An ambulatory electrocardiogram (EKG or ECG) records the electrical
activity of your heart while you do your usual activities. (Ambulatory means that you are able to walk.) Ambulatory monitors
are referred to by several names, including ambulatory electrocardiogram,
ambulatory EKG, Holter monitoring, 24-hour EKG, or cardiac event monitoring.
Many heart problems become noticeable only during activity, such as
exercise, eating, sex, stress, bowel movements, or even sleeping. A continuous
24-hour recording is more likely to detect any abnormal heartbeats that occur
during these activities.
Many people have irregular heartbeats (arrhythmias)
from time to time. The importance of irregular heartbeats depends on the type
of pattern they produce, how often they occur, how long they last, and whether
they occur at the same time you have symptoms. Because arrhythmias can occur
off and on, it may be hard to record an arrhythmia while you are in the
There are several different types of ambulatory monitors. Your doctor will choose the type that is most appropriate for you and is most likely to help diagnose your heart problem.
Why It Is Done
Ambulatory EKG monitoring is done to:
Look for and record irregular heartbeats that
occur intermittently or during certain activities.
Find out what is
causing chest pain, dizziness, or fainting. These are symptoms of possible
Look for poor blood flow to your heart muscle
Check to see if treatment for an irregular heartbeat is
How To Prepare
Many medicines may change the results of this test. Be sure to tell
your doctor about all the nonprescription and prescription medicines you
Since an EKG is often used to monitor a preexisting heart
condition, such as an irregular heartbeat (arrhythmia), make sure that your
doctor has copies of any previous EKG results.
Take a shower or bath before the discs are put on. You will not be
able to get the discs wet during the test. Wear a loose blouse or shirt. Do not
wear jewelry or clothes with metal buttons or buckles, because these can
interfere with the recording. Women should not wear an underwire bra for the
If your doctor asks you to keep a symptom and activity diary, be sure you have a method. In this diary, you will record activities and symptoms and the times they occurred. The accuracy and usefulness of your test depend on how carefully you keep this record.
If you are getting a monitor implanted under your skin, you will receive instructions on how to prepare for the procedure.
Talk to your doctor about any concerns you have regarding the need
for the test, its risks, how it will be done, or what the results will
mean. 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
Continuous recorders are the most common type of ambulatory electrocardiogram monitor. This type includes the Holter monitor.
A continuous recorder provides a 24- to 72-hour record of the electrical signals
from your heart. A standard EKG monitors only 40 to 50 heartbeats during the
brief period you are attached to the machine. A continuous recorder monitors
about 100,000 heartbeats in 24 hours and is likely to find any heart problems
that happen with activity.
For this test, you wear a lightweight, battery-operated tape
recorder (monitor) on a strap over your shoulder or around your waist. The
recorder is connected by wires to small metal discs (electrodes) taped to your
chest. The electrodes detect the electrical signals from your heart. A clock is
connected to the recorder so you can note what time it is when you have any
You will be fitted with the recorder and electrodes by a
technician in a doctor's office or hospital room.
Several areas on your chest may be shaved and
cleaned, and then a small amount of electrode paste or gel will be applied to
The electrode pads will then be attached to the skin
of your chest, with thin wires connecting the electrodes to the monitor.
You may be hooked up briefly to a standard EKG machine to ensure
that the electrodes are working properly.
What you do during the test
While wearing the continuous recorder, you will also be asked to
keep a diary of all your activities and symptoms, including the type of
activity you were doing and the time your symptoms started. In the diary, write
down the exact times when you exercise, climb stairs, eat, urinate, have a
bowel movement, have sex, sleep, get emotionally upset, take medicine, or
perform other activities. If you have any symptoms of heart problems, such as
dizziness, fainting, chest pain, or palpitations, push the event-marker button
on the recorder to mark it and write down the exact time and how long the
symptom lasts. For example, you might write: "12:30 p.m. Ate lunch. 1:00 p.m.
Argument with boss, had chest tightness for several minutes."
When you sleep, try to stay on your back with the recorder
carefully positioned at your side so that the electrodes are not pulled off. If
one of the electrodes or lead wires comes loose, a light on the monitor will
flash. Press on the center of each electrode to see if you can restore the
contact. Call your doctor if one of the electrodes comes off and you can't get
it to stay on.
While you are wearing a monitor, try to stay away from magnets,
metal detectors, high-voltage areas, garage door openers, microwave ovens, and
electric blankets. Do not use an electric toothbrush or shaver. Signals from
these types of electronic equipment can sometimes interfere with the recording.
What you and your doctor do after the test
At the end of the recording period (usually 24 to 72 hours), you will
return to the doctor's office or hospital to have the electrodes removed, or
you may be able to remove the electrodes yourself. You will return the Holter monitor to your doctor's office or hospital. The recorded tape will be
read by computer to provide information about your heart rate, the frequency of
your heartbeats, and any irregularities.
