The Holter monitor was developed at the Holter Research Laboratory in Helena Montana by experimental physicists Norman J. 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 #Holtermonitor 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 electrodes attached 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.