In a normally functioning canine heart, the right side of the heart is responsible for pumping blood to the lungs to be infused with oxygen. This oxygenated blood is then cycled back into the left side of the heart where it is sent out to the rest of the body. There exists, however, a medical condition called pulmonic stenosis that interferes with this natural and medically necessary process. In an animal with pulmonic stenosis, blood flow to the lungs is compromised by an improperly formed pulmonic valve. As a result, the heart must work much harder than normal to pump blood to the lungs, and the ultimate result is a swelling of fluid in the right chambers of the heart, a thickening of the heart muscle, and eventually heart failure and death.

Pulmonic Stenosis is actually the most commonly inherited congenital heart defect. It affects a fairly sizable number of animals each year, from a wide variety of breeds such as the English Bulldog, the Mastiff, the Chihuahua, the Schnauzer, the Samoyed, and any of the terriers or spaniels.

The severity of a case of pulmonic stenosis can vary widely. There are many very mild cases of the disease in which little to no detrimental effect can be observed on the animal's quality of life. More severe forms, however, are progressive, which means that they'll grow worse with age and eventually your dog will come to experience a number of respiratory and circulatory problems. These include fainting spells, quickly tiring out after only moderate exercise, and abnormal heart rhythms. If the disease is progressing at all, even over a long period of time, it is severe enough to eventually lead to death and must be treated.

The first indication that leads to a diagnosis of pulmonic stenosis is a heart murmur. Your veterinarian will listen to this heart murmur and if he or she feels that it matches the profile of an animal with pulmonic stenosis, they will order a series of radiographs of the chest cavity to pinpoint the exact location of the murmur. Long term prognosis is variable, and cannot be determined until more extensive tests such as an echocardiogram (ECG) and cardiac catheterization to determine the extent of the obstruction are carried out. With this knowledge as a basis, your vet will be able to inform you as to the likelihood of a successful surgery.

In mild cases, symptoms are usually just monitored for signs of developing heart disease. In more severe cases, however, a risky surgery must be performed to clear any blockages and repair the pulmonic valve to allow normal blood flow between the heart and lungs. This surgery is most successful when performed in conjunction with certain lifestyle changes such as diet and exercise.

Since pulmonic stenosis is an inherited condition, it is not advisable to breed dogs who have been known to carry it, or have family members who have suffered from it.