Three-dimensional computational modeling of fluid-structure interaction: Study of diastolic function in a thin-walled left heart model.

摘要

Aided by advancements in computer speed and modeling techniques, computational modeling of cardiac function has continued to develop over the past twenty years. These models have grown from static two-dimensional models that looked at either the associated fluid or solid mechanics to simulations that incorporate elaborate three-dimensional geometries with moving boundaries. The goal of the current study was to develop a computational method that provides blood-tissue interaction under physiologic Reynolds numbers, and then apply it to thin-walled models of cardiac chambers. To accomplish this goal, the Immersed Boundary Method was used to provide the interaction of the tissue and blood in response to fluid forces and changes in tissue pathophysiology. The fluid mass and momentum conservation equations were solved by Patankar's Semi-Implicit Method for Pressure Linked Equations (SIMPLE) to provide solution stability at physiologic Reynolds numbers. Initially, these methods were applied to a thin-walled, truncated ellipsoid model that contracted over a 100 msec period to test the feasibility of combining them to achieve physiologic Reynolds numbers. The methods were then applied to a left heart model of diastolic function consisting of the left ventricle, left atrium, and pulmonary flow. The input functions for this model consisted of the pulmonary driving pressure and time-dependent relationship for changes in tissue properties during the simulation. The results obtained from the left heart model were compared to clinically observed diastolic flow conditions for validation. The model was first applied to normal diastolic function. Then, cases involving delayed ventricular relaxation, increased ventricular stiffness, increased atrial contraction, and atrial fibrillation were compared to the normal case to illustrate the effect of these diseases on the flow fields.