We've had two gals on another forum I belong to have puppies diagnosed with heart murmurs recently. They both went to cardiologists and one was told her puppy had an "innocent" heart murmur that he would outgrow. I guess it's not uncommon in puppies to develop a heart murmur during a growth spurt that will close on its own.
I adopted Lady at age four and she was diagnosed with a grade 1 heart murmur. Grade 1 is the mildest. She'll be twelve in a couple of months and it has never gotten any worse. Grade 1's like your puppy has can be hard to hear which is why the breeder's may have missed it.
You should take him to a cardiologist, though, to find out exactly what you are dealing with. One of the puppies I mentioned does have more serious problems (he was actually passing out during walks) and has to be on medication. |