Holter and event monitors are small, portable devices that record the electrical activity of the heart. They work similar to an electrocardiogram which is a simple test that measures and records the heart's electric impulses. The difference is that an electrocardiogram only records the heartbeat for several seconds and can often miss heart rhythm problems because the abnormalities may not take place during the test. Some heart rhythm irregularities may occur during certain activities such as exercise or sleep and these monitors have a greater chance of recording these because they are worn either 24 hours or more. Holter and event monitors are similar but not the same.

Holter Monitor
A holter monitor is a small device with five leads that have electrodes that are placed on the patient's chest. The device is worn in a small pouch attached to a belt or shoulder strap for 24 hours or longer. The patient also maintains a diary of symptoms and activities while wearing it. The patient should continue with his/her normal daily routine. While the patient is wearing the monitor he/she cannot take a shower or bath. The monitor will be put on at one of the offices by a medical assistant or nurse and will be given instructions or what to do while wearing it.

Event Monitor
An event monitor is a small device with two leads that comes with a month supply of electrodes which are attached to the chest. This device is used to detect abnormal heart rhythms when a button is pushed by the patient when he/she is feeling symptoms of an event such as dizziness, shortness of breath, weakness, heart racing or skipping beats. The event monitor will record up to a limited amount of data and will later need to be sent in via telephone for the doctor to review. This monitor should be worn each day for 30 days and only removed during bathing.