A new surgical technique currently in clinical trials has the potential to save thousands of people who have thoracic (chest) aortic aneurysms.

An aneurysm is a widening of a blood vessel, resulting from a weakness in the vessel wall. When it occurs in the aorta, the largest artery in the body, the results can be fatal.

Chest aneurysms are also common. "They usually happen to peopie in their 60s and 70s because of a build-up of plaque in the arteries. The problem is the risk of rupture, especially in the chest," notes Dr. Marc Moon, associate professor of cardiac surgery at Washington University School of Medicine. He was at Stanford University when the first prototype aortic stent graft was performed in 1993, and his interest in the technology continues. "Our problem is that 70% of these aneurysms rupture, which in the chest is about 95% fatal."

Until these aortic stent trials started, the surgical fix for the condition involved an open chest operation, putting the patient on the heart-lung machine, cutting out the aortic section with the aneurysm and replacing it with a dacron tube. Studies have shown that the five year survival rate of patients having that surgery is 70 to 80%, versus 20-30% without the surgery. But the surgery itself can be hazardous.

Under the new treatment, the thoracic aortic stent graft, which consists of a metal mesh tube covered with dacron, can be put into place on the beating heart, and without an incision.

"Once an aneurysm is discovered, we have to determine what to do about it," says Moon. "There are three things we have to balance out: How big is the aneurysm? The larger the aneurysm, the greater the likelihood of rupture. What is the risk of rupture? Many patients don''t progress, and their aneurysms may never rupture. What is the risk of surgery to that patient versus the risk of rupture? Since these patients are typically older and usuatlyl have some other underlying disease, the stress of surgery may not be warranted."

Moon, working with director of cardiac surgery, Dr. Ralph Damiano Jr., and head of the abdominal aortic stent graft program, Dr. Greg Sicard, is getting ready to start a new clinical trial to evaluate a second type of thoracic stent graft. One trial on another version has recently been complete, and the midterm results look favorable, says Moon.

"Despite the millions of people with thoracic aortic aneurysms, an individual internist may see only much experience in the diagnosis and treatment," says Moon. That''s why they have initiated the Washington University School of Medicine Center for Diseases of the Thoracic Aorta. It is a referral center for other physicians and a data bank on cases and technology.

"What the stent graft technology will allow us to do is treat thoracic aneurysm patients who previously would have been inoperable."

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