My friend heart surgery Bypass surgery is always a major procedure and is already a very huge race which we take if and only if the benefit outweighs that is but since the kidney is also having a major issue in your case the risk will be higher than the benefits and nobody will be able to give you an exact percentage of risk or benefits in this case all you can do is consult a couple of more surgeons and if some surgeon as an experience or Dare to do the surgery in this case then you can go forward