STUDENT CLOSE-UP

Students Engineer
Safer Artery Grafts

Engineering class develops new approaches for aortic surgery

Using tacks and glue, MU students created a redesigned vascular graft that will stay in place to prevent rupture of abdominal aortic aneurysms.

Abdominal aortic aneurysm, or the weakening and bulging of the aortic artery where it passes through the abdomen, is a serious medical condition affecting 100,000 patients each year. Nearly 15,000 of those patients die when the aneurysm ruptures and causes massive internal bleeding. The condition is caused by hardening of the arteries, and it is most common in men older than 60. Cigarette smoking, high blood pressure and cholesterol are the leading causes.

Surgeons currently strengthen the weak spot by using an endograft, which is a spring-loaded stent that is placed inside the artery and is held in place by friction between the vessel wall and the artery, says MU vascular surgeon Rumi Faizer.

Endovascular repairs are made by the surgeon cutting a small incision in the groin area and passing the graft through the femoral and iliac arteries to the aneurysm. This method is less risky than open surgery, which requires a large abdominal incision to replace the diseased portion of the aorta with a graft.

However, the safer endovascular grafts have the potential to migrate after they are implanted. That movement can cause leakage or rupture of the original aneurysm, requiring further surgery. MU students worked with Faizer in a biological engineering capstone course to come up with two design modifications to keep the endografts in place.

One student team used four tacks made of Nitonal, a metal that remembers its shape. Tacks were forced through the outermost layer of the aortic wall using the pressure of a ballooning catheter. After puncturing the aorta, the ends of the tacks are bent back outside the aorta to anchor the endograft.

A second team used a bioglue made of purified bovine serum albumin and glutaraldehyde. These two solutions are dispensed with a delivery gun or disposable syringe. Once dispensed, the adhesives create a flexible seal.

The bioglue product is readily available but has not been used in this application. The tacks are a novel design in that the material has properties that make it change shape when it is the human body, allowing it to fit better, Faizer says. Students tested both approaches on aortic tissue from cattle and swine.

“This is a very advanced project and the kind of thinking we need to move medical technology forward,” Faizer says. “It’s exciting in that the students are asked to push the boundaries of what is available today.” Such capstone courses, common in MU undergraduate programs, are intended to let students apply what they have learned in class to real-world problems, says Sheila Grant, assistant professor of biological engineering.

Although the students’ work is theoretical and not approved by the U.S. Food and Drug Administration, Faizer says he hopes further efforts can make fixed endografts a clinical reality.

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Last Update: November 15, 2007