双分叉动脉血流动力学特性的边界元分析

目的通过数值计算判断血流动力学特性的突变对双分叉动脉血管病变发展的影响。方法利用边界元方法计算了一类双分叉侧支型动脉血管主支管病变前后的血液流场、血管壁切应力、压力等血液流体动力学特性,并作了分析和比较,对病变产生、发展和加剧的流体动力学原因做出了合理的解释;通过对病变前后分支管壁切应力和压力的计算结果分析,对主支管的病变是否会影响分支管的血液流体动力学特性做出了判断。结果主支管病变处由于血管腔变窄血液流速明显变大、切应力变大,主支管病变或病变加剧对分支管血液流场分布及切应力并无明显影响,而使分支管壁血压升高。结论血液的流体动力学特性对动脉粥样斑块的形成、发展、加剧、破裂有一定的影响,双分叉动脉主支管病变的加重极易导致分支管分叉处粥样斑块病变的出现。     

T型分叉血管中血液流动对动脉血栓形成的影响

目的 从血流动力学角度研究T型血管分叉处血液流动的改变对血栓形成的影响。主要从血流速度、分支直径、T型分叉角度及血液粘度方面研究血液流动对血栓形成的影响。同时结合相关医学病例,从多学科角度分析并验证医学研究中的有关血栓形成机理的猜测。方法 建立T-型动脉血管的几何模型,采用计算流体动力学方法对血管内流场进行数值分析研究,分析不同条件的流动对血栓形成影响。结果 在分叉血管附近的支血管和主血管中分别形成了两处较大区域的涡流区域,另外,在分叉交接处的下游位置也出现了一处较小的区域,这些区域速度较低,剪应力出现突然增大趋势,符合血栓形成,因此成为“最适成栓位置”。结论 血栓在“最适成栓位置”的形成还与分支血管直径、血管中血流速度、分叉角度以及血液粘度等有密切关系。     

T型分叉管内牛顿与非牛顿血流特性对比分析

目的:动脉粥样硬化是引起心血管疾病的重要因素。结合临床心血管相关病例,从交叉学科的角度分析了入口血流速度和血液粘度对T型分叉管内血流分布的影响,以探索T型分叉管内血流分布与动脉粥样硬化形成的关系,为临床诊断与治疗提供一定的指导。方法:根据血液流动的粘性不可压缩Navier-Stokes方程,运用Auto CAD建立了T型分叉血管的几何模型,并采用计算流体力学方法 (Computational Fluid Dynamics,CFD)对分叉管内血液流动进行数值模拟,分析不同初始条件下分叉管内血流分布对动脉粥样硬化形成的影响。结果:数值模拟结果显示,与牛顿血液粘度模型相比,非牛顿血液粘度模型下血流分布较合理;分叉管的壁面切应力明显大于主血管,而分叉管的壁面压力却小于主血管,表明分叉处管壁受到高切应力与低壁面压力的共同作用,血管内壁易疲劳损伤,促进动脉粥样硬化的产生;这与分叉处附近A与B处存在较大面积的低速涡流区相符合,为动脉粥样硬化的形成提供有利条件。结论:通过对T型分叉管血液流体动力学的数值模拟,表明入口血流速度和血液粘度在动脉粥样硬化形成过程中具有重要作用。另外,数值模拟结果与临床检测结果一致,为进一步研究心血管疾病的机理提供一种有效、可靠的研究方法。     

冠状动脉斑块分型及分叉角度对斑块影响的血液动力学模拟

目的 分析斑块分布分型和血管分叉角度对冠状动脉分叉血管内血液动力学的影响,进一步探讨对斑块易损性发展的影响规律。方法 基于人体冠状动脉分叉血管的平均几何参数,构建不同斑块分布分型和血管分叉角度情况下的流固耦合模型,研究关键部位处的血流速度、压力以及剪切应力分布。结果 斑块上游的肩部是斑块表面剪切应力最大的部位,容易发生溃疡或破裂并进一步发展;当分叉血管单侧有斑块时,分叉脊处的剪切应力大于双侧有斑块的情况。血管分叉脊处的压力和剪切应力随分叉角度减小而逐渐增大。结论 分叉处单侧有斑块时,斑块溃疡或破裂的概率更大。主支血管内斑块的存在会促进分叉处斑块的形成和发展。血管分叉的角度越小,分叉脊处的血管内壁越易受损。研究结果可为易损斑块治疗方案的设计与优化提供理论参考。     

