Pulmonary stenosis is a condition caused by blockage to blood flow from the right ventricle to the pulmonary artery. This blockage (obstruction) is caused by narrowing (stenosis) at one or more points from the right ventricle to the pulmonary artery. Areas of narrowing may include thickened muscle below the pulmonary valve, narrowing of the valve leaflets when in the open position, or narrowing of the pulmonary artery above the valve. The most common form of pulmonary stenosis is obstruction at the valve itself. This is called pulmonary valvar stenosis.

The normal pulmonary valve has three thin and flexible valve leaflets. When the right ventricle pushes blood into the pulmonary artery, the normal pulmonary valve leaflets open easily. They don’t cause any blockage to blood leaving the heart. Often with pulmonary valvar stenosis, the pulmonary valve leaflets are thick and glued together along their separation lines (commissures). As a result, the leaflets become less flexible than normal. This adds to the blockage.

At times, the pulmonary valve is small or hypoplastic (not developed properly), which leads to blockage. When the pulmonary valve is blocked (obstructed), the right ventricle must work harder to push blood into the pulmonary artery. To make up for this additional work, the muscle of the right ventricle slowly gets thicker. The thicker right ventricular muscle, known as hypertrophy, is rarely a problem. But it is a sign that valve obstruction exists.

Signs and Symptoms

Children with pulmonary valvar stenosis are usually symptom-free and in normal health.

A heart murmur is the most common sign found by a doctor that shows that a valve problem may be present. Children with mild-to-moderate degrees of pulmonary valve stenosis have heart murmurs that are heard easily.

When the pulmonary valve is very blocked (critically blocked), the right ventricle cannot push enough blood to the pulmonary artery to keep normal oxygen saturation. In these cases, blue blood bypasses the lungs by flowing from the right atrium directly to the left atrium, through the foramen ovale. The foramen ovale is a "hole" between these two chambers that is normally present in newborns. Newborns with critical pulmonary stenosis will have cyanosis (blue discoloration of the lips and nail beds) due to lower oxygen levels in their blood.

A newborn with critical pulmonary stenosis is an emergency that needs immediate treatment. This treatment is either balloon dilation of the valve or surgery.

In an older child, severe pulmonary valve stenosis may cause them to tire easily. They may become short of breath with activity. Severe pulmonary valve stenosis rarely results in right ventricular failure or sudden death.

Diagnosis of Pulmonary Valvar Stenosis

The diagnosis of pulmonary stenosis is first suspected because a doctor hears a heart murmur.

The heart murmur of pulmonary stenosis is a choppy noise caused by ejection of blood through the obstructed valve. There is often an associated click sound when the thickened valve snaps to its open position. These sounds can be detected through careful examination of the heart by a physician trained in cardiac diagnosis.

Other testing may be needed to confirm the presence of pulmonary stenosis. More testing may help to identify its severity.

The electrocardiogram is typically normal in mild pulmonary stenosis. With moderate-to-severe pulmonary stenosis the electrocardiogram may show enlargement of the right ventricle and thickening of its muscle.

The echocardiogram is the most important non-invasive test to find and evaluate pulmonary valve stenosis. The echocardiogram diagnoses the specific location of the obstruction. Doppler studies are used to find the degree of blockage.

The echocardiogram results can help to exclude other problems that may be associated with pulmonary stenosis. These may be things like atrial septal defect (ASD) or ventricular septal defect (VSD).

Cardiac catheterization is an invasive technique that allows doctors to measure the degree of pulmonary stenosis. During cardiac catheterization, pressure measurements are made above and below the valve to figure out the amount of obstruction. Motion pictures are taken to see the pulmonary valve.

During the past 15 years, echocardiography has replaced cardiac catheterization to find and measure pulmonary valve stenosis. Cardiac catheterization is rarely needed to make the diagnosis, but it is still often the first line therapy to treat it.

Treatment for Pulmonary Valvar Stenosis

Children with mild pulmonary valve stenosis do not need treatment. Patients with mild pulmonary valve stenosis are healthy. They can do all types of activities and sports. They can lead normal lives.

Mild pulmonary valve stenosis in childhood doesn’t get worse after the first year of life. However, mild pulmonary stenosis in a young infant may move to more severe degrees that need follow-up. Children with moderate-to-severe degrees of pulmonary stenosis need treatment. The timing of which is often not urgent and driven by the echo findings and any symptoms that may be present in an older child.

The type of treatment needed depends on the type of valve defect present. Often, the pulmonary valve is of normal size. The obstruction is due to the commissures or lines being stuck together. This "typical" form of pulmonary valve stenosis responds well to balloon dilation. Balloon dilation valvuloplasty (a tube “catheter” is placed inside the femoral artery and threaded up to the heart) is done at the time of cardiac catheterization. It does not need open-heart surgery. In older children, the procedure is done electively on an outpatient basis.

Open-heart surgical procedures are needed for more complex valves, when balloon dilation does not work. These valves may be blocked by thick and abnormal leaflet tissue. The width of the valve may be small in some cases.

For these conditions, surgical pulmonary valvotomy (opening of the valve), partial valvectomy (removal of a portion of the leaflet), and a transannular patch (patch from the right ventricle to pulmonary artery) may be needed during the open-heart surgery repair.

Results and Outcomes

Results of balloon dilation valvuloplasty for pulmonary stenosis have been excellent. Balloon dilation cannot make an abnormal valve "normal." The procedure decreases the degree of pulmonary valve obstruction from severe to mild in most patients.

For children and teens with "typical" pulmonary valve stenosis, a single balloon dilation procedure is usually the only therapy needed. It is rare that an older child will have significant pulmonary valve obstruction again after a successful balloon dilation procedure.

Newborns and young infants with severe pulmonary valvar obstruction have an excellent response to balloon dilation. Outcomes can be less robust (that is, significant valve stenosis can remain) if the valve is underdeveloped in size. Recurrence of significant pulmonary stenosis does occur in 5-10% of children within 10 years of treatment. Occasionally, these patients may need a second balloon dilation, or an open-heart surgical procedure if the valve is small.

Because balloon dilation is the only treatment necessary for most patients, open-heart surgery is only done in patients with more complex forms of pulmonary valve obstruction. Patients with very thick valve leaflets or underdeveloped pulmonary valve sizes also have great long-term outcomes after open-heart surgical repair. If there is no associated heart disease, these children are expected to lead normal, active lives.

All children with pulmonary valve stenosis need to be seen at regular intervals. Long-term follow-up with evaluation by a cardiologist is important to help give the highest quality outcome for patients with pulmonary valve stenosis.

Adult and Adolescent Management

Adults with pulmonary stenosis may need balloon dilation or surgical opening of the valve. Most of these patients will have had an excellent result. They may not need much care or attention as adults. A number of these patients will have a leak of the pulmonary valve. This can lead to enlargement of the right side of the heart. They may need pulmonary valve replacement.