Aortic aneurysms (TAAA and AAA) repair can often be accomplished with minimally invasive stent grafts when surgery is not an option. While the main aneurysm can be managed, the narrow vessels leading to the kidneys are poor candidates for stenting because the stents themselves can cause turbulence that leads to white blood cells settling and causing stenosis.
In this vector velocity model, brighter colors indicate blood flow acceleration as it passes through a bifurcation. CFD modeling provides insight on blood flow through and near the walls of the stent graft.
Dr. Pat Kelly, a vascular surgeon at Sanford Health in Sioux Falls, South Dakota, developed a new stent graft for use within renal arteries that was designed to minimize turbulence near the inner surface of the stent. The idea is that irregular flow close to the stent surface promotes white blood cells to gather, so the new design promotes blood to move more smoothly along the stent graft. In order to receive approval from the FDA to begin a substantial clinical trial using the new stents, Dr. Kelly teamed up with a few researchers at South Dakota State University to model how blood would actually move through the new stents.
The team modeled the five implants (see video below) and how blood would move through them using the Star CCM+ fluidics simulator. The findings have led the FDA to approve further clinical trials and Medtronic has partnered with Dr. Kelly to help commercialize the technology:
More from South Dakota State Univeristy:
To compare the devices, [SDSU grad student Taylor] Suess had to create a geometrically correct model of each graft relative to the same aorta coordinates and positioning in the body trunk and the arteries that feed the organs and extend into the legs.
To capture what was happening to blood flow near the artery walls where atherosclerosis tends to begin, the researchers had to write their own code. They had to consider oscillating shear index, time-averaged wall shear stress, relative residence time and wall shear stress temporal gradient.
“The longer the blood stays at one site, the greater the chance white blood cells will build up and cause thickening of the artery walls,” Suess said. That narrowing then increases the shear stress on the vessel wall.
