A Holter monitor is a small, wearable device that keeps track of your heart rhythm. Your doctor may want you to wear a Holter monitor for one to two days. During that time, the device records all of your heartbeats.
However, sometimes an electrocardiogram doesn't detect any irregularities in your heart rhythm because you're only hooked up to the machine for a short time.
If your signs and symptoms suggest that an occasionally irregular heart rhythm may be causing your condition, your doctor may recommend that you wear a Holter monitor for a day or so.
Over that time, the Holter monitor may be able to detect irregularities in your heart rhythm that an electrocardiogram couldn't detect.