Pulmonic Stenosis in Dogs

Pulmonic stenosis is one of the most common heart conditions in dogs. Here, our Nashua veterinary specialists share important information about pulmonic stenosis in dogs, including the symptoms, treatment options and life expectancy.

What is pulmonic stenosis in dogs?

Pulmonic stenosis is a constriction of the pulmonic heart valve through which blood must pass from the heart to the lung. In pulmonic stenosis, the right ventricular outflow tract is narrowed at or around the valve.

This congenital disorder is most often identified in brachycephalic dogs (e.g., bulldogs, Boston terriers), terriers (Jack Russel terriers), Samoyeds, and Labrador retrievers. Other breeds, such as boxers and Newfoundlands, can also be affected. Congenital means present at birth, and so pulmonic stenosis is present in a puppy from birth.

What causes pulmonic stenosis?

Pulmonic stenosis affects the valve between the right ventricle and the pulmonary artery. The leaflets of this valve thicken and can partially fuse.

Dogs with this congenital defect have a wide range of stenosis, including very mild to severe obstruction to blood flow from the heart to the lungs. This defect may be associated with other congenital defects, such as ventricular septal defect, overriding aorta, and subaortic stenosis. Because this disease is associated with certain breeds, it is likely at least in part due to a mutation in an as yet unidentified gene.

What are the signs and symptoms of pulmonic stenosis?

Mild pulmonic stenosis is of little concern and usually does not affect life expectancy. Luckily, most cases are mild and do not require treatment; fairly severe disease is needed for clinical signs to appear.

Many dogs won't show any signs or symptoms of the disease, but a large portion of dogs with severe pulmonic stenosis will show some or all of the following signs:

• Tiring easily
• Fainting spells (from the abnormal electrical heart rhythm)
• Fluid accumulation in the belly
• Blue-tinge to the gums, especially with exertion

While this condition can be mild, there are more drastic cases, and some dogs with severe disease experience sudden death.

How will a vet diagnose pulmonic stenosis?

Virtually all dogs with clinically important pulmonic stenosis will have a cardiac murmur heard when the chest is listened to with a stethoscope. This is an auscultation of the chest. Often, but not always, how loud the murmur is in this particular disease correlates with severity. An important example of the exception to this general statement is the tetralogy of Fallot, where four congenital (present at birth) defects are present together with pulmonic stenosis.

• Radiography and angiocardiography - Radiographs, or X-rays, provide information regarding the size and shape of the heart's silhouette. Angiocardiography is a type of radiography in which a dye is injected into the vasculature to see the stenosis. 
• Echocardiography – The ultrasound of the heart, which is known as echocardiography, is an important diagnostic tool for fully characterizing the structure and function of the pulmonic valve and the support structures. This test permits the examination not only of the muscle and valve but also of the blood flow. 
• Electrocardiography - An electrocardiogram (ECG) may be performed to further characterize dogs with pulmonic stenosis; however, this test is usually not as important as the physical examination, radiograph, and echocardiogram. Other tests may be ordered to determine the status of other body systems and ensure that all are functioning adequately.

Treatment Options for Dogs With Pulmonic Stenosis

If your dog has severe pulmonic stenosis, treatment options are available to help ease symptoms and allow your dog to lead a comfortable life.

Balloon Valvuloplasty

If the obstruction at the pulmonic valve could be relieved, much of the problem would be solved. Severe pulmonic stenosis cases can be treated by doing just that. A balloon is inserted into the pulmonic valve and inflated, breaking down the obstruction.

Performing this procedure reduces the risk of sudden death by 53% and improves the quality of life as well. Certain types of valve deformity are not amenable to this treatment, and dogs with pulmonic stenosis that have a coronary artery wrapped around the pulmonary artery are similarly not amenable to this treatment. For these dogs, unfortunately, no treatment can be recommended.

There are several risks involved with this procedure. Make sure to talk to your primary vet, who will determine if it is right for your pet.

Surgery

Dogs for whom the stenosis is just before the valve rather than at the valve itself may benefit from surgery. Several techniques can be used to widen the pulmonary valve or bypass it. These procedures require an experienced surgeon and bear significant risk. Balloon valvuloplasty is the preferred treatment for cases where treatment is recommended and where balloon valvuloplasty is applicable.

Medication

Unfortunately, medication is not very helpful for pulmonic stenosis except to manage any right-sided heart failure. In some cases, medications called beta blockers can be used to relax the heart muscles and dilate the stenosis. This will not relieve the constriction but could ease it.

Pulmonic stenosis is a condition that not all veterinarians are comfortable treating. Discuss with your veterinarian whether a referral to a veterinary cardiologist would be best for you and your pet.

What is the life expectancy for dogs with pulmonic stenosis?

Dogs with moderate pulmonic stenosis usually have normal life spans but may experience ongoing symptoms that require medical therapy.

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.