PROS1 and atrial fibrillation: Aortic thrombi can be caused by blood disorders (e.g., protein S or protein C deficiency and anti-phospholipid antibody syndrome), tumors, aortitis, collagen disease, aortic structural abnormalities (e.g., aortic aneurysms), intra-aortic atheroma, hormone therapy, steroid use, and atrial fibrillation.3) In both cases, electrocardiogram showed sinus rhythm.