You need to be angry notoveryet believe me.
How ever horrible it feels now, it's doing good work in your grieving process.
Why shouldn't you be angry? He's been taken and you didn't want that to happen.
He may or may not have benefited from the surgery but that's not really the true focus for you.
You didn't want to be left without him and who can blame you?
So as wise paddyann says, it's normal and it will pass and when it does you will see that it's not your beloved husband you were angry with at all, but life, or death and how unfair it can be.
I think it's worth reiterating paddyann's perceptive post.
Take care of yourself, be kind to yourself when you feel sad or angry or lost - and there will be a light at the end of the tunnel for you when the time is right