On the opening mechanism of the aortic valve: some observations from simulations.

Viewed from the standpoint of mechanical engineering design, the aortic valve is impressive. However, our understanding of its mechanics is limited by our inability to study its in vivo function closely and in detail. Computer simulation methods offer an alternative approach and a first step towards the construction of a more complete cardiac model is described. The model includes the aortic valve, its leaflets and their supporting root, and the sinuses modelled as nonlinear materials. An explicit finite element code has been used to examine the time-varying displacements of the structure that was subject to pressure distributions, which included left ventricular, aortic and thoracic pressures. It was shown that the leaflets of the valve open by a combination of root expansion in a radial direction and leaflet movement in the direction of blood flow. This was compared to a model in which the aortic root was stiffened significantly, and it was found that this modified valve opened by leaflet folding to give a much smaller orifice. These findings, concerning the importance of root expansion, are in agreement with earlier experimental observations.