Issue Description As part of normal circulation in the body, the
right side of the heart (the right ventricle) pumps blood to the lungs
to receive oxygen. The oxygenated blood goes back to the left side of
the heart from which it is pumped out to the rest of the body.
Blood flows from the right ventricle of the heart through the pulmonic
valve into the pulmonary artery and thence to the lungs. With pulmonic
stenosis, there is partial obstruction of normal blood flow, most
commonly due to a malformation of the pulmonic valve ("pulmonic valve
dysplasia") but the abnormality may be immediately above or below the
valve as well.
The effect of this partial obstruction is to
force the heart to work harder to pump blood to the lungs. The extent
to which a dog will be affected depends on the degree of narrowing
(stenosis) of the valve area. With severe stenosis the dog will likely
develop congestive heart failure due to the increased workload of the
Causes Pulmonic stenosis appears to be a polygenic
Symptoms In its milder forms, the slight thickening of
the pulmonary valve will cause minimal or no obstruction and your dog
will not be affected. However with more severe thickening of the
valve, the obstruction of blood flow from the right side of the heart
will cause varying degrees of heart damage which worsens with age.
With moderate-to-severe pulmonic stenosis, your dog may experience
signs associated with low cardiac output and/or right-sided heart
failure, such as respiratory difficulties, fainting, tiring with
exercise, abnormal cardiac rhythms, abdominal swelling due to an
enlarged liver or the accumulation of fluid because of failing
circulation, or sudden death.
Based on your dog's physical
examination and diagnostic tests such as chest x-rays and an
electrocardiogram, your veterinarian will discuss with you the
severity of the pulmonic stenosis. If there are significant changes
evident, he or she will suggest further tests to determine the
pressure gradient across the pulmonic valve. (Normally there is no
pressure difference between the right ventricle of the heart, and the
pulmonary artery to the lungs.) Where there is a pronounced pressure
gradient, surgery to correct the stenosis should be considered.
Diagnosis The first indication that your dog has a
problem may be when your veterinarian hears a heart murmur on an early
physical examination. Alternately, you may see signs in your dog
related to heart disease, such as fainting or fatigue with exercise.
Your veterinarian will listen carefully to try to determine the
location of the murmur and to differentiate it from an "innocent"
murmur which disappears by about 6 months of age. If the murmur is
significant, your veterinarian will suggest further tests such as a
chest x-ray, electrocardiogram, and cardiac ultrasound to help
determine the cause, and to see what changes if any have already
occurred in the heart as a result of the defect. Once pulmonic
stenosis has been diagnosed, Doppler echocardiography or cardiac
catheterization can be done to measure the pressure gradient between
the right ventricle and the pulmonary artery, to determine the
severity of the obstruction. Based on these test results your
veterinarian will discuss with you the long term prognosis for your
dog and whether surgical correction of the defect should be
Treatment With mild-to-moderate stenosis, your
veterinarian will monitor your dog. No other treatment is necessary
unless clinical signs develop which are associated with heart disease.
Surgery is an option in dogs with moderate-to-severe pulmonic
stenosis, with different techniques recommended depending on the site
of the stenosis. Because of the expertise and technical equipment
required and the surgical risk involved, surgery to correct pulmonic
stenosis is generally performed in a referral center.
Surgery is more risky if atrial fibrillation or congestive heart
failure have developed. These conditions should be treated medically
and the dog stabilized before surgery is considered.
Medical management for congestive heart failure is similar no matter
what the cause, and consists of medications to support the heart
muscle and decrease the work load of the heart, together with dietary