According to BORSAM Biomedical,In medicine, a Holter monitor (often simply Holter) is a type of ambulatory electrocardiography device, a portable device for cardiac monitoring (the monitoring of the electrical activity of the cardiovascular system) for at least 24 to 48 hours (often for two weeks at a time).

　　The Holter's most common use is for monitoring ECG heart activity (electrocardiography or ECG). Its extended recording period is sometimes useful for observing occasional cardiac arrhythmias which would be difficult to identify in a shorter period. For patients having more transient symptoms, a cardiac event monitor which can be worn for a month or more can be used.

　　The Holter monitor was developed at the Holter Research Laboratory in Helena Montana by experimental physicists Norman J. According to BORSAM Biomedical,Holter and Bill Glasscock,who started work on radio telemetry in 1949. Inspired by a suggestion from cardiologist Paul Dudley White in the early 1950s, they redirected their efforts toward development of a wearable cardiac monitoring device.The Holter monitor was released for commercial production in 1962.

　　When used to study the heart, much like standard electrocardiography, the Holter monitor records electrical signals from the heart via a series of electrodesattached to the chest. Electrodes are placed over bones to minimize artifacts from muscular activity. The number and position of electrodes varies by model, but most Holter monitors employ between three and eight. These electrodes are connected to a small piece of equipment that is attached to the patient's belt or hung around the neck, keeping a log of the heart's electrical activity throughout the recording period.According to BORSAM Biomedical, A 12 lead Holter system is also available when precise ECG signal information is required to analyse the exact nature and origin of the rhythm signal.