Sternotomy with removal of a large aortic thrombus measuring 1.4 x 1.9 x 0.7cm (Figure 4) was performed on cardiopulmonary bypass under moderate hypothermia. The aorta was inspected with an epi-aortic echo and then cross-clamped beyond the visible thrombus. Transverse aortotomy was then performed to inspect and remove the thrombus. The patient was rewarmed and weaned off by- pass. During surgical aortic thrombectomy, the aortic valve and root were noted to be normal, and the mass was non- infiltrating. There were no signs of atherosclerotic disease or aneurysmal dilation of the aortic root. The macroscopic and microscopic examination of the specimen confirmed it to be a thrombus. Warfarin sodium was started with a target INR of 2-3. The patient had an uncomplicated early postoperative course. Two months later, however, she complained during a follow-up visit of claudication of the left calf and the ankle- brachial indexwas <0.9. Her INRwas >2. ACT angiogramof the abdominal aorta and lower extremities revealed a filling defect in the distal popliteal artery, resulting in diminished distal flow. An arteriogram (Figure 5) percutaneous An- gioJet thrombectomy, and balloon angioplasty were only partially successful in removing the organized thrombus. Left femoral-popliteal bypass surgery was then performed successfully. A CT arteriogram revealed no residual aortic root thrombus. When seen three and six months later, the patient had no symptoms. DISCUSSION Aortic thrombi usually present as emboli from the cardiac chambers or as a thrombus on an atherosclerotic Figure 1: Sixty-four-slice computed tomographic scan of the chest with contrast showing a filling defect (dark grey), with contrast around it (white), in the aortic root/proximal ascending aorta.
plaque. 1,2 The descending aorta and the distal arch are the most common locations of aortic thrombi; whereas the as- cending aorta is the site of aortic thrombus in only 5% of the cases. 6 Aortic root thrombus is rare in an apparently normal, non-aneurysmal, non-atherosclerotic aorta. 2,6-10 The etiology of thrombus formation in a macroscopi- cally normal aorta is not well understood and has been attributed to various hypercoagulable disorders, including combined protein C and protein S deficiency, 1,7,10,11 elevated levels of clotting factor VIII, antithrombin III deficiency, 7 polycythemia vera, 7 essential thrombocythemia, 12 hyperho- mocysteinaemia, 13 increased fibrinogen, 4 as well as autoim- mune diseases with hypercoagulable states, e.g., systemic lupus erythematosus, 14 antiphospholipid syndrome, 10,11 and vasculitis. 10,11 It has also been associated with malignan- cy, 1,6,11 hematologic disorders, 1,6 exogenous steroid, 1,6,15 and estrogen use, 4,6,16,17 primary endothelial disorders, 1,6,11 blunt aortic injury, 6 heparin-induced thrombocytopenia, 1,11,18-20 as well as iatrogenic causes. 11 Generalized hypercoagulation and vascular endothelial disorders have been proposed to be the most important factors for aortic mobile thrombus formation. 6 Aortic thrombus is usually suspected after the occur- rence of a peripheral, 3,4,10,11,21,22 cerebral, 3,9,12,14,23-25 or visceral thrombotic event. 1 Myocardial infarction has been reported as its first presentation. 2,23 Aortic thrombus in the ascending Figure 2: Transesophageal echocardiogram (TEE), upper esophageal view, 120 o , longitudinal, showing a large mass in the ascending aorta, just distal to the aortic valve but not attached to it.
J La State Med Soc VOL 166 July/August 2014 139
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