Figure 1a. Sinus venosus atrial septal defect in a 50-year-old woman with dyspnea on exertion. Axial ECG-gated spin-echo (a) and cine (b) MR images show a defect (arrow) in the portion of the atrial septum between the superior vena cava (SVC) and the left atrium (LA). Ao = ascending aorta, PA = main pulmonary artery.