冠状动脉分叉病变单支架植入术后血流动力学分析

目的分叉病变在即刻手术成功率及远期心脏事件方面是最具有挑战的冠脉病变之一。血流动力学对动脉粥样硬化的形成有重要影响。对分叉病变单支架虚拟植入后的血流动力学参数分布进行分析,探讨其对支架后再狭窄的影响,可为临床治疗提供理论依据。方法本文选取一例冠状动脉分叉病变患者的冠状动脉血管造影(computed tomography angiography,CTA)图像,首先用Mimic软件对所获得冠脉CTA数据进行三维重建得到冠脉血流区域,然后运用类似虚拟去除斑块的方式建立不均匀壁厚血管壁模型,对所得模型在ABAQUS中进行单支架虚拟植入,最后根据虚拟植入前、后的冠脉模型分别生成支架前和真实变形后的血流域有限元模型,并利用ANSYS软件通过瞬态CFD分析模拟动脉血流的流动状态,获得目标血管段的血流动力学参数。结果支架植入后与支架植入前相比,目标血管段的血液流速、壁面剪切应力均降低;支架植入后主支血管远端有振荡的低剪切应力区域;支架边缘位置壁面剪切应力低于其他位置;分支血管直径变小;分支外侧壁壁面剪切应力低于内侧壁。结论分叉病变的单支架植入可改善冠脉主支的狭窄,但术后主支血管远端振荡的低剪切应力区域、支架边缘和边支外侧壁处的低壁面剪切应力,以及斑块和分叉嵴的移位有可能是分叉病变再狭窄的血流动力学机制。     

关于冠状动脉分叉病变角度命名的商榷

正冠状动脉左主干发出左前降支和左旋支形成分叉、前降支发出对角支形成分叉、左旋支发出钝缘支形成分叉等等,以往研究只关注斑块在分叉部位的分布~([1-5]),不重视分叉血管之间的角度。由于血管介入技术的迅速发展,分叉病变的位置直接影响介入技术的选择和预后。国内外关于分叉病变角的名称不统一(图1～3)~([6-8]),为了有效地进行学术交流和临床研究,借鉴数学关于"角"(∠)的命名原则,提出新的冠状动脉分叉角名称(图4)。命名原则如下。(1)主支与分支:冠状动脉分叉前、后血管走行一致(或接近者)者为主支血管(main vessel,MV),而另一条血管称为侧支     

Y型血管血流动力学边界元分析

目的：通过数值计算,判断Y型动脉血管中,血流动力学特性对分叉处粥样斑块病变产生和发展的影响。方法：利用边界元方法[4,5],计算了Y型动脉血管,主管病变前后的血液流场、血管壁切应力、压力等血液流体动力学特性,通过对计算结果的分析和比较对粥样病变产生和发展的原因做出了分析。边界元方法由于只在边界离散时作了近似,因而计算精度较高,对于象分叉血管这类复杂边界问题,有较强的适应性。结果：计算结果显示,分叉处管壁切应力明显大于主管壁切应力,说明了分叉处易产生粥样斑块的流体动力学原因;而病变的产生使血管腔变窄,病变斑块顶部血流速度、切应力变大,上、下游血流速度、切应力变小,说明了粥样斑块变厚和附壁延伸的流体动力学原因[7];另外,病变前后血管壁压力的计算结果显示,病变的产生对动脉血压有一定的影响。结论：通过对Y型分叉血管血液流体动力学特性的计算,进一步说明,边界元方法对分叉血管,以及分叉处有病变血管,这类复杂边界问题的计算,方便、快捷、精度高、节约机时,可为生物流体力学的深入研究提供一种可靠、有效的方法[8,9]。     

锁骨下动脉、颈总动脉和椎动脉分叉处血流动力学数值模拟

目的:探讨锁骨下动脉、颈总动脉和椎动脉分叉处的血流动力学特性,分析该处发生血管狭窄引起大脑供血不足的 血流动力学原因。方法:采用内蒙古民族大学附属医院神经内科提供的CT数据,应用医学建模软件MIMICS20.0将患者 二维CT数据进行三维血管重建,经过网格划分及边界条件设置后导入计算流体力学软件FLUENT14.5中。计算和分析 不同血液入口速度的锁骨下动脉、颈总动脉和椎动脉分叉处的血流动力学特性。结果:在血液入口速度不同的情况下,锁 骨下动脉、颈总动脉和椎动脉分叉处的血液流场分布、血液压力分布和血管壁面切应力分布有显著变化。在血液入口速 度增大时,锁骨下动脉分叉处和颈总动脉分叉处的血液流速快、血管壁压力大,颈总动脉内侧血管壁面切应力大,但锁骨 下动脉分叉处和颈总动脉分叉处血管壁面切应力数值和变化幅度小,属于低切应力区。结论:通过血流动力学数值模拟 研究,分析锁骨下动脉、颈总动脉和椎动脉分叉处易发生粥样斑块病变导致大脑供血不足的血流动力学原因。     

