Pulmonic stenosis is serious. It is a shame the breeder did not seem to care.
We had a puppy with it who died very young...his name was Cowboy. This is his story....we at first thought he had PDA:
http://www.yorkietalk.com/forums/sic...rgery-pda.html
There is a procedure that can be done with some of them. Unfortunately Cowboy was too sick and too tiny at the time for it to be done. I highly recommend that you see a board certified cardiologist.
Here is a link that you may find helpful:
http://www.vet.upenn.edu/Portals/0/m...20stenosis.pdf
Best wishes to you and your pup.