Mini-Abstract A 33-year-old female presented to the outpatient clinic with progressive exertional dyspnea. Transthoracic echocardiography revealed enlarged right heart chambers with left-to-right shunting. Two-dimensional transesophageal echocardiography confirmed these findings and showed three defects on interatrial septum. Real time three-dimensional transesophageal echocardiography was performed to better visualize the anatomy of the interatrial septum. Reconstruction of the three-dimensional images revealed multiple defects of interatrial septum like a Swiss cheese. The patient underwent surgical closure of the atrial septal defect.