Man I know how scary that is. My grandfather had an aortic rupture last year..Thankfully he made it out okay. I am wishing the best for Neil as well.
I know how it can be scary to have a partner dealing with heart related issues. My boyfriend was born with a Bundle Branch Block(can't remember if right or left), making him have three heartbeats and always the fear of heart complications.
Surgery is always scary, even when it's just explorative. But I know my grandpa had his ruptured aorta replaced and is still walking around today. Doctors are very smart, I'm sure they will be performing at their best. I wish him luck on a speedy recovery!