Simulating the Motion of Heart Valves Under Fluid Flows Induced by Cardiac Contraction

The motions of natural and replacement valve leaflets are complex functions of a large number of interactions. The principle concern of the simulation work is the investigation of how natural valves operate whilst attached to a deformable aorta close to its connection with the left ventricle. This involves the interaction of a fluid flow with soft, highly deformable structures. LS-DYNA was used to analyse the system using a series of models with fluid- solid interaction. A ventricle model helped create a detailed prediction of the temporal and spatial variation of flow into the aorta as the ventricle contracts. The principle input to this model was experimental data on displacements. This allowed a flow pattern to emerge naturally in the ventricle. This flow pattern was then available for input into the aortic valve model. The creation of this was a significantly non-trivial task. There are several aspects whose computational demands can be mutually destructive without care in the modelling. These include the effects of contact, spatially moving flow gradients, and the large deformations of the aortic wall and the sinuses. The development of the aortic valve model used linear elastic properties for the different solid materials. Subsequently the simulation progressed to using fully non-linear properties. The paper highlights some of the difficulties encountered and the solutions found, as well presenting some of the results.