Abdominal Aortic Aneurysms (AAA)
What is an Aneurysm An aneurysm is defined as a localized widening of a blood vessel. When a vessel grows to 1.5 times its normal size is it classified as an aneurysm. What is an Abdominal Aortic Aneursym (AAA)? The aorta is the main artery in the body. It comes off of the heart in the chest, then loops around and descends in the body to level of the belly button. There it branches, with a main artery going down each of the legs. It gives off the blood supply to all the major organs including the brain, intestines, and kidneys. Below the kidney arteries it is called the abdominal aorta. This is the most common site of an aneurysm. At this level, the normal size of the aorta is approximately 2 centimeters. Therefore, when it reaches 3 centimeters in size or greater, it is called an abdominal aortic aneurysm (AAA).
Why is AAA dangerous?
As the aorta increases in size, the pressure within it builds up. Like a balloon, the larger it gets, the more likely it is to burst (rupture). When the aorta, which is the main blood vessel in the body, ruptures, it is almost always fatal.
What are the Risk Factors for AAA?
The most common risk factor is atherosclerosis, and therefore the risk factors are the same as those for all types of atherosclerosis:
- Smoking
- High Blood Pressure
- Diabetes
- High Cholesterol
- Family history of stroke, heart attack, or PAD
- Age (>65)
- Prior history of coronary heart disease or peripheral vascular disease (PAD)
- Obesity
In addition, there are risk factors specific for AAA:
- Smoking – not only increases the risk of developing an AAA, but also increases the risk of AAA rupture.
- Genetics – there is a strong family tendency to developing AAA. Individuals with a family member having an AAA have a higher risk of developing an AAA than the general population. They also tend to develop aneurysms at an earlier age, and have a higher likelihood of rupture.
- Connective tissue disease – patients with diseases such as Marfan’s syndrome and Ehlers-Danlos syndrome have a higher incidence of AAA
- Post traumatic – after injury to the aorta
- Infections – infections of the aorta from things such as drug abuse, heart surgery, etc, can lead to AAA
What are the Symptoms of AAA?
The majority of patients with AAA has no symptoms and is diagnosed by accident when a patient has X-ray tests of the abdomen for other conditions. However, when they do produce symptoms, the most common is pain. The pain typically has a deep quality as if it is boring into the person. It is felt most often in the lower abdomen and lower back. The patient may also notice a prominent abdominal pulsation. Sometimes, if the AAA is large, it can causes obstructive symptoms such as difficulty urinating or moving one’s bowels. If a person experiences any of these symptoms, it often represents rapid expansion of the aneurysm and impending rupture, and he must seek medical attention immediately. Immediate medical attention can save your life.
How is AAA Diagnosed?
Sometimes a doctor can feel an abnormally wide pulsation of the aorta during a physical exam. Abdominal ultrasound is safe, painless, and noninvasive. It has a close to 100% accuracy in measuring the size of the AAA, and is the best initial test. Unfortunately, it cannot accurately define the extent of the AAA and is inadequate for planning intervention. Therefore, once the diagnosis is made, further testing, usually with a CT scan, is necessary.
A CT Scan is the most accurate test to define the full extent of the AAA and is essential before a doctor can recommend further treatment options.
Do I need treatment?
The natural history of AAA depends on there size and rate of growth. AAA is one of the most well studied diseases in vascular medicine. Over the years, many studies have given doctors good evidence that have led to generally agreed upon recommendations for treatment. AAA less than 5 centimeters in size almost never rupture. Once they become larger than 5 centimeters, however, the risk of rupture rises dramatically. In addition, AAA that grow rapidly, more than 0.5 centimeters in one year, have a higher risk of rupture. Based on this data, AAA that are less than 5 centimeters should be treated medically with close ultrasound surveillance. AAA that are greater than 5 centimeters in size, or that increase greater than 0.5 centimeters in one year should be surgically repaired. Obviously, any symptomatic or ruptured AAA must be surgically repaired emergently.
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How is AAA Treated?
