I wouldn't necessarily assume the worst, it could be something as simple as heartburn. Many young boys and men with DMD have acid reflux/more sensitive guts.
Just a thought,
Ryan gets chest pains too. The doctor has checked him over and thinks they are just normal muscle type things. Not the heart. Ryans sometimes last a few minutes other times longer. I just try to get him to relax and take slow deep breaths.
It might be a good idea to get a referral from Cincinnati for a local Cardiologist to establish your son with so you have someone to see in between visits to Cincinnati if the need ever arises. I'm in Long Beach, not that far from you and my son's Cardiologist is very well versed on the effects of Muscular Dystrophy on the heart and even though he is a pediatric Cardiologist has offered to keep Jon on as a patient after he turns 21 (he is 18 now) because he feels that most adult cardiologists are more used to dealing with heart attacks, clogged arteries and the more common adult ailments and would not be as familiar to the involvement of MD and the heart. It is also nice to have someone local in case you ever need a check up for any possible surgery, my son has had 3 procedures for kidney stones this year and it was necessary to get clearances from the cardiologist and pulmonologist and since they were both local it made our lives so much easier.