考虑流固耦合作用的主动脉弓血液流动分析

流固耦合作用对血液的流动速度、回流速度和壁面剪应力有较大的影响。但迄今已有的研究工作较少考虑血液．血管相互作用和生理脉动作用的影响，可能难以真实地反映血液在主动脉弓中的流动情况。将升主动脉、主动脉弓和降主动脉联系起来，根据生理脉动流条件，利用有限元软件，分析流固耦合作用下主动脉弓中的血液流动问题。研究表明，流固耦合作用对血液流动速度、回流速度和壁面剪应力的变化趋势影响较小，对血液回流速度幅值、壁面剪应力幅值影响较大。结果表明：在心脏收缩与舒张转换期，主动脉内的血液向心室方向反流；考虑流固耦合作用总体上降低血液回流速度的幅值；在流固耦合作用下，壁面最大剪应力幅值比非流固耦合偏低约25％。     

人体主动脉弓内三维血流动力学数值分析

目的阐明基于核磁共振数据进行数值建模的关键技术,利用计算流体动力学方法对人体主动脉弓内的血液流场进行了三维数值模拟。方法通过对临床核磁共振成像进行图像处理完成主动脉弓及分支血管的三维数字化重构,结合相关脉动血流量,模拟主动脉弓在心动周期不同时刻的血液流动细节。结果计算得到了人体主动脉弓内的血液流动在心动周期不同时刻的速度场、压力、壁面剪切应力的分布特征。结论基于核磁共振数据进行数值建模的关键技术有利于生物流体力学研究的深入开展,对主动脉弓进行血液流场的数值模拟有利于临床动脉粥样硬化、主动脉夹层的诊断和治疗。     

有锥度角的主动脉弓血液脉动流数值分析

目的 探求在正常生理脉动流条件下主动脉弓内血液流动速度和压力脉动分布，为动脉粥样硬化的成因和排除方法的研究提供理论依据。方法 运用计算流体力学方法和血流动力学的基本原理，对具有锥度角的主动脉弓内血液脉动流动进行数值模拟和可视化分析。结果 计算获得了具有锥度角的主动脉弓内血液流动在心动周期不同时刻的压力分布、速度分布、流线分布。结论 主脉弓内的血液脉动流流态表现复杂的原因是多方面的，而其中最为重要的原因就是主动脉弓的锥度角和曲率。     

基于计算流体力学方法进行不同个体的主动脉弓内血流模拟对比分析

目的:应用医学CT图像数据三维重构技术和计算流体力学方法进行人体主动脉内血流数值模拟分析,通过对不同个体正常主动脉弓内血流数值模拟获得的血流动力学参数进行比较,分析讨论血流动力学参数与血管结构形状的关系及对血液流动的影响,为阐明血管疾病的发病机理提供理论依据。方法:应用医学图像后处理软件对通过临床获得的增强CT二维医学图像数据进行处理重构而得到不同个体的主动脉弓三维立体模型并转化为可用于模拟计算的CAD模型。应用CFD软件模拟主动脉弓内的血流情况,获得相关血流动力学参数。结果:计算得到了不同个体主动脉弓在心动周期内不同时刻的血流动力学参数。结论:计算流体力学数值模拟方法为个体主动脉弓内进行仿真模拟血流动力学分析提供了可靠方法。在心动周期内主动脉弓弯曲处存压力变化明显,出现漩涡等复杂血液流动现象,为研究血流动力学及各种脉管疾病提供一定的理论依据。     

人升主动脉-主动脉弓的几何形态与显微结构

目的 为主动脉弓生物力学和血流动力学研究提供开矿学基础。方法应用组织学和计算机图像分析方法,对５例正常成人升主动脉－主动脉弓进行计量形态学研究。结果 获得了人升主动脉－主动脉弓几何形态和显微结构成分含量沿轴向和周向连续变化的完整数据。升主动脉根部结构成分以胶原纤维为主,左、右、后瓣环、窦壁的厚度和结构成分含量在血管财向无显著差异。结论 人主动脉弓几何形态与结构存在纤维和平滑肌显著,与其力学性质相符     

