Surgical repair of congenital aortic regurgitation by aortic root reduction: A finite element study

Abstract

During surgical reconstruction of the aortic valve in the child, the use of foreign graft material can limit durability of the repair due to inability of the graft to grow with the child and to accelerated structural degeneration. In this study we use computer simulation and ex vivo experiments to explore a surgical repair method that has the potential to treat a particular form of congenital aortic regurgitation without the introduction of graft material. Specifically, in an aortic valve that is regurgitant due to a congenitally undersized leaflet, we propose resecting a portion of the aortic root belonging to one of the normal leaflets in order to improve valve closure and eliminate regurgitation. We use a structural finite element model of the aortic valve to simulate the closed, pressurized valve following different strategies for surgical reduction of the aortic root (e.g., triangular versus rectangular resection). Results show that aortic root reduction can improve valve closure and eliminate regurgitation, but the effect is highly dependent on the shape and size of the resected region. Only resection strategies that reduce the size of the aortic root at the level of the annulus produce improved valve closure, and only the strategy of resecting a large rectangular portion-extending the full height of the root and reducing root diameter by approximately 12% – is able to eliminate regurgitation and produce an adequate repair. Ex vivo validation experiments in an isolated porcine aorta corroborate simulation results.

Computational Modeling for Surgical Reconstruction of Aortic Valve by Using Autologous Pericardium

“…To define the local orthotropic material for each leaflet, a v-vector was given along with the centerline of the aortic vessel, and the preferred direction of the material for each element of the leaflet was determined by the v-vector cross-product of the normal vector of that element. The aortic root was also assumed to be orthotropic [17] and defined with the same scenario.…”

“…Morphological abnormalities of aortic root were believed to affect the normal motion of the aortic valve [17]. In the patient specific diseased model, the LC (left coronary) sinus and the NC (non-coronary) sinus were found excessively bulged near the root, and the aortic annulus that attached with LC and NC leaflets in these two sinuses were deformed and dilated either (Figure 1.b).…”

Surgical reconstruction of semilunar valves in the growing child: Should we mimic the venous valve? A simulation study

“…The meshes representing the leaflet grafts do not grow and in fact may constrain the vessel during growth. In order to achieve a dilated state of the mesh boundary points that is consistent with the physical problem, we apply circumferential and axial forces to the boundary points representing stresses in the dilated vessel for a given diameter and pressure, and we also apply nodal forces due to stresses in the leaflets in elements that have an edge on the cylindrical boundary (Hammer 2015). From this condition representing the pressurized aortic root, the locations of mesh boundary points are held constant while surface normal forces representing transleaflet diastolic pressure are applied to close and load the leaflets.…”

“…The structural finite element analysis method that we have developed and applied was validated in previous work using simulated biaxial loading of square patches of leaflet tissue (Hammer 2011) and using ex vivo experiments of pressurized isolated aortic valves (Hammer 2012). See our previous work for details of the simulation methods (Hammer 2015). …”

“…We have previously used computer simulation to study how different techniques for aortic valve surgical reconstruction affect the robustness of valve closure immediately following surgery (Hammer 2012, Hammer 2015). For these studies, the primary advantage of simulation was that it allowed a single dimension or feature of valve reconstruction to be varied while keeping all others constant.…”