My grandpa had a heart bypass last april. now his heart is ok but he has become over anxious abt very trivial things. what to do?

This is very common: After bypass surgery anxiety is very common. This is often due actually to depression. In some cases bypass surgery can unveil early dementia. I would recommend treatment with an ssri initially to see if this helps. Sertraline or escitalopram work well for anxiety. I would avoid benzodiazepines at all cost. Do not use ativan, xanax (alprazolam) or valium type medications to treat this anxiety.