Ambulatory Cardiac Monitoring

(Holter Monitoring; Ambulatory Electrocardiography [EKG])


Ambulatory cardiac monitoring watches and records heart activity during the day. Most devices are about the size of a mobile phone.

Heartbeat on EKG Monitor

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Reasons for Test

This test is done to find out whether the heart is beating too slow or too quickly. It also looks for heart rhythm problems.

The test records your heart’s electrical activity for long periods of time. This makes it more likely to find a problem that comes and goes. It may be used to learn more about:

  • Fainting spells thought to be caused by the heart
  • A feeling that the heart is racing
  • Whether treatment for heart rhythm problems is working

Possible Complications

This test does not cause problems.

What to Expect

Prior to Test

An ECG will be done to check the electrical activity of your heart.

Description of Test

The test steps depend on how it will be done:

  • Holter monitoring —A small device will be strapped to you. Wires from it will be attached to small sticky pads (electrodes) on your chest. You may be taught to replace them or asked not to take them off during the test. Some devices have an event button. You will push the button each time you have a symptom that bothers you. You will need to keep a diary of the things you do for the next 24 to 48 hours. You will return the device and your diary.
  • Looping monitor —The electrode may be a wrist band, finger attachment, or chest plate. It records many minutes at a time, then starts over. You will push a button during or after an event to save the data. There is an implantable version that records longer periods of time. It is surgically placed under your skin.
  • Event recorder —This device is only used when you have symptoms. It may be a wrist band with a button or a pager-sized device that you press onto your chest. Some of these are connected to a 24-hour base that can find a problem right away and respond to an event when you activate the signal.
  • Mobile cardiac outpatient telemetry —A special service monitors your heartbeat at all times. It will respond right away when it finds a serious problem.

You will need to stay away from things like magnets, metal detectors, high-voltage wires, microwave ovens, and electric devices. They may cause problems with the test.

After Test

You will return the device after the test.

How Long Will It Take?

The test is often done for 24 hours. Some people may need to be monitored longer.

Will It Hurt?

This test will not hurt.


Your doctor will look at the data and let you know whether you need more tests or treatment.

Call Your Doctor

Call your doctor if you have trouble breathing, chest pain, or any other problems.

If you think you have an emergency, call for medical help right away.


American Heart Association
Heart Rhythm Society


Canadian Cardiovascular Society
Heart and Stroke Foundation of Canada


Ambulatory cardiac telemetry monitoring. EBSCO DynaMed website. Available at: https://www.dyname.... Updated June 7, 2017. Accessed November 19, 2019.
Ambulatory monitors. Cleveland Clinic Heart Center website. Available at:
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Updated April 22, 2019. Accessed November 19, 2019.
Priori SG, Blomström-Lundqvist C, et al. 2015 European Society of Cardiology (ESC) Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Endorsed by: Association for European Paediatric and Congenital Cardiology (AEPC). Eur Heart J. 2015 Nov 1;36(41):2793-2867.
Last reviewed September 2019 by EBSCO Medical Review Board James P. Cornell, MD
Last Updated: 9/25/2020

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