I've never heard of it to be honest but I'm not very clued up on the terminology, - our vet discovered recently that Humphrey (2) has what he called (in German) heart "sounds" and we have to go back to have it checked again. I've spoken to quite a few people who' s dogs have had heart mumures, not sure if that's the same thing (?), and they all seem to be living to good ages. There was a similar thread on here recently aswell and there are several on here with heart conditions.
Hope Cleo's condition isn't anything serious and that it's manageable, please keep us updated, I'd be interested to hear what the vet says on your next visit.
All the best!