She underwent CT angiogram of abdomen and pelvis with run-off protocol. There is a large filling defect in the left atrium abutting the interatrial septum measuring approximately 4.5 x 3.1 x 4.4 cm. (with HU equal 44, 88, 66, and 50 during the non-contrasted, arterial, portal venous, and delayed GU phases respectively, HU of non-opacified left atrial blood equal 61).