How safe to have angioplasty, when a person already have open heart surgery since 10 years back?

Safe. Depends on why being done and what ur looking for but safe to do if indication is right.
Depends. What was done. What grafts used. Where is the recurrent or new blockage. Vein grafts with blockage can be more difficult. Who, where is doing the work.
Angioplasty. If a person has had previous coronary artery bypass graft surgery, and the graft has occluded and requires angioplasty, there is an increased chance of complications. If the angioplasty is not going to be performed in the area of the graft there should be no added risk.