Figure 6. Superior sinus venosus defect at non-gated CT performed for preoperative evaluation in a 38-year-old woman. Thin-section axial reformatted image demonstrates interatrial communication between the right atrium (RA) and left atrium (LA) through a large defect in the mouth of the superior vena cava (SVC), at the level of the upper portion of the atrial septum (arrow).