The child has a fever and a rapid heartbeat.

Because the child is in a high fever state, it will consume a lot of energy and oxygen, so the heartbeat will speed up. Generally, when the child has a fever, the heartbeat can increase by 25 times per minute. If it exceeds 25 times, it is recommended to see a doctor in time, improve the blood routine, ECG, myocardial enzymes and other examinations, and rule out myocarditis.