He didn’t have a heart attack or stroke. He suffers from anoxic/hypoxic injury (lack of oxygen to brain)
I understand that, but he might qualify under stroke studies.
Here’s the page.
http://clinicaltrials.gov/ct2/search
It will let you subscribe by RSS, so you can click on a bookmark and see the changes from the last two weeks.
It’s only a matter of time until some one starts exactly the sort of study your gson needs.
The great hope though, is that he’s at an age where healing is very, very possible on its own. I’ll pray for him and your family.