My Shih Tzu got diagnosed with a heart murmur and my vet wants to do tests on her and put her on meds for the rest of her life…should I get a second opinion?

~ Michela

Dear Michela,

Second opinions are a good idea whenever you are not comfortable with a diagnosis. Let’s look at what causes heart murmurs, and what a murmur may mean to your dog. This should help you decide on your plan of action.

As you know, the heart pumps blood throughout the body and lungs. There are four chambers, or compartments, of the heart. There are valves between the chambers. The right atrium receives blood from the body, passes it through the tricuspid valve to the right ventricle, which sends the blood through the pulmonic valve to the lungs, where the blood collects oxygen. The left atrium receives the blood from the lungs, passes it through the mitral valve to the left ventricle, which sends the blood throughout the body through the aortic valve. Normally, this blood flow is smooth, and the heart sounds are a clean “lub-dup” as the valves close cleanly. Murmurs occur when the flow of blood through the heart is not smooth; this is called turbulent blood flow.

Turbulent blood flow has several causes. Some causes are common, some are not. The murmur resulting from turbulent blood flow may be graded from 1 (very soft) to 6 (very loud). Murmurs are most easily heard over the part of the heart where the turbulence is occurring.

  1. The most common cause is improper function of one of the heart valves; the valve most commonly affected is the mitral valve.
  2. If there is a hole in the walls between the chambers, blood will move in an abnormal manner, causing turbulence. This is more often found in young animals as a developmental problem.
  3. The valves or chamber walls can be too narrow, causing turbulent flow.
  4. Anemia can cause turbulent flow, because the blood is thinner than normal.
  5. Extreme excitement can cause turbulent flow as the heart pumps harder and faster than usual.
  6. Puppies can have soft murmurs which disappear by 15 weeks of age. The cause of these is not known, but the important fact is that they go away completely. These are called benign (not dangerous) murmurs.

Benign puppy murmurs do not require any treatment. Murmurs caused by anemia or extreme excitement are also considered benign, though the anemia will need to be addressed.

Murmurs are significant as an indicator of turbulent blood flow in the heart. This turbulent blood flow may be a sign of heart disease. We treat the cause of the murmur, not the murmur itself. It is important to treat problems that will lead to illness, or that are causing illness at the time. Many murmurs do not indicate serious disease, and therefore no treatment is required. Loud murmurs (4-6) are more often associated with heart disease, but soft murmurs can also indicate problems. X-rays provide an initial evaluation of heart size, and can indicate the presence of heart disease. The best way to tell what is going on in the heart is by an ultrasound evaluation with a board certified cardiologist.

Michela, you don’t mention the age of your dog, or if she has signs of heart disease. These are significant factors in determining appropriate therapy. Dogs with heart disease can all benefit from a high quality diet, and the addition of antioxidants such as ubiquinol (coenzyme Q) and omega fatty acids. Constitutional and symptomatic homeopathic treatment can be very helpful, and there are herbal therapies for heart disease as well. I would suggest that you investigate all your treatment options, once you definitely know what you are (or aren’t) treating. As discussed above, a heart murmur is a sign of possible heart disease, not a diagnosis of heart disease!


S.F. Chapman DVM, MRCVS, VetMFHom