What is an electrocardiogram?
An electrocardiogram (ECG or EKG) is one of the simplest and fastest tests used to
evaluate the heart. Electrodes (small, plastic patches that stick to the skin) are
placed at certain spots on the chest, arms, and legs. The electrodes are connected
to an ECG machine by lead wires. The electrical activity of the heart is then measured,
interpreted, and printed out. No electricity is sent into the body.
Natural electrical impulses coordinate contractions of the different parts of the
heart to keep blood flowing the way it should. An ECG records these impulses to show
how fast the heart is beating, the rhythm of the heart beats (steady or irregular),
and the timing of the electrical impulses as they move through the different parts
of the heart. Changes in an ECG can be a sign of many heart-related conditions.
Why might I need an electrocardiogram?
Some reasons your healthcare provider may request an ECG include:
To look for the cause of chest pain
To evaluate problems that may be heart-related, such as severe tiredness (fatigue),
shortness of breath, dizziness, or fainting
To identify irregular heartbeats
To help assess the overall health of the heart before procedures, such as surgery;
after treatment for a heart attack (myocardial infarction), endocarditis (inflammation
or infection of one or more of the heart valves), or other condition; or after heart
surgery or cardiac catheterization
To see how an implanted pacemaker is working
To find out how well certain heart medicines are working
To get a baseline tracing of the heart's function during a physical exam, which can
be compared with future ECGs
There may be other reasons for your provider to advise an ECG.
What are the risks of an electrocardiogram?
An ECG is a quick, easy way to assess the heart’s function. Risks associated with
ECG are minimal and rare.
You won't feel anything during the ECG. You may feel some discomfort when the sticky
electrodes are taken off. If the electrode patches are left on too long, they may
cause skin irritation.
There may be other risks depending on your specific medical condition. Be sure to
discuss any concerns with your provider before the test.
Certain factors or conditions may interfere with or affect the results of the ECG.
Anatomical considerations, such as the size of the chest and the location of the heart
within the chest
Movement during the test
Exercise or smoking before the test
Electrolyte imbalances, such as too much or too little potassium, magnesium, or calcium
in the blood
How do I get ready for an electrocardiogram?
Your healthcare provider or the technician will explain the test to you and let you
Generally, fasting (not eating) isn't required before the test.
Tell your provider about all the prescription and over-the-counter medicines, vitamins,
herbs, and supplements that you take.
Tell your provider if you have a pacemaker.
Based on your medical condition, your provider may request other specific preparation.
What happens during an electrocardiogram?
An ECG may be done on an outpatient basis or as part of a hospital stay. Steps may
vary depending on your condition and your provider’s practices.
Generally, an ECG follows this process:
You'll be asked to remove any jewelry or other objects that may interfere with the
You'll be asked to remove clothing from the waist up. You will be given a sheet or
gown to wear so that only the necessary skin is exposed during the test.
You'll lie flat on a table or bed for the test. It's important for you to lie still
and not talk during the ECG, so that you don’t change the results.
If your chest, arms, or legs are very hairy, the technician may shave or clip small
patches of hair so that the electrodes will stick to your skin.
Electrodes will be attached to your chest, arms, and legs.
The lead wires will be attached to the electrodes.
Once the leads are attached, the technician may enter identifying information about
you into the machine's computer.
The ECG will be started. It will take only a short time for the tracing to be completed.
Once the tracing is completed, the technician will disconnect the leads and remove
What happens after an electrocardiogram?
You should be able to go back to your normal diet and activities, unless your provider
tells you differently.
Generally, there is no special care needed after an ECG.
Tell your provider if you have any chest pain, shortness of breath, dizziness, fainting,
or other symptoms that you had before the ECG.
Your provider may give you other instructions after the test, depending on your situation.
Before you agree to the test or the procedure make sure you know:
The name of the test or procedure
The reason you're having the test or procedure
What results to expect and what they mean
The risks and benefits of the test or procedure
What the possible side effects or complications are
When and where you're to have the test or procedure
Who will do the test or procedure and what that person’s qualifications are
What would happen if you didn't have the test or procedure
Any alternative tests or procedures to think about
When and how you'll get the results
Who to call after the test or procedure if you have questions or problems
How much you'll have to pay for the test or procedure