The rapid heart rate of a baby with a cold and no fever may be caused by normal physiological characteristics, or it may be caused by a severe cold combined with viral myocarditis and other factors. 1. Physiological characteristics: heart rate and age have a certain relationship, the baby will usually be due to a higher basal metabolic rate, the heart rate will be faster than the normal adult heart rate. In infancy, the heart rate usually exceeds 100 beats per minute, and with age, the heart rate will gradually decrease to 60-100 beats per minute. 2. Combined viral myocarditis: If the cold is caused by a viral infection, untimely treatment may cause viral myocarditis, which can induce heart failure and sudden death in severe cases, and can easily cause cardiac arrhythmia, resulting in an increased heart rate. Baby cold without fever, fast heart rate, may also be due to other reasons such as decreased blood volume. Should be sent to the hospital in a timely manner, to clarify the cause of the disease, and then follow the doctor’s instructions for treatment.