If your child is limiting his activity due to the way he is feeling, then it is important to find out the underlying cause. If he is having a cardiac arrhythmia, then it is important to know what the heart rate is at the time he is symptomatic. It would be important to get a baseline electrocardiogram (ECG) to see if there are abnormalities present that would suggest a predisposition to arrhythmias. Then it is important to document the heart rate during symptoms. It is necessary for the doctor to either have a number (heart rate) or a rhythm strip of the heart rate during an event, to decide what the cause is. You should speak with your doctor about getting a referral to a cardiologist, or at least having a 24 hour holter monitor to try to capture an event. If the events are few in number then an event monitor could be used. In any case, you should learn how to take a pulse rate, and become familiar with your child's heart rate at rest and with activity. That way you will be able to see the difference when he is symptomatic. Pushing fluids is always a good idea, but may not be enough here.
My cousin just told me her son was saying the same thing,His heart was beating so fast she rushed him to the ped and they did an EKG and it was bypassing a node.This is what she told me.
There are 2 nodes on your heart that shock it. The AV node is the main one and it send impulses to the SA node. His SA node gets bypassed sometime. If it was really bad and happened all the time, they would operate.His ped told her that he can take meds for it if its really interrupting his life.
Maybe someone else will have some other options for you.
thank you all i am calling the dr now ,