Zhongjie Wang1, Yue Xuan1, Julius M. Guccione1, Elaine E. Tseng1, Liang Ge1,21Department of Surgery, University of California San Francisco and San Francisco Veterans Affairs Medical Centers, San Francisco, CA, USA
2Electronic correspondence: Liang.Ge@gmail.com
Background and aim of the study: Finite element analysis (FEA) can be used to determine ascending thoracic aortic aneurysm (aTAA) wall stress as a potential biomechanical predictor of dissection. FEA is dependent upon zero-pressure three-dimensional geometry, patient-specific material properties, wall thickness, and hemodynamic loading conditions. Unfortunately, determining material properties on unoperated patients using non-invasive means is challenging, and significant material property differences have been shown previously among aTAA patients. The study aim was to determine the impact of patient-specific material properties on aTAA wall stress. Using FEA, an investigation was conducted to determine if patient-specific wall stress could be reasonably predicted by using population-averaged material properties, as this would greatly simplify dissection prediction.
Methods: ATAA patients (n = 15) with both computed tomography (CT) imaging and surgical aTAA specimens were recruited. Patient-specific aTAA CT geometries were meshed and pre-stress geometries determined as previously described. Patient-specific material properties were derived from biaxial stretch testing of aTAA tissue and incorporated into a fiber-enforced hyperelastic model, while group-averaged material properties were estimated using mean values of each parameter.
Population-averaged material properties were also calculated from the literature and studied. Wall stress distribution and its magnitude were determined using LS-DYNA FEA software. Peak and averaged stresses and stress distributions were compared between patient-specific and both group- and population-averaged material property models.
Results: Patient-specific material properties had minimal influence on either peak or averaged wall stress compared to the use of group- or population-averaged material properties. Stress distribution was also nearly superimposed among models with patient-specific versus group- or population-averaged material properties and provided similar prediction of the sites most prone to rupture.
Conclusion: FEA using population-averaged material properties likely provides reliable stress prediction to indicate which sites are most prone to rupture. Population-averaged material properties may be reliably used in computational models to assess wall stress, and significantly simplify the risk prediction of aTAA dissection.
Presented at the Biomedical Engineering Society Meeting, 11th-14th October 2017, Phoenix, Arizona, USA
The Journal of Heart Valve Disease 2018-19;27:275-284
|Impact of Patient-Specific Material Properties on Aneurysm Wall Stress: A Finite Element Study|
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