PA and AA parallel and do not cross at 90 (degrees)
(a)Transposition- The origins of the great arteries may be reversed, resulting in the aorta arising from the RV, and the pulmonary artery from the LV. There must be a communication between these circulations by means of septal defects and the ductus arteriosus to allow survival. Sonographically the aorta arises at 90° to the pulmonary artery but in transposition the aorta arises anterior to the pulmonary artery and runs parallel to it. This abnormality is frequently missed on the four chamber view.