Electrocardiogram (ECG or EKG)
An electrocardiogram records the electrical signals in the heart. It's a common and painless test used to quickly detect heart problems and monitor the heart's health.
An electrocardiogram — also called ECG or EKG — is often done in a health care provider's office, a clinic or a hospital room. ECG machines are standard equipment in operating rooms and ambulances. Some personal devices, such as smartwatches, offer ECG monitoring. Ask your health care provider if this is an option for you.
Why it's done
An electrocardiogram is a painless, noninvasive way to help diagnose many common heart problems. A health care provider might use an electrocardiogram to determine or detect:
- Irregular heart rhythms (arrhythmias)
- If blocked or narrowed arteries in the heart (coronary artery disease) are causing chest pain or a heart attack
- Whether you have had a previous heart attack
- How well certain heart disease treatments, such as a pacemaker, are working
You may need an ECG if you have any of the following signs and symptoms:
- Chest pain
- Dizziness, lightheadedness or confusion
- Heart palpitations
- Rapid pulse
- Shortness of breath
- Weakness, fatigue or a decline in ability to exercise
The American Heart Association doesn't recommend using electrocardiograms to assess adults at low risk who don't have symptoms. But if you have a family history of heart disease, your health care provider might suggest an electrocardiogram as a screening test, even if you have no symptoms.
If symptoms tend to come and go, they may not be detected during a standard ECG recording. A health care provider might recommend remote or continuous ECG monitoring. There are several different types.
- Holter monitor. A Holter monitor is a small, wearable device that records a continuous ECG, usually for 24 to 48 hours.
- Event monitor. This portable device is similar to a Holter monitor, but it records only at certain times for a few minutes at a time. You can wear it longer than a Holter monitor, typically 30 days. You generally push a button when you feel symptoms. Some devices automatically record when an irregular rhythm is detected.
An electrocardiogram is a safe procedure. There is no risk of electrical shock during the test because the electrodes used do not produce electricity. The electrodes only record the electrical activity of the heart.
You may have minor discomfort, similar to removing a bandage, when the electrodes are removed. Some people develop a slight rash where the patches were placed.
How you prepare
No special preparations are necessary for a standard electrocardiogram. Tell your health care provider about any medications and supplements you take. These can often affect the results of an ECG.
What you can expect
An electrocardiogram can be done in a health care provider's office or hospital.
You may be asked to change into a hospital gown. If you have hair on the parts of your body where the electrodes will be placed, the care provider may shave the hair so that the patches stick.
Once you're ready, you'll typically be asked to lie on an examining table or bed.
During an ECG, up to 12 sensors (electrodes) are attached to the chest and limbs. The electrodes are sticky patches with wires that connect to a monitor. They record the electrical signals that make the heart beat. A computer records the information and displays it as waves on a monitor or on paper.
You can breathe during the test, but you will need to lie still. Make sure you're warm and ready to lie still. Moving, talking or shivering may interfere with the test results. A standard ECG takes a few minutes.
You can typically return to your usual activities after your electrocardiogram.
Your health care provider might discuss results with you the same day as your electrocardiogram or at your next appointment.
ECG results can give a health care provider details about the following:
- Heart rate. Usually, heart rate can be measured by checking the pulse. An ECG may be helpful if your pulse is difficult to feel or too fast or too irregular to count accurately. An ECG can help identify an unusually fast heart rate (tachycardia) or an unusually slow heart rate (bradycardia).
- Heart rhythm. An ECG can detect irregular heartbeats (arrhythmias). An arrhythmia may occur when any part of the heart's electrical system doesn't work properly.
- Heart attack. An ECG can show evidence of a previous heart attack or one that's currently happening. The patterns on the ECG may help determine which part of the heart has been damaged, as well as the extent of the damage.
- Blood and oxygen supply to the heart. An ECG done while you're having symptoms can help your health care provider determine whether reduced blood flow to the heart muscle is causing the chest pain.
- Heart structure changes. An ECG can provide clues about an enlarged heart, heart defects and other heart problems.
If results show a heart rhythm problem, you may need another ECG or other test, such as an echocardiogram. Treatment depends on what's causing your signs and symptoms.