弯曲动脉中非线性脉动流的计算机模拟

非线性脉搏波在主动脉弓及任意弯曲动脉内传播的问题是生物流体力学中尚未很好地研究解决的重大课题之一。作为研究非线性脉搏波在弯曲动脉血管内传播问题的第一步,我们对主动脉弓内的非线性脉动流进行了计算机模拟。在本研究中做如下基本假设：将主动脉弓模拟为等圆截面的圆环形刚性管;血液为不可压缩牛顿流体;主动脉弓内的血液流动为发展中的层流,且在下游远处（出口处）变为充分发展的流动。我们利用SIMPLE方法对狗主动脉弓内的生理脉动流进行了数值模拟,得到了主动脉弓内的速度场和压力场的全部数值解。数值计算结果表明,血液…     

主动脉弓离断的产前超声诊断价值

目的探讨产前超声对胎儿主动脉弓离断的产前诊断价值。方法回顾性分析经外科手术或经上级医院证实的9例胎儿主动脉弓离断的产前心脏超声表现。结果9例符合诊断的产前胎儿超声心动图表现为四腔心切面不对称,左心室较右心室小。主动脉内径较肺动脉明显小,升主动脉直行。升主动脉与降主动脉的连接关系不能显示,只能显示动脉导管弓切面,在三血管-气管平面显示升主动脉或主动脉弓与降主动脉间连续中断。结论胎儿主动脉弓离断具有特征性超声表现,不合并其他复杂畸形时多数预后良好,仔细的产前超声检查有助于早期发现病变并给予适当的遗传咨询。     

搭桥术治疗DeBakey Ⅲ型主动脉夹层的流固耦合数值模拟

目的研究旁路搭桥转流术治疗DeBakey Ⅲ型主动脉夹层的力学机理,并探讨该术式的有效手术方案。方法构建升-腹搭桥和锁-腹搭桥前后通腔型式和盲腔型式的DeBakey Ⅲ型主动脉夹层个性化模型,利用计算流体力学的方法,在生理流动条件下进行流固耦合数值模拟。结果搭桥后假腔的血液流动速度、压力和血管壁位移分别平均下降38.86%、15.347 kPa和39.46%。结论搭桥手术是一种在特定情况下治疗DeBakey Ⅲ型主动脉夹层的有效手术方式,具有很好的临床应用前景。     

人体主动脉弓周向应力的非线性数值模型研究

目的 为了解主动脉弓的受力状况,选择适当的本构关系,为进一步分析人体主动脉弓的生物力学特性提供参考依据,并为临床治疗主动脉弓夹层瘤提供生物力学依据。方法 使用有限元方法分析了两种约束条件（第1种约束条件：沿升主动脉管轴方向的约束;第2种约束条件：升主动脉端可自由运动,但端部用半球封闭）的3种本构关系（线性本构、指数函数本构和M-R两参数本构）在两种载荷（10.67 kPa和26.66 kPa）下主动脉弓模型的周向应力,并对计算结果进行探讨。结果 建立了两种约束条件下的模型,并分别得出了在这两种约束条件下的3个本构关系在两种载荷下主动脉弓的周向应力的云图和周向应力沿弧长的分布。结论 指数函数本构关系可以较全面地反映主动脉弓血管的物理属性。第2种约束条件能够更真实地反映主动脉弓的物理特性。     

超声心动图在诊断主动脉弓离断中的应用价值

目的 探讨主动脉弓离断的超声心动图特征,以提高对该疾病的认识及诊断能力。方法 回顾性分析我院16例经手术、心血管造影及双源CT证实的主动脉弓离断的超声特征。结果 超声心动图正确诊断11例（68.75%）均为A型;误诊5例（31.25%）,其中3例IAA-A型,2例IAA-B型;主动脉弓离断超声心动图特征为:主动脉弓与降主动脉之间的连续性中断,升主动脉发育不良,肺动脉明显扩张,明显增宽肺动脉通过未闭动脉导管与降主动脉连接。结论 超声心动图是诊断主动脉弓离断的首选方法,在超声检查中发现肺动脉明显扩张,升主动脉发育不良,并且肺动脉高压与心内畸形不匹配者,应警惕主动脉弓离断可能,仔细探查主动脉弓,若主动脉及分支显示不清,联合MRI、CT检查可提高诊断率。     

