triple bypass surgery

I had a triple heart bypass done 3 months ago. I was just admitted back in hospital with congestive heart failure and had to have stents put in my heart. My cardiologist says that 2 of the veins used in my bypass have just disappeared. He has no explantion what could have happened to them. Can they just disappear if so what causes it and where could they have gone. If not does that mean something could have gone wrong with my surgery.

[adam247]

my grandfather had a triple heart bypass surgery about 10 years ago. After the surgery he started having vision slurs and now(10 years later) he is almost completly blind. He says he see's patterns on walls and see's people and animals in rooms when he is watching tv. Can anybody help by previding a diagnosis??