There are different kinds of shunt and differing severity of the problem. You can use the search on this site to look for info from other threads on this subject or
www.vetinfo.com has an explanation. The breeder needs to be notified immediately so she does not breed those dogs again. This is a genetic problem. She should be liable for vet bills up to the purchase price of the pup. Many breeders do not honor this and will only offer a replacement pup...The guarantee will let you know how much recourse you have. Good luck.