Canine Pulmonary Stenosis: Diagnosis and Treatment

Pulmonary stenosis, after patent ductus arteriosus and aortic stenosis, is one of the most common cardiovascular malformations among our furry companions.

That said, this condition can be present from birth but show no symptoms, or only start showing them from the first year of age onward. That's why at Soyunperro we want to show you how it's diagnosed, what its main symptoms are, and, of course, what the best treatment is.

What Is Pulmonary Stenosis?

The heart is made up of four chambers: the right and left atria and the right and left ventricles, connected to each other and to the blood vessels through valves. The left side is responsible for making sure oxygenated blood reaches the whole body, and the right side is responsible for collecting it from the body to send it to the lungs.

This particular condition involves a narrowing of the tract between the right ventricle and the pulmonary artery, which carries blood to the lungs. It can be located at the level of the pulmonary valve, the most common location, or at the subvalvular or supravalvular level.

Regardless of the type of stenosis, the result is increased pressure in the right ventricle, causing concentric hypertrophy of it. In other words, a thickening of the heart's muscle layer, known as the myocardium, reducing the ventricular chamber's capacity and cardiac output.

Sometimes, due to the high pressure in the area, turbulent flow occurs, eventually causing dilation of the pulmonary artery, secondary to the stenosis.

Pulmonary stenosis is more common in males and shows a clear breed influence — small breeds, and specifically the ones shown below, carry a higher risk of developing it:

• Beagle
• Boxer
• English and French Bulldog
• Miniature Schnauzer
• Airedale Terrier
• Boykin Spaniel
• Chihuahua
• Cocker Spaniel
• Bullmastiff
• Samoyed
• West Highland Terrier

Normally, pulmonary stenosis is an isolated malformation, but it can sometimes be linked to others, such as tricuspid valve dysplasia or various ventricular septal defects.

Symptoms of Canine Pulmonary Stenosis

Usually, pulmonary stenosis in dogs is detected during a routine check-up or one done for another reason, since in most patients, pulmonary stenosis shows no visible symptoms. Only in severe cases will we see exercise intolerance, potentially leading to fainting episodes or even sudden death in extremely severe cases.

We may also find arrhythmias, rhythm disturbances caused by reduced cardiac output, or fluid buildup in the abdomen, ascites, generally associated with other malformations.

Diagnosis and Treatment of Pulmonary Stenosis

Thanks to the history, physical exam, and detecting a systolic murmur on auscultation, pulmonary stenosis can be suspected. However, there are various tests the specialist can perform before confirming the diagnosis.

The most precise and recommended method for confirming this condition is echocardiography and the use of Doppler to measure blood flow velocity, determining the degree of obstruction. Other tests of interest could include an electrocardiogram and chest X-rays, especially in the dorsoventral view.

These techniques will confirm whether or not this malformation is present, or whether it's another condition, such as pulmonary hypoplasia, subaortic stenosis, tetralogy of Fallot, etc., which can show similar symptoms. And once the stenosis is confirmed, what's the next step? Well, depending on how severe the problem is, the vet will recommend the treatment they consider most suitable.

Patients with mild stenosis usually don't have too many complications, don't need treatment, and have a very favorable prognosis. On the other hand, dogs with severe stenosis have a worse prognosis unless they undergo surgery. Previously, and still today in some patients, medical treatment based on giving beta-blockers can be carried out, aimed at reducing oxygen consumption and the presence of arrhythmias.

But in more severe cases, surgery is necessary. The most recommended technique is balloon valvuloplasty, which increases the size of the narrowed area's opening using a balloon introduced via catheterization through the jugular vein until it reaches the heart. Thanks to this technique, we'll improve our furry companion's prognosis and quality of life.

Care a Dog With Pulmonary Stenosis Needs

Besides the treatment indicated, there's some special care a dog with pulmonary stenosis will need. Some tips that can be useful in this case are:

• Prevent the dog from doing intense physical exercise, since this could cause fainting or an arrhythmia.
• Follow all the vet's instructions and bring the dog to every check-up for thorough monitoring of how this condition progresses.
• It's not recommended to breed these animals, to prevent the hereditary transmission of the condition.