The Holter is a recording device that comes in two different forms:

• a small portable tape recorder (like a walkman), or
• a small digital device the shape of a pager.

You wear the device on a belt round your waist. Anything between three to twelve ECG leads from the device are taped to your chest. The device records the electrical activity of your heart for 24 to 48 hours, or for up to 7 days if a digital one is used. The doctor can then analyse the electrical activity and rhythm of your heart to find out if you have any arrhythmias or other features which may be present in certain conditions such as long QT syndrome and Brugada syndrome.