narrowing of either the pulmonary valve—the valve through which blood flows from the right ventricle, or lower chamber, of the heart on its way to the lungs—or the infundibulum, or of both. The infundibulum (Latin: “funnel”) is the funnel-shaped portion of the right ventricle that opens into the pulmonary artery. Its narrowing is also called infundibular stenosis. Pulmonary stenosis is usually a congenital defect and may be associated with other cardiovascular congenital defects.

Persons may have mild pulmonary stenosis without being conscious of the defect or may experience difficulty in breathing and have a tendency to faint after exertion. Characteristic heart sounds lead to the diagnosis.

If the stenosis is severe, the right ventricle is enlarged and under abnormal pressure in the effort to maintain normal blood flow to the lungs. Failure to maintain adequate blood flow—right-sided heart failure—causes increased pressure in the peripheral veins, enlargement of the liver, cyanosis (a bluish tinge to the skin), and accumulation of fluid in the legs. The treatment for severe pulmonary stenosis is the surgical correction of the defect.