Thoracic aortic aneurysms are caused by hardening of the arteries (atherosclerosis), high blood pressure (hypertension), congenital disorders such as Marfan's syndrome, trauma, or less commonly, syphilis. Atherosclerosis is by far the most common cause. Thoracic aneurysms occur in the ascending aorta (25% of the time), the aortic arch (25% of the time), or the descending thoracic aorta (50% of the time). Risk factors include various connective tissue disorders (such as Marfan's syndrome), atherosclerosis, previous dissection of the aorta, prolonged hypertension, and trauma (usually falls or motor vechicle accidents).
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