Dog cough

[Sandybardotbella]

Hi,
I took my 11 year old 4lb yorkie for her yearly checkup a month and a half ago. While having her ex ray something happened and her knee cap was dislodged. When they brought her back to me they just handed her to me and I was holding her while going over the ex ray's. They said everything looked perfectly normal. Just a skin iritation and told me to use special shampoo three times a week.
Got home and started to get her ready for bath and noticed something was wrong with her back leg. She couldn't walk on it and was falling. I immediately called vet and they told me was probably a sprain and to give it overnight to see if it gets better. Gave her aspirin and waited. Next day, same thing. Finally I just took her into vets office and they took responsibility for the injury. They had to operate to correct it. While under anesthesia I had her teeth cleaned and two teeth was removed.
Now, my main question.....after she came home from surgery the next day all went well with recovery until a week and then she starting coughing. Always the same cough. About six to seven dry cough's that ends with a big gag like cough. Almost like she is trying to expel something from her throat. Took her in again and they gave her medication for kennel cough. It's been a month and just went back in to get another ex ray and the vet told me it had nothing to do with the surgery and recommended a heart specialist.
She has never coughed before and she is 11 years old.
I find it hard to believe that it is not related to the surgery.
Please, any advice would be appreciated.
By the way, her best, life long partner of life passed away two weeks before all this happened so I feel so bad for her. She has been through so much trauma.
Thank you