豚鼠肝内胆管和肝动脉的分支型式及胆管周围血管丛的观察

以解剖显微镜及扫描电镜观测了豚鼠肝内胆管和血管的甲基丙烯酸甲酯聚合法取代铸型15个。铸型显示豚鼠肝内胆管和肝动脉相伴而行,二者分支型式和分叉角相似,均为主侧支型分布,依所在肝叶的大小和形状不同,主支有7～11级不等。主支多为二分叉型,分叉角平均为52.4°±13.05(N=158)。各级主支都发出许多细小侧支,侧支与主支的夹角多为90°。豚鼠的整个胆管树均有明显的血管丛缠绕。依胆管径的大小可分为两种类型的胆管周围血管丛:胆管径大于95～100μm 时,其胆管周围血管丛呈网鞘样;胆管径小于95～100μm 时,其胆管周围血管丛是纵行小动脉性的。测量了78支血管丛,其长度范围为2000～4000μm 的占79.5%,依纵行小动脉的起源和行程可以断定其血流方向与其围绕的胆管内胆汁流方向相反。     

切割球囊与半顺应性球囊用于冠状动脉分叉病变预扩张的比较

文题释义：切割球囊：是一类将微切割技术和球囊扩张结合一起的特殊球囊,由一枚球囊组成,球囊外层表面上纵向装有三片或四片粥样硬化切开刀。在球囊未到达病变之前,刀片被紧密包绕在经过特殊折叠的球囊材料之内,不会损伤所过路径的正常血管。到达病变后,在扩张球囊时刀片伸出球囊外面,造成血管中膜的纵形切口。切割球囊适用于2-4 mm直径的血管,直径选择为其与血管直径之比不要超过1∶1,否则会造成内膜撕裂。目前切割球囊主要用在支架内再狭窄病变、开口病变、分叉病变、小血管病变和钙化病变。相对禁忌证为病变严重成角(>45°)、严重钙化、血栓及血管严重扭曲的病变。 紫杉醇药物涂层球囊：是一个由2部分组成的组合产品,一个标准的血管成形球囊导管来提供基础的输送装置,扩张靶向病变部位;另一部分是药物涂层,其在球囊表面的紫杉醇量为3 μg/mm²,该产品主要靠药物在血管内壁的释放发挥作用,可用于治疗小血管病变、分叉病变、部分冠状动脉血管原发病变,以及不能耐受或不适合长期服用抗血小板药物的患者。紫杉醇药物涂层球囊虽然能有效抑制血管平滑肌细胞再生,但不能有效抑制血管壁弹性回缩,后者在血管再狭窄中起着至关重要的作用。 背景：目前冠状动脉分叉病变治疗尚无高效统一的最佳方案,较多采用主支植入药物洗脱支架、分支用药物涂层球囊扩张的简单策略,但单纯直接的药物涂层球囊扩张不能克服血管壁弹性回缩难题,远期仍存在分支丢失的风险。 目的：比较切割球囊与半顺应性球囊用于冠状动脉分叉病变预扩张的疗效和安全性。 方法：选择2016年8月至2018年5月焦作市人民医院收治的冠状动脉分叉病变患者110例,其中男83例,女27例,年龄18-88岁,按照分层区组随机化原则分为观察组(n=55)和对照组(n=55)。两组均进行经皮冠状动脉介入治疗,观察组主支采用切割球囊预扩张后植入药物洗脱支架,分支采用切割球囊预扩张后行药物涂层球囊扩张;对照组主支采用半顺应性球囊预扩张后植入药物洗脱支架,分支采用半顺应性球囊预扩张后行药物涂层球囊扩张。术后即刻造影,判定主支、分支的前向血流TIMI分级及有无血管夹层发生;术前、术后即刻、术后6个月、12个月应用冠状动脉造影定量分析主支及分支血管参考直径、最小内径及狭窄程度;记录两组术后12个月内的主要心血管不良事件。研究已获得焦作市人民医院道德伦理委员会审核批准。 结果与结论：①术后即刻造影,观察组主支、分支的前向血流TIMI 3级达标率高于对照组(P=0.007,0.015),主支、分支的血管夹层发生率低于对照组(P=0.023,0.012),主支、分支的紧急靶血管重建率低于对照组(P=0.006,0.026);②观察组术后即刻、6个月及12个月的冠状动脉保持成功率高于对照组(P均 < 0.001);③术后即刻、6个月及12个月,观察组的主支、分支最小内径均大于对照组(P均 < 0.01),主支、分支内径狭窄程度均小于对照组(P均 < 0.05);④术后12个月内,观察组的主支、分支靶血管再狭窄率低于对照组(P=0.038,0.043),主要心血管不良事件发生率低于对照组(P=0.025);⑤结果表明,在适用主支病变植入药物洗脱支架、分支病变植入药物涂层球囊治疗冠状动脉分叉病变中,切割球囊预扩张较半顺应性球囊预扩张更加安全、有效,并能降低靶血管再狭窄率及主要心血管不良事件发生率。 ORCID: 0000-0002-6099-4241(晋辉) 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

