Abdominal Aortic Aneurysm

What is an abdominal aortic aneurysm?

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The aorta is the largest blood vessel in the body. It delivers oxygenated blood from the heart to the rest of the body. An aortic aneurysm is a bulging, weakened area in the wall of the aorta. Over time, the blood vessel balloons and is at risk for bursting (rupture) or separating (dissection). This can cause life threatening bleeding and potentially death.

Aneurysms occur most often in the portion of the aorta that runs through the abdomen (abdominal aortic aneurysm). An abdominal aortic aneurysm is also called AAA or triple A. A thoracic aortic aneurysm refers to the part of the aorta that runs through the chest.

Once formed, an aneurysm will gradually increase in size and get progressively weaker. Treatment for an abdominal aneurysm may include surgical repair or removal of the aneurysm, or inserting a metal mesh coil (stent) to support the blood vessel and prevent rupture.

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What causes an abdominal aortic aneurysm to form?

Many things can cause the breakdown of the aortic wall tissues and lead to an abdominal aortic aneurysm. The exact cause isn't fully known. But, atherosclerosis is thought to play an important role. Atherosclerosis is a buildup of plaque, which is a deposit of fatty substances, cholesterol, cellular waste products, calcium, and fibrin in the inner lining of an artery. Risk factors for  atherosclerosis include:

• Age (older than age 60)

• Male (occurrence in males is 4 to 5 times greater than that of females)

• Family history (first degree relatives such as father or brother)

• Genetic factors

• High cholesterol

• High blood pressure

• Smoking

• Diabetes

• Obesity

Other diseases that may cause an abdominal aneurysm include:

• Connective tissue disorders such as Marfan syndrome, Ehlers-Danlos syndrome, Turner's syndrome, and polycystic kidney disease

• Congenital (present at birth) defects such as bicuspid aortic valve or coarctation of the aorta

• Inflammation of the temporal arteries and other arteries in the head and neck

• Trauma

• Infection such as syphilis, salmonella, or staphylococcus (rare)

What are the symptoms of abdominal aortic aneurysms?

About 3 out of 4 abdominal aortic aneurysms don't cause symptoms. An aneurysm may be found by X-ray, computed tomography (CT or CAT) scan, or magnetic resonance imaging (MRI) that was done for other reasons. Since abdominal aneurysm may not have symptoms, it's called the "silent killer" because it may rupture before being diagnosed.

Pain is the most common symptom of an abdominal aortic aneurysm. The pain associated with an abdominal aortic aneurysm may be located in the abdomen, chest, lower back, or groin area. The pain may be severe or dull. Sudden, severe pain in the back or abdomen may mean the aneurysm is about to rupture. This is a life-threatening medical emergency.

Abdominal aortic aneurysms may also cause a pulsing sensation, similar to a heartbeat, in the abdomen.

The symptoms of an abdominal aortic aneurysm may look like other medical conditions or problems. Always see your doctor for a diagnosis.

How are aneurysms diagnosed?

Your doctor will do a complete medical history and physical exam. Other possible tests include:

• Computed tomography scan (also called a CT or CAT scan). This test uses X-rays and computer technology to make horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than standard X-rays.

• Magnetic resonance imaging (MRI). This test uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

• Echocardiogram (also called echo). This test evaluates the structure and function of the heart by using sound waves recorded on an electronic sensor that make a moving picture of the heart and heart valves, as well as the structures within the chest, such as the lungs and the area around the lungs and the chest organs.

• Transesophageal echocardiogram (TEE). This test uses echocardiography to check for aneurysm, the condition of heart valves, or presence of a tear of the lining of the aorta. TEE is done by inserting a probe with a transducer on the end down the throat.

• Chest X-ray. This test uses invisible electromagnetic energy beams to make images of internal tissues, bones, and organs onto film.

• Arteriogram (angiogram). This is an X-ray image of the blood vessels that is used to assess conditions such as aneurysm, narrowing of the blood vessel, or blockages. A dye (contrast) will be injected through a thin, flexible tube placed in an artery. The dye makes the blood vessels visible on an X-ray.

What is the treatment for abdominal aortic aneurysms?

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Treatment may include:

• Monitoring with MRI or CT. These tests are done to check the size and rate of growth of the aneurysm.

• Managing risk factors. Steps, such as quitting smoking, controlling blood sugar if you have diabetes, losing weight if overweight, and eating a healthy diet may help control the progression of the aneurysm.

• Medicine. Used to control factors such as high cholesterol or high blood pressure.

• Surgery:

  • Abdominal aortic aneurysm open repair. A large incision is made in the abdomen to let the surgeon see and repair the abdominal aorta aneurysm. A mesh, metal coil-like tube called a stent or graft may be used. This graft is sewn to the aorta, connecting one end of the aorta at the site of the aneurysm to the other end. The open repair is the surgical standard for an abdominal aortic aneurysm.

  • Endovascular aneurysm repair (EVAR). EVAR requires only small incisions in the groin. Using X-ray guidance and specially-designed instruments, the surgeon can repair the aneurysm by inserting the stent  or graft inside the aorta. The graft material may cover the stent. The stent helps hold the graft open and in place.

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A small aneurysm or one that doesn't cause symptoms may not require surgery until it reaches a certain size or is rapidly increasing in size over a short period of time. Your doctor may recommend "watchful waiting." This may include an ultrasound, duplex scan, or CT scan every 6 months to closely monitor the aneurysm, and blood pressure medicine may be used to control high blood pressure.

If the aneurysm is causing symptoms or is large, your doctor may recommend surgery.

What is aortic dissection?

An aortic dissection starts with a tear in the inner layer of the aortic wall of the thoracic aorta. The aortic wall is made up of 3 layers of tissue. When a tear occurs in the innermost layer of the aortic wall, blood is then channeled into the wall of the aorta separating the layers of tissues. This generates a weakening in the aortic wall with a potential for rupture. Aortic dissection can be a life-threatening emergency. The most commonly reported symptom of an aortic dissection is sudden, severe, constant chest or upper back pain, sometimes described as "ripping" or "tearing." The pain may move from one place to another.

When a diagnosis of aortic dissection is confirmed, immediate surgery or stenting is usually done.

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What causes aortic dissection?

The cause of aortic dissection is unclear. However, several risk factors associated with aortic dissection include:

• High blood pressure

• Connective tissue disorders, such as Marfan's disease, Ehlers-Danlos syndrome, and Turner's syndrome

• Cystic medial disease (a degenerative disease of the aortic wall)

• Aortitis (inflammation of the aorta)

• Atherosclerosis

• Bicuspid aortic valve (presence of only 2 cusps, or leaflets, in the aortic valve, rather than the normal 3 cusps)

• Trauma

• Coarctation of the aorta (narrowing of the aorta)

• Excess fluid or volume in the circulation (hypervolemia)

• Polycystic kidney disease (a genetic disorder characterized by the growth of numerous cysts filled with fluid in the kidneys)