ran this by my wife (she's a pediatric ICU Nurse, worked in the SICU @ All Childrens for years and is in the pediatric ICU up here in TN @ Vandy). She's said that a lot of those can and will close on their own (determined by the size of the hole, age of the child, etc). If it comes to surgery, the surgeon she reccomends is Quintecenta (no idea of the spelling), says he's the best around...
It's a scary thing I'm sure, however i'm sure he'll be fine.. it's amazing how resiliant our kids can be... regardless, he's in our prayers.