In medicine

Medicine

Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, a Holter monitor (often simply "Holter" or occasionally ambulatory electrocardiography device) is a portable device for continuously monitoring various electrical

Electricity

Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 activity of the cardiovascular system for at least 24 hours (often for two weeks at a time). The Holter's most common use is for monitoring heart

Heart

The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 activity (electrocardiography or ECG), but it can also be used for monitoring brain activity (electroencephalography

Electroencephalography

Electroencephalography is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain...

 or EEG).