The rapid heartbeat of infants may be related to emotions, fever and heart diseases. 1. Emotions: When babies feel irritable or cry, it will cause their heart to beat fast, which is a normal physiological phenomenon, and will return to normal after their emotions are stabilized. 2. Fever: When infants have a fever, it will affect the normal metabolism of the body and cause the heart to beat faster. 3. Heart disease: Suffering from heart disease, such as congenital heart disease, the heart is affected, the heart function can not run normally, can appear fast heartbeat, arrhythmia and other symptoms. There may be other reasons for the rapid heartbeat of infants, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then under the guidance of the doctor’s treatment.