Thoracic aortic aneurysm

A thoracic aortic aneurysm (TAA) is a ballooning of a portion of the aorta, the largest artery in the human body. Aneurysms are the result of weakening and thinning of the aortic wall. When a portion of it stretches and swells to more than 50 percent of the original diameter, this is called an aneurysm. Aneurysms in the thoracic or chest portion of the aorta are relatively rare.

The biggest threat posed by an aneurysm is rupture. A ruptured aneurysm, which requires emergency treatment, can lead to severe pain, internal bleeding, a sudden drop in blood pressure and, if not treated quickly, death.

Aneurysms that have been discovered prior to rupture need to be measured, closely monitored and evaluated for treatment.

Thoracic aneurysms are less common than abdominal ones. In some individuals with a thoracic aortic aneurysm, an underlying cause is Marfan’s Syndrome, a connective-tissue disorder that results in the characteristic weakening of the aortic wall. Other TAAs may be related to hypertension. In this case, the increased blood pressure is responsible for breaking down the elasticity of the aorta.

Basic Anatomy

The aorta, which carries freshly oxygenated blood to all parts of the body, is divided into four parts: 1) the ascending aorta which rises up from the left ventricle of the heart 2) the aortic arch, which curves like the hook connecting to the 3) descending thoracic aorta which extends downward through the chest cavity to the 4) abdominal aorta.

Aneurysms of the descending thoracic aorta are the most common of the thoracic aneurysms, followed by the ascending segment and then the arch.

Most patients do not experience symptoms of a thoracic aortic aneurysm until it begins to leak, expand or rupture. When symptoms do appear, the location of the aneurysm will determine the kind of symptoms that are experienced by the patient.

Symptoms of an ascending thoracic aneurysm may include:

• Pain in the chest, neck and/or back
• Swelling of the head, neck and arms
• Heart failure caused by blood backing up into the heart

Symptoms of an aortic arch aneurysm or a descending thoracic aneurysm may include:

• Pain in the chest and/or back
• Wheezing, coughing or shortness of breath due to pressure on the trachea, or windpipe
• Coughing up blood
• Hoarseness due to pressure on the nerves to the vocal chords
• Difficulty swallowing due to pressure on the esophagus

Thoracic aortic aneurysm (TAA) shares risk factors with atherosclerosis, or hardening of the arteries. The most common risk factors for TAA include:

• Smoking
• Age over 55 years
• Male gender
• High blood pressure (hypertension)
• Family history of TAA

Other diseases and factors that may cause TAA include:

• Genetic disorder of connective tissue (e.g., Marfan’s Syndrome)
• Congenital syndromes (birth defects)
• Giant cell arteritis (a diseased that causes inflammation in the arteries)
• Infectious aortitis (e.g., infections by syphilis or staphylococcus)
• Trauma (e.g., car accidents)
• Cystic medial degeneration (necrosis, most common in aneurysm of the ascending thoracic aorta)

Thoracic aortic aneurysms are identified and/or confirmed through X-ray and chest CT scans, which can also be used to measure the diameter of the aneurysm and its exact location. An aortogram, a special set of X-ray images made after the injection of dye into the aorta, may also be used to identify the extent of the aneurysm and whether any branch arteries are involved

Thoracic aortic aneurysms (TAAs) are considered high risk for rupture if they are located below the aortic arch and greater than 6.5 centimeters in diameter, about the size of a lemon, or if the aneurysm is rapidly increasing in diameter (greater than 1 centimeter per year). If the aneurysm is located in the arch or the ascending portion of the thoracic aorta, it is considered at risk for rupture at a diameter of 5.5 centimeter or larger. These numbers are not absolute. For example, surgeons treating patients with Marfan’s Syndrome may choose to repair smaller aneurysms.

Slowly growing aneurysms should be closely monitored. Smoking cessation and medication to control blood pressure may help to slow the rate of enlargement of an intact aneurysm. Surgical repair of the aorta is the only definitive cure. However, risk of rupture must be weighed against the risks associated with surgery and to the patient’s pre-existing conditions.

Open surgical repair

The incisions made during traditional surgical repair will depend on the location of the TAA. If located in the ascending thoracic aorta or the aortic arch, the surgeon must make an incision in the sternum. If located in the descending thoracic aorta, the incision is made in the back below the shoulder blade and extends around the side of the rib cage to just under the breast.

Repair of the aneurysm involves removing the distended portion of the aorta and replacing it with a tube called a graft. The cylinder-like graft, which is made of polyester fabric, is sewn in place. A hospital stay of between seven and 10 days is usually required if no complications occur. Complete recovery and return to a normal routine takes two to three months.

Endovascular aneurysm repair (EVAR)

Endovascular aneurysm repair (EVAR) is a less-invasive surgical treatment that involves a small incision in the groin and the insertion of a stent graft through a catheter placed in the femoral artery. Physicians use X-ray imaging to guide the stent graft to the diseased area. The graft is then expanded inside the aorta and held in place by metallic stents rather than stitches. Blood now flows through the stent graft, and blood-flow is excluded from the dilated segment of the aorta.

The hospital stay is usually one to two days and some patients return to their normal activities within about a week. However, EVAR may not be for everyone. Patients must have arterial anatomy compatible with the available stent grafts and delivery systems. The Vascular Center’s specialists are experienced with EVAR, routinely receiving referrals from area physicians faced with the most challenging cases.