Electrocardiogram

An electrocardiogram (ECG) is a simple, painless, and quick test that records the electrical activity of your heart. Every time your heart beats, an electrical signal goes through your heart. The signal triggers the contraction (compression) of your heart's four chambers in the right rhythm so that your heart can pump blood back to your body.

An ECG recording of these signals looks like wavy lines. Your provider may read these lines to look for abnormal heart activity that could be a sign of heart disease or damage.

An ECG can show:

• How fast does your heart beat
• If your heartbeat is regular or irregular
• The strength and timing of electrical signals that pass through each part of your heart

Sometimes, information from an ECG can help measure the size and position of your heart's chambers.

An ECG is often the first test you'll take if you have signs of a heart condition. It can be done in your provider's office, at an outpatient clinic, in the hospital before surgery, or as part of another heart test called an exercise test.

An ECG test is also called an ECG. ECG is based on the German spelling, Elektrokardiogramm. ECG may be preferred over ECG to avoid confusion with an EEG, a test that measures brain waves.

Other names: ECG test, Holter monitor, ambulatory electrocardiography, continuous electrocardiograms, transtelephonic event monitors

An EKG test is used to help diagnose and monitor many types of heart conditions and their treatment. These conditions include:

• Arrhythmia
• Cardiomyopathy
• Coronary heart disease
• Myocardial infarction
• Heart failure
• Heart valve diseases
• Congenital heart defects

EKG tests are primarily used for people who have symptoms of heart disease or who have already been diagnosed with heart disease. They're generally not used to screen for people who don't have symptoms unless they have an increased risk of developing heart disease. Your provider can explain your risk of heart disease and let you know if you need to have an EKG test. In some cases, your provider may refer you to a cardiologist, a doctor who specializes in heart disease.

You may need an EKG test if you have symptoms of heart disease, including:

• Chest pain
• Fast or irregular heartbeat
• Shortness of breath
• Vertigo
• Fatigue
• Decreased ability to exercise

You may also need an EKG to:

• Determining if you have had a heart attack in the past without knowing it
• Check your heart if you have a known heart condition
• Check the effectiveness of your heart treatment, including medications and/or pacemakers
• Check your heart health:
  • Before undergoing surgery
  • If you have an increased risk of developing heart disease because:
    • Heart disease is common in your family
    • You have another condition, such as diabetes, that increases your risk beyond normal

You do not need any special preparations for an EKG test.

There is very little risk in having an EKG done. You may experience slight discomfort or skin irritation after the electrodes are removed. The EKG does not send any electricity into your body. It only records electrical signals from your heart, so there's no risk of electric shock.

Your provider will check your EKG results for a regular heart rate and heart rate. If your results are not normal, it may be a sign of heart disease. The specific condition depends on what part of your EKG was not normal.

You may need to have additional heart health tests before your provider can make a diagnosis. Your provider can explain what your test results mean for your heart health and treatment.

Learn more about lab tests, reference ranges, and understanding results.

An EKG is a “snapshot” of your heart's activity over a very short period of time. If you have heart symptoms that come and go, a regular EKG may not detect the problem. In this case, your doctor may recommend that you wear a small, portable EKG monitor that can record your heart for days or longer while doing your normal activities. You may also need a longer EKG record if your doctor wants to check how well your heart is working after a heart attack or to see if treatment is helping.

There are many types of long-term EKG monitors. The two main groups are Holter monitors, which can be worn for up to two days, and the event monitors, which can record your heart's activity for weeks to years depending on the type.

A Holter monitor is about the size of a small camera. You usually wear it on a belt or strap around your neck for a day or two. Wires under your clothes are attached to electrodes that stick to your chest. The monitor records your heart's electrical signals all the time you wear it. You may be asked to keep a diary of your symptoms during the test period. After the test period, you remove the monitor and return it according to instructions. A doctor will look at the monitor's record of your heart's electrical activity.

An event monitor records your heart's electrical activity when you press a button or when the device detects abnormal heart activity. There are two main types of event monitors:

• Event monitors that you carry or take with you. You wear some monitors on your chest or wrist. Other monitors are designed to be worn. If you have symptoms, hold the monitor to your chest. These event monitors can be used for weeks to months. Some of them wirelessly transmit information about your heart to a doctor. Others need to be returned so that a doctor can review the recorded information.
• Event monitors that are inserted under the skin of your chest. These are called implantable event monitors. They are placed under your skin during a small surgery procedure that is often performed in a doctor's office. These monitors can track your heart's electrical activity for years. You may need this type of EKG monitor if you have had a stroke or frequent fainting and your doctor has not found the cause. Implantable monitors wirelessly transmit the information they record so your doctor can check it regularly.

