### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
Hi, may I answer your health queries right now ?  Please type your query here...My 19 year old son periodically has his heart race uncontrollable and so hard that it feels like it is going to pop out of his chest. It did it yesterday for no reason. He was talking to us and suddenly he said my heart is doing it again. I felt his chest and his heart was pounding so hard and fast it scared me. Than about 4 minutes later as I was holding my hand on his chest while he was sitting down. It suddenly stopped beating fast. In fact I couldnt even find his heart beat for awhile. Then it remained normal for about 3 minutes and started quickly again just as before for about 4 minutes and stopped again suddenly. It didnt do it again all night. Is it the lower part of the heart Ventricular or upper heart. Last August he wore a 24 hour heart monitor and the Dr.s found nothing wrong.

### output:

Episodes of tachycardia which are not related to physical exertion may occur in cardiac arrhythmia, pheochromocytoma, anxiety, panic attacks, autonomic instabilities, congenital heart diseases etc. Your son is 19 years old now, so I presume that he was not having any congenital heart problems. Your doctor suspected arrhythmias therefore he put your son on 24 hour heart monitoring. But during that monitoring had your son suffered episodes of tachycardia, if not then that monitoring will not help as in cases of arrhythmias heart activity can be absolutely normal in between the episodes of arrhythmias. Ask your doctor for 24 hour heart monitoring repeatedly till it captures episodes of tachycardia. Also ask your doctor for investigations like echocardiography, catecholamine excretion tests etc.