My Husband Heart Works 25% He Has No Blockages About

My husband heart works 25% he has no blockages about a year ago he was in heart failure he is in a-fib .blood pressure was always high but it has been staying normal now for about 4 months. He stays tired and weak and fluid builds up on his stomach and has to have it drained every once in awhile . cardiologist wants to shock his heart back to normal would this be safe? Also could he have a long life on 25% heart. Ty