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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and keywords: pulse-temperature deficit; relative bradycardia


Table 1. Physiologic pulse-temperature relationship

Body Temperature

106􏰄°F (41.1􏰄°C)
105􏰄°F (40.6°C)
104􏰄°F (40.0􏰄°C)
103􏰄°F (39.4°C)
102􏰄°F (38.9°C)

Pulse Rate

150 bpm
140 bpm
130 bpm
120 bpm
110 bpm

Pulse-Temperature Deficit

<140 bpm
<130 bpm
<120 bpm
<110 bpm
<100 bpm
Table 2. Classic infectious etiologies associated with relative bradycardia

Faget's sign refers to a significant pulse-temperature deficit relative to the degree of fever.

Historical Perspective

Feget's sign is named after Jean Charles Faget, who characterized the unusual constellation of fever and bradycardia in 1859.[1]


Physiologically, fever is accompanied by tachycardia rather than bradycardia. For every degree of temperature elevation in degrees Fahrenheit, there is a commensurate increase in pulse rate of 10 beats per minute. This physiologic relationship between temperature and pulse rate is known as Liebermeister's rule (Table 1). When fever is associated with bradycardia, it is referred to as Faget's sign.

Clinical Significance

Abnormalities in the pulse-temperature relationship may be indiscernible when the body temperature falls below 102􏰄°F. Relative bradycardia should not be applied to patients with paced rhythms or advanced AV block or to those taking beta-blockers. Digoxin, angiotensin-converting enzyme inhibitors, and dihydropyridine calcium channel blockers do not affect pulse-temperature relationships as do ˜beta-blockers.[2]

Relative bradycardia may aid differential diagnosis in selected clinical contexts. Faget's sign may be used to discriminate Legionella pneumophila from Mycoplasma pneumoniae in community-acquired pneumonias.[3][4] When relative bradycardia is associated with fever of unknown origin, certain non-infectious causes including central nervous system lesions, lymphomas, drug fever, factitious fever, and beta-blockers should be considered in addition to the infectious etiologies (Table 2).


Common Causes

Causes by Organ System

Cardiovascular No underlying causes
Chemical/Poisoning No underlying causes
Dental No underlying causes
Dermatologic No underlying causes
Drug Side Effect Beta blocker, drug fever
Ear Nose Throat No underlying causes
Endocrine No underlying causes
Environmental No underlying causes
Gastroenterologic No underlying causes
Genetic Cyclic neutropenia
Hematologic Babesiosis, cyclic neutropenia, lymphoma, malaria
Iatrogenic No underlying causes
Infectious Disease Atypical pneumonia, babesiosis, brucellosis, campylobacter fetus, chagas disease, chlamydia, chlamydophila psittaci, colorado tick fever virus, coxiella burnetii, cytomegalovirus mononucleosis, dengue fever, ehrlichia canis, enteric fever, francisella tularensis, group A streptococcus, Guanarito virus, Junin virus, Legionnaires' disease, leishmaniasis, leptospirosis, listeria monocytogenes, Machupo virus, malaria, mycoplasma, orientia tsutsugamushi, plasmodium vivax , Q fever, rickettsiosis, rickettsia typhi, rocky mountain spotted fever, salmonella enterica, typhoid fever, viral hemorrhagic fever, yellow fever
Musculoskeletal/Orthopedic No underlying causes
Neurologic Central nervous system lesion
Nutritional/Metabolic No underlying causes
Obstetric/Gynecologic No underlying causes
Oncologic Lymphoma
Ophthalmologic No underlying causes
Overdose/Toxicity No underlying causes
Psychiatric No underlying causes
Pulmonary Atypical pneumonia
Renal/Electrolyte No underlying causes
Rheumatology/Immunology/Allergy Anaphylaxis
Sexual No underlying causes
Trauma No underlying causes
Urologic No underlying causes
Miscellaneous Factitious fever

Causes in Alphabetical Order


  1. Jean-Charles Faget. Études médicale de quelques questions importantes pour la Louisiane, et exposé succinct d’une endémie paludéenne de forme catarrhale qui a sévi à la Nouvelle-Orléans, particulièrement sur les enfants, pendant l’epidémie de fièvre jaune de 1858. New Orleans, 1859.
  2. 2.0 2.1 Cunha, BA. (2000). "The diagnostic significance of relative bradycardia in infectious disease". Clin Microbiol Infect. 6 (12): 633–4. PMID 11284920. Unknown parameter |month= ignored (help)
  3. 3.0 3.1 3.2 Johnson, DH.; Cunha, BA. (1993). "Atypical pneumonias. Clinical and extrapulmonary features of Chlamydia, Mycoplasma, and Legionella infections". Postgrad Med. 93 (7): 69–72, 75–6, 79–82. PMID 8493198. Unknown parameter |month= ignored (help)
  4. Cunha, B. A.; Quintiliani, R. (1979-09). "The atypical pneumonias: a diagnostic and therapeutic approach". Postgraduate Medicine. 66 (3): 95–102. ISSN 0032-5481. PMID 471855. Check date values in: |date= (help)
  5. Senanayake, S. (2006). "Dengue fever and dengue haemorrhagic fever--a diagnostic challenge". Aust Fam Physician. 35 (8): 609–12. PMID 16894436. Unknown parameter |month= ignored (help)
  6. Erdogan, H.; Erdogan, A.; Lakamdayali, H.; Yilmaz, A.; Arslan, H. (2010). "Travel-associated Legionnaires disease: clinical features of 17 cases and a review of the literature". Diagn Microbiol Infect Dis. 68 (3): 297–303. doi:10.1016/j.diagmicrobio.2010.07.023. PMID 20955914. Unknown parameter |month= ignored (help)
  7. Wittesjö, B.; Björnham, A.; Eitrem, R. (1999). "Relative bradycardia in infectious diseases". J Infect. 39 (3): 246–7. PMID 10714809. Unknown parameter |month= ignored (help)