My Bro. Had Heart Artack In The 90's And In

My bro. Had heart artack in the 90's and in 1994 had bypass surgery. The clamps came off right surgery. He bled out and was in a coma with brain swelling for 900 days. Little by little brain function returned to pretty near normal. Since then he had several stents put in
He is now functioning on one main artery with heart at 50 percent. Takes lots of meds. He is scheduled for heart cath. After something showing up on stress test. What is prognosis for future health condition