Holter Monitor: Why Do I Have to Wear This Small Device for a Whole Day?

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Each year, thousands of patients will suffer some sort of heart disorder. There exist numerous possibilities of what could go wrong. Physicians do not have enough time to test and diagnose each individual patient. For those whose cardiac condition does not appear immediately life-threatening, many will be ordered to wear a Holter monitor from one to three days and then return to the hospital. It is important to know more about these monitors before your physician asks you to wear one. Most often, they will explain what it is and what it does, but it is always good to arm yourself with as much knowledge as you can gather.

Physicians will order a patient to wear a monitor for several reasons. Most often, it is used to detect irregular heartbeats, called arrhythmias. Other reasons include chest pain, to aid in the diagnosis of symptoms such as shortness of breath or dizziness, and to determine how a patient is reacting to certain medications. After a heart attack or after a pacemaker has been inserted, patients may wear a Holter monitor to ensure that the heart is functioning properly.


A Holter monitor is a small, battery-operated electronic device. It is portable enough to be carried in a small purse or jacket pocket, though they can also be carried by the strap that is attached to the monitor. There are many different brands, which will look different from one to the next, but they will usually contain a small screen and should have an “Event” button on them. If you are to experience a cardiac event, be it chest pain or abnormal rhythms, you would press the button and the monitor would record this.

Out of the monitor, there will be at least five wires which will connect to sticky pads. These small pads will be stuck to your torso. Men with hairy chests may be required to shave on the spots where these pads, called electrodes, will be placed. It will also be necessary to wear a loose fitting button-up shirt or blouse, so that the leads will not be interrupted for the duration of the testing.

The monitors are not waterproof, so patients wearing them are not permitted to shower during the test period. However, patients should eat, drink and perform normal daily activities while wearing the monitor. A careful sponge bath is allowed.

What It Does

The heart uses electrical signals to cause the muscle to contract and the heart to beat at regular intervals. In hospitals, doctors use electrocardiography to determine that the electrical impulses of a patient’s heart are working correctly. The record of this test is called an electrocardiogram (ECG or EKG). Holter monitors are merely portable versions of an EKG. They are often referred to as ambulatory electrocardiograms.

Most tests last about 24 hours. During this time, the device keeps a running record of your heart rhythm during your normal activities, including sleep. After you return the device, a technician will interpret the data recorded by the monitor, and your physician will make a diagnosis based on this data or prescribe further testing.


Mayo Clinic: Holter Monitor

Harvard Health Publications: Holter Monitor

University of Pittsburgh Medical Center: Holter Monitor

Cleveland Clinic: Ambulatory Monitors

National Heart Lung and Blood Institute: EKG Holter and Event Monitors

University of Michigan Cardiovascular Center: Holter Monitor

Johns Hopkins Medicine Heart and Vascular Institute: Holter Monitor

University of Alabama at Birmingham Medicine: Holter Monitoring

University of Maryland Medical Center: Holter Monitor (24h)