Your doctor will also look at your records of activities and symptoms and times they occurred. Your doctor will compare the timing
of your activities and symptoms with the recorded heart pattern.
Implantable continuous recorders
Another type of continuous recorder can be implanted under the
skin of the chest. This recorder can be kept in your chest for more than a year
to record the electrical signals from your heart.
Another kind of ambulatory EKG monitoring is the intermittent
recorder, which is used when symptoms of an abnormal heart rhythm do not occur
very often. An intermittent recorder can be used for a longer time than a
continuous recorder. The information collected by an intermittent recorder can
often be sent over the phone to a doctor's office, clinic, or hospital.
You may be instructed to call your doctor, clinic, or hospital
while you are having symptoms or soon after you record your heart rhythm so
that the information on the monitor can be analyzed right away.
The procedure for intermittent recording depends on the type of
Loop recorder. A loop recorder constantly
records your heartbeats. This recorder lets you indicate when you have symptoms. Loop recorders also save a small amount of
information about how your heart was beating when you pressed the recording
button (presymptom recording). This feature is especially useful for people who
lose consciousness when their heart problems occur and can press the button
only after they wake up.
Electrodes will be attached to
your chest in the same way as a continuous recorder. When you have symptoms, you press a button on the
monitor to record your heart rhythm. If you pass out, you should
start the recorder as soon as you wake up. Also, be sure a friend or family
member knows how to start the recorder if you pass out.
implantable form of the loop recorder can be worn for several weeks and may be
a good choice for people who have symptoms that occur rarely, such as once
every 6 months. It is surgically placed under the skin of the
chest. The recorder might automatically start recording when it detects an arrhythmia. Or, you might use a handheld device to start the monitor when symptoms
Event monitor. This small device records your heartbeats only
when symptoms of the heart problem occur. You are not attached to the machine.
There are two types of event monitors.
One type is worn on the wrist like a watch. When symptoms occur, you press a
button to start the EKG recording.
The other type is a device that you carry
where you can reach it easily, such as in your purse or pocket. When symptoms
occur, you press the back of the device against your chest and then press a
button to start the recording. The back of the device has small metal discs
that work like electrodes. These handheld monitors can be very small (some are
about the size and shape of a credit card). The
event monitor records heart signals only when you are holding it against your
How It Feels
If you have electrodes placed on your skin, the electrode sites may itch slightly during the ambulatory EKG
recording, and the skin on your chest may look or feel irritated when the
electrodes are removed. The recording unit is very lightweight, so carrying it
usually is not uncomfortable.
There is no risk from ambulatory EKG monitoring. The electrodes
placed on your skin detect only the electrical signals from your heart. No
electricity is sent through your body, and there is no possibility of receiving
an electric shock.
An ambulatory electrocardiogram (EKG or ECG) is a test that records
the electrical signals that control your heartbeat while you do your everyday
No abnormal heart rhythms are found in the EKG information
collected by the recorder. Your heart rate may go up when you are active and go
down when you are sleeping.
Many kinds of irregular heartbeats can be detected by
Abnormal slow or fast heart rhythms are
detected. Alternating slow and fast rhythms may also occur
A slow heart rhythm in a person with a
pacemaker may mean that the pacemaker is not working
Abnormal patterns may mean that the heart muscle is not
getting enough oxygen (ischemia) because the arteries feeding the heart are too
The results of ambulatory heart monitoring are compared with your
medical history, symptoms, and other test results. You may need to have the
test repeated if the results aren't clear.
What Affects the Test
You may not be able to have the test or the results may not be
You do not keep a detailed diary of your daily
activities and symptoms. The intermittent recorder will give accurate results
only if you remember to start the recorder when symptoms of possible heart
The electrodes are not in the right spot.
monitoring is most effective when you are able and willing to carefully follow
instructions throughout the monitoring period.
If you tend to pass out from a heart problem, your doctor will choose a monitor that will record these episodes. The
continuous recorder and the loop recorder work best for people who pass out
when they have symptoms of a heart problem. The loop recorder is not useful if
you lose consciousness for more than a few minutes or if you are so confused
when you wake up that you are unable to start the recorder.
What To Think About
Many people have irregular heartbeats from time
to time. What this means depends on the type of pattern these heartbeats
produce, how often they occur, how long they last, and whether they occur at
the same time you have symptoms. Irregular heartbeats that occur at the same
time you have other symptoms, such as dizziness or chest pain, may mean that
the irregular heartbeats are causing your symptoms.
standard 12-lead electrocardiogram (EKG) is safe, inexpensive, and provides
valuable information, your doctor will try it first before using an ambulatory
monitor to test your heart function. A continuous recorder generally has 5
leads and provides less complete information than a 12-lead EKG. But a
continuous recorder is more effective than a standard EKG for evaluating heart
symptoms that occur intermittently. For more information, see the topic
How this information was developed to help you make better health decisions.