The diagnostic significance of relative bradycardia in infectious disease

Abstract

In summary, relative bradycardia is an important clinical finding if properly defined and applied. Non-infectious causes of relative bradycardia should be excluded before one can utilize this finding in the differential diagnosis of infectious diseases. Relative bradycardia is most useful in differentiating infectious diseases that resemble each other if a pulse temperature deficit is the discriminating variable, e.g. Legionnaire's disease versus Mycoplasma pneumonia, psittacosis or Q fever from tularemia pneumonia. Relative bradycardia is not helpful in differentiating malaria from typhoid fever or yellow fever from African hemorrhagic fevers, since all of these infections are regularly associated with relative bradycardia. As the clinicians' awareness of relative bradycardia increases, more studies will be done on different organisms to determine the pulse temperature relationships in known Legionnella diseases as well as emerging infectious diseases, e.g. babesiosis. Relative bradycardia, properly defined and applied, remains an important clinical sign in the differential diagnosis of selected infectious diseases.