Louis Sigurd Fridericia

Louis Sigurd Fridericia (1881 – 1947)

Louis Sigurd Fridericia (1881 – 1947) was a Danish physician.

In 1920 Fridericia found that the duration of the QT interval was related to the cube root of the RR interval (Fridericia’s formula) – independent of the relationship defined by Bazett (1920) where he related the corrected QT interval to the square root of the RR interval (Bazett’s formula)

Investigated the relationship between vitamin deficiency and night blindness in rats…

Introduced the term ‘refection‘ following studies demonstrating rats could grow and thrive without ‘vitamin B’ in their diet. Refection enabled rats to make use of the vitamins synthesized in the caecum by ‘microbial agents’ activated in vitamin B deficiency

We propose to name this restoring change: refection (Latin: reficere = restore). To induce refection will be termed to refect: and agencies capable of refecting will be termed refectious.‘ [Fridericia LS, 1925]


  • Born 24 February 1881 Copenhagen, Denmark
  • 1906 – Medical degree, University of Copenhagen
  • 1907 – Assistant to Christian Bohr at the Physiological Laboratory, University of Copenhagen
  • 1909 – Assistant to Carl Julius Salomonsen at the Institute of General Pathology, University of Copenhagen
  • 1910 – Doctoral thesis – Undersøgelser over fosterstofskifte [Fetal metabolism studies]
  • 1913-18 assistant physician at the Rigshospitalet, Kommunehospitalet and Bispebjerg Hospital with special interest in cardiology
  • 1918 – Professor of hygiene, Hygienic Institute of the University of Copenhagen
  • 1920 – Country Editor of the Nordic Hygiene Journal
  • 1935 – President, Medical Society of Copenhagen
  • 1943 – Escaped Nazi persecution in Denmark being smuggled in a fishing boat to Sweden and then to London
  • Died 26 February 1947

Medical Eponyms

  • Fridericia’s formula – mathematical equation for calculating the corrected QT interval at varying heart rates

Major Publications

  • Fridericia LS. Die Systolendauer im Elektrokardiogramm bei normalen Menschen und bei Herzkranken [The Duration of Systole in an Electrocardiogram in Normal Humans and in Patients with Heart Disease]. Part I: Beziehung zwischen der Pulsfrequenz und der Dauer des Ventrikelelektrokardiogramms bei normalen Menschen in der Ruhe [Relationship of the pulse frequency and the duration of the ventricular electrocardiogram in normal humans at rest]. Acta Med Scand 1920;53:469–486 [Translated reprint: Ann Noninvasive Electrocardiol. 2003 Oct;8(4):343-51.]
  • Fridericia LS, Holm E. Experimental Contribution to the Study of the Relation Between Night Blindness and Malnutrition. American Journal of Physiology, 1925 Vol 73 pp63-78
  • Lund H, Spur B, Fridericia LS. Fridericia LS. The biological and titrimetric determination of vitamin C. Biochem J. 1934;28(5):1825-8. [PMC1253406]
  • Fridericia LS, Freudenthal P, Gudjonnsson S, Johansen G, Schoubye N. Refection, a Transmissible Change in the Intestinal Content, enabling Rats to grow and thrive without Vitamin B in the Food. J Hyg (Lond). 1927 Nov;27(1):70-102. [PMC2167713]
  • Fridericia LS. Undersøgelser over fosterstofskifte. [Fetal metabolism studies] København, Høegh Vogelius, 1910


  • Danish biographical research and portrait: Louis Sigurd Fridericia. Flemming and Agnes Voss – Hørsholm, Denmark (Personal communication)
  • Norgaard A. LS Fridericia. Denstoredanske.dk (Danish Biographical Lexicon)
  • Kon SK. Professor Dr Med. Louis Sigurd Fridericia. British Journal of Nutrition. Vol 1, Issue 2-3 December 1947, pp111-112
  • Moss AJ Introductory note to a translated classic article of L. S. Fridericia. Ann Noninvasive Electrocardiol. 2003 Oct;8(4):341-2. [PMID 14516291]
  • Todhunter EN. Biographical notes from the history of nutrition. Louis Sigurd Fridercia–February 24, 1881-February 26, 1947. J Am Diet Assoc. 1969 Oct;55(4):420. [PMID 4898921]

eponymictionary CTA 2


the person behind the name

Posted by Dr Mike Cadogan

Emergency physician with a passion for medical informatics and medical education/textbooks. Asynchronous learning #FOAMed evangelist | @sandnsurf | + Mike Cadogan | LinkedIn

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