Chest pain with physical activity is a cause for concern, although the good news is that the majority of the time there is no cardiac problem found in young patients. It is appropriate to see a cardiologist, as you have done, and make sure that the ECG and echocardiogram (ultrasound of the heart) show no abnormalities. In particular you need to make sure that they looked at the origins and courses of the coronary arteries on the echocardiogram. If those were normal, good. If those were not seen, then either the echo needs to be repeated or some other type of imaging is done to document that the coronary arteries are not abnormal. Finally, it may be necessary to do an exercise stress test and try to reproduce the chest pain. Usually the cardiologist can tell by the history and type of pain whether it is likely to be cardiac chest pain (angina) vs. non-cardiac chest pain (usually musculoskeletal). If you still have concerns you should voice them to your child's cardiologist. Discuss whether a stress test is indicated given his symptoms.
Thanks so much for taking your time to give us some advice. My wife called our doctor back today and we are going to go back for another visit. We had a ultrasound done of his heart, they had him lie in different positions and said everything was normal but I will ask the questions that you mentioned. We have discussed it and we are going to ask for a stress test to be done. The crazy part that I have a hard time understanding is that he has had conditioning practice for 6 weeks and hasn't had a problem until Monday of this week. Again thank you for your time and advice it is greatly appreciated.