Finite-element analysis of aortic valve-sparing: Influence of graft shape and stiffness

Aortic valve incompetence due to aortic root dilation may be surgically cor rected by resuspension of the native valve within a vascular graft. This st udy was designed to examine the effect of graft shape and material properti es on aortic valve function, using a three-dimensional finite-element model of the human aortic valve and root. First, the normal root elements in the model were replaced with graft elements, in either a cylindrical or a "pse udosinus" shape. Next, the elements were assigned the material properties o f either polyethylene terephthalate, expanded polytetrafluoroethylene, or p olyurethane. Diastolic pressures were applied, and stresses, strains, and c oaptation were recorded for the valve, root, and graft. Regarding shape, th e cylindrical graft models increased the valve stresses by up to 173%, wher eas the root-shaped graft model increased valve stresses by up to 40% as co mpared to normal. Regarding material properties, the polyurethane models de monstrated valve stress, strain, and coaptation values closest to normal, f or either root shape. Graft shape had a greater effect on the simulated val ve function than did the material property of the graft. Optimizing the sha pe and material design of the graft may result in improved longevity of the spared valve if a normal environment is restored.