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).

Syncope refers to a generalized weakness of muscles with loss of postural tone, inability to stand upright, and loss of consciousness. Once the patient is in a horizontal position, blood flow to the brain is no longer hindered by gravitation and consciousness is regained. Unconsciousness usually lasts for seconds to minutes. Headache and drowsiness (which usually follow seizures) do not follow a syncopal attack. Syncope results from a sudden impairment of brain metabolism usually due to a reduction in cerebral blood flow.