Dose distributions in bifurcated coronary vessels treated with catheter-based photon and beta emitters in intravascular brachytherapy

The dose distributions in the bifurcated vessels treated with intravascular brachytherapyline sources are complicated and depend on the bifurcation geometry consisting of a main and a branch vessel at different angles. To investigate the dosimetric effects at the bifurcation, calculations were performed on branching vessels of various bifurcation angles ranging from 20 degrees to 90 degrees. Two catheter based delivery systems were considered in the calculations using a 40 mm long radioactive sources of 192Ir or 90Sr/Y. It was assumed that the bifurcated vessel was treated in twoseparate source insertions, once for the main vessel and later for the branch vessel. Calculations were performed for different values of source gap from 0 to 9 mm, at the junction of main and branch vessels. Our results indicate that main vessel always receives a higher dose (up to 200%) when the branch vessel is also treated. Hot spots at portions of the main vessel near the junction cannot be totally avoided without severely underdosing the branch vessel. For bifurcation angle greater than 45 degrees, a 4 mm source gap can almost ensure that overdosing of the main vessel does not exceed 60% and underdosing of the branch vessel does not exceed 10% for 192Ir. However, for 90Sr/Y, the same is not possible unless the bifurcation angle is larger than 70 degrees. Dose heterogeneity using 90Sr/Y is more sensitive to the value of source gap than 192Ir because 90Sr/Y source provides a sharper dose-fall-off than 192Ir. For both photon and beta emitters, there is no acceptable solution for bifurcation angles less than 30 degrees, where the activity of the line source has a uniform distributions. Appropriate choice of gap at the junction can only help to reduce either overdosing of the main vessel or underdosing of the branch vessel, but not both.     

Atherosclerosis in theHuman Common Carotid Artery. A Morphometric Study of 31 Specimens

The carotid artery bifurcation is of special interest to both the pathologist because of its frequent atherosclerotic depositions, and to the fluidmechanicist because of its complex flow properties. However, current knowledge is incomplete regarding the level and position of atherosclerotic plaques in the carotid bifurcation and their quantitative correlation with its geometry. The study presented here is intended to fill that knowledge gap and try to quantify the geometrical risk factors. During the post-mortem the arteries were excised and filled with a resin at the proper transmural pressure of 80mmHg. Thirty-one vessel casts of the carotid artery from twenty-three autopsied individuals were made. The vessel casts were used to measure several geometrical parameters. After fabrication of the vessel casts each artery was investigated according to pathomorphological procedure. An atherometric system (AS) indicating the level of atherosclerotic lesions was applied. The specimens were divided into three groups according to the level of atherosclerosis. The comparison was made between the level of wall alteration of the main branches of the carotid bifurcation (common, internal and external carotid branch), and between these three groups themselves. Further, we conducted a comparison of the averaged geometric parameters in different groups to define the correlations between atherosclerotic lesions and geometric parameters. The results show that the most advanced lesions (fibrous and severe plaques) with about 70% of all lesions were mainly found in the internal and the external carotid branches, compared with only 25% for the common carotid branch. The comparative analysis showed that a relatively high carotid sinus enlargement of >1.2 of the common carotid branch diameter is a most significant geometric risk factor among those investigated, whereas there was no correlation between branch angles and atherosclerosis. In conclusion, the quantification of atherosclerotic risk factors is very important in the investigation of atherosclerotic disease development.     

