An abdominal aortic aneurysm (AAA) is a bulging or ballooning out in the wall of the abdominal aorta. This large artery carries oxygen-rich blood from the heart to the lower portion of the body.
Aortic aneurysm kills about 15,000 people every year in the United States. It is more common among men than women, and the likelihood of developing an AAA increases with age. It is estimated that abdominal aortic aneurysms occur in up to 13 percent of all men and up to 6 percent of women over age 65. They are very rare among younger people.
The causes of AAA are not known, but it is clear that smoking greatly increases a person’s risk of developing AAA. A family history of aneurysms also increases risk. In addition, high blood pressure (hypertension) and atherosclerosis is connected to aneurysm growth.
Most AAAs have no symptoms, which partially accounts for their high mortality rate. When an aneurysm ruptures, it can result in massive internal bleeding and acute symptoms. Half of all patients with an AAA rupture die before they reach the hospital.
However, if detected before it ruptures an AAA can be treated surgically or with less invasive techniques. These techniques have a good success rate, so it is very important to identify and treat an AAA before rupture.
About abdominal aortic aneurysm (AAA)
An abdominal aortic aneurysm (AAA) is a bulging or ballooning out in the wall of the abdominal aorta. The aorta is the artery through which blood flows out of the heart to the body. It is the “trunk” of the arterial tree and the largest artery in the body. All other arteries branch from the aorta.
Continuing from the upper (or thoracic) aorta, the abdominal aorta is the portion that travels the length of the abdomen. It carries blood down through the abdomen until it eventually splits off into two smaller iliac arteries that deliver blood to the pelvis and lower limbs.
Abdominal aortic aneurysms (AAA) are far more common than thoracic aortic aneurysms, comprising up to 75 percent of known aortic aneurysms. It is more common among men than women, among whites than blacks, and the likelihood of developing an abdominal aortic aneurysm increases with age. It is estimated that abdominal aortic aneurysms occur in up to 13 percent of all men and up to 6 percent of women over age 65.
Untreated, AAA can be a very dangerous medical condition as it can enlarge and rupture. An aortic aneurysm rupture can result in massive bleeding and often death (mortality rates for ruptured aneurysm are 70 to 90 percent). Therefore, early diagnosis and treatment of an aortic aneurysm is vital in preventing an aortic rupture.
The causes of AAA are unknown, but it is clear that smoking is a major risk factor, and it promotes the rate of aneurysm growth. AAA is more common in patients with atherosclerosis. Furthermore, high blood pressure (hypertension) is also associated with aneurysms, although to a lesser degree. Finally, recent research suggests that a genetic component may play a role in developing AAA.
Recent research suggests that inflammation may also play an important role in the development of aneurysms. Increasingly, inflammation is linked to a number of chronic health problems, including atherosclerosis. Studies have shown that patients with AAA tend to have elevated levels of inflammatory blood markers, such as C-reactive protein and interleukin-6. It's important to note, however, that there is a subclass of AAA called an inflammatory aneurysm. This is a distinct clinical entity from more conventional AAA and occurs in less than 10 percent of cases.
Aortic aneurysms are usually discovered during ultrasound exams or CT scans performed for other reasons. Symptoms can include abdominal, back or, more rarely, testicular pain. During the examination, the physician may note a bruit, a “whooshing” sound that a physician can hear with a stethoscope. There might be a pulsing mass in the abdomen of thin people where the aneurysm is pushing against the torso wall.
Once the aneurysm has ruptured, signs and symptoms often manifest themselves rapidly because of massive blood loss. These symptoms range from unconsciousness and sudden death to severe back pain and weakness (e.g., low blood pressure, dizziness, nausea, pale skin, “cold” sweat).
Approximately one half of patients with ruptures do not make it to the hospital before dying from the event. Of those who do receive surgery, approximately one half will survive operative repair, with the remainder dying in the hospital. It is for these reasons that the identification of AAA prior to rupture is so important.
