Fluid-structure interaction in the aortic valve: Implications for surgery and prosthesis design.

摘要

The aortic valve is a complex and dynamic structure, which, with age, degenerative disease, or genetic abnormality, can become pathological and cease to function as in its natural state. A particularly prevailing disease of the aortic valve occurs when the valve becomes abnormally dilated, and regurgitation, or backflow of blood occurs. When this condition becomes severe and is accompanied by debilitating clinical manifestations, the standard procedure has been to replace the entire aortic root and valve with a composite valve graft incorporating either a mechanical or a bioprosthetic valve, during a type of surgery known as the Bentall procedure. However, both of these options have significant drawbacks for the patient, and for cases in which only the aortic root wall is dilated but the leaflets are still intact, novel surgical reconstruction techniques known as "valve-sparing procedures" have been adopted in recent years. The main idea is to excise only the dilated part of the wall, suturing a synthetic graft conduit in its place and thereby leaving the leaflets intact. A number of variants have been proposed, with a vigorous debate in the surgical community as to which is preferable in restoring valve dynamics and hemodynamics, thus leading to a more durable repair and a more favorable outcome for the patient. The objective of this work is to develop numerical simulation techniques to simulate the behavior of the normal aortic valve, and to quantify the effect that these various procedures, as compared to the benchmark native aortic valve. Various types of computational methods have been developed in the past to study the aortic valve, with an increasing level of sophistication as computational resources have evolved. Most of these studies have been structural finite element analyses, where the valve structures have been loaded with uniform distributed pressure loads in order to simulate the effect of blood. Recent efforts have focused on fluid-coupled simulations, whereby the blood flow acting as the dynamic driving force of valve motion is directly incorporated. This more complex strategy has intended to model a more physiological condition, but initial studies using this approach have reported several limitations and have been limited to investigations of the normal valve. In this work, we describe the developments leading towards a model of the aortic valve incorporating fluid-structure capabilities, including the initial developments of a dynamic structural model.