I Have A 16 Year Chihauna Mixed That Has Congestive

I have a 16 year chihauna mixed that has congestive heart failure, she is on vetmed,enapril, and fluid meds.all of her blood work at all is great, she eats and plays but she has a really bad cough which I am sure it is associated with her heart. our vet gave her cough med, but it really isn't helping. is there anything you can suggest. thanks