It is a horrible condition. Here is a thread on YT about a foster YHR had. His name was Cowboy.
http://www.yorkietalk.com/forums/sic...rgery-pda.html
The only suggestion I have is a board certified cardiologist. There are meds and also a procedure that can sometimes be done. It all depends upon the severity.
Here is a link from the University of Pennsylvania:
http://www.vet.upenn.edu/Portals/0/m...20stenosis.pdf