The electrocardiogram (ECG or EKG) is a test used to evaluate the rhythm and electrical activity of the heart. A stress test is an ECG that is recorded while you exercise.


Chest, heart


An ECG is used to diagnose heart attacks and rhythm abnormalities. It can also provide clues about other heart conditions and certain medical conditions.

Heart problems can cause a variety of symptoms. Other conditions that can alter the body’s balance of electrolytes (especially potassium and calcium) can also cause symptoms and changes in the ECG. An ECG is also used to detect problems that are not primarily related to the heart, such as overdoes of certain drugs. Symptoms that may prompt an ECG include the following:

  • Chest discomfort or pain
  • Shortness of breath
  • Palpitations (fast heartbeats)
  • Anxiety
  • Weakness
  • Nausea
  • Abdominal pain
  • History of fainting
  • Ingestion of certain drugs

An ECG is also typically obtained from people who:

  • Are about to have surgery with general anesthesia, for purposes of detecting heart conditions that could worsen under the stresses of certain procedures
  • Are in occupations that stress the heart, or where public safety is a concern
  • Are over age 40, as a routine baseline
  • Already have heart disease, particularly to periodically monitor their status and to check their reaction to new medication
  • Have had a heart-related procedure such as a pacemaker insertion


The actual process of obtaining an ECG carries no risk of complications. In addition, the test is painless. When an ECG is obtained while you exercise, the only risk is related to the exercise, not the performance of the ECG. During exercise the ECG serves to monitor your heart function and capture warning signals of heart trouble. In certain cases an ECG may be normal even though heart disease is present.


Prior to Procedure

  • You will have a physical exam and be asked about your medical history.
  • If you have a very hairy chest, several patches of chest hair may need to be shaved.
  • For an exercise ECG (stress test):
    • Allow two hours between your last meal and the stress test
    • Wear comfortable clothing and walking shoes.

During Procedure – You’ll be asked to lie quietly on your back, with your shirt off. Six small adhesive pads or suction cups with attached wires will be placed across your chest. Others will be placed on your arms and legs. The wires will connect to the ECG machine.

If you’re having a stress test, your ECG will be recorded while you exercise, usually on a treadmill or bicycle. For treadmills, the speed and slope will be gradually increased as you walk. The test will continue until you have reached a certain heart rate, certain ECG changes occur, or you are too tired to continue, are short of breath, or have chest pain.

Anesthesia – None

Description of the Procedure – When your heart beats, it generates electrical signals. The ECG detects these signals from the surface of your skin and records them on a piece of graph paper. You will not feel anything during the procedure.

After Procedure – Depending on your condition and your doctor’s assessment, you may be required to have additional tests. If you have a heart condition or abnormal ECG, keep a recent copy of your ECG in your wallet, purse, or car.

How Long Will It Take – A resting ECG takes approximately 3 or 4 minutes. An exercise ECG will take longer since it includes several minutes to up to a half hour of exercise (depending on what you can tolerate), as well as some monitoring after exercise.

Will It Hurt – No

Possible Complications – There are no complications for a resting ECG. Complications of an exercise ECG would be related to exercise and your heart’s response to the exercise.

Average Hospital Stay – Hospitalization is usually not required, unless symptoms are potentially serious and additional tests, treatment, or surgery are needed.

Postprocedure Care – You may resume activities as recommended by your doctor.


Your doctor will interpret the ECG. Based on the results and additional information about your health, he or she may make recommendations for treatment during a follow-up appointment.


  • Worsening of your heart-related symptoms

American Heart Association


The Harvard Medical School Family Health Guide Web site, Diagnostic Tests: Electrocardiogram available at:
Emedicine, Electrocardiogram, available at:
University of Michigan Web site, Electrocardiogram, available at:

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