Detection of patent foramen ovale by transoesophageal echocardiography with right heart contrast (e.g. agitated saline-blood mixture). (A) View of left (LA) and right atrium (RA) before contrast injection. The arrow points to the patent foramen ovale. (B) Contrast injection, with passage of a few bubbles from right to left atrium across the atrial septum through the patent foramen ovale (arrow). Also see 4.35.