Poor Callie, and poor you. You are fine - you have done your best for her, and it's so hard to take care of a sick animal - they can't tell you what they need, and you can't explain to them what's best for them. A ray of hope: my mother's cat has a heart murmur, and she has been fine all these 11 years. I hope that 11 years from now you can say the same for Callie.