Medial Therapy: Medical therapy consists of lifestyle modifications and close surveillance. Lifestyle Modifications:
- Quit smoking
- Control high blood pressure and diabetes
- Control high cholesterol
- Regular exercise
Medication: There are no medications that can prevent AAA or slow its growth. Aspirin is usually recommended to help improve the patient’s overall cardiovascular health. Surveillance: Patients with a known AAA should have ultrasound examinations on a 6 month basis. If at any time during this surveillance the AAA reaches 5 centimeters or shows rapid growth of greater than 0.5 centimeters, surgical repair is indicated.
Open Surgical Repair: Open surgical repair has a long history and is a very durable solution to AAA. It is a major surgical procedure, and is very stressful to the heart and lungs. It is done in the operating room under general anesthesia with a breathing tube in place. A large incision is made vertically over the entire abdomen. The AAA is located, and the aorta is clamped above and below the aneurysm sac. The AAA is then opened, and a plastic blood vessel, called a graft, is sewn into the normal aorta. This completely removes the AAA from the circulation and cures the problem. After the surgery, the patients remain in the intensive care unit for about 3 days, and are usually in the hospital for 7-10 days. There is significant post operative recovery required, and often physical rehabilitation is needed. The patient will be ambulatory during this time, but a full recovery to a normal lifestyle can take up to 3 months.
Because this is major surgery, complications can include bleeding requiring blood transfusion, heart attack, kidney failure, and infections, Fortunately, these complications are rare. The good news is that the surgery is relatively common, very durable and is almost always a lifetime cure.Dr. Esposito is a board certified vascular surgeon, and has performed hundreds of successful open surgical AAA repairs. These procedures are performed at
Milford Hospital. Endovascular Aneursym Repair (EVAR): EVAR is a combined surgical and endovascular procedure. This means that it is performed from the inside of the blood vessel, using catheters, balloons, and stents. It is done in a specially equipped room, Specials Radiology, which is a combination X-ray room and operating room that is unique to Milford Hospital. The patient receives a spinal anesthetic and is awake for the procedure. Sometimes a light sedative is given.
A small incision is made in each groin and the arteries in the groin are exposed. These arteries are then accessed using a catheter. Using X-ray guidance, a plastic tube reinforced by a metal skeleton, called a stent graft (see picture at right) is positioned above and below the aneurysm. This stent graft is custom made for the patient’s anatomy as defined by the preoperative CT scan. Special balloons expand the stent graft and secure it in the appropriate position. This completely removes the AAA from the circulation and cures the problem.
EVAR is a relatively new procedure that has only been approved for use in the United States since the late 1990’s. There is no conclusive evidence that it is superior to surgery. Everyone is not a candidate for EVAR, and this decision is made based on the anatomy of the AAA and the patient’s characteristics. It is usually reserved for older patients and those with serious medical conditions that would be at high risk for the open surgical repair. You should discuss these options thoroughly with your doctor before deciding on the most appropriate therapy for your AAA.
VIDEO: animated recreation of the EVAR technique
Which procedure is best for me?
The decision of open surgical aneurysm repair versus endovascular aneurysm repair (EVAR) is made on a case-to-case basis. Some factors that go into the decision are as follows: Surgical Repair
- Better for younger patients (<60 years). There is no long term follow-up as to the durability of EVAR since this is such a new procedure. We do not know how these grafts will hold up over 20 to 30 years.
- Less follow-up required. Once the AAA has been successfully treated in an open fashion, almost no surveillance is required.
- Anatomic considerations. This is the most common reason that patients are excluded from EVAR. The characteristics of some AAA make it impossible to fit a stent graft into appropriate position, and open repair is the only option.
- Rupture. At this time, ruptured aneurysms are best treated in an open manner. This may change in the near future as more device modifications are made.
EVAR
- Better for older patients. This procedure is remarkably well tolerated, and we have performed it on patients in their 90’s without difficulty.
- Better for patients with multiple medical problems. Patients who would be at high risk for complications from the open repair and general anesthesia tolerate this procedure remarkably well.
- More intense follow-up required. Patients are followed for life with multiple CT scans each year. This is inconvenient and there is a slight risk from the intravenous dye and the radiation exposure. This is usually outweighed by the many benefits of the procedure.
Once again, there is no right or wrong answer. Your doctor will discuss the pros and cons of each technique with you at the time of your consultation.
