Congenital pulmonary stenosis (PS) is a congenital heart malformation (see this term) that is characterized by a right ventricular outflow obstruction with a clinical presentation that may vary from critical stenosis presenting in the neonatal period to asymptomatic mild stenosis. The obstruction in PS can be at the valvular, subpulmonary, or supravalvular levels (valvular, subpulmonary, supravalvular PS; see these terms).

In utero, the ductus arteriosus (DA) serves to divert ventricular output away from the lungs and toward the placenta by connecting the main pulmonary artery to the descending aorta. A patent ductus arteriosus (PDA) in the first 3 days of life is a physiologic shunt in healthy term and preterm newborn infants, and normally is substantially closed within about 24 hours after bith and completely closed after about three weeks. Failure of physiologcal closure is referred to a persistent or patent ductus arteriosus (PDA). Depending on the degree of left-to-right shunting, PDA can have clinical consequences.