Effects of graded pulsatile pressure on the reflex vasomotor responses elicited by changes of mean pressure in the perfused carotid sinus-aortic arch regions of the dog

1. In the anaesthetized dog, the carotid sinuses and aortic arch were isolated from the circulation and separately perfused with blood by a method which enabled the mean pressure, pulse pressure and pulse frequency to be varied independently in each vasosensory area. The systemic circulation was perfused at constant blood flow by means of a pump and the systemic venous blood was oxygenated by an extracorporeal isolated pump-perfused donor lung preparation.2. We have confirmed our previous observations that under steadystate conditions the vasomotor responses elicited reflexly by changes in mean carotid sinus pressure are modified by alterations in carotid sinus pulse pressure, whereas those evoked by changes of mean aortic arch pressure are only weakly affected by modifications of aortic pulse pressure.3. When the carotid sinus and aortic arch regions are perfused in combination at constant pulse frequency (110 c/min), the relationship between mean carotid sinus-aortic arch pressure and systemic arterial perfusion pressure is dependent on the size of the pulse pressure.4. Increasing the pulse pressure alters the curve relating the mean carotid sinus-aortic arch pressure to systemic arterial perfusion pressure in such a way that the perfusion pressure is lower at a given carotid sinus-aortic arch pressure within the range 80-150 mm Hg. The larger the pulse pressure, up to about 60 mm Hg, the greater the fall in systemic arterial perfusion pressure. Above a mean carotid sinus-aortic arch pressure of about 150 mm Hg, alterations of pulse pressure have little effect.5. There is a family of curves representing the relation between mean carotid sinus-aortic arch pressure and systemic vascular resistance, depending on the pulse pressure.     

支架治疗主动脉弓内侧动脉瘤的仿真研究

血管内支架是治疗主动脉弓动脉瘤的一种新技术。目前还没有人对具有局部突起的动脉瘤支架治疗血流动力学进行过研究。基于这样的事实,本仿真研究对主动脉弓内侧动脉瘤的支架治疗进行血流动力学分析。为便于比较,分别建立了有支架和无支架的主动脉弓动脉瘤模型。利用计算流体力学的方法对两个模型中的生理性血液流动进行了仿真。对流动情形、压力和壁面切应力分布进行了比较和分析,以便评价血管内支架对主动脉弓动脉瘤治疗的效果。结果表明,有支架的模型和无支架的模型,在瘤腔内的流动情形具有显著的不同。有支架模型瘤腔内的流动受到明显的抑制,特别是局部突起处的压力和壁面切应力大大地减小了。这些现象使我们有理由推断,血管内支架可以促进瘤腔内血栓的形成,并能减小动脉瘤破裂的危险。     

Dependence of Aortic Arch Morphogenesis on Intracardiac Blood Flow in the Left Atrial Ligated Chick Embryo

