In medicine, a Holter monitor (also called an ambulatory electrocardiography device), named after its inventor, Dr. Norman J. Holter, is a portable device for continuously monitoring the electrical activity of the heart for 24 hours or more. Its extended recording period is useful for observing occasional cardiac arrhythmias that would be otherwise difficult to identify in a shorter period of time.

Configuration

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Much like standard electrocardiography (EKG), the Holter monitor records electrical signals from the heart via a series of electrodes attached to the chest. The number and position of electrodes varies by model, but most Holter monitors employ from three to seven. These electrodes are connected to a small piece of equipment that is attached to the patient's belt, and is responsible for keeping a log of the heart's electrical activity throughout the recording period.

Typical devices use a standard C60 or C90 audio cassette run at a very slow speed to record the data. More modern units record onto digital flash memory devices. The data is uploaded into a computer which then automatically analyses the input, counting ECG complexes, calculating summary statistics such as average heart rate, minimum and maximum heart rate, and finding candidate areas in the recording worthy of further study by the technician.

Electrodes should be placed over bones to prevent artifacts from muscular activity.

Event diary

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In addition to receiving the device itself, most patients are also asked to keep a diary of activities such as running and sleeping, symptoms, and times that their symptoms occur. This information is used by doctors and technicians to rapidly pinpoint problem areas in the vast amount of data recorded during the monitoring period.

External links

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• Holter monitor - MedLine Plus
• Holter monitor - Texas Heart Institute
• Holter Monitor information from Children's Hospital Heart Center, Seattle.

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