I found this for you: Only a veterinary professional can diagnose heart murmurs, and they can be difficult to verify simply by listening to the heartbeat. Heartbeat irregularities in puppies are sometimes detected at birth. Murmurs sometimes show up during annual checkups with older dogs. In other cases, pet owners may notice that something just doesn't seem right about the sound of their dog's heartbeat. If you notice anything unusual about your pet's heartbeat, you should immediately make an appointment with your veterinarian for an official diagnosis. The process of diagnosing a dog's heart murmur isn't that different from confirming the presence or absence of the same problem in a human. The initial examination will involve listening to the heart with a stethoscope. If a murmur is present, the heartbeat will make a softer, longer sound than the steady, short thump of a normal canine heartbeat. However, in many cases murmurs are very faint, and can't be confirmed without further testing. When a murmur is suspected, veterinarians typically follow up a general exam by running an electrocardiogram (ECG) to determine if there is a problem with the dog's heart. If necessary, the ECG may be followed up with an echocardiogram and chest X-rays to determine the extent of the problem and/or damage that it may have caused.
Electrocardiogram: ECG tests can reveal if there is a problem with your dog's heart. This test allows the vet to measure the heart rate and determine whether or not there are abnormal heart rhythms.
Echocardiogram: This procedure allows the veterinary professional to determine if there are problems with the valves of your dog's heart and to determine how well the heart if functioning. This test helps the vet decide if your pet needs treatment for his or her heart condition.
X-Ray: Viewing radiographic images of your dog's heart allows the veterinarian to see if there seem to be any abnormalities of the cardio-pulmonary system related to heart problems
Did your vet do what is in red? If not can you suggest that he do it? I am hoping for you that it is not a very serious one. I was born with a murmur a one hundred gazillion years later I am here typing this to you. Keep us posted please.