today i had to put down one of my pups at 2 1/2 weeks old with a heart murmur who went into heart failure over night.
I have not had the rest of the litter checked yet but will get them all checked, basically i was wanting to know what people here would do in terms of if another pup had a heart murmur (a serious one not one that should correct itself)
and would you breed the bitch again?

many thanks

depends on the prevalence of heart problems in the breed. I know someone who had several pups with hearth murmurs in a litter. Grades 1-3 so not life threatening. She wasn't going to breed from the bitch again and told the stud owner who took the attitude that it wasn't their dogs fault and carried on using him.  The bitch then had an accidental mating to a dog of the same breed but different lines and all the puppies were fine. I can't remember if the stud produced any more pups with heart problems but it might be just that the two both carried a faulty gene and were fine mated to other dogs.

If you know the exact nature of the problem and it isn't in either parent and not prevalent in the breed, Id say it was congenital ( something gone wrong in the development in the womb) and can happen to any puppy in any Litter.
All pups and mother need to be checked for the anomaly and then you will have your answer.