Fem Fem Bypass

My dad who is 86 had a fem fem bypas a few years ago. His cardiologist told him yesterday that he wants to do an angiogram next week because he thinks his bypass is "clogged up". He anticipates doing angioplasty. My dad lives in FL and I live in TN. My sister lives near him and will go with him for the procedure. What are the risks associated with this, especially considering his age? How often is this done? I'm not even sure how common a fem fem bypass is. I went down for that surgery and it was a very lengthy procedure. At 86, my dad forgets things, but still is in fairly good shape. He lives alone. I plan on trying to get in touch with his doctor, but you know how that goes. He may or may not return my call, although I do have Durable Power of Attorney for Medical Care.