Absent pulmonary valve syndrome is a rare pathology, and many present as a neonate with stridor due to airways compression from hugely dilated central pulmonary arteries. The plain chest film is variable and often quite bizzare: in this case the left pulmonary artery is grossly dilated. It is difficult to make the diagnosis from the plain film but the clinical history leads to it. I have heard it said that this is the only cause of a loud systolic murmur on the first day of life.
This lateral RV angio shows the large pulmonary arteries, and the waisted pulmonary valve ring. Tetralogy of Fallot may accompany it.