A Holter monitor is a device that continuously records the heart’s rhythms. The monitor is usually worn for 24 to 48 hours during normal activity.

How the test is performed. The technologist will attach several small electrodes to your chest. It may be necessary to shave or clip some hair so the electrodes will stick to the skin. The electrodes are attached to a small recording monitor, which you carry in a pocket or small pouch worn around your neck or waist. While you wear the monitor, it records your heart’s electrical activity. For the duration of the test, you keep a diary of your activities and how you feel. Your doctor will later match your activities and symptoms with the Holter monitor findings.

How to prepare for the test. Don’t apply creams to your body on the day of the test. Make sure to shower or bathe before the test, as you will not be able to do so while you are wearing the Holter monitor. Bring a list of your medications.

How the test will feel. The test is painless. However, keeping the monitor close to your body may make it hard for you to sleep.