Pulmonary stenosis – why is my dog breathing so heavily?

Pulmonary stenosis, also known as pulmonary artery stenosis, is one of the most common congenital heart diseases in dogs and describes the narrowing of the pulmonary artery, which originates in the right ventricle. This heart disease is extremely rare in cats.

INHALT
Cause Origin Classification Symptoms Diagnosis Treatment Forecast Prophylaxis
Cause

This is a congenital heart defect that is present from birth. It is caused by a genetic defect, which means that pulmonary stenosis occurs more frequently in certain breeds; there is a so-called breed predisposition. These include Chihuahuas, Boxers, English and French Bulldogs, Miniature Schnauzers, West Highland White Terriers, Beagles, and some Pinschers.

Origin

During the contraction phase of the heart, known as systole, blood is pumped from the right ventricle through the open pulmonary valve and into the lungs via the pulmonary artery to be oxygenated. A narrowing in the area where the pulmonary artery originates leads to reduced blood flow from the heart to the lungs. As a result, the right ventricle has to exert increased pressure to pump blood into the pulmonary circulation. The high pressure causes the ventricular muscle to thicken, which simultaneously reduces the volume of the ventricle and increasingly restricts the normal function of the heart.

In severe cases, the muscle is so thickened that the heart's own blood supply through the coronary arteries is no longer sufficient, leading to oxygen deficiency in the heart muscle, which can result in severe cardiac arrhythmias.

Schematic diagram of pulmonary stenosis
1 Aorta | 2 Tricuspid valve | 3 Altered pulmonary valve | 4 Right ventricle | 5 Pulmonary artery | 6 Mitral valve | 7 Aortic valve | 8 Left ventricle
Classification

Depending on the location of the narrowing, different forms of pulmonary stenosis can be distinguished. First, the narrowing can be located below the pulmonary valve in the right ventricle. In this case, it is usually caused by muscular changes. However, PS is most commonly located directly on the valves. This is usually caused by deformed, stuck, or thickened valves. The first two forms can occasionally occur in combination. Finally, the narrowing can also be located above the valve in the pulmonary artery.

In severe cases in particular, pulmonary stenosis may be accompanied by insufficiencies (leaks) in both the pulmonary and tricuspid valves (heart valves between the right atrium and right ventricle), leading to further symptoms.

Symptoms

Depending on the severity and extent of the stenosis, the disease can be accompanied by mild to severe symptoms. Mild stenosis is often overlooked for a long time, as it does not cause thickening of the heart muscle and therefore does not lead to clinical symptoms. It does not reduce the animal's life expectancy and therefore does not require treatment. However, affected dogs should not be used for breeding due to the hereditary nature of the disease.

However, in moderate and severe cases, once thickening of the heart muscle occurs or additional changes such as valve insufficiency develop, clear symptoms appear that are attributable to cardiac arrhythmia and reduced blood ejection from the heart. Affected animals may show signs of poor performance, fainting spells (syncope) or breathing difficulties. If valve insufficiency is also present, fluid may accumulate in the abdomen (ascites) or chest (pleural effusion). In the worst case, severe stenosis can lead to sudden cardiac death.

Diagnosis

Pulmonary stenosis is often discovered by chance during routine veterinary examinations. Every general clinical examination performed by a veterinarian, for example before a vaccination or routine surgery, includes listening to the heart (auscultation), during which the veterinarian may detect a heart murmur. A cardiac ultrasound examination is essential to determine the severity and extent of pulmonary stenosis. This allows the thickness of the muscles, the condition of the valves, and the speed of blood flow to be measured and assessed.

Treatment

Pulmonary stenosis cannot be cured. However, mild pulmonary stenosis does not require treatment due to its lack of harmful effects. In cases of moderate changes, treatment is only indicated if there is ascites or a pleural effusion caused by valve insufficiency. In such cases, diuretics and medications that support circulation are used.

Severe pulmonary stenosis can be treated with drugs that counteract arrhythmias and prevent further changes to the heart. However, in most cases of severe changes, balloon dilatation is recommended. This procedure requires only a small incision in the skin, through which a catheter is inserted into a large vein in the neck. A small balloon is advanced through this catheter into the heart muscle, where it is then inflated in the area of the stenosis to widen the narrowing. This significantly reduces the pressure in the right ventricle. However, this procedure should always be performed by a specialist.

Your veterinarian will advise you in detail on the individual treatment plan for your pet.

Forecast

The prognosis depends greatly on the severity and extent of the disease. Mild forms have a very good prognosis and do not limit the animal's quality of life. Moderate forms can also have a good prognosis without valve insufficiency, whereas severe forms have significantly poorer prospects of recovery. However, balloon dilatation can significantly improve the prognosis in these cases.

Prophylaxis

As this is a hereditary disease, its occurrence cannot be completely prevented. However, breeding hygiene measures can significantly reduce the incidence of the disease. In order to obtain breeding approval, some breeding associations already require special heart examinations. Regular veterinary check-ups of the heart, especially in predisposed breeds, also help to ensure that potential changes are detected early and treated if necessary.