3D magnetic resonance angiography (GRASP) showing a 19 mm side-to-side communication of the superior vena cava and the right upper pulmonary vein due to unroofing of the wall that normally separates the right upper pulmonary vein from the superior vena cava. The right upper pulmonary vein retains connection to the left atrium in its course (cavopulmonary window, see also Figure 1B). The connection of the right upper pulmonary vein with the superior vena cava is at the ostium of the superior vena cava with the right atrium. GRASP, Golden-angle RAdial Sparse Parallel MRI.