What are the risks with regards to angioplasty for angina after bypass?

Generally same as: Before cabg. Bleeding, infection, heart attack, stroke and death although these are very small.

Several: Depends on what vessel? A graft an unbypassed native artery whatever is thought to be instrumental to the angina symptom how long since the bypasses? If the bypases are open and generally perfusing the major coronaries the risk should be quite low. If not, the usual risks of dissecting, clotting, embolizing a vessel or graft are there. The general list is; death bleeding, recurrence, stroke.