Ambulatory Electrocardiogram

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. An ambulatory electrocardiogram 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.
  • Check to see if treatment for an irregular heartbeat is working.

How To Prepare

Your preparation may depend on the type of monitor you are getting.

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.

If you are going to have electrode pads or a patch, take a shower or bath before the electrode pads are put on. You may not be able to get the pads wet during the test. Your doctor will give you instructions on how to wear the electrodes. Wear a loose blouse or shirt.

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

Talk to your doctor if you have any concerns about 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 .

How It Is Done

Your doctor will choose the type of heart monitor that is most likely to help diagnose your heart problem. You may have a monitor that records your heart activity all of the time or only some of the time.

  • A continuous monitor records your heart activity all of the time. Examples are a Holter monitor and a wireless patch monitor.
  • An event monitor records your heart activity only when you have symptoms or a change in your heart rhythm. It may monitor you all of the time and record only when it detects a problem. Or it may only work when you start the monitor at the times you have symptoms.

Continuous monitors

Continuous recorders are a common type of monitor used for this test.

A Holter monitor gives a 24- to 48-hour record of the electrical signals from your heart. Wireless patch monitors can be used for many days. 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.

You will see a doctor or technician to get your heart monitor and to learn how to use it.

  • Several areas on your chest may be shaved and cleaned.
  • The pads or patch will be attached to the skin of your chest. For pads, 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.

Event monitors

Event monitors are 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 event monitor can often be sent over the phone or online 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.

There are different types of monitors.

Loop recorders.
  • A loop recorder constantly monitors your heartbeats. It records your heartbeats only when you have symptoms or an abnormal heart rhythm. The device might start recording when you press a button, or it might automatically record when an abnormal heart rhythm happens. Loop recorders are called this because they save a small amount of information about how your heart was beating right before the monitor started 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.
    • Electrode pads or a patch may 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. You might have this monitor for a year or more. 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.
Handheld event monitors.
  • This small device records your heartbeats only when you have symptoms. You are not attached to the machine. There are different 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.

Using your heart monitor

Your doctor will explain the details of how to use your monitor. If you have to do anything to send your heart data, your doctor will show you how.

What you do during the test

Your doctor may ask you to keep a diary of all of your activities and symptoms while you wear the monitor. 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 (if you have the type that allows you to). 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."

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.

Your doctor will tell you if you need to stay away from strong electromagnetic fields while wearing a monitor. These may include magnets, microwave ovens, and electric blankets. 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, your doctor will give you instructions. If you had electrode pads or a patch, you may go to the doctor's office or hospital to have them removed. Or you may be able to remove them yourself. Your doctor will let you know how to return the monitor.

Your doctor will review the data from your monitor and 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.

How It Feels

If you have electrodes or pads 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.

Heart monitors are typically very lightweight. So carrying or wearing them is usually is not uncomfortable.

For an implantable heart monitor, you will get medicine to numb the area of your chest where the monitor will be put in. You will be awake when the doctor makes a small cut and places the monitor under the skin. You shouldn't feel any pain.


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.
  • Certain 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. Your doctor will also compare the results with your diary of activities and symptoms. 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 do not keep a detailed diary of your daily activities and symptoms, if that is required.
  • You have an event monitor, and the recorder is not started when you have symptoms. The event 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.

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.



  1. Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.

Other Works Consulted

  • Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
  • Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.
  • Pagana KD, Pagana TJ (2014). Mosby's Manual of Diagnostic and Laboratory Tests, 5th ed. St. Louis: Mosby.
  • Shen W-K, et al. (2017). 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope. Circulation, published online March 9, 2017. DOI: 10.1161/CIR.0000000000000499. Accessed March 30, 2017.


Current as of: August 31, 2020

Author: Healthwise Staff
Medical Review:
Rakesh K. Pai MD, FACC - Cardiology, Electrophysiology
E. Gregory Thompson MD - Internal Medicine
Martin J. Gabica MD - Family Medicine
Elizabeth T. Russo MD - Internal Medicine
Adam Husney MD - Family Medicine
George Philippides MD - Cardiology

Ambulatory Electrocardiogram