We just found out yesterday that Harley has a heart murmur. (She went to the vet because she has been coughing real bad. We found out that she has Kennel Cough.) The vet said it wouldn't affect her until she was about 3 or 4 years old. Does anyone know how heart murmurs affect dogs. My sister and I are both pretty worried about her, and we don't know much on the subject. Any information you could give me would be greatly appreciated.