Definition: A Holter monitor is a portable device that allows doctors to diagnose abnormal heart rhythms missed by a regular electrocardiogram performed in the doctor’s office. The device records the heart’s electrical activity for as long as the patient is connected to it. Because the monitor is small, it can easily be carried around by a person during his normal daily activities. Most people carry the monitor for one to two days, as this is usually enough time to detect an abnormality.

