Investigation Into Influence Factors On Prognosis Of Endovascular Abdominalaortic Aneurysm Repair And Hemodynamics Analysis Of A Stented Aortic

Background and ObjectiveBoth aortic aneurysm and dissecting aneurysm are very common in interventional radiology.During traditional surgery the patients are often harmed badly and can not endure the operation.Endovascular repair avoid seriously complication of traditional surgery and the period in hospital is shorten,which give a lot of patients the chance to treat.Though Endovascular repair have developed for about ten years in china,the Retrospective Research on treating the disease of aorta by endovascular abdominalaortic aneurysm repair has not been reported.Though endovascular abdominalaortic aneurysm repair became better and approaching perfection day by day in recently years,there are still many problems demanding prompt solution.When the former supporting part of stent exactly locate in the inlet of left subclavian artery.It is difficult to select the supporting part and dangerous to do endovascular abdominalaortic aneurysm repair.The feasible solution of this problem is to put a stent into the left subclavian artery,which can protect the left subclavian artery involvement and prevent the stent sliding into false lumen.As we all know,the implant of stent will induce the change of Hemodynamics,and this change have a intimate connection with restenosis of implanted stent.Because of the appearance of double stents in aorta and left subclavian artery,the branch structure is formed which is entirely different with traditional tube-shape stent structure,the hemodynamics change after the implant of branch stent is more complicated than usual. According to the different situation of the stent structure in the inlet of subclavian artery, the change of hemodynamics is different too.So it is necessary to do hemodynamic analysis for different stent sturct and choose the best one.Our research explored the regular pattern of aneurysm change though following up the patients after endovascular abdominalaortic aneurysm repair,and set up CoX survival prognostic model,analyze the correlation of the prognosis and hypertension,renal insufficiency etc and filter the relative factors that influence the curative of endovascular abdominalaortic aneurysm repair.To analyze the effect of stent structure change on the formation of in-stent restenosis by researching the influence of these change on hemodynamic using Pro/engineer wildfire3.0 and computational fluid dynamics software Ansysl 1.0-CFX and choose the best stent structure.Material and MethodThe experimental subjects composed of 102 cases after endovascular abdominalaortic aneurysm repair in the affiliated hospital of China Medical University between 2000-11 and 2007-10.All of them were all confirmed by medical imaging proof,46 patients was diagnosed as aortic aneurysm and another 56 dissecting aneurysm.All patients were examined by 3D-CTA.There are three kinds of stent including Talent aorta stent(Medtronic),Zenith aorta stent(Cook),aorta stent made in china(Yuhengjia company) which were used in the operation.Endovascular abdominalaortic aneurysm repair was executed in catheter room.Though retrospective analysis and look up the medial record,we fill up the table.The content of table include age of onset,sex,diameter of aneurysm,the position,life time,hypertension,coronary heart disease,renal insufficiency etc.Multiple factor regression model were conducted by SPSS 13.0 to filter the related factor of prognosis.For 27 cases which have completed imaging data,variance analysis was done to reveal the regular pattern of aneurysm change.The models were builded up in Pro/engineer wildfire3.0 according to the measurement of normal aorta and left subclavian artery,the diameter of aorta is 27mm, the diameter of left subclavian artery is 8mm,the angle between of them is 76°.The structure of aorta stent is the most common used stent structure in clinic,the thickness of stent is 1mm,the length of every circle is 8mm,every circle include 6"V"stent structure.Because our research only aimed at hemodynamic change of the branch part, so there are two circles in length.model A:the healthy aortic arch model without any stent;model B:the inlet of LSA open completely;model C:the"V"stent struts protruding into the inlet of LSA;model D:the single stent struts protruding into the inlet of LSA.Then the models were imported into ANASYS11.0-CFX to build up the fluid model,computational fluid dynamics analysis were executed after setting the boundary conditions.Results1.The correlative factors of affecting the prognosis of endovascular abdominalaortic aneurysm repair are hypertension,renal insufficiency and the diameter of aneurysm.2.The deflation of aneurysm is most remarkable in 6^th month after endovascular abdominalaortic aneurysm repair.The difference between 6^th month and 12^th month is not so obvious.3.Velocity vectors in the vertical plane of aorta,the velocity vectors of model B is similar to model A,The percentage of the low velocity and eddy area in model A,B,C,D are 31.2%,33.4%,41.2%,59.4%.the low velocity vectors of model C is a little more than model A,model D is full of low velocity vectors and vertex flow.4.Velocity vectors in the transverse section of LSA inlet,the velocity vectors of model B is similar to model A,The percentage of the low velocity and eddy area in model A,B are 21.2%,22.8%.there are high velocity vectors between two stent struts in model C,model D is full of low velocity vectors and vertex flow because of the single stent strut5.Velocity vectors in longitudinal section of LSA,the velocity vectors of model B is similar to model A,there are low velocity vectors around the stent struts of model C,LSA in model D is full of low velocity vectors and decentered vertex flow6.Wall shear stress distributions of 4 models,low shear stress distributions in model B and C are a little more than model A,The percentage of the low shear stress area in model A,B,C,D are 12.8%,18.1%,20.2%,65.8%.low shear stress distributions spread all over in model D7.The velocity vectors and shear stress area of model B is similar to model A.The stent structures in the inlet of LSA in Model D influent hemodynamics in LSA most seriously,blood velocity slow down obviously,a lot of eddy area and low shear stress conformed,model C is between model B and D.Conclusion1.The correlative factors of affecting the prognosis of endovascular abdominalaortic aneurysm repair are hypertension,renal insufficiency and the diameter of aneurysm.2.The change of stent construction can obviously influence hemodynamic,the increase of the thickness and/or meshes density is the main factor that induce the formation of low wall shear stress,which can lead to in-stent restenosis,the vertical link structure can reduce the formation oflow wall shear stress and the chance to be in-stent restenosis.3.The stent strcuts protruding into the inlet of LSA induced the conspicuous decrease of blood speed and the emergence of large-scale low shear stress,which will cause thrombogenesis,neointimal hyperplasia and result in in-stent restenosis,so it would be judicious to use dedicated bifurcated stents to treat bifurcation lesions.