“A Holter monitor is a small, wearable device that records the heart’s rhythm. It’s used to detect or determine the risk of irregular heartbeats (arrhythmias).

A Holter monitor test may be done if a traditional electrocardiogram (ECG or EKG) doesn’t provide enough details about the heart’s condition. If the irregular heartbeats are infrequent, a longer term monitor called an event recorder may be needed.

Some personal devices, such as smartwatches, offer electrocardiogram monitoring. Ask your health care provider if this is an option for you.

If you have infrequent arrhythmias, an ECG may not detect them. A Holter monitor may be able to spot irregular heart rhythms that an ECG missed.”

MAYO CLINIC