A thoracic aortic aneurysm is a widening (bulging) of part of the wall of the aorta, the body's largest artery.

Thoracic aneurysms most often occur in the descending thoracic aorta. Others may appear in the ascending aorta or the aortic arch.

The most common cause of a thoracic aortic aneurysm is hardening of the arteries (atherosclerosis).

Other risk factors include various connective tissue disorders such as Marfan syndrome, atherosclerosis, previous dissection of the aorta, having high blood pressure for a long time, trauma such as falls or motor vehicle accidents, and syphilis.

Most patients have no symptoms until the aneurysm begins to leak or expand. Most non-leaking thoracic aortic aneurysms are detected by tests -- usually a chest x-ray or a chest CT scan -- run for other reasons. Chest or back pain may mean sudden widening or leakage of the aneurysm.

The physical examination is often normal. A chest x-ray and chest CT scan show if the aorta is enlarged. A chest CT scan shows the size of the aorta and the exact location of the aneurysm.

An aortogram (a special set of x-ray images made during injection of dye into the aorta) can identify the aneurysm and any branches of the aorta that may be involved.

The treatment depends on the location of the aneurysm.

For patients with aneurysms of the ascending aorta or aortic arch, surgery to replace the aorta is recommended if the aneurysm is larger than 5-6 centimeters. The aorta is replaced with a fabric substitute. This is major surgery that requires a heart-lung machine. If the aortic arch is involved, a specialized technique called "circulatory arrest" -- a period without blood circulation while on life support -- may be necessary.

There are two options for patients with aneurysms of the descending thoracic aorta. If the aneurysm is larger than 6 centimeters, major surgery is done to replace the aorta with a fabric substitute.

Endovascular stenting is a less invasive option. A stent is a tiny metal or plastic tube that is used to hold an artery open. Stents can be placed into the body without cutting the chest. Instead, tiny, hollow tubes called catheters are inserted into the groin area. The stent is passed through the catheter and into the area of the aneurysm. Not all patients with descending thoracic aneurysms are candidates for stenting, however.

The long-term prognosis for patients with thoracic aortic aneurysm is determined by other medical problems such as heart disease and diabetes, which may have caused or contributed to the condition.

Serious complications after aortic surgery can include heart attack, irregular heartbeats, bleeding, stroke, paralysis, graft infection, and kidney damage. Death soon after the operation occurs in 5-10% of patients.

Complications after aneurysm stenting include damage to the leg, which might require another operation.

Patients with chest or back discomfort should consult their physician. Patients with a family history of connective tissue disorders should notify their physician.

Prevention measures for atherosclerosis, in general, include not smoking, controlling blood pressure and blood lipid levels, and exercising routinely.