What are the important findings?
Aneurysmal dilatation of the main pulmonary artery. Dilated left pulmonary artery shadow is seen within the contour of the dilated main pulmonary artery. Right pulmonary artery is also grossly dilated. Such a picture is usual in pulmonary hypertension due to long standing increased pulmonary blood flow as in a large atrial septal defect with left to right shunt. One would have expected the end on views of multiple large vessels in the lung fields in such a situation. Primary pulmonary hypertension is another cause for such grossly dilated main pulmonary artery and branch pulmonary arteries. In post stenotic dilatation of main pulmonary artery seen with valvar pulmonary stenosis, right pulmonary artery will not be dilated. But left pulmonary artery can be dilated in pulmonary stenosis as the jet is directed towards the left pulmonary artery.