An aortic aneurysm (say a-OR-tik AN-yuh-rih-zum) is a bulge in a section of the aorta, the body's main artery. The aorta carries oxygen-rich blood from the heart to the rest of the body. Because the section with the aneurysm is overstretched and weak, it can burst.lood flow often slows in the bulging section of an aortic aneurysm, causing clots to form. If a blood clot breaks off from an aortic aneurysm in the chest area, it can travel to the brain and cause a stroke. Blood clots that break off from an aortic aneurysm in the belly area can block blood flow to the belly or legs.