Medical Edge Newspaper Column

Repairing Damaged Arteries Nonsurgically

Feb. 5, 2007
Dear Mayo Clinic
What information do you have on a procedure called endoluminal graft? -- Great Falls, Mont.

Answer:
Because a lumen is the cavity within a tubular organ, "endoluminal" refers to medical procedures that take place within such a cavity. Actually, we often use the term "endovascular" instead, because these techniques are used almost exclusively to correct two main problems of blood vessels: an arterial aneurysm (an outward bulging of the vessel) or the opposite condition of stenosis (a narrowing of the artery, usually resulting from the build-up of atherosclerotic plaque). Because endoluminal or endovascular procedures do not require major incisions, they are often called "minimally invasive."

A common application of the endovascular approach is the placement of a graft -- a substitute for the damaged portion of a blood vessel -- in the treatment of an aneurysm. Commonly, such grafts are placed within aneurysms of the abdominal aorta, the lower end of the body's largest artery. In the endovascular repair of an abdominal aortic aneurysm (AAA), the graft is an artificial channel composed of a metal such as nitinol (a nickel-titanium alloy), stainless steel, and an impermeable and durable synthetic material such as Teflon or Dacron. The graft spans the distance, and then some, where the aneurysm is located to relieve pressure on its stretched wall. This minimizes the likelihood of rupture and creates a channel, contiguous with the normal sections of the native vessel above and below the graft, through which blood may safely flow.

The metal portion of the graft, called a stent, is a cylindrical mesh that provides support for the Teflon or Dacron. It is inserted in a compressed form over a guide wire through the femoral artery in the groin. Once the stent has been advanced to its proper position, as verified by X-ray imaging, the compressed stent self-expands into its natural, predetermined size. This size can be as narrow as a soda straw or as wide as the thin end of a baseball bat, depending on the normal size of the vessel that needs grafting.

When used to widen a narrowed blood vessel, the bare metal stent is inserted without need for a synthetic channel. The blood vessel is expanded by a balloon, inflated before or after the stent is placed into the arterial wall.

Endovascular grafting for AAAs has essentially revolutionized their treatment, especially among elderly patients. Many of these patients have other medical conditions that make it unacceptably risky for them to have the traditional surgical treatment, an open procedure, which replaces or bypasses the portion of bulging artery via a major incision in the abdomen. The FDA approved the first two types of grafts for AAAs in 1999. At present, five types in total have been approved, and endovascular grafting is used in about 80 percent of AAA patients. Surgeons tend to opt for the open procedure in younger patients because endovascular grafting has not yet compiled a many-year track record. Thus, its long-term performance is uncertain.

For patients who qualify for the graft procedure, it is seemingly a godsend. It can be performed under local anesthesia and results in a shorter hospital stay, less pain than after traditional surgery, a lower risk of complications and mortality, and a short recovery period. Moreover, repair of AAAs by endovascular grafts has thus far been as durable as those done by open surgery.

Endovascular grafting does pose a small risk of some unique complications. These include possible injury to the femoral artery during placement of the graft, kidney damage caused by the contrast material used in imaging during the procedure, and dislodging of atherosclerotic plaque (which could impede blood flow "downstream"). The complication of greatest concern, however, is an "endoleak," bleeding caused by a poor fit at the top or bottom of the graft or between two adjacent graft segments. These risks are minimized through due care before and during the procedure and imaging studies afterward.

-- Albert G. Hakaim, M.D., Professor of Surgery, Section of Vascular Surgery, Mayo Clinic, Jacksonville, Fla.