Norman Jefferis Holter was an American physicist who made a significant contribution to medical technology with his invention of the first portable cardiac monitoring device. Patients today benefit from both ambulatory electrocardiography and the other devices made possible by it, such as pacemakers and implantable cardiac defibrillators. Now 60 years since Holter found a way to make a wearable monitor, "Holter" has become a synonym for the simple yet effective device that is used routinely by physicians worldwide to detect, document, and characterize cardiac rhythm abnormalities. [ABSTRACT FROM AUTHOR]