What is pulmonary stenosis?
Pulmonary stenosis is a congenital (present at birth) defect that occurs due to abnormal development of the fetal heart during the first eight weeks of pregnancy.
The pulmonary valve is found between the right ventricle and the pulmonary artery. It has three leaflets that function like a one-way door, allowing blood to flow forward into the pulmonary artery, but not backward into the right ventricle.
With pulmonary stenosis, problems with the pulmonary valve make it harder for the leaflets to open and permit blood to flow forward from the right ventricle to the lungs. In children, these problems can include:
A valve that has leaflets that are partially fused together.
A valve that has thick leaflets that do not open all the way.
The area above or below the pulmonary valve is narrowed.
There are four different types of pulmonary stenosis:
Valvar pulmonary stenosis. The valve leaflets are thickened and/or narrowed
Supravalvar pulmonary stenosis. The pulmonary artery just above the pulmonary valve is narrowed
Subvalvar (infundibular) pulmonary stenosis. The muscle under the valve area is thickened, narrowing the outflow tract from the right ventricle
Branch peripheral pulmonic stenosis. The right or left pulmonary artery is narrowed, or both may be narrowed
Pulmonary stenosis may be present in varying degrees, classified according to how much obstruction to blood flow is present. A child with severe pulmonary stenosis could be quite ill, with major symptoms noted early in life. A child with mild pulmonary stenosis may have few or no symptoms, or perhaps none until later in adulthood. A moderate or severe degree of obstruction can become worse with time.
Pulmonary stenosis is a component of half of all complex congenital heart defects.
Pulmonary stenosis is the second most common congenital heart defect, comprising 5 to 10 percent of all cases.