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Electrocardiogram
     
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Electrocardiogram

ECG; EKG

 

An electrocardiogram (ECG) is a test that records the electrical activity of the heart.

 

How the Test is Performed

 

You will be asked to lie down. A technician will clean several areas on your arms, legs, and chest, and then will attach small patches called electrodes to those areas. It may be necessary to shave or clip some hair so the patches stick to the skin. The number of patches used may vary.

The patches are connected by wires to a machine that turns the heart's electrical signals into wavy lines, which are often printed on paper. The health care provider reviews the test results.

You will need to remain still during the procedure. The technician may also ask you to hold your breath for a few seconds as the test is being done.

It is important to be relaxed and warm during an ECG recording because any movement, including shivering, can alter the results.

Sometimes this test is done while you are exercising or under light stress to look for changes in the heart. This type of ECG is often called a stress test.

 

 

How to Prepare for the Test

 

Make sure your provider knows about all the medicines you are taking. Some medicines can interfere with test results.

Do not exercise or drink cold water immediately before an ECG because these actions may cause false results.

 

How the Test will Feel

 

An ECG is painless. No electricity is sent through the body. The electrodes may feel cold when first applied. In rare cases, some people may develop a rash or irritation where the patches were placed.

 

Why the Test is Performed

 

An ECG is used to measure:

  • Any damage to your heart
  • How fast your heart is beating and whether it is beating normally
  • The effects of medicines or devices used to control your heart (such as a pacemaker)
  • The size and position of your heart chambers
 

An ECG is often the first test done to determine whether a person has heart disease. Your provider may order this test if:

  • You have chest pain or palpitations
  • You are scheduled for surgery
  • You have had heart problems in the past
  • You have a strong history of heart disease in the family

 

Normal Results

 

Normal test results most often include:

  • Heart rate: 60 to 100 beats per minute
  • Heart rhythm: Consistent and even

 

What Abnormal Results Mean

 

Abnormal ECG results may be a sign of:

  • Damage or changes to the heart muscle
  • Changes in the amount of certain electrolytes (such as potassium and calcium) in the blood
  • Congenital heart defect
  • Enlargement of the heart
  • Fluid or swelling in the sac around the heart
  • Inflammation of the heart (myocarditis)
  • Past or current heart attack
  • Poor blood supply to the heart arteries
  • Abnormal heart rhythms (arrhythmias)

Some heart problems that can lead to changes on an ECG test include:

  • Atrial fibrillation/flutter
  • Heart attack
  • Heart failure
  • Multifocal atrial tachycardia
  • Paroxysmal supraventricular tachycardia
  • Sick sinus syndrome
  • Wolff-Parkinson-White syndrome

 

Risks

 

There are no risks.

 

Considerations

 

The accuracy of the ECG depends on the condition being tested. A heart problem may not always show up on the ECG. Some heart conditions never produce any specific ECG changes.

 

 

Open References

References

Easter JS, Brady WJ, Chan TC. Basic electrocardiographic techniques. In: Birnbaumer DM, ed. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. 8th ed. Philadelphia, PA: Elsevier; 2026:chap 14.

Ganz L, Link MS. Electrocardiography. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 42.

Wu JC, Cikes M, Gillam LD, Solomon SD, Bulwer B. Electrocardiography. In: Bonow RO, Mann DL, Tomaselli GF, et al, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 13th ed. Philadelphia, PA: Elsevier; 2026:chap 14.

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    ECG

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    Atrioventricular block - ECG tracing

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  • High blood pressure tests

    High blood pressure tests

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  • Electrocardiogram (ECG)

    Electrocardiogram (ECG)

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  • ECG electrode placement

    ECG electrode placement

    illustration

    • ECG

      ECG

      illustration

    • Atrioventricular block - ECG tracing

      Atrioventricular block - ECG tracing

      illustration

    • High blood pressure tests

      High blood pressure tests

      illustration

    • Electrocardiogram (ECG)

      Electrocardiogram (ECG)

      illustration

    • ECG electrode placement

      ECG electrode placement

      illustration

    Self Care

     

      Tests for Electrocardiogram

       
       

      Review Date: 4/28/2026

      Reviewed By: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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