| Objective Abdominal aortic aneurysm(AAA) is a common disease with aortic dilation. Hemodynamics is the most important factor in the progression of the AAAs, and lead the AAAs rupture in the end. This research is to observe the progression of rabbit AAAs with its biological characters and biomechanical principles, and to simulate the aneurysm's wall stress distribution and the hemodynamics influence on the wall of the AAAs in different period of the progression. The result is to predict the developing tendency and rupturing risk of AAAs.Methods Twenty-four New Zealand rabbits were used to create infrarenal AAA models with arterial patchs from the other rabbits' infrarenal aorta. We get the data of blood pressure and blood fat, survey and evaluate the material properties of the abdominal aortas or aneurysms in experimental groups (EG) and control groups (CG), and fit and analyze the stress-strain-curves of the normal rabbit abdominal aorta and the AAA models. The AAA models were scanned by spiral computed tomography in different periods. The CT datas were used to reconstruct three-dimensionally finite element models respectively by MIMICS software. Based on the material properties and the related boundary condition measured, the different AAA models' wall stress distribution were calculated with ADINA software in finite element method. And the developing tendency of AAA models was evaluated.Result Under the stable raising conditions, there are no statistic difference in blood pressure and blood fat between EG and CG(P＞0.05), systolic pressure in the aneurysm in EG is lower than in CG(P＜0.01), diastolic pressure in the aneurysm in EG is higher than in CG(P＜0.01), pulse pressure decrease significantly in EG than in CG(P＜0.01). The diameter of the aneurysms in 45-day-EG exceed it in the time just creating the aneurysms significantly(P＜0.01), and the diameter of the aneurysms in 90-day-EG exceed the one in 45-day-EG significantly too(P ＜0.01). MMP-2 expresses in high level in the AAA wall in 45-day-EG and 90-day-EG. Fitting the aortic wall stress-stain-curve in ter-multinomial function is better than in exponential function, and the aortic wall was defined as hyperelastic Ogden material. The maximum stress spot in the aneurysm shifts its place after creating the model than before, it fixed in the back wall of the aneurysm after the aneurysm reformed, and the stress of the maximum spot become larger as time went by. The aneurysm model become twisted deformation when the deforming calculation were executed under the situation of fixing the two terminals of the model. The further calculation proved the deformation was positive correlated with blood pressure.Conclusions The variation of hemodynamics from the aortic deformation may cause the diameter of the patched AAA models increased under the situation that the other related factors were controlled. The simple variation of hemodynamics may provoke MMP-2 express in high level on the wall of AAA models in early period, and keep it for a long time. The deformation of aorta, the variation of hemodynamics and the pathological representation come to a cyclic chain reaction to advance the progression of AAA. The wall stress was redistributed under the moulding effect of the blood flow after creating AAA model. The maximum stress spot located in the posterior wall which adjacent to the spinal column. The diversified stress distribution would advance the aneurysm mould itself. With the hemodynamics contribution, the tendency of the AAA is that the diameter become larger, the wall stress become enhanced, the stress distribution of the whole become more asymmetrically, mural thrombosis occurs, the shape of the AAA become deformed, and this deformation become more obviously if combined with high blood pressure. The theoretic rupturing risk spot located in the place which is adjacent to the spinal column, and the actual rupturing one maybe located in the lateral wall of the aneurysm.
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