It doesn't sound good. Its very unlikely that a congenital heart defect gets symtomatic at his age, even more unlikely when he has already went thru a whole college career in sports like he has with out any problems but still possible. Other reasons could be an infectious heart disease, idiosyncratic drug interactions including steroids among other etiologies. I feel for him, really and hope he gets well soon.
Star was a risky pick though anyway. The guy looked like Suh at beginning of the USC game but then is pretty much invisible for 3 quarters. If u could get the guy that started the USC game every snap he played even with reduced snaps he would be well worth a Top 10 pick. U just rarely see him play that well
If he clears medical, I don't think he slips at all. If he doesn't clear medical, chances are his career is over. That will also really mess up the DT projects in the first round if that was where we were planning to pick a DT.