Why it's done

Your doctor may recommend that you wear a Holter monitor for a day or so if you have signs and symptoms of an irregular heart rhythm (arrhythmia) or unexplained fainting.

Before you get a Holter monitor, you'll have an electrocardiogram (ECG). An ECG is a quick and painless test that uses sensors (electrodes) taped to your chest to check your heart's rhythm.

However, sometimes an ECG doesn't detect any changes in your heart rhythm because you're hooked up to the machine for only a short time. A Holter monitor may be able to spot occasionally abnormal heart rhythms that an ECG missed.

A Holter monitor test may also be done if you have a heart condition that increases your risk of an abnormal heart rhythm.