Dear Mom,
Your son's case sounds interesting. I am no expert in cardiology but I will respond with interest to your son's condition.
I have attended symposiums on pediatric cardiology which included congenital heart defects and conditions and therapies. SVT and ablation therapy was of great interest to me during that symposium!
The first thing that comes to mind after reading your son's S/S's is symptomatic Paroxysmal Supraventricular Tachycardia (PSVT). It is good news to hear that he has had nearly 8 non-episodic years of this event reoccuring. Apparently, it hasn't gone away.
Another point of interest is your son's resting heart rate while sleeping of 38 - 52 bpm. Unless your son is a exceptional athlete (or a young U.S. Marine!) his heart rate should be higher than 52 bpm. This would direct my thinking to a problem with his pacemaker, the Sinoatrial (SA) node. If his SA node is not functioning his inherent heart rate would be 40-60 bpm which could be driven by his Atrioventricular (AV) node.
Sick Sinus Syndrome is another condition that comes to mind. This condition is uncommon and usually appears in the ederly but is also of interest because it's signs and symptoms mimic those of your son's., especially the bradycardia / tachycardia syndromes. It has presented itself in children as well. One website that I found is:
http://www.nlm.nih.gov/medlineplus/e...cle/000161.htm. I hope this is of help to you.
Sincerely, illusiondweller