Does anyone know what is the recommended treatment for a dog with a heart murmur?

Just got back from the emergency vet clinic and I had to leave my pup there. He is 11 years old and he was having difficulty breathing today. I could tell he had fluid in his lungs. We had to leave him there over night so they could monitor his condition.

He looked pretty good but they think it was caused by fluid his heart. They were surprised that no other vet ever caught it but they said it can get worse with age and just wasn’t problematic before.

Any how, tomorrow he will see an internist and the doc said that heart murmurs can be treated with medications.
He said on a scale of 1–6 with six being the worst that he feels his heart is either a 4–5 on the scale.

Can someone please tell me what is the possibility of a good healthy recovery.

He generally has never been this sick before so I would appreciate any information on the subject and what to expect or ask the docs tomorrow.