, or write, these results to be analyzed by a doctor.
The ECG and EKG machine, called an electrocardiograph, is attached to the body in specific places via wired electrodes. Electrical impulses in the heart signal the heart muscle to contract, which causes a heartbeat. These electrical impulses can be detected through the skin by the electrocardiograph's electrodes. It records the electric signals, in the form of wavy lines, either digitally onto a computer screen or onto a piece of paper using moving ink needles. These machines are sensitive enough to detect tiny irregularities, which can then be used to diagnose many types of heart problems.
The procedure itself is painless, noninvasive, and generally over quickly, within a period of a few minutes, including the time it takes to set up and take down the machine and electrodes. Many people are alarmed at the thought of an electrical instrument being attached to the body, and often worry about the risk of electric shock. People with pacemakers also often worry that the procedure will interfere with the pacemaker. During an ECG or EKG, however, no electricity is actually passed through the body at all; the device is simply used to detect the body's own electrical energy. ECGs or EKGs are generally considered to be free of health risks and complications, although some people may develop some skin irritation or allergic reaction to the adhesive used on the electrodes.