A heart murmur is an abnormal heart sound that is heard when listening to the heart with a stethoscope. It is cause by abnormal turbulent blood flow. Abnormal turbulent blood flow can occur when blood passes across abnormal heart valves or across abnormal structures within the heart. It can also occur when blood flows very fast across normal structures (such as when an animal is excited). An echocardiogram (ultrasound of the heart) is a non-invasive test that is performed to determine the cause of the murmur.
Your veterinarian will grade the heart murmur. They are graded as grades one to grade six, with 6/6 being the loudest murmur. In some instances, the louder the murmur, the more significant the abnormality within the heart.
Soft heart murmurs (grade 1/6 to 2-3/6) can occur in young puppies and kittens and are of no consequence to them. These types of murmurs are called “innocent” murmurs. They are soft and usually go away by six months of age.
Loud heart murmurs (Grade 3-4/6 to 6/6) in a new puppy or kitten should be evaluated by a cardiologist. This may indicate that congenital (present at birth) heart disease is present.
The cardiologist will perform an echocardiogram as well as other tests (EKG, blood pressure, etc.) to assess the heart and determine if congenital heart disease is present. Depending on the disease present, some congenital diseases can be fixed or made better with medication or an interventional catheter procedure. Many do not need any medication or treatment if the murmur is a lower grade. If monitored properly the heart murmur may not get any higher in grade level. But, you must be sure to keep them examined by your vet or cardiologist as stipulated by the specialists.
Never assume it will not get any worse especially if a grade 3 or above.
Just remember many can live a long healthy life if cared for properly.