What is an abdominal aortic aneurysm (AAA) ?
The aorta is the largest blood vessel in the body, originating from the heart, supplying oxygen rich blood to organs in your chest and abdomen, and dividing into the iliac arteries supplying blood to your legs. An abdominal aortic aneurysm is a dilatation of the aorta greater than one and a half times its normal size, due to weakening of the wall. The most common location is below your kidney arteries, although it may involve the kidney arteries or extend above them, involving the arteries supplying blood to the intestines, liver, stomach and spleen. About 1.7 million people have AAAs in the United States and 190,000 new cases are diagnosed annually. The incidence has tripled since 1970, and about 50,000 repairs are performed annually.
How does an AAA occur?
An abdominal aortic aneurysm occurs from weakening of the wall. Genetics, cholesterol and fatty buildup (plaque), smoking, high blood pressure and inflammation can lead to weakening of the wall and aneurysm formation.
Why is it dangerous?
An abdominal aortic aneurysm may be lethal because as it enlarges, it may rupture. Most AAAs have a significantly higher chance of rupturing when they exceed 5 cm in size, or if they grow rapidly (> 0.5 cm/yr). When they rupture, bleeding occurs and usually leads to death. Ruptured AAA is the 13th leading cause of death in the United States, accounting for 15,000 deaths annually. When rupture occurs, half of patients die before reaching the hospital, another quarter arrive at the hospital but die before surgery. The overall mortality ranges between 75-90%. If a AAA does not rupture, it can shower clot into the legs resulting in limb loss.
How do I know if I have an AAA?
Your medical doctor on routine history may ask you if you have had a family member with an aneurysm, or a history of flank, back, or abdominal pain, or blue toes. Also, on routine physical examination, your doctor may identify a pulsatile abdominal mass.
Three quarters of patients with AAAs have no symptoms when they are detected.
Are there tests to identify if I have an AAA?
Yes. A quick, painless, non-invasive ultrasound can detect an aneurysm. A CT scan can relatively accurately determine the size of a AAA.
When should an AAA be repaired?
It should be repaired when it exceeds 5 cm in size, grows more than 0.5 cm/ year, is causing back, flank, or abdominal pain, is showering clots to the legs causing blue toes, or if it ruptures.
How is an AAA repaired?
There are two ways to repair a AAA, by open surgery, or minimally invasive, endovascular surgery.
How is open repair performed?
Open surgery consists of an incision in the flank or down the middle of the abdomen, with possible incisions in the groins. In simple terms, organs are moved to access the aorta, it is clamped above and below the aneurysm, the aneurysm is opened, and clot is removed. A synthetic graft is sewn to normal aorta above and below the aneurysm, and the wall of the aorta is wrapped around the graft. Circulation is then restored, and the abdomen is closed.
What are the advantages and disadvantages of open surgery?
The advantage of open surgery is that it is a durable and proven medical procedure. After successful completion of aneurysm repair, usually no further imaging studies are required for followup. The disadvantage is that general anesthesia is required, it takes about 3-5 hours to complete, and requires an overnight stay in the ICU, and usually 5-7 days in the hospital, with full recovery as long as up to 3 months.
What are the risks of open surgery?
Risks include infection, bleeding, kidney failure, blood clots in the legs, limb loss, spinal cord injury and paralysis, injury to blood supply to the colon, erectile dysfunction, heart attack, stroke, and death.
How is endovascular repair performed?
Endovascular repair can be performed under local, spinal, or general anesthesia. Either small incisions, or needle punctures are made in the groins. Needles, wires, sheaths and catheters are directed into the aorta, and under X-ray guidance, measurements are made and a stent-graft is deployed inside the aneurysm, excluding it from circulation. The stent graft is held in place by stents, hooks, or pins against the wall of the aorta. A completion picture is taken to make sure no leak is present, and the groins or puncture sites are closed.
What are the advantages and disadvantages of endovascular stent-grafting?
Advantages include that the operation may be performed with the patient awake, under local anesthesia, or spinal / epidural anesthesia, and on patients who are too high risk of open repair. Also, surgery is usually shorter, between 1-3 hours. Finally, patients may eat the same evening, walk and be discharged as early as the next day, and return to full activity within 6 weeks. Disadvantages include that stent-grafting is a relatively new procedure, some people are not candidates due to aneurysm anatomy, long-term safety and effectiveness have not been established, and graft migration, and leaks can occur, leading to continued aneurysm flow and rupture. Additionally, routine, lifelong imaging studies, either ultrasound or CT scan (with exposure to radiation and contrast) needs to be performed to evaluate for leaks.
What are the risks of endovascular stent-grafting?
The risks are essentially the same as open surgery, but leaking around the graft or between graft segments can occur early or late and lead to continued blood flow to the aneurysm and rupture. These are called endoleaks.