A Holter monitor is a small, wearable device that records the heart’s rhythm, usually for 24 hours. It’s used to look for irregular heartbeats, also called arrhythmias. Usually, an ECG will be done prior to a Holter monitor.

A Holter monitor may be able to find irregular heartbeats that an ECG missed.

If standard Holter monitoring doesn’t find an irregular heartbeat, you may need to wear a device called an event monitor. The device records heartbeats over several weeks.