Identification of normal and transposed great arteries by contrast M-echocardiography in the newborn: a combined suprasternal and precordial approach.

Diagnosis of complete transposition of the great arteries (TGA) by M-mode echocardiography depends on the correct identification of the aorta and the pulmonary artery at their roots. We describe a contrast M-mode echocardiographic technique which combines suprasternal and precordial views in which the two great arteries are visualized simultaneously. After venous injection of 1-3 ml 5% dextrose, the sequence and relative intensity of opacification of the great arteries are recorded in both views and then matched to each other. Because in the suprasternal view the aorta is always superior and the pulmonary artery inferior, the characteristics of opacification of these two arteries in the suprasternal view are used as markers for their proper identification in the precordial view. In four normal newborns contrast medium filled only the pulmonary artery. In six newborns with cardiovascular malformations with shunts and normally related great arteries, in which the contrast medium preferentially filled either the aorta (five patients) or the pulmonary artery (one patient), matching the record from the precordial view to that from the suprasteral view proved that the anterior vessel was indeed the pulmonary artery, and the posterior vessel the aorta. In five newborns with d-TGA the contrast medium preferentially filled the aorta, and the combined suprasternal and precordial approach proved that the aorta was anterior and the pulmonary artery posterior. This method is independent of the direction of venous drainage or site of injection.