Mungo has a heart murmur

A friend of mine has a pair of boy cats - they are about 2 years old and are siblings. He's not long come back from 2 weeks in Greece - he lives at home and whilst he was away, his mum looked after the boys.

When my friend got back, his mum told him that she thought Mungo might be sick because he had pretty much refused to eat or eaten very little whilst he had been away. He tried to get Mungo to eat but didn't have much luck

Mungo went to the vets over the weekend and the vet has diagnosed Mungo as having a heart murmur and has given him 6-12 months to live. He's given my friend some meds for Mungo and sent them both home. Mungo has been taking the meds for a couple of days now but doesn't appear to have improved any. Worse, my friend let him out into the garden this afternoon, as per usual but Mungo never came back. Until today, he has never ever strayed beyond the boundaries of the garden and my friend is frantic about him

Two questions:-
1. Is it worth getting a second opinion on Mungo's condition? The vet who examined him wasn't his regular vet
2. In the event that the initial prognosis is correct, is it true that heart murmurs are untreatable?

It depends on how bad it is.
My Meeko has one but she is ok.
She was 3 months when we found out.
I would get a 2nd opinion.
Did he have a echo?
My old cat had a echo and she was fine.
It tells alot.
Some cats do not live long with heart problems.

Just a quick update...

Mungo came home Tuesday evening but he was really ill. He was crying and his heart was racing. My friend stayed up with him all night but yesterday morning, decided that it wasn't fair to let Mungo keep suffering so had him pts

Thanks for all your advice

So sorry about Mungo.