Hi, Angiogram is a procedure involving injecting dye into blood vessel to check the patency. If there is block or partial block it shows. It is done to check the heart vessel s normally. If there is partial or complete block, patient risks cardiac arrest in future. Complications most common is allergic reaction, which can be life threatening. It is rare. As she requires surgery, her heart ability to manage surgery stress requires evaluation. You need to discuss the pros and con s with your grandma and finalize. Can she be bedridden? If you have any further queries, happy to help.