What is a portable heart rhythm monitoring system (Holter monitor)?

A Holter monitor, also known as a portable heart rhythm monitoring system, is a small, portable electrocardiogram that measures your heart’s activity as you perform your everyday activities. Your doctor will indicate how long you should wear the device — typically between 24 and 48 hours.

Who is a candidate for a Holter monitor?

Your doctor may recommend using a Holter monitor if you are experiencing abnormal heart rhythms or other cardiac symptoms. Because the timing of arrhythmias is uncertain, your doctor can not always see any abnormal activity during an in-office electrocardiogram. A Holter monitor allows your doctor to evaluate your heart’s activity over a longer period so he or she can catch an irregular event. 

What to expect when wearing a Holter monitor?

During a clinic visit, a cardiovascular technician will attach the Holter monitor to your chest via electrodes that connect to the battery-operated device. Your technician will instruct you to keep detailed notes on your activities and symptoms, such as chest pain, shortness of breath, abnormal heart beats or dizziness, while wearing the device. Your notes should include very specific details on what time the symptoms began and what you were doing when the symptoms began. 

While you have the device on do not:

  • Get the device wet - do not bathe, shower or swim with a Holter monitor
  • Have an X-ray
Also make sure to avoid any high voltage areas or large magnets.

What are risks associated with using a Holter monitor?

Using a Holter monitor does not pose any real risks. The monitor does not cause any pain or interfere with your body’s normal functioning.


After the testing period, the Holter monitor should be returned to your doctor so your Mercy Health cardiac team can analyze your heart activity. Your doctor will review your results and schedule a follow-up appointment if you have any abnormal activities.

Find a heart and vascular doctor nearby

Mercy Health locations that can treat you