|Model 445 Mini-Holter Recorder, illustration from a brochure, 1976|
|Norman J. Holter|
|Holter's business card|
|Patient attached to heart monitoring equipment: slide of a cartoon, undated|
With the development of transistors, radioelectrocardiography was made obsolete and it became possible for the amplifier, tape recorder, temperature-control circuits, motor speed control circuits, and batteries to be placed in a single unit small enough for a coat pocket or purse. In 1952, Holter succeeded in creating a small unit that weighed approximately 1 kg. Wilford R. Glassock, a senior engineer working with Holter, traveled to Cedars of Lebanon Hospital (now Cedars-Sinai Hospital of Los Angeles) in 1962 to demonstrate the Holter monitor system and discuss making it more practical. At Cedars, Dr. Eliot Corday, a cardiologist, observed the practicality of the system, embracing the technology and becoming an early promoter of the technology to both industry and physicians. Holter and Glassock were issued US Patent 3,215,136 on November 2, 1965 for the Electrocardiographic Means. The Holter Research Foundation ultimately sold exclusive rights to the patent to Del Mar Engineering Laboratories, who became the acknowledged leader in Holter monitoring technology for over 40 years.
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Engineering Laboratories, 1965
“After visiting several plants and talking with qualified people, we became aware that many interested manufacturers were not qualified to make an adequate instrument. Out of these meetings evolved a set of ground rules to assist me in selecting a manufacturer who could produce our equipment. 1) A dependable high quality trouble free system; 2) as low a sale price as possible to encourage wide distribution; 3) as rapidly as possible through the use of a team of experienced production and marketing people; 4) with adequate financial backing to avoid company failure during the course of bringing the instrument to market; and 5) last, but very important, with youthful aggressive enthusiasm for the technical ideas involved and an understanding of the revolutionary approach to what I consider obsolete present methods for electrocardiography.”
Del Mar Avionics fit Holter’s “ground rules.” Not surprisingly, Del Mar employed a youthful, aggressive, and enthusiastic staff. The company strove to create an environment “for creativity and growth opportunities.” It would be a mutually beneficial partnership for both parties.
Bruce Del Mar’s role as an innovator and collaborator with Holter is especially important because his work spurred the development of an entire diagnostic industry. In November of 1963 Holter wrote to Del Mar, “Do not be too discouraged; careful evaluated clinical research goes even slower than R & D. My visits around the country convince me that you will encounter a chain reaction in time. Physicians have to be especially conservative in evaluating the results of such a revolutionary approach but once they have, interest will develop by geometric progression.”
|Bruce Del Mar|
Corday, Eliot. “Historical Vignette Celebrating the 30th Anniversary of Diagnostic Ambulatory Electrocardiographic Monitoring and Data Reduction Systems,” American Journal of Cardiology. 1991, pp. 286-292.
Del Mar, Bruce Eugene. Ready for Takeoff: An Autobiography. 2010.
Kennedy, Harold L. “The History, Science, and Innovation of Holter Technology,” Annals of Noninvasive Electrocardiology, January 2006, pp. 85-94.
Roberts, William C. and Marc A. Silver. “Norman Jefferis Holter and Ambulatory ECG Monitoring,” American Journal of Cardiology, 1983, pp. 903-906.
By Alison Oswald, Archives Center, National Museum of American History