An ECG (electrocardiogram) records the electrical activity of your heart at rest. It is a diagnostic tool that displays your heart rate and rhythm, and detects abnormalities such as an enlarged heart from high blood pressure (hypertension), or evidence of a previous heart attack (myocardial infraction).
A resting ECG is different from a stress or exercise ECG or cardiac imaging test. You may need an ECG test if you are at risk for heart diseases such as high blood pressure, or symptoms such as heart palpitations and chest pains.
It is typically done at a doctor’s office, clinic, or hospital, and have become standard equipment in operating rooms and ambulances. An ECG is noninvasive and painless with quick results. During the test, sensors (electrodes) that can detect the electrical activity of your heart are attached to your chest and sometimes your limbs. These sensors are usually left on for just a few minutes.
Each beat of your heart is triggered by an electrical impulse typically generated from special cells in the upper right chamber of your heart (pacemaker cells). An electrocardiogram records the timing and strength of these signals as they travel through your heart.
An electrocardiogram is also called a 12-lead EKG or 12-lead ECG because it gathers information from 12 different areas of the heart. The electrodes, typically 10, is placed on the skin of your chest and sometimes your limbs. The electrical activity is recorded as waves on a graph, with different patterns corresponding to each electrical phase of your heartbeat.
A standard ECG can record abnormal heart rhythm only if it happens during the test. Some abnormal heart rhythms come and go, so your doctor may have you undergo a different type of heart rhythm monitoring, such a with a Holter monitor, to help diagnose the cause of your symptoms.
However, it does not show whether you have asymptomatic blockages in the heart’s arteries or predict your risk of a future heart attack.