Other Projects
Aortic Root Geometry on Aortic Valve Replacement Surgery
Hoda Hatoum and Dorma Flemister
Aortic stenosis is the pathological condition whereby the aortic valve opening becomes narrowed, hindering flow from the left ventricle to the rest of the body. One of the most common causes for aortic stenosis is calcific aortic valve disease (CAVD), which is characterized by a process of leaflet thickening and the formation of calcium nodules that further hinder proper leaflet opening. It is thought that this disease might be initiated in part by damage to endothelial cells due to increased mechanical stress.
To explore the influence of aortic root geometry, data from patients undergoing aortic valve replacement surgery were compiled and analyzed statistically. In addition to standard measurements of root geometry and valve function such as valve diameter, systolic jet velocity, and pressure gradient, patient CT data were reconstructed using segmentation in order to quantify calcium volumes in each aortic valve leaflet. Interestingly, the sinotubular junction (STJ – where the sinuses of Valsalva end and the ascending aorta begins) size was identified as being strongly correlated with the severity of aortic valve stenosis. STJ size previously was only studied in the context of aortic aneurysm and dissection. To further elucidate the influence of STJ size on valve function and sinus hemodynamics, semi-idealized aortic root geometries with various STJ sizes were created. These chambers in turn, were tested in the left heart simulator apparatus, and quantification of sinus hemodynamics was performed using particle image velocimetry (PIV). In these models, it was noted that once a certain threshold level of STJ dilation was exceeded, that the direction of the canonical sinus vortex reversed, and continued to weaken in strength with increasing STJ size. Digital simulations of these experiments and the development of fluid structure interaction (FSI) models are currently underway.