1. AAFP [Internet]. Leawood (KS): American Academy of Family Physicians; c2022. Choosing wisely® annual electrocardiograms for low-risk patients; [accessed Nov. 4, 2022]; [approximately 4 screens]. Available at: https://www.aafp.org/family-physician/patient-care/clinical-recommendations/all-clinical-recommendations/cw-ekg.html
2. American Heart Association [Internet]. Dallas (TX): American Heart Association Inc.; c2022. Electrocardiogram (ECG or EKG); [revised July 31, 2015; accessed Oct. 20, 2022]; [approximately 4 screens]. Available at: http://www.heart.org/en/health-topics/heart-attack/diagnosing-a-heart-attack/electrocardiogram-ecg-or-ekg
3. Christiana Care Health System [Internet]. Wilmington (DE): Christiana Care Health System; EKG; [accessed Oct. 20, 2022]; [approximately 4 screens]. Available at: https://christianacare.org/us/en/care/heart-and-vascular-care/cardiovascular-imaging/ekg
4. Cleveland Clinic: Health Library: Diagnostics and Tests [Internet]. Cleveland (OH): Cleveland Clinic; c2022. Electrocardiogram (EKG); [revised May 13, 2022; accessed Nov. 4, 2022]; [approximately 9 screens]. Available at: https://my.clevelandclinic.org/health/diagnostics/16953-electrocardiogram-ekg
5. Cleveland Clinic: Health Library: Diagnostics and Tests [Internet]. Cleveland (OH): Cleveland Clinic; c2022. Cardiac event monitor; [revised June 11, 2022; accessed Nov. 4, 2022]; [approximately 10 screens]. Available at: https://my.clevelandclinic.org/health/diagnostics/23272-cardiac-event-monitor
6. Johns Hopkins Medicine [Internet]. Johns Hopkins University, Johns Hopkins Hospital, and Johns Hopkins Health System; c2022. Health, treatments, tests, and therapies: Event monitor; [accessed Nov. 4, 2022]; [approximately 5 screens]. Available at: https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/event-monitor
7. KidsHealth from Nemours [Internet]. The Nemours Foundation; c1995—2022. ECG (Electrocardiogram); [accessed Oct. 20, 2022]; [approximately 2 screens]. Available at: https://kidshealth.org/en/parents/ekg.html
8. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998—2022. Electrocardiogram (ECG or EKG): About; [accessed Oct. 20, 2022]; [about 7 screens]. Available at: https://www.mayoclinic.org/tests-procedures/ekg/about/pac-20384983
9. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998—2022. Holter monitor; [accessed Nov. 4, 2022]; [approximately 7 screens]. Available at: https://www.mayoclinic.org/tests-procedures/holter-monitor/about/pac-20385039
10. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998—2022. Electrocardiogram (ECG or EKG), Implantable Loop Recorder: A cardiac monitoring device; [accessed Nov. 4, 2022]; [approximately 1 screen]. Available at: https://www.mayoclinic.org/tests-procedures/implantable-loop-recorder/pyc-20384986
11. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co., Inc.; c2022. Electrocardiography (ECG; EKG); [revised Jul 2021; accessed Oct 20, 2022]; [approximately 2 screens]. Available at: https://www.merckmanuals.com/home/heart-and-blood-vessel-disorders/diagnosis-of-heart-and-blood-vessel-disorders/electrocardiography
12. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Heart Tests; [updated on March 24, 2022; accessed on Oct. 20, 2022]; [approximately 19 screens]. Available at: https://www.nhlbi.nih.gov/health/heart-tests
13. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; How the Heart Works: How the Heart Beats; [updated March 24, 2022; accessed Oct. 20, 2022]; [approximately 6 screens]; [approximately 6 screens]. Available at: https://www.nhlbi.nih.gov/health/heart/heart-beats
14. Seconds Count [Internet]. Washington D.C.: The Society for Cardiovascular Angiography and Interventions; Diagnosing a Heart Attack; Nov. 4, 2014 [accessed Oct. 20, 2022]; [approximately 4 screens]. Available at: http://www.secondscount.org/heart-condition-centers/info-detail-2/diagnosing-heart-attack
15. UF Health: University of Florida Health [Internet]. Gainesville (FL): University of Florida Health; c2022. Electrocardiogram: Overview; [revised July 7, 2020; accessed Oct. 20, 2022]; [approximately 2 screens]. Available at: https://ufhealth.org/electrocardiogram
16. UF Health: University of Florida Health [Internet]. Gainesville (FL): University of Florida Health; c2022. Cardiac event monitors; [revised Dec 7, 2020; accessed Nov 4, 2020]