A heart murmer in a dog is exactley the same as in a Human. All it means is that the heart skips a beat once in a while. Dont give up exercising, but dont over exercise. Your Vet is probably waiting to see if the heart becomes worse, in which case they will probably prescribe tablets to be taken each day by the dog. I am speaking from some experience, my beagle had the same problem, and so do I. My heart murmer was diagnosed when in my teens and I am now in my sixties, so its not that dangerous Hope this has been some help to you