From the Guidelines
Fever leads to tachycardia through physiological mechanisms that increase heart rate to maintain adequate cardiac output and tissue perfusion during febrile states. When body temperature rises during a fever, the metabolic rate increases, requiring more oxygen delivery to tissues. This triggers the sympathetic nervous system, which releases catecholamines like epinephrine and norepinephrine, directly increasing heart rate 1. Additionally, fever causes peripheral vasodilation to help dissipate heat, resulting in relative hypovolemia. The heart compensates for this decreased blood pressure by beating faster. For every 1°C (1.8°F) increase in body temperature, heart rate typically increases by approximately 10 beats per minute. This relationship, known as Liebermeister's rule, helps maintain adequate cardiac output and tissue perfusion during febrile states. The tachycardia response is particularly pronounced in children, who may experience significant heart rate increases even with mild fevers. According to the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia, physiological sinus tachycardia may result from pathological causes, including infection with fever, dehydration, anemia, heart failure, and hyperthyroidism 1.
Some key points to consider:
- The increase in heart rate is a normal physiological response to fever and typically resolves as the fever subsides, either naturally or with antipyretic medications like acetaminophen or ibuprofen.
- The American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care note that sinus tachycardia is common and usually results from a physiologic stimulus, such as fever, anemia, or hypotension/shock 1.
- In cases where tachycardia is expected to resolve with correction of the underlying cause, no specific drug treatment is required, and therapy is directed toward identification and treatment of the underlying cause 1.
From the Research
Relationship Between Fever and Tachycardia
- Fever is known to affect heart rate, with studies indicating a correlation between increased body temperature and heart rate [ 2 ].
- For every degree rise in temperature, the change in heart rate (ΔHR/°C) is approximately 7.2±0.4 beats per minute (bpm) [ 2 ].
- Adjusting for age, oxygen saturation, and mean blood pressure, the results show a ΔHR/°C of 6.4±0.4 bpm [ 2 ].
Mechanism of Fever-Induced Tachycardia
- The pathophysiology of fever involves the production of prostaglandins, which play a crucial role in fever production [ 3 ].
- Antipyretics such as acetaminophen and ibuprofen are effective in reducing fever by inhibiting prostaglandin synthesis [ 3 ].
- However, the exact mechanism by which fever leads to tachycardia is not fully understood and may involve complex interactions between various physiological systems.
Clinical Implications
- Fever can be a symptom of various underlying conditions, including cardiac diseases such as endocarditis, pericarditis, and myocardial infarction [ 4 ].
- In some cases, fever can be a manifestation of post-cardiotomy syndrome, a special type of perimyocarditis [ 4 ].
- The treatment of fever often involves the use of antipyretics such as acetaminophen and ibuprofen, which can be effective in reducing fever and associated symptoms [ 5 , 6 ].