To treat this often silent problem, which is the 12th leading cause of death in the United States, a new endovascular surgical approach called an endograft is being used at the University of Michigan Health System. It has proven to be highly effective and less invasive than other methods, and has worked to save patients' lives.

About 80 percent of aortic aneurysms, a bulging or ballooning of the aortic artery, occur in the abdominal aortic segment below the kidney arteries. Each year, roughly 3 percent to 9 percent of those between the ages of 60 to 70 have abdominal aortic aneurysms, and many of them go undetected, says Gilbert R. Upchurch Jr., M.D., a vascular surgeon at the U-M Health System.

"(The chance for an aneurysm) is higher in patients who smoke, have asthma, high blood pressure or elevated diastolic hypertension," says Upchurch. "These factors and genetics contribute to the formation of aneurysms from an epidemiological stand point."

An aneurysm affects the wall of the aorta, the main blood vessel that supplies blood from the heart to the lower extremities, including all of the major abdominal organs. Aneurysms usually occur when the arterial wall becomes weak or damaged from accumulation of cholesterol-containing fatty deposits (arteriosclerosis), a birth defect, or an injury. This weakening, along with the pumping force of the heart, reduces the elasticity of the artery, causing the artery to slowly stretch and bulge, and posing the risk of a rupture if left untreated.

Many aneurysms, however, are difficult to detect with just a physical exam. Most physicians become aware of the aneurysm through radiological exams, such as X-ray angiography, magnetic resonance imaging (MRI) or computed tomography (CT), that are performed for other medical reasons.

Once detected, Upchurch says the aneurysm needs to be treated immediately, if greater than five centimeters, to avoid the risk of a potentially fatal rupture.

"The way to treat ruptured abdominal aortic aneurysm is to treat electively, or to treat it before it ruptures -- if you have an aneurysm that's diagnosed and is repaired through open surgery or the endovascular technique, the mortality rate for that patient in the state of Michigan is about 5 percent," says Upchurch. "If, however, you have it done after the (aneurysm) has ruptured, the mortality rate is about 80 percent."

For the past 50 years, the most common way to treat an aneurysm before it ruptured was to perform an elective, but highly invasive, surgery. This extensive surgical procedure required a very large abdominal incision in order to repair the aneurysm.

"(With the open surgical procedure) we would essentially get above and below the aneurysmal portion of the artery and then open it up, place clamps on it, and then sew a graft, literally a piece of polyester, from normal aorta to normal aorta," says Upchurch.

However, the new endograft procedure for abdominal aortic aneurysms, recently approved by the FDA, treats the aneurysm from the inside out. An access route to the aneurysm is created through the arteries in the groin, says David Williams, M.D., an interventional radiologist at the U-M Health System.

With this procedure, incisions are made high in the groin area to gain access to the arteries. When the artery is exposed, a needle is put into it and a guide wire is used to pass through a series of catheters -- varying in diameter -- to gain access to the aneurysm and the arteries in the pelvis.

"Through one of the arteries we put a very large device, about the size of a pencil in diameter, all the way up to the mid-abdomen region and deploy the endovascular graft," says Williams. "Just imagine the old 'ship in a bottle' procedure where the ship needs to expand after entering through the narrow mouth of the jar or bottle."

Similar to building a ship in a bottle, a small device is passed through a narrow pathway to the abdominal aorta, released and expanded. This expansion seals the aorta below the patient's arteries to the kidneys and allows the surgeons to deploy the other end that seals off the arteries to the pelvis. The next step involves passing another device through the one in the aorta and down to the artery on the other side of the pelvis.

"The final result of this procedure is a device (in the damaged artery) that has a large upper end and two smaller lower ends, sort of like an upside-down wishbone," says Williams. "The upper end seals in the aorta above the aneurysm; the two lower prongs of the 'wishbone' seal in the arteries to the pelvis."

With the endograft device in place, blood travels from the heart, through the device, into the pelvis, and bypasses the aneurysm. Using this new procedure, there has been an 80 percent to 90 percent success rate for patients whose endografts have remained securely in place with no evidence of residual filling of the aneurysm sack, says Williams.

The endograft procedure also has a faster recovery rate than the other surgical procedure that takes some patients weeks to recover from. With the new procedure, however, patients are frequently sitting up and ready to eat the same day, and then sent home the following day.

Since the durability of the endograft is still unknown, Williams says the U-M has taken a conservative approach to the new procedure.

"Someone who is healthy should get the durable, proven procedure," says Williams. "But a patient who is at risk, either because of advanced age or coexisting medical problems, would be a good candidate for this device."

Facts about endografts:

· The new endograft procedure involves a stent graft, a woven polyester tube, being placed inside a diseased vessel without surgically opening the tissue surrounding the diseased vessel.

· With the endograft in place, blood travels from the heart, through the device, into the pelvis, and bypasses the aneurysm. The device has an 80 percent to 90 percent success rate for patients.

· Unlike past surgical procedures to treat abdominal aortic aneurysms, the endograft procedure is less invasive and has a faster recovery time for patients. - By Krista Hopson

Related websites:

U-M Health Topics A - Z: Stent Placement (Endografts)

U-M Health Topics A - Z: Dissecting Aneurysms

American Heart Association: Aneurysm

19-Feb-2001