My son is tachycardic heart rate 120 for 4 hours now, what to do? my son is 7 years old

A : A normal resting heart rate for a child under 10 years of age can be anywhere from 70-130 beats per minute. However, your son's heart rate being on higher end for 4 hours is concerning. Many things can cause a fast heart rate such as: -an arrhythmia such as supraventricular tachycardia or wolf-parkinson-white syndrome -anxiety or stress -medications such as cold remedies or asthma medicines -caffeine -pneumonia or other lung disease -thyroid disorder -heart failure if your child appears ill or is having other symptoms such as chest pain, fainting, dizziness, fever, swelling of hands and feet, or difficulty breathing, you should take him to the emergency room or call his doctor immediately.

Nothing drastic: As far as his heart goes he can sustain this rate for extended periods without damage. It would be reasonable to have him seen to identify any contributing factors. Heart rate, like fever is a non-specific indicator of health. It could be many things but if this is his resting rate it is not normal.