Tests & Procedures

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Holter Monitor

What is a Holter monitor?

A Holter monitor is a type of portable electrocardiogram (ECG). It records the electrical activity of the heart over 24 hours or longer while you are away from your healthcare provider's office.

A standard or resting ECG is one of the simplest and fastest tests used to check the heart. Small, plastic patches (electrodes) are put on certain points on the chest and belly (abdomen). The electrodes are connected to an ECG machine by wires. The electrical activity of the heart can be measured, recorded, and printed. No electricity is sent into the body.

Man's torso showing two ECG leads attached to chest, connected to event monitor clipped to belt.

Natural electrical impulses help control the different parts of the heart. This keeps blood flowing the way it should. An ECG records these impulses to show how fast the heart is beating. It also checks the rhythm of the heartbeats (steady or irregular). It records the strength and timing of the electrical impulses. Changes in an ECG can be a sign of many heart-related conditions.

Your healthcare provider may request a Holter monitor ECG if you have symptoms such as dizziness, fainting, and low blood pressure. They may also request a Holter monitor if you have ongoing tiredness, palpitations, or a resting ECG doesn’t show a clear cause. A Holter monitor may also be ordered if your resting ECG shows a problem but more information is needed. You wear the same kind of ECG electrode patches on your chest and the electrodes are connected by wires to a small monitor box (portable recording device). Newer devices don't use electrode patches and wires. They are a single unit that attaches to the chest like a patch.

Certain abnormal heart rhythms may happen only now and then. Or they may happen only under certain conditions, such as stress or activity. These are hard to record on an ECG done in the office. Because of this, the healthcare provider might request a Holter monitor to get a better chance of catching any abnormal heartbeats or rhythms that may be causing the symptoms. Some Holter monitors also have an event monitor feature that you activate when you notice symptoms. Holter monitors record every single heartbeat and can give information on the minimum, maximum, and average heart rate.

You will get instructions on how long you will need to wear the monitor (usually 24 to 48 hours but sometimes longer). Your provider will also tell you how to keep a diary of your activities and symptoms during the test, and about any personal care and activity instructions. For instance, you will need to keep the device dry while you are wearing it if wires are used.

Why might I need a Holter monitor?

Some reasons your healthcare provider may ask for a Holter monitor recording or event monitor recording include:

To evaluate symptoms that may be heart-rhythm related. Symptoms can include e chest pain, tiredness, shortness of breath, dizziness, or fainting.
To identify irregular heartbeats or palpitations.
To assess your risk for future heart-related events in certain conditions. These conditions can include thickened heart walls (hypertrophic cardiomyopathy) after a heart attack that caused weakness of the left side of the heart. This is called Wolff-Parkinson-White syndrome. In this syndrome, an abnormal electrical conduction pathway exists in the heart.
To see how well a pacemaker is working.
To find out how well treatment is working for complex abnormal heart rhythms;
To see how fast or slow your heart rate gets during the day. And to see if you have any pauses in your heart rhythm.

Your healthcare provider may have other reasons to advise a Holter monitor.

What are the risks of a Holter monitor?

The Holter monitor is an easy way to check the heart’s function. Risks of a Holter monitor are minimal and rare.

It can be hard to keep the electrodes stuck to your skin. Extra tape may be needed. It may be uncomfortable when the sticky electrodes and tape are taken off. If the electrodes are on for a long time, they may cause skin irritation or blistering.

There may be other risks depending on your specific health condition. Talk to your healthcare provider about any concerns before wearing the monitor.

Some factors or conditions may affect the results of the Holter monitor reading. These include:

Being near magnets, metal detectors, high-voltage electrical wires, and electrical appliances. Appliances can include shavers, toothbrushes, and microwave ovens. Cell phones can also interfere with the signals. Keep them at least 6 inches away from the monitor box.
Excessive sweating, which may cause the leads to loosen or come off

How do I get ready for a Holter monitor?

Your healthcare provider will explain the procedure and you can ask questions.
You don't need to fast (not eat or drink).
Your healthcare provider may have other instructions for you.

What happens during a Holter monitor?

A Holter monitor recording is often done on an outpatient basis. Procedures may be different depending on your condition and your healthcare provider's practice.

Generally, a Holter monitor recording follows this process:

You will be asked to remove any jewelry or other objects that may interfere with the recording.
You will be asked to remove your clothing from the waist up so that electrodes or a patch can be attached to your chest. The technician will give you privacy by covering you with a sheet or gown and exposing only the necessary skin.
The areas where the electrodes or patch is placed are cleaned. In some cases, hair may be shaved or clipped so that the electrodes will stick closely to the skin.
Electrodes will be attached to your chest and belly (abdomen). The Holter monitor will be connected to the electrodes with wires. The small monitor box may be worn over your shoulder like a shoulder bag, around your waist, or it may be clipped to a belt or pocket. If you were given a newer device, it will be attached to your chest like a patch.
Find out if you will have to change the batteries in the monitor box. Make sure you know how to do it and have extra batteries on hand.
If your provider says it is OK, you can return to your normal activities once you have been hooked up to the monitor box and given instructions. These are activities such as work, household chores, and exercise. This will let your provider find problems that may only happen with certain activities.
You may be told to keep a diary of your activities while wearing the monitor. Write down the date and time of your activities, especially if any symptoms such as dizziness, palpitations, chest pain, or other previously experienced symptoms happen.

What happens after a Holter monitor?

You should be able to go back your normal diet and activities unless your healthcare provider advises differently.

Usually, there is no special care after a Holter monitor recording.

Tell your healthcare provider if you have any symptoms you had before the recording. For instance, if you have chest pain, shortness of breath, dizziness, or fainting.

Your healthcare provider may give you other instructions after the procedure.