4. Fever
Fever is a non-specific response of the whole body before a threat, often an infection that runs in the organism and that must be eradicated in order to protect the individual’s health. The basic symptom of fever is an increase in body temperature, which is meant to threaten the life of bacteria and other germs that have invaded the organism, but there are other symptoms that are commonly associated with fever as well.
Sinus tachycardia is one of them, and it is most common to find sinus tachycardia in patients with high fever than in those with mild fever. When presenting with a febrile episode, sinus tachycardia is very rarely a sign of a dangerous condition, but more like a common symptom of the entire episode. However, the presence of fever itself indicates the activation of the body to fight a threat to the health; it could be an infection or another problem that comes from inside the body, including an auto-immune disease.