Imaging the Atrial Septum Using Real-Time Three-Dimensional Transesophageal Echocardiography: Technical Tips, Normal Anatomy, and Its Role in Transseptal Puncture

Extraordinary advances in technology have made possible percutaneous catheter-based treatment of a wide spectrum of specific pediatric and adult "structural" heart diseases. Many of these percutaneous interventional procedures require access to the left heart via transseptal catheterization. Being able to see the anatomy can be a considerable advantage. However, septal anatomy is more complex than perceived at first sight. The true interatrial septum comprises a valvelike flap forming the floor of the fossa ovalis. On the right atrial aspect, the muscular rim surrounding the fossa is an infolding of the atrial wall. Hence, the target area for safe crossing, without exiting the heart, is the fossa floor and its immediate margin of the rim. Real-time (RT) three-dimensional (3D) transesophageal echocardiography is a recently developed technique that provides 3D images of the heart. Because of lack of interference from bone and lung and the closer proximity of the transducer to the posterior structures of the heart, this technique provides 3D RT images of atrial structures of unprecedented quality. In this review, the authors describe two key areas: a step-by-step approach for acquiring and processing RT 3D transesophageal echocardiographic images of the interatrial septum and, second, septal anatomy as it is visualized by RT 3D transesophageal echocardiography. To demonstrate their consistency with actual anatomy, several RT 3D transesophageal echocardiographic images are matched to equivalent anatomic specimens.