Transoesophageal echo represents an excellent tool for viewing deep structures of the heart. The proximity of the oesophagus to the heart presents an excellent acoustic window to the atria, aortic and mitral valves and great vessels. In these images the left atrium is seen at the top of the image and the right atrium below it. The atrial septum can be clearly defined, and using a colour flow Doppler box placed over the area of interest a blue jet is observed. This indicates the passage of blood from the left atrium to the right atrium during the cardiac cycle. This jet indicates the presence of an Atrial Septal Defect (ASD).