EKG Testing

What is an EKG (Electrocardiogram)?

How is an EKG Done?

Why has my doctor ordered an EKG?

Will the EKG Hurt?

Do I need an appointment for an EKG?

What information will the laboratory need from me?

How long will it take to perform the EKG?

What will the laboratory ask me to do?

What does an EKG tracing look like?

(Sample only) 

What happens to my EKG tracing?




This information about EKGs is courtesy of WebMD. 

Here is the link to the the article http://www.webmd.com/hw/heart_disease/hw213248.asp

An electrocardiogram (EKG, ECG) is a test that measures the electrical signals that control the rhythm of your heartbeat.

The heart is a muscular pump made up of four chambers. The two upper chambers are called atria, and the two lower chambers are called ventricles. A natural electrical system causes the heart muscle to contract and pump blood through the heart to the lungs and the rest of the body.

The electrical activity of the heart can be detected through the skin by small metal discs called electrodes. During an electrocardiogram, the electrodes are attached to the skin on the chest, arms, and legs. The electrodes are also connected to a machine that translates the electrical activity into line tracings on paper. These tracings are often analyzed by the machine and then carefully reviewed by a doctor for abnormalities.

An electrocardiogram may show:

An electrocardiogram cannot predict whether you will have a heart attack.

An electrocardiogram (EKG, ECG) is done to:

An electrocardiogram may be used to evaluate symptoms of heart disease (such as unexplained chest pain, shortness of breath, dizziness, faintness, or palpitations) or when risk factors for heart disease (such as high blood pressure, high cholesterol, cigarette smoking, diabetes, or a family history of early heart disease) are present.

How To Prepare

Tell your health professional if you are taking any medications. Certain medications can affect the results of your electrocardiogram.

Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How It Is Done

An electrocardiogram (EKG, ECG) is usually done by a health professional, and the resulting EKG is interpreted by a doctor, such as an internist, family medicine doctor, electrophysiologist, cardiologist, anesthesiologist, or surgeon.

You may receive an EKG as part of a physical examination at your health professional's office or during a series of tests at a hospital or clinic. EKG equipment is often portable, so the test can be done almost anywhere. If you are hospitalized, your heart may be continuously monitored by an EKG system; this process is called telemetry.

You should remove all jewelry from your neck, arms, and wrists. You will also need to remove your clothing above the waist and keep your forearms and lower legs exposed. If you are wearing stockings, you should take them off. You will be given a cloth or paper covering to use during the test.

During an electrocardiogram, you will lie on a bed or table. Areas on your arms, legs, and chest where electrodes will be placed are cleaned and possibly shaved to provide a clean, smooth surface to attach the electrode discs. A special EKG paste or small pads soaked in alcohol may be placed between the electrodes and your skin to improve conduction of the electrical impulses, but in many cases disposable electrodes are used that do not requite paste or alcohol.

Several metal electrodes or "leads" are attached to the skin on each arm and leg and on your chest. If an older machine is used, the electrodes may be repositioned at different times during the test to measure your heart's electrical activity from different locations on your chest. After the procedure, the electrode paste is wiped off.

It is important not to move or talk during the recording because muscular activity can cause inaccurate results. For best results, lie very still and breathe normally. Sometimes you may be asked to hold your breath.

An electrocardiogram usually takes 5 to 10 minutes to complete. Sometimes a longer period of recording (a "rhythm strip") is done to measure your heart's rhythm for a minute or longer.

How It Feels

An electrocardiogram is a painless procedure. The electrodes and conducting paste may feel cold when they are first applied. You may feel a burning or stinging sensation when the area where electrodes will be placed is cleaned and shaved. Your hair and skin may be pulled when the EKG leads are removed, which may cause some brief discomfort.


There is no risk associated with an electrocardiogram (EKG, ECG). An EKG is a completely safe test. In most cases, there is no reason why you should not be able to get an EKG.

The electrodes only detect electrical impulses produced by your heart. No electricity passes through your body from the machine, and there is no danger of getting an electrical shock.


An electrocardiogram (EKG, ECG) tracings show a characteristic pattern of electrical impulses that are generated by the heart. The different parts of an EKG tracing of a heartbeat are called the P wave, the QRS complex, the ST segment, and the T wave.

Electrocardiogram (EKG, ECG)
Normal: The heart rate (usually between 60 and 100 beats per minute) and rhythm appear regular. A normal heartbeat originates in the upper chambers of the heart (atria).
P waves, QRS complexes, T waves appear normal.
ST segments are not elevated above or depressed below the baseline of the EKG tracing.
A normal-appearing EKG can occur even in the presence of heart disease. For this reason, the EKG should always be interpreted along with your symptoms, history, physical examination, and, if necessary, other test results.
Abnormal: When the electrical pattern of the EKG tracing is abnormal, it may indicate some type of heart disease. Sometimes an electrocardiogram may detect an abnormality only during exercise or when symptoms are occurring. In these cases, special forms of an EKG called an exercise EKG or an ambulatory EKG may be needed. For more information, see the medical tests Exercise Electrocardiogram and Ambulatory Electrocardiogram.
  • Heart rhythm. There are many different kinds of irregular heartbeats (arrhythmias). A heart rate less than 60 beats per minutes is called a bradycardia. A heart rate greater than 100 beats per minutes is called a tachycardia. Examples of tachycardias may include a fast, irregular heart rhythm that originates in the ventricle (ventricular fibrillation) or a fast, regular heart rhythm that begins in the atrium (atrial flutter). Abnormal conduction of the electrical impulse in the heart can also be seen in other types of arrhythmias.
  • Coronary artery disease and heart attack (myocardial infarction). If the coronary arteries supplying blood to the heart muscle are blocked, the muscle may receive less oxygen and may even die (heart attack). This damage to the heart muscle may show up on the electrocardiogram. Early EKG signs of poor blood flow to the heart may include lowered (depressed) ST segments. Early EKG signs of heart attack often include raised (elevated) ST segments. Later, as the heart attack persists, Q waves on the EKG may appear and become deeper.
  • Thickened chamber walls (hypertrophy). Certain changes in the EKG may suggest thickening of the muscle walls of one or more heart chambers. Conditions that may cause hypertrophy of one or more heart chambers include high blood pressure, coronary artery disease, heart failure, cardiomyopathy, or heart valve disease.
  • Inflammation of the heart. Elevated ST segments on the EKG may indicate an inflammation of the heart muscle (myocarditis) or the sac that surrounds the heart (pericarditis).
  • Chemical changes (electrolyte imbalance). Proper contraction of the heart depends upon normal levels of chemicals (called electrolytes) in the blood, such as calcium and potassium. Too much or too little of these electrolytes results in certain rhythm abnormalities, such as abnormal changes in the P wave, QRS complex, or T wave that can be seen on an electrocardiogram.
  • Medications. Certain medications for the heart and other conditions can result in EKG changes.


More Information:
  • How does my doctor interpret my EKG?
  • What conditions can be diagnosed with electrocardiogram?

What Affects the Test

Factors that can interfere with your test and the accuracy of the results include:

An elevated ST segment with a depressed T wave may occur in healthy African Americans and usually disappears during an exercise EKG test.

What To Think About


Author Jan Nissl, RN, BS
Author Kattie Payne, RN, PhD
Editor Susan Van Houten, RN, BSN, MBA
Associate Editor Daniel Greer
Associate Editor Tracy Landauer
Primary Medical Reviewer Adam Husney, MD

- Family Medicine
Specialist Medical Reviewer George Philippides, MD

- Cardiology
Last Updated April 22, 2004