Hemodynamic Analysis Of Localized Atherosclerotic Stenosis Of Vertebral Basilar Artery

Among the many causes of human death,cardiovascular and cerebrovascular diseases occupy the first place.Fifteen million people die of cardiovascular and cerebrovascular disease worldwide every year.According to statistics,there are already 290 million people with diseases in China.and the affected population is getting younger.Atherosclerosis and aneury sms are the main manifestations of vascular lesions.Vascular surgery is an effective method to treat cardiovascular and cerebrovascular diseases such as atherosclerosis and aneurysms.Clarifying the hemodynamic environment of atherosclerosis and aneurysms is of great significance for determining the precise surgical plan and the timing of interventional surgery.However,the biomechanical environment of atherosclerosis and aneurysm is complex.Through clinical means,only parameters such as flow rate could be obtained.The mechanical behavior interaction between blood and vessel wall still could not be evaluated.The purpose of this study was to establish a bidirectional fluid-structure coupling model of vertebral and basilar arteries and then evaluate the hemodynamic performance of intracranial atherosclerosis and aneurysms by finite element simulation.In this paper,patients with both local atherosclerosis and aneurysms were selected as research objects.Based on their CTA images of vertebrobasilar artery,the geometric model of diseased vessels was constructed by reverse modeling method.The blood was characterized by a non-Newtonian fluid model.A vertebrobasilar artery two-way fluid-structure coupling model was established to study the hemodynamic response during a cardiac cycle.And different blood pressure(120 mmHg,140 mmHg,160 mmHg,180 mmHg)with different stenosis rates(0%,40%,50%,60%,70%,80%)were added into the fluid-solid coupling model as variables.The response of different blood pressure and different stenosis rates to hemodynamics was studied.The effectiveness of the coupled model was verified by comparing the clinical flow rates of unilateral vertebral artery stenosis before and after surgery.The model bone method was proposed to realize the rapid change of vertebral artery dilatation simulation model.The vascular model was prepared by 3D printing technology.The flow ratio of posterior cerebral artery was obtained by vertebral-basilar artery flow experiment in vitro.This study found that under normal blood pressure,there were a large low-velocity area and a low-wall shear stress area at the front of the atherosclerotic vessel.Unilateral vertebral artery stenosis caused laminar flow in the intersection area and accelerated blood flow in the upper basilar artery.Eddy phenomenon appeared in the apex aneurysms of the basilar artery.Different blood pressure simulations showed that the local wall shear stress of the aneurysm and blood flow velocity of the narrow side decreased with the increase of blood pressure.In the simulation of unilateral vertebral artery terminal stenosis rate,the wall shear stress in the stenosis area increased slowly in the stenosis rate stage of 0%-40%followed by a downward trend.The wall shear stress changed to a rapidly increasing state in the stenosis rate stage of 40%-70%,and the blood flow rate decreased rapidly after the stenosis rate of 70%.The largest deformation area of the vessel without stenosis occurred in the aneurysm during the simulation of vertebral artery tortuous,and the size of which was related to the length of the vertebral artery.In vitro flow experiments,fluid retention was found in the stenosis of the original vertebral artery,which easily aggravated the degree of atherosclerotic stenosis.This study provided hemodynamic data reference for vertebrobasilar artery,theoretical basis for determining the mechanical behavior interaction between blood and vessel wall and determining the surgical plan.