Slide 1: What eponymous physical exam finding is defined as “fever-induced bradycardia”?

Slide 2: Faget’s sign, aka relative bradycardia, aka pulse-temperature disassociation

Slide 3: Faget’s sign occurs when a febrile patient’s heart rate does not rise as expected given their elevated body temperature. 101F -> 100 BPM. 102F -> 110 BPM. 103F -> 120 BPM. 104F -> 130 BPM. 105F -> 140 BPM.

Slide 4: The sign is named after Jean-Charles Faget, a 19th-century physician who first observed this “relative bradycardia” in yellow fever patients. However, the sign is broadly associated with infection by some (but not all) gram-negative intracellular bacteria, intracellular parasites and viruses.

Slide 5: Diseases specifically associated with relative bradycardia include: Bacterial – typhoid fever, legionella, rocky mountain spotted fever, psittacosis, leptospirosis. Parasitic – malaria, protozoa, babesiosis. Viral – sandfly fever, dengue fever, ebola (and other hemorrhagic viruses). Non-infectious – drug fever, central fever, lymphoma, beta-blocker use.

Slide 6: The pathogenesis of infection-induced relative bradycardia remains a subject of debate, and is in all likelihood multifactorial. Proposed mechanisms include: 1. Release of inflammatory cytokines (LPS, NO, TNFa, IL-6) that modulate autonomic (vagal) tone. 2. Pathogens directly affecting myocardium. 3. Electrolyte abnormalities.


  • Mittal J, Estiverne C, Kothari N, Reddi A. Fever and Relative Bradycardia: A Case Presentation and Review of the Literature. Int J Case Rep Short Rev. 2015;1(1):4-8. Link.
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  • Ye F, Winchester D, Stalvey C, et al. Med Hypotheses. Proposed mechanisms of relative bradycardia. 2018 Oct;119:63-67. Epub 2018 Jul 17. PMID 30122494.
  • Ye F, Hatahet M, Youniss MA, Toklu HZ, Mazza JJ, Yale S. The Clinical Significance of Relative Bradycardia. WMJ. 2018 Jun;117(2):73-78. PMID 30048576.

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