The study of mechanical properties on heart valves can provide an important theoretical basis for doctors to repair heart valves and prosthetic valve materials research. In this paper, we present the current status of the mechanical property study methods of heart valve, expound the methods and special requirements about uniaxial tensile test and biaxial tensile test of the heart valve, and further discuss several establishment methods of heart valve constitutive models. We also discuss the development trend of heart valve mechanics.
Heart Valve Prosthesis ; Heart Valves ; physiology ; Humans ; Prostheses and Implants

Hemodynamic situation is an important factor of recurrence of postoperative carotid artery aneurysm. In order to investigate the hemodynamic factors of postoperative carotid artery aneurysm affect carotid artery aneurysm recurrence, we established a 3D finite element carotid artery aneurysm for the preoperative and postoperative periods using the three-dimensional reconstruction techniques. And then we measured the hemodynamic factors of carotid artery aneurysm of preoperative and postoperative by the finite element method. The carotid artery aneurysm model has an accurate and realistic shape; the pressure of the recurrence of aneurysm was reduced significantly after surgery,wall shear stress increased significantly at residual neck, and blood flow velocity increased significantly, which will increase the risk of recurrence. The hemodynamic analysis provides a reference for development of aneurysm clinical treatment programs and prevention of recurrence.
Aneurysm ; pathology ; surgery ; Blood Flow Velocity ; Carotid Arteries ; pathology ; surgery ; Computer Simulation ; Hemodynamics ; Humans ; Stress, Mechanical

Objective: To study the different ischemic characteristics of cerebral gray matter and deep white matter in patients with chronic cerebral artery severe stenosis or occlusion. Methods: A retrospective study was conducted on 30 patients with chronic unilateral cerebral artery severe stenosis or occlusion from April 2014 to April 2018 in our hospital. Cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time of peak time (TTP) and time to delay(TTD) of cerebral cortex gray matter and deep white matter in the blood supply area of the responsible artery (the affected side) and the contralateral hemisphere (the healthy side) were measured. Statistical analysis of the perfusion parameters of cerebral cortex gray matter and deep white matter in the affected side and contralateral side were performed using SPSS13.0 software package. T test was used for variance homogeneity, and t′ test was used for variance discrepancy, and P<0.05 was statistically significant. Results: The average values of CBF and CBV of the ipsilateral and contralateral cerebral cortex were increased than those of ipsilateral and contralateral cerebral deep white matter respectively(P<0.01). MTT, TTP and TTD of the ipsilateral and contralateral cerebral cortex were decreased than that of ipsilateral and contralateral cerebral deep white matter (P<0.01); CBF of ipsilateral cerebral cortex and CBV of ipsilateral cerebral deep white matter were not different from those of the contralateral cerebral cortex and deep white matter respectively, but CBF of ipsilateral cerebral deep white matter is decreased than that of the contralateral deep white matter (P<0.01). CBV of ipsilateral cerebral cortex is increased than that of the contralateral cerebral cortex (P<0.01). MTT, TTP and TTD of ipsilateral cerebral cortex and deep white matter were increased than those of contralateral cerebral cortex and deep white matter respectively(P<0.01). Conclusion Deep cerebral white matter perfusion decreased more significantly than cortical gray matter in the supply region of chronic cerebral artery severe stenosis or occlusion. CT perfusion imaging can quantify the degree of chronic cerebral ischemia and can provide quantitative diagnostic information for clinical treatment and efficacy evaluation.

Objective To discuss the hemodynamic features of internal carotid aneurysm,and study the relationship between hemodynamics and occurrence,development and rupture of internal carotid aneurysm .Methods The 3D model of internal carotid aneurysm was established by materialise's interactive medical image control system(MIMICS).The finite element analysis software ANSYS was used to carry out numerical simulation.Results Low wall shear stress of internal carotid aneurysms were located at the same area.The wall shear stress at different region were positive correlation with the blood flow velocity.Conclusion The blood flow velocity and wall shear stress at the top of aneurysm are relatively low.This position is consistent with the rupture position.The significant changes of hemodynamic at the top of aneurysm may trigger a series of mechanical biological effects on the internal carotid aneurysm wall.The changes alters cells'gene and protein's expression,causes rupture of the aneurysm.

Objective To study the different ischemic characteristics of cerebral gray matter and deep white matter in patients with chronic cerebral artery severe stenosis or occlusion. Methods A retrospective study was conducted on 30 patients with chronic unilateral cerebral artery severe stenosis or occlusion from April 2014 to April 2018 in our hospital. Cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time of peak time (TTP) and time to delay(TTD) of cerebral cortex gray matter and deep white matter in the blood supply area of the responsible artery (the affected side) and the contralateral hemisphere (the healthy side) were measured. Statistical analysis of the perfusion parameters of cerebral cortex gray matter and deep white matter in the affected side and contralateral side were performed using SPSS13.0 software package. T test was used for variance homogeneity, and t′test was used for variance discrepancy, and P<0.05 was statistically significant. Results The average values of CBF and CBV of the ipsilateral and contralateral cerebral cortex were increased than those of ipsilateral and contralateral cerebral deep white matter respectively(P<0.01). MTT, TTP and TTD of the ipsilateral and contralateral cerebral cortex were decreased than that of ipsilateral and contralateral cerebral deep white matter (P<0.01); CBF of ipsilateral cerebral cortex and CBV of ipsilateral cerebral deep white matter were not different from those of the contralateral cerebral cortex and deep white matter respectively, but CBF of ipsilateral cerebral deep white matter is decreased than that of the contralateral deep white matter (P<0.01). CBV of ipsilateral cerebral cortex is increased than that of the contralateral cerebral cortex (P<0.01). MTT, TTP and TTD of ipsilateral cerebral cortex and deep white matter were increased than those of contralateral cerebral cortex and deep white matter respectively(P<0.01). Conclusion Deep cerebral white matter perfusion decreased more significantly than cortical gray matter in the supply region of chronic cerebral artery severe stenosis or occlusion. CT perfusion imaging can quantify the degree of chronic cerebral ischemia and can provide quantitative diagnostic information for clinical treatment and efficacy evaluation.