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.A Holter monitor test is usually performed after a traditional test to check your heart rhythm (electrocardiogram) if the electrocardiogram doesn't give your doctor enough information about your heart's condition.Your doctor uses information captured on the Holter monitor to figure out if you have a heart rhythm problem. If standard Holter monitoring doesn't capture your irregular heartbeat, your doctor may suggest a wireless Holter monitor, which can work for weeks.While wearing a Holter monitor may be a little inconvenient, it's an important test that may help your doctor diagnose your condition.