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Electrocardiogram

Show Alternative Names
ECG
EKG

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

Electrocardiogram - Animation

If your heart has been beating too fast, or you've been having chest pain, both you and your doctor will want to find out what's causing the problem so you can get it treated. One way to diagnose heart problems is with a test of the heart's electrical activity, called an electrocardiogram or ECG, or EKG for short. Your heart is controlled by an electrical system, much like the electricity that powers the lights and appliances in your home. Electrical signals make your heart contract so that it can pump blood out to your body. Heart disease, abnormal heart rhythms, and other heart problems can affect those signals. Using an ECG, your doctor can identify problems in your heart's electrical system and diagnose heart disease. So, how is an ECG done? First you'll lie down on a table. You'll have to lie very still while the test is done. Small patches, called electrodes, will be attached to several places on your arms, legs, and chest. The patches won't hurt, but some of the hair in those areas may be shaved so the patches will stick to your skin. The patches are then attached to a machine. You'll notice that when the machine is turned on, it produces wavy lines on a piece of paper. Those lines represent the electrical signals coming from your heart. If the test is normal, it should show that your heart is beating at an even rate of 60 to 100 beats per minute. Many different heart conditions can show up on an ECG, including a fast, slow, or abnormal heart rhythm, a heart defect, coronary artery disease, heart valve disease, or an enlarged heart. An abnormal ECG may also be a sign that you've had a heart attack in the past, or that you're at risk for one in the near future. If you're healthy and you don't have any family or personal history of heart disease, you don't need to have an ECG on a regular basis. But if you are having heart problems, your doctor may recommend getting this test. An ECG is pretty accurate at diagnosing many types of heart disease, although it doesn't always pick up every heart problem. You may have a perfectly normal ECG, yet still have a heart condition. If your test is normal but your doctor suspects that you have a heart problem, he may recommend that you have another ECG, or a different type of test to find out for sure.

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 the 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:

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.

Review Date: 5/8/2024

Reviewed By

Thomas S. Metkus, MD, Assistant Professor of Medicine and Surgery, Johns Hopkins University School of Medicine, Baltimore, MD. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

References

Brady WJ, Harrigan RA, Chan TC. Basic electrocardiographic techniques. In: Roberts JR, Custalow CB, Thomsen TW, eds. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 14.

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

Mirvis DM, Goldberger AL. Electrocardiography. In: Libby P, Bonow RO, Mann DL, Tomaselli GF, Bhatt DL, Solomon SD, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 12th ed. Philadelphia, PA: Elsevier; 2022:chap 14.

Disclaimer

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, timeliness, or correctness of any translations made by a third-party service of the information provided herein into any other language. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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Electrocardiogram - Animation

If your heart has been beating too fast, or you've been having chest pain, both you and your doctor will want to find out what's causing the problem so you can get it treated. One way to diagnose heart problems is with a test of the heart's electrical activity, called an electrocardiogram or ECG, or EKG for short.

Your heart is controlled by an electrical system, much like the electricity that powers the lights and appliances in your home. Electrical signals make your heart contract so that it can pump blood out to your body. Heart disease, abnormal heart rhythms, and other heart problems can affect those signals. Using an ECG, your doctor can identify problems in your heart's electrical system and diagnose heart disease.

So, how is an ECG done?

First you'll lie down on a table. You'll have to lie very still while the test is done. Small patches, called electrodes, will be attached to several places on your arms, legs, and chest. The patches won't hurt, but some of the hair in those areas may be shaved so the patches will stick to your skin. The patches are then attached to a machine. You'll notice that when the machine is turned on, it produces wavy lines on a piece of paper. Those lines represent the electrical signals coming from your heart. If the test is normal, it should show that your heart is beating at an even rate of 60 to 100 beats per minute.

Many different heart conditions can show up on an ECG, including a fast, slow, or abnormal heart rhythm, a heart defect, coronary artery disease, heart valve disease, or an enlarged heart. An abnormal ECG may also be a sign that you've had a heart attack in the past, or that you're at risk for one in the near future.

If you're healthy and you don't have any family or personal history of heart disease, you don't need to have an ECG on a regular basis. But if you are having heart problems, your doctor may recommend getting this test. An ECG is pretty accurate at diagnosing many types of heart disease, although it doesn't always pick up every heart problem. You may have a perfectly normal ECG, yet still have a heart condition. If your test is normal but your doctor suspects that you have a heart problem, he may recommend that you have another ECG, or a different type of test to find out for sure.

 

Electrocardiogram - Animation

If your heart has been beating too fast, or you've been having chest pain, both you and your doctor will want to find out what's causing the problem so you can get it treated. One way to diagnose heart problems is with a test of the heart's electrical activity, called an electrocardiogram or ECG, or EKG for short.

Your heart is controlled by an electrical system, much like the electricity that powers the lights and appliances in your home. Electrical signals make your heart contract so that it can pump blood out to your body. Heart disease, abnormal heart rhythms, and other heart problems can affect those signals. Using an ECG, your doctor can identify problems in your heart's electrical system and diagnose heart disease.

So, how is an ECG done?

First you'll lie down on a table. You'll have to lie very still while the test is done. Small patches, called electrodes, will be attached to several places on your arms, legs, and chest. The patches won't hurt, but some of the hair in those areas may be shaved so the patches will stick to your skin. The patches are then attached to a machine. You'll notice that when the machine is turned on, it produces wavy lines on a piece of paper. Those lines represent the electrical signals coming from your heart. If the test is normal, it should show that your heart is beating at an even rate of 60 to 100 beats per minute.

Many different heart conditions can show up on an ECG, including a fast, slow, or abnormal heart rhythm, a heart defect, coronary artery disease, heart valve disease, or an enlarged heart. An abnormal ECG may also be a sign that you've had a heart attack in the past, or that you're at risk for one in the near future.

If you're healthy and you don't have any family or personal history of heart disease, you don't need to have an ECG on a regular basis. But if you are having heart problems, your doctor may recommend getting this test. An ECG is pretty accurate at diagnosing many types of heart disease, although it doesn't always pick up every heart problem. You may have a perfectly normal ECG, yet still have a heart condition. If your test is normal but your doctor suspects that you have a heart problem, he may recommend that you have another ECG, or a different type of test to find out for sure.

 
 
 
 

 

 
 
 
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