Children’s heartbeat is particularly fast when they have a fever, due to increased blood circulation and metabolism during fever, which can promote heat dissipation and is a common phenomenon of fever, but if there is arrhythmia, cyanosis, etc., you need to be vigilant against myocarditis. Children’s metabolism is faster, the body needs more blood supply, so the base heart rate is higher than adults, and the younger the age, the higher the heart rate. During fever, blood circulation increases and metabolic rate rises further increasing the level of heart rate, so a faster heart rate in children with fever is common. Fever is usually caused by viral or bacterial infections, but if a child has arrhythmia, dyspnea, chest pain, irritability, or cyanosis, he or she may have myocarditis. Children’s heartbeat is particularly fast when fever, there may also be other causes, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.