tell you vet to check for heart disease, it's very hard to diagnose heart disease, I found out the hard way. The only way would be with an ultra sound, my kitty's heard sounded fine when they checked it, even on the x ray it looked fine. Cats can hide heart disease very well. My kitty had the same problem two years ago with her legs. Then last month she got really sick - I posted the story on the forum. We didn't know what it was, they finally put her on meds but she lasted a month. Still grieving as I'm writing this I loved her so much. Then the vet told me that looking back that would've been a sign, but at the time they also had no idea what it was. If you catch it early a cat can live a long live with heart disease, so please get her heart checked out. My kitty was only six and I wish they could've saved her, but they tried everything. Please keep us updated.