What is a heart murmur?
Murmurs are whooshing sounds heard between heartbeats. They are a sound of blood flowing more rapidly than normal through the heart. Murmurs can be benign but they can also be an indication that something is wrong in the heart.
Are puppy heart murmurs something to worry about?
Not necessarily. Many murmurs in young puppies are not significant and will go away as the puppy matures. But murmurs in a puppy could also indicate problems with the heart. The most likely causes of serious murmurs in Aussie puppies would be Patent ductus arteriosus or Persistent Right Aortic Arch. You are unlikely to notice a murmur yourself so most will be detected when your vet is examining your puppy. If anything is suspicious further exam or testing will be needed to determine the cause.
If a puppy has an apparently benign murmur have it checked again in a couple of months to make sure it has gone away.