Closure of Patent Foramen Ovalis and Atrial Septal Defect

Abstract

The atrial septum (AS) is bordered anteriorly by the aortic root and posteriorly by the posterior atrial walls. Because the left atrium is posterior and to the left of the right atrium, the plane of the AS is oriented obliquely and runs from a right posterior to a left anterior position. The best way to visualize the AS by ultrasound is by transesophageal echocardiography (TEE). However, two-dimensional (2D) TEE planes always intersect the septum perpendicular to its surface. Consequently, although this structure is anatomically a fibromuscular membrane dividing the atrial cavities, it is imaged as a linear structure, which may be thicker around the fossa ovalis (FO) and thinner at the level of the floor. Conversely, a unique quality of three-dimensional (3D) TEE is the ability to image internal surfaces of the heart from an en face perspective. Thus, both the left and the right sides of the AS can be visualized en face as they appear in anatomic specimens. The proximity of the transesophageal transducer to the AS (and the nearly perpendicular angle of incidence of the ultrasound beam), the use of transducers at higher frequencies, and, finally, the lack of interference from bones and lung allow the AS to be seen in 3D images of unprecedented quality. This chapter describes the acquisition of real-time (RT) 3D TEE images of the AS, the normal 3D TEE appearance of both left and right surfaces of the AS, the appearance of patent foramen ovalis (PFO) and secundum atrial septal defects (ASDs) on 3D TEE images, and, finally, the use of 3D TEE to guide percutaneous closure procedures for both PFOs and ASDs.