Why Does Typhoid Fever Cause a Slow Heart Rate? Explained

If your doctor noticed a relatively slow heart rate despite your high fever, you may be experiencing a clinical clue known as pulse-temperature dissociation or the Faget sign ^[1]. Under typical circumstances, a person’s heart rate tends to increase as their fever rises ^[1]. However, in certain infections like typhoid fever, the heart rate can remain lower than expected for the degree of fever ^[1]. While this is a well-known feature of typhoid, it is only a nonspecific clue—meaning it cannot confirm or rule out the disease on its own ^[2].

What is Pulse-Temperature Dissociation?

When the body fights an infection and your temperature rises, your heart typically pumps faster to help circulate blood and heat. On average, a person’s heart rate predictably increases alongside their fever ^[1].

In typhoid fever, this normal relationship is often disrupted ^[1]. Even though your body temperature is highly elevated, your pulse remains lower than expected for that specific level of fever. Medical professionals refer to this phenomenon as relative bradycardia (“bradycardia” meaning slow heart rate) ^[1]. It is important to note that “relative” bradycardia means the heart rate is slower relative to the fever; it does not necessarily mean your pulse has dropped below a normal resting rate of 60 beats per minute ^[1].

Why Does This Happen?

The exact reason typhoid fever causes a slower-than-expected heart rate is not fully resolved. Researchers believe it is a complex reaction involving both the bacteria and your body’s immune response ^[1]. Several mechanisms have been proposed:

• Inflammatory Signals (Cytokines): When your immune system detects Salmonella Typhi (the bacteria that causes typhoid), it releases inflammatory chemicals called cytokines. It is hypothesized that these chemicals might temporarily alter the electrical signals in the heart’s natural pacemaker cells ^[1][3].
• Nervous System Changes: The infection may stimulate a part of your nervous system that controls resting heart rate, increasing what is called vagal tone. High vagal tone naturally tells the heart to beat slower ^[1][3].
• Bacterial Components: Components of the typhoid bacteria, such as lipopolysaccharide (often referred to as endotoxin), can trigger inflammatory and temperature-regulating pathways in the body. Researchers are studying whether these components directly contribute to the unusual heart rate response ^[4][5].

How Doctors Use This Clue

During the early stages of illness, typhoid fever can look a lot like other diseases, such as malaria or dengue fever ^[1]. If a doctor notices relative bradycardia, they might use it as one of many bedside clues to suspect typhoid ^[1][2].

However, a relatively slow pulse cannot diagnose typhoid on its own, and a fast or normal pulse does not rule it out ^[2]. The Faget sign is not exclusive to typhoid; it can happen with other infections like dengue and scrub typhus, as well as due to medications (like beta-blockers) or underlying heart conditions ^[6][7][8].

To confirm a diagnosis, doctors typically rely on a blood culture, where a blood sample is placed in a laboratory system to look for growing bacteria ^[9][2]. Because blood cultures are not always perfect—they may take time, require multiple samples, or come back negative if you have already taken antibiotics—your medical team will look at the whole picture, including your symptoms, travel history, and other lab tests to determine the best course of action ^[9][2].

When to Seek Urgent Care

While relative bradycardia is a known feature of typhoid, a very slow heart rate can sometimes be a sign of a more serious issue, such as severe infection, electrolyte imbalance, or heart inflammation ^[10][8]. If you are at home and experience any of the following, seek emergency medical care immediately:

• Fainting, severe dizziness, or lightheadedness ^[10]
• Chest pain or severe shortness of breath ^[10]
• Confusion or marked weakness ^[10]
• A new, noticeably lower-than-usual pulse that concerns you ^[10]

If you are currently taking any prescribed medications, do not stop taking them without consulting your doctor first, even if you suspect they might be affecting your heart rate ^[8].