Shear accumulation as a means for evaluating risk of thromboembolic events in novel endovascular stent graft designs

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Objective:This study proposes to establish a simulation-based technique for evaluating shear accumulation in stent grafts and to use the technique to assess the performance of a novel branched stent graft system.Methods:Computational fluid dynamics models, with transient boundary conditions, particle injection, and rigid walls, simplifying assumptions were developed and used to evaluate the shear accumulation in various stent graft configurations with a healthy aorta as comparison.Results:Shear streamlines are presented for the various configurations. Shear accumulation was also calculated for each configuration. The number of particles with shear accumulations >3.5 Pa-s for each configuration was compared with the shear accumulation values of commercially available mechanical aortic valves from the literature.Conclusions:The stent graft configuration with the diaphragm does have particles with shear accumulation >3.5 Pa-s. However, the percentage of particles with shear accumulation above 3.5 Pa-s is less than the two commercially available mechanical aortic valves, and more surprisingly, is smaller than in the healthy aorta.Clinical Relevance:This study includes some advanced computational fluid dynamic analysis. Shear accumulation, as discussed in this report, is an important predictor of thromboembolic events with mechanical valves; thus, the parameter is of interest to the United States Food and Drug Administration. To date we believe this analysis has not been performed on stent grafts and published in a peer reviewed journal. With stent graft designs becoming more complex and the anatomic variations of patients with complex aneurysms increasing, we determined it was an important method to introduce to the community of vascular surgeons.

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