None — Abdominal Aortic Aneurysm
The aorta is the main artery carrying oxygenated blood from the heart to the body. The wall of the blood vessel consists of three layers. In an aneurysm, the middle and outer layers in the affected section of the vessel are weak. As blood pulses through the artery, the force pushes on the weakened area, causing it to balloon out.
An abdominal aortic aneurysm (AAA) occurs in the abdominal portion of the aorta (an aneurysm located in the chest area is a thoracic aortic aneurysm). Risk for an AAA increases with age. The Society of Interventional Radiology estimates about 8 percent of those over 65 have an AAA. The condition is four times more common in men than in women. Smoking, high blood pressure, atherosclerosis and family history are associated with an increased risk for AAA. It is also more common in people with certain medical conditions, like Marfan syndrome.
While smaller aneurysms are usually not a problem, larger ones can rupture, causing a massive loss of blood, shock and death. Researchers estimate only 20 to 25 percent of those who have a ruptured aneurysm survive. In fact, AAA accounts for more than 15,000 deaths each year in the U.S.
Treating AAAs
The problem with AAA is that the condition develops slowly and is often not detected until a rupture occurs. By then, it's often too late for the patient. If an AAA is detected through screening, there are several options. Since smaller aneurysms (less than 5 centimeters) are not likely to rupture, doctors may recommend a watchful waiting approach. Patients will have regular follow-up ultrasound exams to see if the aneurysm is expanding and requires treatment.
If the aneurysm is larger or needs to be treated (to reduce the risk of rupture), doctors may recommend open surgical repair or an endovascular repair. In open repair, an incision is made into the abdomen. The aorta is temporarily clamped to stop the flow of blood. Next, the weakened section of blood vessel is cut and replaced with a man-made graft. Once the graft is securely attached, the clamp is removed. Blood flows through the new "pipe work" and on to the body.
Endovascular repair fixes the aneurysm from the inside of the vessel. A catheter is fed from the femoral artery in the groin up to the aneurysm. Then a stent graft (expandable mesh covered tube) is released, opened and fastened in place. The stent serves two purposes. First, it covers over the weakened area of the wall. Second, blood flows through the stent, protecting the aneurysm from more pressure.
Treating Complicated AAAs
Endovascular surgery is less invasive than open surgery, so patients have less pain and a faster recovery. However, the procedure can't be used for everyone. Joseph Ricotta, M.D., Endovascular Surgeon at Emory University Hospital in Atlanta, says about 50 percent of patients with AAA have an aneurysm located below the area where the renal arteries (those that feed the kidneys) branch off from the aorta. Placement of a traditional stent would block the entrances to the renal arteries and cut off the blood supply to the kidneys.
In these cases, the only other option would be open surgical repair. However, Ricotta says some of these patients are very sick and would not survive the surgery. Now, there may be another option, called fenestrated grafts.
While standard stent grafts are simply a hollow tube, fenestrated grafts have smaller tubes that branch out from the sides, like small limbs that feed out from a main tree branch. There are no fenestrated grafts approved for use yet in the U.S. So, currently, each must be made by hand.
The graft is constructed using the patient's CT scans as a guide. The scan information is placed into a computer, which provides 3-dimensional measurements for size and placement of each of the branches from the main stent. Then, that information is used to sew the side grafts onto the main stent. Ricotta says a graft can be tailor-made before the surgery, so there is no waiting time for the patient.
Trials are underway in the U.S. to test the fenestrated grafts. Ricotta is hopeful the technology will be available in a few years.
AUDIENCE INQUIRY
For general information on abdominal aortic aneurysms: National Heart, Lung, and Blood Institute, nhlbi.nih.gov
Society for Interventional Radiology, sirweb.org