I rescued a little tiny farm kitten once who was only about 4 weeks old and had flu, i found her in my aunties jack russels mouth!!
When she went for her vaccinations they diagnosed a heart murmer but said she should grow out of it!
When she went in to be spayed at 6months they said her heart was enlarged and postponed her spaying, she went back a month later, again they said her heart was enlarged and she was tiny! We decided that we would have to risk spaying her as having a litter would have put extra strain on her heart.
Any way to cut a long story short my little 'Syrup' was spayed and lived a very healthy 17 years!!!!!!!! (she never did need any treatment for her murmer or enlarged heart, it was her kidneys that finally got the better of her)
I am not saying that this will be the case with your kitten but we can only hope and pray, i thought you could do with a happy ending story!!
Here is a picture of my very special little lady!