Diagnosis methods for AAA
Most abdominal aortic aneurysms (AAA) do not have any symptoms. They are usually detected during the course of tests for other conditions, or they are detected during routine check-ups after the physician finds a pulsing mass in the abdomen. Detecting an AAA before it ruptures is extremely important. Tests that may detect AAA include:
Ultrasound of the abdominal aorta. This painless test uses sound waves to visualize the structures and functions of the aorta. Ultrasound is extremely effective at detecting AAAs. For this reason, the U.S. Preventive Services Task Force (USPSTF) recommends that anyone aged 65 to 75 who has ever smoked undergo a one-time ultrasound screening for AAA.
CAT scan (computed axial tomography scan). A highly accurate test that uses both x-rays and a contrast medium. In addition to diagnosing AAA, it is often the main test used to plan the repair of the AAA through either open operation or endovascular repair.
MRI (magnetic resonance imaging). A test that provides images very similar to a CAT scan but does not use x-rays or the x-ray contrast medium, instead relying on magnets to produce an image of the aorta.
Aortogram. This test is an arteriogram of the aorta. It is frequently used before and during the repair of AAA. It involves injecting x-ray contrast medium directly into the aorta through a catheter placed into the femoral artery (the artery at the groin level).
Treatment options for AAA
If testing reveals an abdominal aortic aneurysm (AAA), the decision to monitor or treat the AAA must be made. In general, three factors help determine treatment:
The size of the aneurysm. AAAs less than 5.5 centimeters can often be observed without surgical or endovascular repair. However, some centers may recommend surgery for smaller aneurysms, depending on the patient's age, gender and cadiovascular status.
The rate of growth of the aneurysm. AAAs that grow quickly will frequently require surgery, even if they are relatively smaller.
The presence of symptoms. Physicians are more likely to recommend surgical repair of an aneurysm that has symptoms, even if it is relatively smaller.
If surgery is not required, physicians will usually recommend yearly ultrasounds to carefully watch the aneurysm. They may also prescribe quitting smoking and certain medications to help keep the aneurysm stable. In addition, patients may be advised to control as many risk factors for heart disease as possible, including cholesterol levels and blood pressure. This may require medications and lifestyle changes. Although the link between treating risk factors for heart disease and the risk of aneurysm rupture or growth remains mysterious, a number of studies have shown that patients with AAA live longer on average by addressing these issues. This is also true for patients who have already undergone treatment for AAA, including surgery.
If surgery is required, one of two general methods will be performed to repair AAAs: surgery and endovascular repair. During surgery, the physician will open the torso to expose the aorta, clamp it above and below the AAA, and sew in a synthetic graft.
An endovascular procedure is a minimally invasive, catheter-based treatment using a stent. It is usually recommended for patients who are poor candidates for open surgery. The stent is usually delivered on a catheter that is introduced to the body through the femoral artery (near the thigh) and guided up into the aorta. In this way, blood flow is diverted away from the aneurysm. Only half of aneurysms can be treated with stent grafts as the procedure can only be performed if the aneurysm has certain features. The success rate of this procedure has been estimated at 90 percent in some studies.
However, the procedure is not without the risk of complications, such as endoleak (an incomplete seal around the stent causing blood to leak back into the aneurysm). Researchers are also testing so-called “fast track” endovascular repair, with more specialized instruments, smaller incisions and shorter operating time.
Patients are encouraged to have a detailed discussion with their physicians regarding the differences, advantages and disadvantages of open or endovascular repair. Vascular surgeons, interventional cardiologists or radiologists who have been specifically trained in each treatment area may conduct these procedures.
Questions for your doctor about AAA
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about abdominal aortic aneurysms (AAA):
Is AAA genetic?
Are there any special tests I can have to detect if I have AAA?
Is my gender in the high risk group for AAA?
What could cause an AAA?
Does the fact that I smoke increase my risk for developing AAA?
Is surgery a viable option for me?
Is my age a risk factor for developing AAA?
Does high blood pressure increase the risk of AAA?
What symptoms will I experience if my aneurysm ruptures?
high mortality rate. When an aneurysm ruptures, it can result in massive internal bleeding and acute symptoms. Half of all patients with an AAA rupture die before they reach the hospital. 