腹主动脉叉血流动力学边界元分析

本文利用边界元方法计算了腹主动脉叉。在动脉粥样硬化前后的血液流场、血管壁切应力等血液流体动力学特性,通过对动脉粥样硬化产生前后,左、右髂总动脉壁切应力的计算结果分析,对粥样斑块病变产生和发展的血液流体动力学原因做出了判断。结果显示:腹主动脉叉几何形状的不对称性导致分叉处血液流速、血管壁切应力分布的不对称,内侧壁切应力大于外侧壁,右髂总动脉内侧壁切应力大于左髂总动脉。动脉粥样硬化处由于血管腔变窄血液流速明显变大、切应力变大,容易使斑块表面撕裂出现组织增生,粥样斑块下游处血流速度、切应力减小,形成血液分离区,使血细胞聚集,造成动脉粥样硬化发展、加剧。     

A Novel Simulation Strategy for Stent Insertion and Deployment in Curved Coronary Bifurcations: Comparison of Three Drug-Eluting Stents

The introduction of drug-eluting stents (DES) has reduced the occurrence of restenosis in coronary arteries. However, restenosis remains a problem in stented coronary bifurcations. This study investigates and compares three different second generation DESs when being implanted in the curved main branch of a coronary bifurcation with the aim of providing better insights into the related changes of the mechanical environment. The 3D bifurcation model is based on patient-specific angiographic data that accurately reproduce the in vivo curvatures of the vessel segments. The layered structure of the arterial wall and its anisotropic mechanical behavior are taken into account by applying a novel algorithm to define the fiber orientations. An innovative simulation strategy considering the insertion of a folded balloon catheter over a guide wire is proposed in order to position the stents within the curved vessel. Straightening occurs after implantation of all stents investigated. The resulting distributions of the wall stresses are strongly dependent on the stent design. Using a parametric modeling approach, two design modifications, which reduce the predicted maximum values of the wall stress, are proposed and analyzed.     

Hemodynamics of Stent Implantation Procedures in Coronary Bifurcations: An <Emphasis Type="Italic">In Vitro</Emphasis> Study

Stent implantation in coronary bifurcations presents unique challenges and currently there is no universally accepted stent deployment approach. Despite clinical and computational studies, the effect of each stent implantation method on the coronary artery hemodynamics is not well understood. In this study the hemodynamics of stented coronary bifurcations under pulsatile flow conditions were investigated experimentally. Three implantation methods, provisional side branch (PSB), culotte (CUL), and crush (CRU), were investigated using time-resolved particle image velocimetry to measure the velocity fields. Subsequently, hemodynamic parameters including wall shear stress, oscillatory shear index (OSI), and relative residence time (RRT) were calculated. The pressure field through the vessel was non-invasively quantified and pressure wave speeds were computed. The effects of each stented case were evaluated and compared against an un-stented case. CRU provided the lowest compliance mismatch, but demonstrated detrimental stent interactions. PSB, the clinically preferred method, and CUL maintained many normal flow conditions. However, PSB provided about a 300% increase in both OSI and RRT. CUL yielded a 10 and 85% increase in OSI and RRT, respectively. The results of this study support the concept that different bifurcation stenting techniques result in hemodynamic environments that deviate from that of un-stented bifurcations, to varying degrees.     

Flow and stress characteristics in rigid walled and compliant carotid artery bifurcation models

Computer simulation of pulsatile non-Newtonian blood flow has been carried out in different human carotid artery bifurcation models. In the first part of the investigation, two rigid walled models are analysed, differing in the bifurcation angle (wide angle and acute angle bifurcation) and in the shape of both the sinus (narrow and larger sinus width) and the bifurcation region (small and larger rounding of the flow divider), in order to contribute to the study of the geometric factor in atherosclerosis. The results show a significant difference in the wall shear stress and in the flow separation. Flow recirculation in the sinus is much more pronounced in the acute angle carotid. An important factor in flow separation is the sinus width. In the second part of the study, flow velocity and wall shear stress distribution have been analysed in a compliant carotid artery bifurcation model. In the mathematical model, the non-Newtonian flow field and the idealised elastic wall displacement are coupled and calculated iteratively at each time step. Maximum displacement of approximately 6% of the diastolic vessel diameter occurs at the side wall of the bifurcation region. The investigation demonstrates that the wall distensibility alters the flow feld and the wall shear stress during the systolic phase. Comparison with corresponding rigid wall results shows that flow separation and wall shear stress are reduced in the distensible wall model.