The holter monitor measures and records electrical impulses in the heart. Patches with wires are applied to the chest and connected to a portable monitor that can be attached to the patient's belt. The monitor is usually worn for 24 hours and it records heart rhythm and rate information that is later analyzed for arrhythmias and other abnormalities. A diary kept by the patient during the wearing of the monitor correlates symptoms with abnormal heart rhythms. There are no special preparations or instructions for this test.
Event monitoring is a more in-depth form of holter monitoring. Traditionally a holter monitor is worn for 24 hours. An event monitor can be worn for up to 30 days to evaluate a patient for arrhythmias. There are no special preparations for this test.