A Holter monitor is a small battery clinical instrument that detects your heart's action, such as sound and rhythm. Your doctor may ask you to use one if you need more details about how your heart works than a routine electrocardiogram (EKG) can give you. The EKG is a clinical tool used to evaluate your heart rate and rhythm. It is also used to look for other disorders that may impact normal heart function. Only during EKG, implants are attached to your chest to check the rhythm of your heart. You may encounter heart rhythm disturbances that don't show up when the EKG is done because you've only been hooked to the device for a very short time. Irregular heartbeat rhythms and other types of cardiac signs may come and go. Monitoring is appropriate for a longer time to record these events. Holter monitor lets professionals see how your heart works on a long-term basis.