ABSTRACT
Atrial Septal Defect(ASD) is usually suspected clinically but requires a confirmative diagnostic procedure before surgical repair. Conventional transthoracic echocardiography has relatively high sensitivity and specificity for ASD, but difficulty in visualizing the ASD occasionally. Transesophageal echocardiography has special advantages for investigating the posteriorly located cardiac structures, including the atrial septum, which is imaged perpendicularly at a relatively short distance. We describe a case in which ostium secundum ASD was not visualized by conventional transthoracic echocardiography, but was diagnosed confidently by transesophageal echocardiography. It is concluded that transesophageal echocardiography appears to be a promising diagnostic tools for the evaluation of ASD on the basis of its ability to provide excellent imaging of the entire atrial septum and related posterior cardiac structures.