Dear Jmacgu5,
Without knowing how slow your son’s heart rate is, I can’t tell exactly what’s going on. However, what it sounds like his doctor may be referring to is atrioventricular block. If his heart rate is in the 30’s at rest, it could be complete atrioventricular block, which is an interruption in the single electrical connection between the upper and the lower chambers of the heart. If his heart rate is in the 50’s, though, your son may just be in good physical condition. I obviously don’t have that information to be able to say. I would guess, though, that if your son is able to exercise without problems, he likely does not have complete atrioventricular block.
I’m not sure what specialist your son will be seeing. It should be a pediatric (and not an adult) cardiologist. A thorough history and physical examination will be performed, and an electrocardiogram (ECG) will likely be performed. Depending on the findings from these 3 sets of information, your son will either be found to be normal or, if there are concerns or abnormalities, he may require further testing. Other potential kinds of testing include an echocardiogram, which is a cardiac ultrasound, a 24-hour Holter monitor, which records all the electrical activity of the heart for one full day, and an exercise stress test, which assesses exercise tolerance as well as the heart rate and electrical system response to exercise.
I am not a doctor.
It is extremely improbable, though not impossible for your son to have a blockage of the coronary arteries.
More likely, he was talking about an arrhythmia called heart block. The electrical system for the most part is out of my area of knowledge. Most likely he'll get a EKG, and depending on that, he may get other tests. What you'll get from the specialist is the ability to discern if it is just something to note, or if it needs further investigation.