What is Pulmonic Stenosis in Dogs
Pulmonic stenosis refers to a constriction of the pulmonic heart valve through which blood must pass on its way from the heart to the lung. In pulmonic stenosis, the right ventricular outflow tract is narrowed either at or around the valve.
This congenital disorder is most often identified in brachycephalic (e.g. bulldogs, Boston terriers), terriers (Jack Russel terriers), Samoyeds, and Labrador retrievers. Other breeds can also be affected such as boxers and Newfoundlands.
What Causes Pulmonic Stenosis in Dogs
Pulmonic stenosis is a congenital heart defect of the valve that is between the right ventricle and the pulmonary artery. The leaflets of this valve thicken and can partially fuse.
Dogs that have 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 as yet unidentified gene.
Signs of Pulmonic Stenosis in Dogs
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 approximately 35 percent 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 it is estimated that approximately 30 percent of dogs with severe disease experience sudden death.
How Is Pulmonic Stenosis in Dogs Diagnosed
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 with tetralogy of Fallot where several congenital defects are present together with pulmonic stenosis.
- Radiography and angiocardiography - Radiographs which are made with X-rays provide information regarding the size and shape of the silhouette of the heart. Angiocardiography is a type of radiography where a dye is injected into the vasculature to see the stenosis.
- Echocardiography - An important diagnostic tool to fully characterize the structure and function of the pulmonic valve and the support structures involves the ultrasound of the heart known as echocardiography. 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 to ensure that all are functioning adequately.
Treatment For Pulmonic Stenosis in Dogs
If your dog is suffering from severe pulmonic stenosis, there are treatment options 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 where it is 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 the type of pulmonic stenosis that has 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 vet and they will determine if this procedure 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 in an attempt to relax the muscles of the heart 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.
Dog's Life Expectancy With Pulmonic Stenosis
Dogs with moderate pulmonic stenosis usually have normal life spans, but they may experience symptoms that require medical therapy. Dogs with severe pulmonic stenosis are 16 times more likely to suddenly pass away, according to the Journal of Veterinary Internal Medicine
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.