The device uses 5 electrodes that attach to the patient’s chest. Wires from the electrodes lead to a small battery-powered device that can be clipped onto a waistband or belt. The device constantly monitors the heart and records the heart’s rhythms onto a memory card.

Patients should keep a diary of their activities, such as sleeping, eating or exercising so that physicians can associate any arrhythmia with a specific activity. During Holter monitor testing, patients should avoid taking showers or baths and limit the use of small electrical devices, such as electric toothbrushes, razors or microwaves.