When a person has a fever, the pulse usually increases along with the temperature. Relative bradycardia refers to a pulse-temperature deficit, with the pulse less than that expected for a given temperature. 

Criteria for using relative bradycardia in clinical diagnosis:

(1) age of patient >= 13 years

(2) temperature >= 102°F and <= 106°F

(3) The pulse is taken simultaneously with the temperature,

(4) The patient has normal sinus rhythm with no arrhythmias, second or third degree heart block, or pacemaker.



Pulse in Beats per Minute

102°F (38.9 °C)


103°F (39.5 °C)


104°F (40.0 °C)


105°F (40.6 °C)


106°F (41.1 °C)



pulse in beats per minute =

= (10 * (temperature in °F)) – 910


Infectious causes of relative bradycardia:

(1) Legionnaires' disease

(2) psittacosis

(3) Q fever

(4) typhoid fever

(5) typhus

(6) malaria

(7) babesiosis

(8) leptospirosis

(9) yellow fever

(10) dengue fever

(11) Rocky Mountain spotted fever


Noninfectious causes of relative bradycardia:

(1) beta-blockers

(2) CNS lesions

(3) malignant lymphoma

(4) factitious fever

(5) drug-related fever


Relative bradycardia is not found with the "typical" bacterial pneumonias.

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