Contrast echocardiography: the descending thoracic aorta and the left atrial posterior wall in neonates.

Contrast echocardiographic studies were performed in two neonates. Glucose injections through umbilical arterial catheters demonstrate that the descending thoracic aorta is in close contact with the left atrial posterior wall (LAPW) and with the atrioventricular junction. The recognition of this particular part of LAPW is extremely important since it shows that the ultrasound beam is not in the standard direction. Probably the left atrium cannot so easily expand in that direction. Consequently, the left atrial dimension should not be measured here for the purpose of controlling variations in left atrium dilatation.