Abdominal Aortic Aneurysm

What is an abdominal aortic aneurysm?

An abdominal aortic aneurysm (AAA) is a permanent bulging or ballooning in the wall of the main artery extending the length of the abdomen. The aorta, the largest artery in the body, consists of segments. The abdominal aorta is the portion of the artery below the diaphragm that extends through the abdomen before splitting into two smaller arteries. The thoracic aorta is the portion above the diaphragm. The abdominal aorta delivers oxygenated blood to the lower trunk and legs. While an aneurysm can occur anywhere along the length of the aorta, they most commonly occur below the kidneys in the infrarenal abdominal aorta. In addition to location, doctors classify aneurysms as true or false, and by their size and shape. Arteries are muscular tubes with three-layered walls; a true aneurysm involves all three layers, while a false aneurysm, or pseudoaneurysm, is often more likely to burst because it is not contained by all three of the layers. The diameter of the widest part of an aneurysm is measured in centimeters to determine its size. The shape is either fusiform, enlarged all the way around the vessel, or saccular, having a balloon-like enlargement or sac at one place on the circumference of the vessel. Occurring in approximately 6% of women and 15% of men older than 65, abdominal aortic aneurysms cause about 15,000 deaths each year in the United States.

What are the symptoms of an abdominal aortic aneurysm?

Most of the deaths due to an abdominal aortic aneurysm occur from massive internal bleeding when the aneurysm ruptures. An abdominal aortic aneurysm can be dangerous because it may not have any symptoms until it ruptures. The symptoms of an aneurysm that has not yet ruptured may include the following: a pulsating bulge or a strong pulse in the abdomen, abdominal pain, back pain, a feeling of fullness after minimal food intake, nausea, testicular pain, vomiting, or a bruit/whooshing sound with a stethoscope. Some of these symptoms are unspecific making aneurysms difficult to diagnose clinically.

What are the dangers of an untreated or undetected abdominal aortic aneurysm?

When abdominal aortic aneurysms rupture, they often cause massive internal bleeding, which may cause a dangerously reduced blood pressure (circulatory collapse or “shock”). The symptoms of this rupture may include the following: cold sweat, confusion, dizziness, light-headedness, low blood pressure, loss of consciousness, nausea, numbness or tingling, pale skin, rapid heart beat, severe back pain, shortness of breath, and weakness. Any of these symptoms by itself or in conjunction with a previous symptom associated with an aneurysm that has not yet ruptured may indicate a need for immediate emergency medical care. Ruptured aneurysm has a mortality rate of about 70 to 90%, with about half of patients dying before they reach the hospital. Expedient care is essential in cases of ruptured aneurysms. Also a medical emergency, sometimes a piece of a blood clot that formed in the aneurysm will break off and lodge in a blood vessel. Depending on where the blood clot fragment lodges, it can cause a stroke; a heart attack; numbness; weakness; tingling; pallor; arm or leg coldness; light-headedness; localized pain; or problems with the lungs, liver, or kidneys.

What causes an abdominal aortic aneurysm?

Weakening or deterioration of the wall of the abdominal aorta at birth or from disease or injury can make the artery susceptible to a permanent bulge. The proteins collagen and elastin in the middle layer of the artery wall provide strength for the artery. These proteins can gradually deteriorate with age, but a problem with naturally occurring enzymes or inflammation from atherosclerosis can accelerate this process such that even younger people can have weakened arteries. Atherosclerosis is a process by which an artery becomes lined with plaque deposits. Plaque, which is composed of cholesterol, calcium, waste products, and fatty and other substances, can weaken the wall of an artery making it susceptible to an aneurysm. Uncontrolled diabetes can accelerate atherosclerosis. Marfan syndrome and Ehlers-Danlos syndrome are genetically inherited disorders that can cause the middle layer of the artery wall to weaken. Heart valve disease and pregnancy can have the same effects on an artery. High blood pressure can cause a bulge in an artery by putting stress on an already weakened wall. Though rare, some bacterial infections and inflammatory conditions can cause aneurysms. The term mycotic aneurysm refers to an aneurysm caused by a fungal infection of the arteries; this term is also used to describe aneurysms caused by bacterial infections. Psoriasis and rheumatoid arthritis are inflammatory conditions known to occur in the arterial wall. Though several possible causes for aneurysms have been identified, many of the causes of an abdominal aortic aneurysm are still unknown.

What are the risk factors for an abdominal aortic aneurysm?

Ruptured abdominal aortic aneurysms are the thirteenth leading cause of death in the United States. The following risk factors have been correlated with abdominal aortic aneurysms: age older that 55, atherosclerosis, high blood pressure (hypertension), male sex, smoking, and a positive family history for aortic aneurysm.

How is an abdominal aortic aneurysm found and diagnosed?

Because aortic aneurysms often have lack symptoms or have unspecific symptoms, they are often discovered while looking for other problems. A physical examination may detect an aneurysm, but it is more likely that an ultrasound exam, an echocardiogram, a CT scan, an angiogram, or an MRI will be able to reveal a problem. Many of these exams will also show the size of the bulge.

What treatment options are available for an abdominal aortic aneurysm?

While doctors may elect to monitor aneurysms depending on the size, location, growth rate, symptoms, and patient's health, many aneurysms will require treatment. The two treatment options for an abdominal aortic aneurysm that has not yet ruptured include standard open surgery and a less invasive, endovascular aneurysm repair (EVAR).

What are the differences between endovascular aneurysm repair (EVAR) and standard open surgery for an abdominal aortic aneurysm?

Doctors have been performing successful, curative open surgeries to repair abdominal aortic aneurysms for about 50 years with more than 90% of patients making a full recovery from surgery. During open surgery, a surgeon opens the abdomen with a major incision and general anesthesia. He then stops blood flow using a heart and lung machine to provide oxygen to the vital organs so that he can remove the damaged piece of the aorta and replace it with an artificial blood vessel (a Daflon or Teflon graft). This surgery usually involves a seven to ten day hospital stay; a long recovery time; and risks to the heart, brain, lungs, and kidneys. The catheter-based endovascular aneurysm repair is less invasive, faster, has a shorter recovery time, involves fewer complications, and can be performed on some patients with medical conditions that preclude an open surgery. However, this procedure utilizes a specially manufactured endovascular graft that will not work for all patients. Additionally, the durability and long term affects of the procedure are uncertain. Though endovascular repair has a lower complication rate than open surgery, one common complication is called endoleak. Endoleak occurs when blood leaks back into the aneurysm despite the new graft. In the endovascular aneurysm repair, the surgeon uses x-ray guidance to deliver a special graft to the aneurysm through a small incision in the groin. Once in place, the heat-activated graft expands in the artery and small metal hooks hold it firmly in place.