Try to be as supportive as possible... does he like to read? Tell him to read right before he sleeps and perhaps teaching him some breathing techniques.
I have had anxiety/panic disorder since I was 8 years old, and it's awful as a child with not knowing what to do and no support from your parents. (I have had NONE up until a couple years ago, and I've suffered with this disorder for much longer than that)
So PLEASE be supportive because he definately going to need it. A good support system will help him get through this much easier.
It's a pity that the appt. is a month away, I can only imagine what the poor kid is going through (as I've been there), I'm glad you're taking action though to take him to some type of doctor.
Tell him everything will be okay, (do not tell him to calm down, we panic disorder sufferers HATE those words LOL, it makes us stress even more!!) give him a hug and maybe sit with him a couple nights before he goes to bed and let him know he is far too young to die of a heart attack.
(then again we all have those fears.. .I always thinking I'm having a heart attack, but I'm not.)
I hope this helps.
"Be glad of life because it gives you the chance to love and to work and to play and to look up at the stars."
DX: Panic Disorder, Depression, TMJ (Temporomandibular Joint Disorder), Chronic Migraines
RX: Lorazepam (1 MG a day), Lexapro (20 MG a day), Tylonel for the TMJ and Migraines