From the Guidelines
The mechanism behind relative bradycardia in typhoid fever is not explicitly explained by the provided evidence, but it is characterized by an insidious onset of sustained fever, headache, malaise, anorexia, relative bradycardia, and other symptoms 1. The relative bradycardia in typhoid fever is a complex phenomenon that involves the interplay of various factors, including the effects of Salmonella Typhi endotoxins on the cardiovascular system.
- Typically, in febrile illnesses, the heart rate increases by about 10 beats per minute for each 1°C rise in temperature.
- However, in typhoid fever, the heart rate is slower than expected for the degree of fever, which is known as relative bradycardia or pulse-temperature dissociation.
- This occurs due to the stimulation of the vagus nerve by typhoid endotoxins, increasing parasympathetic tone to the heart, and potentially direct depression of the sinoatrial node function.
- The release of cytokines like tumor necrosis factor-alpha and interleukin-6, triggered by the bacteria, may also affect cardiac function. The provided evidence 1 describes the clinical characteristics of typhoid fever, including relative bradycardia, but does not provide a detailed explanation of the underlying mechanism.
- Relative bradycardia is considered a classic clinical sign of typhoid fever, although it can also occur in other infections.
- It is most noticeable during the first week of illness and can be a valuable diagnostic clue when evaluating patients with prolonged fever of unknown origin.
From the Research
Mechanism of Relative Bradycardia in Typhoid Fever
The mechanism behind relative bradycardia in typhoid fever is not fully understood. However, several studies have proposed possible mechanisms, including:
- Release of inflammatory cytokines 2
- Increased vagal tone 2
- Direct pathogenic effect on the myocardium 2
- Electrolyte abnormalities 2
Pathogenesis of Relative Bradycardia
Relative bradycardia is found in a wide variety of infectious and noninfectious diseases, and its pathogenesis remains poorly understood 2. The incidence of this sign varies widely, which may be attributable to multiple factors, including population size, time course for measuring pulse and temperature, and lack of a consistent definition used 2.
Clinical Significance of Relative Bradycardia
Relative bradycardia is a sensitive but nonspecific clinical sign that may be an important bedside tool for narrowing the differential diagnosis of potential infectious and noninfectious etiologies 2. Recognizing this relationship may assist the clinician by providing bedside clinical clues into potential etiologies of disease, particularly in the setting of infectious diseases and in circumstances when other stigma of disease is absent 2.
Relative Bradycardia in Typhoid Fever
Relative bradycardia is a characteristic feature of typhoid fever, and it is often used as a clinical sign for diagnosis 3, 4. The classic findings of typhoid fever include rose spots, relative bradycardia, and stepwise fevers, but unfortunately, these signs are frequently absent 4.
Treatment of Typhoid Fever
The treatment of typhoid fever typically involves the use of antibiotics, such as fluoroquinolones, ceftriaxone, and azithromycin 4, 5. The choice of antibiotic depends on the severity of the disease, the presence of multidrug resistance, and the patient's clinical condition 5.