Personally i think the most appropriate course of action would be to put the heart doctor together with the doc that diagnosed the ADHD so they are completely on the same page with one another so that one thing does not cause issues with the other or that meds that could be counterproductive are not given in tandem. I would personally tread pretty lightly on this and have the docs do a consult with one another to provide your son with a safety net so that no errors are made...in this situation the right hand definately needs to know what the left hand is doing....you don't want to end up being one of those sad stories that a simple phone call could have taken care of the red flags...good luck to you and your family
I am sending you a link I found--check your inbox. Of course make sure whatever drug is offered, research for his heart condition.