Partial left atrial ligation before cardiac septation redistributes intracardiac blood flow and produces left ventricular hypoplasia in the chick. We hypothesized that redistributed intracardiac blood flow adversely alters aortic arch development. We ligated the left atrial appendage with a 10‐0 nylon suture at stage 21 chick embryos, then reincubated up to stage 34. Sham embryos had a suture tied adjacent to the atrial wall, and normal controls were unoperated. We measured simultaneous atrioventricular (AV) and dorsal aortic (DAo) blood velocities from stage 24 embryos with an ultrasound pulsed‐Doppler flow meter; and the left and right third and fourth aortic arch blood flow with a laser‐Doppler flow meter. Ventricular and atrial cross‐sectional areas were measured from sequential video fields for planimetry. Intracardiac flow patterns were imaged on video by injecting India ink into the vitelline vein. In separate embryos, radiopaque microfil was injected into the cardiovascular system for μ‐CT scanning. We analyzed the morphologic characteristics of the heart at stage 34. Active AV and DAo stroke volume (mm³), right third and fourth aortic arch blood flow (mm³/s) were all decreased in ligated embryos (P < 0.05) when compared with normal and sham embryos. Ventricular end‐diastolic volume versus normal and sham embryos decreased by 45% and 46%, respectively (P < 0.05). India ink injection revealed altered right aortic arch flow patterns in the ligated embryos compared with normal embryos. μ‐CT imaging confirmed altered arch morphogenesis. Alterations in intracardiac blood flow disrupt both early cardiac morphogenesis and aortic arch selection. Anat Rec, 2009. © 2009 Wiley‐Liss, Inc.     

Aortic Arch Morphogenesis and Flow Modeling in the Chick Embryo

Morphogenesis of the “immature symmetric embryonic aortic arches” into the “mature and asymmetric aortic arches” involves a delicate sequence of cell and tissue migration, proliferation, and remodeling within an active biomechanical environment. Both patient-derived and experimental animal model data support a significant role for biomechanical forces during arch development. The objective of the present study is to quantify changes in geometry, blood flow, and shear stress patterns (WSS) during a period of normal arch morphogenesis. Composite three-dimensional (3D) models of the chick embryo aortic arches were generated at the Hamburger–Hamilton (HH) developmental stages HH18 and HH24 using fluorescent dye injection, micro-CT, Doppler velocity recordings, and pulsatile subject-specific computational fluid dynamics (CFD). India ink and fluorescent dyes were injected into the embryonic ventricle or atrium to visualize right or left aortic arch morphologies and flows. 3D morphology of the developing great vessels was obtained from polymeric casting followed by micro-CT scan. Inlet aortic arch flow and cerebral-to-lower body flow split was obtained from 20 MHz pulsed Doppler velocity measurements and literature data. Statistically significant variations of the individual arch diameters along the developmental timeline are reported and correlated with WSS calculations from CFD. CFD simulations quantified pulsatile blood flow distribution from the outflow tract through the aortic arches at stages HH18 and HH24. Flow perfusion to all three arch pairs are correlated with the in vivo observations of common pharyngeal arch defect progression. The complex spatial WSS and velocity distributions in the early embryonic aortic arches shifted between stages HH18 and HH24, consistent with increased flow velocities and altered anatomy. The highest values for WSS were noted at sites of narrowest arch diameters. Altered flow and WSS within individual arches could be simulated using altered distributions of inlet flow streams. Thus, inlet flow stream distributions, 3D aortic sac and aortic arch geometries, and local vascular biologic responses to spatial variations in WSS are all likely to be important in the regulation of arch morphogenesis. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

基于流固耦合计算机流体力学模拟分析人体主动脉弓内血液流动

目的比较分析应用弹性血管壁的流固耦合计算流体力学（CFD）方法和刚性血管壁的CFD方法模拟获得的正常主动脉弓内血流动力学参数,同时比较两种方法的优劣,为深入研究血液流动状态与动脉疾病的关系提供帮助。方法取46岁男性,胸主动脉正常CT图像,格式为Dicom,层间距为0.5mm,每片图像的平面分辨率为512×512,像素大小为0.5mm。应用医学图像后处理软件,对通过临床获得正常人体主动脉CT二维医学图像数据进行重构,得到主动脉血流及血管壁的三维立体模型并应用于模拟计算。结果在设定边界条件和初始条件的基础上,经多次迭代耦合计算,获得血管壁形变、等效应力、血流速度、壁面振荡切应力等相关血流动力学参数。结论在心动周期内弹性血管壁的主动脉内血流情况较刚性血管壁主动脉内血流情况更为复杂,管壁等效压力变化较大,血管壁的振荡切应力更高,表明弹性血管壁的流固耦合的CFD模拟更能体现真实主动脉内复杂血流情况,为深入研究血流动力学与心脑血管疾病的关系提供了一定的技术支持。     

