Katie, I am so sorry to hear your baby is so sick. I don't have any experience with CT, but I do have a dog that was diagnosed with an enlarged heart over two years ago, at age 13. She will be 15 in a month and a half. Also, Lisaly also had a yorkie with enlarged heart and she just lost Ashley at nearly 17 yrs old. There are things that can be done to help that, if it isn't too advanced.
My Opal actually has mitral valve prolapse, and it's the right atrium that is enlarged and pressing on her trachea, making her cough. She isn't having the problem with coughing right now.
Check out this thread
http://www.yorkietalk.com/forums/sic...ged-heart.html