12 year old boy with syncope?

My 12 year old brother has experienced 3 episodes of syncope, 2 of them happened 3 years ago and the last happened today. He was doing fine all through this time interval. the symptoms he had in these 3 episodes in addition to fainting are dizziness, nausea and 'chest pain' (according to him... i cudn't make sure if he had a real pain or just tightness) and this concerns me the most.
What cud be the cause? HOCM? Long QT syndrome? cud it be just vasovagal attack?  

[ireneo]

I know a woman with a young son who occasionally passes out. They said his was a drop in BP. Not sure what caused it but he's healthy otherwise. He has no heart problems. Has your brother seen a doctor for this? That's the first step.

[grendslori]

Your brother should certainly be evaluated by a pediatric cardiologist. He could have an arrhythmia problem or even HCM which is more common than HOCM which is the obstructive type of HCM. It could also be a vaso response that children and teens sometimes go through which is totally harmless. Have him evaluated.

[Mom2four85]

I've fainted since I was 9; but didn't have a doctor take me seriously until I was 42.

Please mention a tilt table test to your parents or the dr to check and see if it's heart or ANS (Autonomic nervous system) related; plus HCM/HOCM as grendslori said should be ruled out.

Fainting can be caused by a vast number of things from things like dehydration, low blood pressure, infection to HOCM like I was diagnosed with.