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EKG Testing

What is an EKG (Electrocardiogram)?

  • An EKG is a record of your heart's electrical activity.

How is an EKG Done?

  • Ten sensors are attached to your arms and chest (around the heart area).
  • This is indicated with a square and circle symbol on the following diagram:

  • These sensors "listen" to your heartbeat and make a wave pattern on graph paper.
  • Electrical impulses associated with heart contraction and relaxation are recorded.
  • From the pattern on your EKG tracing, your doctor can check on how your heart is doing

Why has my doctor ordered an EKG?

  • Sometimes an EKG is ordered as part of a regular physical exam.
  • To check up on a chest pain you may have told your doctor about.
  • To follow the course of a heart condition or heart disease.

Will the EKG Hurt?

  • An EKG is completely painless.
  • No electricity goes into your body.
  • There is no chance of electrical shock.

Do I need an appointment for an EKG?

  • No appointment is necessary, however, you will require a laboratory requisition completed by your doctor ordering an EKG.

What information will the laboratory need from me?

  • Your height and weight (this is required for the cardiologist to interpret the tracing).
  • Your name, address, date of birth, and personal health number.

How long will it take to perform the EKG?

  • No more than 20 minutes and usually much less.

What will the laboratory ask me to do?

  • Undress ONLY to your waist (we require a bare chest to position the EKG sensors).
  • You can keep all jewelry on.
  • Lie flat on your back on the EKG table (bed).
  • RELAX!

What does an EKG tracing look like?

(Sample only) 

What happens to my EKG tracing?

  • Your EKG tracing is read by a cardiologist (doctor who specializes in the heart).
  • The results of your EKG tracing will be returned to the doctor that ordered this test, usually within one week.
  • Any urgent requests can be done the same day.




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:

  • Evidence of heart enlargement.
  • Signs of insufficient blood flow to the heart.
  • Signs of a new or previous injury to the heart (heart attack).
  • Heart rhythm problems (arrhythmias).
  • Changes in the electrical activity of the heart caused by an electrolyte imbalance in the body.
  • Signs of inflammation of the sac surrounding the heart (pericarditis).

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

An electrocardiogram (EKG, ECG) is done to:

  • Evaluate unexplained chest pain, especially when a heart attack is a possibility. Other possible causes of chest pain or discomfort that can be identified by an EKG include irregular heartbeats (arrhythmias), a heart chamber with thickened walls (hypertrophy), inflammation of the sac surrounding the heart (pericarditis), and reduced blood flow to the heart muscle (ischemia).
  • Monitor the heart's electrical activity.
  • Determine whether thickening of the walls (hypertrophy) of a ventricle is present.
  • Monitor the effectiveness and possible side effects of certain medications that may affect the heart.
  • Check the function of mechanical devices (pacemakers or defibrillators) implanted in the heart to maintain a regular heart rhythm.

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.

  • The P wave is a record of the movement of electrical activity through the upper heart chambers (atria).
  • The QRS complex is a record of the movement of electrical impulses through the lower heart chambers (ventricles).
  • The ST segment usually appears as a straight, level line between the QRS complex and the T wave. Elevated or lowered ST segments may mean the heart muscle is damaged or not receiving enough blood.
  • The T wave corresponds to the period when the lower heart chambers are relaxing electrically and preparing for their next muscle contraction.
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:

  • Defects in electrocardiogram (EKG, ECG) equipment or electrical interference from improperly grounded equipment or from other nearby electrical equipment in the testing room.
  • If electrodes are not securely attached to the skin.
  • If you move or talk during the test.
  • Strenuous exercise before the test.
  • Anxiety or heavy, deep breathing.
  • Inaccurate placement of the EKG leads on the chest, such as switching the position of the right and left arm leads, or switching the position of the left leg leads.

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

  • If an electrocardiogram (EKG, ECG) is done during a heart attack, it may initially appear normal or unchanged from a previous EKG. Therefore, the EKG may be repeated over several hours and days (called serial EKGs), and is usually done along with blood tests, to look for characteristic signs of heart muscle damage.
  • There are several other types of electrocardiograms, including telemetry, ambulatory (Holter) monitoring, and exercise EKG testing.
    • Telemetry and ambulatory (Holter) monitoring are used if you need continuous monitoring of your EKG while you are in the hospital or at home.
    • Telemetry is used when you are hospitalized. It requires the placement of at least two electrodes, which are plugged into a small pocket-sized transmitter and secured to your clothing or held in a pocket. The transmitter emits a signal that is picked up and displayed on a central monitoring system. Abnormal heart rhythms are recorded and may trigger an alarm.
    • Ambulatory (Holter) monitoring records the activity of the heart continuously over a 24- to 48-hour period while you go about your normal daily activities. For more information, see the medical test Ambulatory Electrocardiogram.
    • Exercise EKG testing measures changes in the EKG during exercise. For more information, see the medical test Exercise Electrocardiogram test).
  • A resting EKG is always done before an exercise EKG test because certain types of abnormalities in the electrical activity of the heart may make proper interpretation of the test results during an exercise EKG more difficult. A resting EKG may also suggest that the heart has severely reduced blood flow, which might make an exercise EKG unsafe.
  • Some health professionals encourage people over age 35 to have a baseline EKG before problems develop. This baseline EKG may be compared to later EKGs to see if changes have occurred. However, a baseline EKG is not cost-effective for everyone. Baseline EKGs may be most useful in people who have several risk factors for heart disease.
  • Sometimes EKG abnormalities can be seen only during exercise or while symptoms are present. To detect these changes in the heartbeat, an ambulatory EKG or stress EKG may be done. An ambulatory EKG is a type of portable, continuous EKG monitor. A stress EKG is a type of EKG done during exercise. For more information, see the medical tests Ambulatory Electrocardiogram and Exercise Electrocardiogram.
  • After an EKG, other tests may be needed to diagnose a heart condition. For more information, see the medical tests Exercise Electrocardiogram, Echocardiogram, Cardiac Blood Pool Scan, Cardiac Perfusion Scan, and Cardiac Catheterization.


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