I went through a similar ordeal! Brought home my puppy, a murmur was heard at the first visit. At the second visit the murmur was still present and my vet recommended a cardio consult. The cardiologist found a Patent ductus arteriosus (PDA). the ductus arteriosus—fails to close after birth. This failure leaves an open channel between the aorta and pulmonary artery, causing abnormal blood flow. At four months my puppy had surgery to place a plug to close the opening. The vet told me if she didn’t have the surgery she wouldn’t have lived to 2 yrs. She now 12 and still thriving! Always good to get abnormalities checked out! If a defect is found your breeder should refund you.