Hemodynamic simulation study of a novel intra-aorta left ventricular assist device

The intra-aorta pump proposed here is a novel left ventricular assist device (LVAD). The mathematic model and the in vitro experiment demonstrate that the pump can satisfy the demand of human blood perfusion. However, the implantation of LVAD will change the fluid distribution or even generate a far-reaching influence on the aorta. At present, the characteristics of endaortic hemodynamics under the support of intra-aorta pump are still unclear. In this article, a computational fluid dynamics study based on a finite-element method was performed for the aorta under the support of intra-aorta pump. To explore the hemodynamic influence of intra-aorta pump on aorta, fully coupled fluid-solid interaction simulation was used in this study. From the flow profiles, we observed that the maximum disturbed flow and nonuniform flow existed within the aortic arch and the branches of the aortic arch. Flow waveforms at the inlets of aortas were derived from the lumped parameter model that we proposed in our previous study. The results demonstrated that the intra-aorta pump increased the blood flow in the aorta to normal physiologic conditions, but decreased the pulsatility of the flow and pressure. The pulsatility index changed from 2,540 to 1,370. The pressure gradient (PG) for heart failure conditions was 18.88 mm Hg/m vs. 25.51 mm Hg/m for normal physiologic conditions; for intra-aorta pump assist conditions, normal PG value could not be regained. Furthermore, our experimental results showed that the wall shear stress (WSS) of aorta under heart failure and normal physiologic conditions were 1.5 and 6.3 dynes/cm, respectively. The intra-aorta pump increased the WSS value from 1.5 to 4.1 dynes/cm.     

Comparison of the reflex vasomotor responses to separate and combined stimulation of the carotid sinus and aortic arch baroreceptors by pulsatile and non-pulsatile pressures in the dog

1. In the anaesthetized dog the carotid sinuses and aortic arch were isolated from the circulation and separately perfused with blood by a method which enabled the mean pressure, pulse pressure and pulse frequency to be varied independently in each vasosensory area. The systemic circulation was perfused at constant blood flow by means of a pump and the systemic venous blood was oxygenated by an extracorporeal isolated pump-perfused donor lung preparation.2. When the vasosensory areas were perfused at non-pulsatile pressures within the normal physiological range of mean pressures, the reflex reduction in systemic vascular resistance produced by a given rise in mean carotid sinus pressure was significantly greater than that resulting from the same rise of aortic arch pressure.3. On the other hand, when the vasosensory areas were perfused at normal pulsatile pressures and within the normal physiological range of mean pressures, there was no difference in the size of the reflex vascular responses elicited by the same rise in mean pressure in the carotid sinuses and in the aortic arch.4. Whereas the vasomotor responses elicited reflexly by changes in mean carotid sinus pressure are modified by alterations in pulse pressure, those evoked by the aortic arch baroreceptors through changes of mean pressure are only weakly affected by modifications in pulse pressure. Evidence for this was obtained from single stepwise changes of mean pressure in each vasosensory area during pulsatile and non-pulsatile perfusion, and from curves relating the mean pressure in the carotid sinuses or aortic arch and systemic arterial perfusion pressure.5. The vasomotor response elicited by combined stimulation of the carotid sinus and aortic arch baroreceptors was greater than either response resulting from their separate stimulation.6. When the mean perfusion pressures in the two vasosensory areas are changed together, the curve relating mean pressure to systemic arterial pressure during pulsatile perfusion of the areas is considerably flatter than that for non-pulsatile perfusion.7. Increasing the pulse pressure in the carotid sinuses or aortic arch caused a decrease in systemic vascular resistance, the response elicited from the carotid sinuses being the larger.8. Altering the phase angle between the pulse pressure waves in the carotid sinuses and aortic arch had no effect on systemic vascular resistance.9. In both vasosensory areas, increasing the pulse frequency caused a reduction in systemic vascular resistance.