Computer modeling of drag forces in endoluminal stent-graft

Migration of the forces in patient specific aorta stent grafts is very important phenomena. Several complications remain to be fully resolved and hemodynamics drag forces seem to be one of the most important factor. The objective of this work was to investigate maximal drag force in endoluminal stent-graft in simplified and patient specific computer model. A simple curved tube with minimal and maximal diameter of 24 and 46 mm was used to simulate extreme cases of 90° bent stent for drag force calculation. A patient specific computer model was reconstructed from dual 64 multislice CT (MSCT) device. Finite element method with steady and transient laminar flow solver is implemented. Pressure, shear stress and velocity distributions for simplified curved tube and patient specific case were presented. Also a total drag force was calculated for steady and full transient case. The maximum migration forces is 8.15 N for 0.024m graft bent under 90°, and 29.88 N for 0.046 m graft bent under 90°. A real case patient shows maximal drag force of 12.6 N at peak systole. We found that maximal migration forces for the worst scenario could be as high as 29.88 N in certain situations. However, this is by far the worst case scenario where the entire unsupported length of the largest available size of thoracic aortic aneurysm (TAA) graft makes up the 90 bend. Computer simulation may predict for each specific patient the drag force magnitude which may be a clear benefit for patient follow-up study.