What Does It Mean That Collateral Vessels And The Great Cardiac Vein Are Supplying The Heart When There Is 100% Blockage?

My Father recently went in for a heart cath with possible stenting after a Nuclear stress test was performed. During the cath procedure the Interventionalist said he was unable to do stenting and that my dad would most like be a candidate for a CABG X 2 and that he has had at least one heart attack. He also said that a minimum of 25% of his hear is dead . My dad said that he s never had any chest pain which led the answer of a silent heart attack. When he went to the Cardiothoracic Surgeon for a consult, the doctor began by saying I m quite stunned. Both your left and right coronary arteries are 100% blocked. You shouldn t be alive. I have to consult with some physicians at a meeting in a few days about this. I m confused by this since I was always led to believe that you can t live when both arteries are 100% clogged. The Surgeon also stated what is currently keeping your blood flowing through your heart is your Great Cardiac vein and the development of new vessels . My dad asked what steps do I need to take to ge this remedied in which the Surgeon said, I can t give a definitive answer to this at the moment and I need to consult with some local colleagues to determine the best avenue to take . Although it more than welcoming news that my dad is still alive, I m confused as to what is going on and was hoping that I could get an answer. I ve tried researching both arteries being clogged but have been unsuccessful so far. Any information would be appreciated. Thank you.