Ambulatory Electrocardiogram

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Test Overview

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 during the test. This type of monitoring may also be called ambulatory EKG, Holter monitoring, 24-hour EKG, or cardiac event monitoring.

Many heart problems are noticeable only during certain activities. These include exercise, eating, sex, stress, bowel movements, and even sleeping. A constant 24-hour recording is more likely to find abnormal heartbeats that occur during these activities.

Many people have irregular heartbeats (arrhythmias) from time to time. What this means 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 come and go, it may be hard to record one while you are in the doctor's office.

There are several different types of ambulatory monitors. Your doctor will choose the type that works best 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 come and go or happen during certain activities.
  • Find out what is causing chest pain or pressure, dizziness, or fainting. These may be symptoms of heart problems.
  • Look for poor blood flow to your heart muscle. This is called ischemia.

How To Prepare

Be sure to tell your doctor about all the medicines you take, even over-the-counter ones. Many medicines can change the results of this test.

An EKG is often used to monitor a preexisting heart problem, such as an irregular heartbeat. So make sure that your doctor has copies of any previous EKG results.

Take a shower or bath before the electrode pads are put on. You will not be able to get the pads wet during the test. Wear a loose blouse or shirt. Do not wear jewelry or clothes with metal buttons or buckles. They can affect the recording. Women should not wear an underwire bra for the same reason.

If your doctor asks you to keep a symptom and activity diary, be sure that you keep track of these things closely. In this diary, you will record activities and symptoms and the times they occurred. You need to carefully keep this record for your test to be accurate and useful.

If you are getting a monitor put under your skin, you will get instructions on how to prepare for the procedure.


How It Is Done

Continuous recorders

Continuous recorders are the most common type of monitor used for this test. This type includes the Holter monitor .

A continuous recorder gives 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 time you are attached to the machine. A continuous recorder monitors about 100,000 heartbeats in 24 hours. It is likely to find any heart problems that happen with activity.

For this test, you wear a lightweight, battery-operated tape recorder (monitor). It attaches to a strap that goes over your shoulder or around your waist. The recorder is connected by wires to small pads or patches (electrodes) taped to your chest. These detect the electrical signals from your heart. The recorder has a clock on it. This is so you can note what time it is when you have any symptoms.

The recorder and electrodes will be put on in a doctor's office or hospital room.

  • Several areas on your chest may be shaved and cleaned. Then a small amount of paste or gel will be put on those areas.
  • The electrode pads will then be attached to the skin of your chest. Thin wires will connect the electrodes to the monitor.
  • You may be hooked up briefly to a standard EKG machine. This is done to check that the electrodes are working as they should.

What you do during the test

You will need to keep a diary of all your activities and symptoms while you wear the continuous recorder. You will write down the type of activity you were doing and the time your symptoms started. For example, write down the exact times when you:

  • Exercise or climb stairs.
  • Eat.
  • Urinate or have a bowel movement.
  • Have sex.
  • Sleep.
  • Get upset.
  • Take medicine.

If you have any symptoms of heart problems, such as dizziness, fainting, chest pain, or abnormal heartbeats, push the event-marker button on the recorder to mark it. Then 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."

Try to sleep on your back with the recorder placed carefully at your side. This will help keep the electrodes from getting 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, remote controls for garage door openers, microwave ovens, and electric blankets. Do not use an electric toothbrush or shaver. And try to stay away from metal detectors and high-voltage areas. Signals from these types of electronic equipment can sometimes affect 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 go to the doctor's office or hospital to have the electrodes removed. Or you may be able to take off the electrodes yourself. You will return the monitor to your doctor's office or hospital. The recording will be read by a computer. This will give information about your heart rate, how often your heart beats, and any signs of an abnormal heartbeat.


Implantable continuous recorders

Another type of continuous recorder can be put under the skin of the chest. This recorder can be kept in your chest for more than a year. During that time, it records the electrical signals from your heart.

Intermittent recorders

Another kind of ambulatory EKG monitoring is the intermittent recorder. This is used when symptoms of an abnormal heart rhythm do not happen very often. This kind of 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 told to call your doctor, clinic, or hospital while you are having symptoms or soon after you record your heart rhythm. This way the information on the monitor can be looked at right away.

The way intermittent recording is done depends on the type of monitor being used.

  • Loop recorder. A loop recorder constantly records your heartbeats. It lets you track 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. This is called presymptom recording. This feature is especially useful for people who pass out 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 with 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.
    • One type of loop recorder can be placed under the skin of your chest. This is done with surgery. The recorder can be worn for several weeks. This may be a good choice for people who have symptoms that happen rarely, such as once every 6 months. The recorder may start recording on its own when it detects an abnormal heartbeat. Or you might use a handheld device to start the monitor when symptoms occur.
  • Event monitor. This small device records your heartbeats only when you have symptoms. 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 you have symptoms, 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 you have symptoms, you press the back of the device against your chest. Then you 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 hold it against your chest.

How It Feels

If you have electrodes on your skin, those places may itch slightly during the test. 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. So there is no chance of getting 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 normal activities.

Results of ambulatory EKG monitoring usually are looked at by a cardiologist or cardiac electrophysiologist. The results are most often available in a few days.

Ambulatory electrocardiogram (EKG or ECG) footnote 1

No abnormal heart rhythms are found. Your heart rate may go up when you are active and go down when you are sleeping.


Many kinds of abnormal heartbeats can be found by ambulatory monitoring.

  • Abnormal slow, fast, or irregular heart rhythms are found. Alternating slow and fast rhythms may also occur now and then.
  • A slow heart rhythm in a person with a pacemaker may mean that the pacemaker is not working as it should.
  • Abnormal patterns may mean that the heart muscle is not getting enough oxygen. This is called ischemia. It may happen if the arteries feeding the heart are too narrow.

The results of this test are compared with your medical history, symptoms, and other test results. You may need to have the test again if the results aren't clear.

What Affects the Test

The test results may not be accurate or helpful if:

  • You don't start the recorder when you have symptoms. The intermittent recorder will give accurate results only if you start the recorder when you have symptoms of possible heart problems.
  • The electrodes are not in the right spot.

Ambulatory heart monitoring works best when you carefully follow instructions while you're being monitored.

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 pass out for more than a few minutes. And it's not helpful if you are so confused when you wake up that you can't 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 happen at the same time you have symptoms. When irregular heartbeats occur at the same time you have other symptoms, such as dizziness or chest pain, it may mean that these heartbeats are causing your symptoms.
  • A standard 12-lead electrocardiogram (EKG) is safe, inexpensive, and gives helpful information. So 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 works better than a standard EKG for checking heart symptoms that come and go. To learn more, see the topic Electrocardiogram.

Other Places To Get Help


American Heart Association (AHA)

Related Information




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ByHealthwise Staff
Specialist Medical Reviewer George Philippides, MD - Cardiology

Current as ofFebruary 20, 2015