Holter monitor

This wearable device keeps track of the heart's rhythm during daily activities. Learn when you might need one and what to expect.


A Holter monitor is a small, wearable device that records the heart's rhythm. It's used to detect or determine the risk of irregular heartbeats (arrhythmias).

A Holter monitor test may be done if a traditional electrocardiogram (ECG or EKG) doesn't provide enough details about the heart's condition. If the irregular heartbeats are infrequent, a longer term monitor called an event recorder may be needed.

Some personal devices, such as smartwatches, offer electrocardiogram monitoring. Ask your health care provider if this is an option for you.

Holter monitor

A Holter monitor uses electrodes and a recording device to track the heart's rhythm for 24 to 72 hours. A health care provider can print an electrocardiogram strip using the data on the recording device to see the heart's rhythm during the period the monitor was worn.

Why it's done

A health care provider may recommend a Holter monitor if you have:

  • Signs and symptoms of an irregular heart rhythm (arrhythmia)
  • Unexplained fainting
  • A heart condition that increases the risk of arrhythmias

Before you get a Holter monitor, you'll have an electrocardiogram (ECG or EKG). An ECG is a quick and painless test that uses sensors (electrodes) taped to the chest to check the heart's rhythm.

If you have infrequent arrhythmias, an ECG may not detect them. A Holter monitor may be able to spot irregular heart rhythms that an ECG missed.

If standard Holter monitoring doesn't capture an irregular heartbeat, a device called an event monitor may be recommended to record heartbeats over several weeks.


There are no significant risks involved in wearing a Holter monitor. Some people have minor discomfort or skin irritation where the sensors (electrodes) were placed.

Holter monitors aren't usually affected by other electrical appliances. But some devices may interrupt the signal from the electrodes to the Holter monitor. If you have a Holter monitor, you should avoid the following:

  • Electric blankets
  • Electric razors and toothbrushes
  • Magnets
  • Metal detectors
  • Microwave ovens

Also, keep cellphones and portable music players at least 6 inches from the Holter monitor for the same reason.

How you prepare

A Holter monitor is placed at a care provider's office during a scheduled appointment. Unless your health care provider tells you otherwise, plan to bathe before this appointment. Most monitors can't be removed and must be kept dry once monitoring begins.

A care provider will place sensors (electrodes) on your chest. These electrodes detect the heartbeat. They're about the size of a silver dollar. If you have hair on your chest, some of it may be shaved to make sure the electrodes stick.

Wires attached to the electrodes connect to the Holter monitor recording device. The device is about the size of a deck of cards.

Once your Holter monitor is fitted and you've received instructions on how to wear it, you can leave your provider's office and return to everyday activities.

What you can expect


A Holter monitor is typically worn for 1 to 2 days. During that time, the device records all of the heartbeats.

Holter monitoring is painless and noninvasive. The sensors (electrodes) and wires can be hidden under clothing. The device is worn on a belt or attached to a strap.

Don't take the Holter monitor off — it must be worn during the entire recording period, even while sleeping.

Water can damage a Holter monitor. Don't swim, shower or bathe for the entire time you're wearing a Holter monitor. If you have a wireless Holter monitor, you'll be shown how to disconnect and reconnect the sensors and the monitor so that you can shower or bathe.

While you wear a Holter monitor, you can do most other daily activities unless your provider tells you otherwise. You may be given a form to record your activities and any symptoms. It's particularly important to note if and when you have any of the following symptoms:

  • Pounding, fluttering or skipped heartbeats
  • Shortness of breath
  • Chest pain
  • Lightheadedness

Write down what activities you do and exactly what time you do them.


Once your monitoring period is over, you'll return the device to your health care provider's office. If you were asked to keep a record of symptoms that you had while wearing the device, your provider can compare the Holter monitor's data with your notes. This can help your provider make an accurate diagnosis.


Your care provider will review the Holter monitor test results and discuss them with you. Information from Holter monitor testing can tell your provider if you have a heart condition and if any heart medicines you currently take are or aren't working.

If you didn't have any irregular heart rhythms while you wore the monitor, your provider may recommend a wireless Holter monitor or an event recorder, both of which can be worn longer than a standard Holter monitor. Event recorders are similar to Holter monitors and generally require you to push a button when you feel symptoms. There are several different types of event recorders.

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