News Release

The bulged shape of an abdominal aortic aneurysm leads to a “separation” of blood flowing through the region from the wall of the vessel.

March 22, 2005, San Diego, CA – Engineers at the University of California, San Diego described how abnormal patterns of blood flow typical of abdominal aortic aneurysms lead to enlargement of the blood vessel, during an address at the March meeting of the American Physical Society being held at the Los Angeles Convention Center. 

Speaking at a news conference, Anne-Virginie Salsac, one of three scientists to present the research, explained that the bulged shape of an aneurysm leads to a separation of blood flowing through the region.    She said the abnormally low shear stresses on endothelial tissue lining the blood vessels in the dilated region make the arterial wall more permeable and weak. 

Anne-Virginie Salsac talks about her research on the mechanics of abdominal aortic aneurysms. Length: 3:44

Rupture of an aneurysm is usually fatal. Men are four times more likely to develop them than women, and aneurysms are most common after age 60. The risks are also higher among smokers, people who are sedentary, and those who have other health problems, such as high blood pressure or high blood levels of cholesterol. 

Salsac, who successfully defended her Ph.D. thesis in February, performed four years of research under the supervision of Juan Lasheras, a professor in the UCSD Jacobs School of Engineering’s Department of Mechanical and Aerospace Engineering. She also collaborated with Professor Steven Sparks, the chief vascular surgeon at UCSD Medical School. 

Salsac made particle image velocimetry (PIV) measurements involving aneurysm models, while systematically changing their size and geometry. Her research focused on the region of the aneurysm where fluid flow detaches from the wall and vortices develop. Salsac found that vortices impact the blood vessel downstream where the aneurysm narrows, producing a detrimental gradient of shear forces. Both low shear forces and large gradient of shear forces lead to abnormal cell-to-cell adhesion of endothelial cells, abnormal cell growth, and cell death. 

Salsac is writing a paper on her research for the Journal of Fluid Mechanics while she prepares for a post-doctoral fellowship in Paris. “I’ve been building a bridge between fluid mechanics, mechanical engineering and medicine in order to determine how blood flow patterns in an enlarged region of the aorta might affect the mechanics of the wall, and how that affects growth of the aneurysm,” said Salsac. “We need, however, a lot more research to understand the processes leading to the formation of aneurysms.”