主动脉出口血压对左心室血流特性的影响

采用Mimics对心脏进行三维重构,用3-matic进行模型优化以及模型误差分析,对左心室室壁运动做速度分布假设,基于UDF宏文件对左心室室壁运动编写程序,将血液视为非牛顿流体,采用动网格技术研究不同血压对左心室血液流动的影响。模拟发现当左心室收缩时,压力梯度明显,内部压力减小。当左心室舒张时,内部压力逐渐增高。二尖瓣口处的速率先增大后减小。血压升高,左心室内剪切应力持续增大,极易破坏红细胞结构,产生溶血现象,导致心脏功能紊乱。     

主动脉瓣狭窄对左心室血流特性的影响

基于CT断层扫描数据,对心脏左心室进行三维重构和模型优化。结合心肌壁面的运动特性,建立左心室几何模型过流边界运动的数学模型。通过水力半径表征主动脉瓣的狭窄程度,采用动网格技术研究主动脉瓣狭窄对左心室血液流动的影响。研究发现不同程度主动脉瓣狭窄时,水力半径与主动脉瓣狭窄程度负相关,出口面积减小,收缩期出口处速度与压力升高,剪切应力增加。舒张期,速度与压力出现先增大后减小的规律。当水力半径较小时,左心室瓣膜处剪切应力较大,收缩初期剪切应力最大为0.81 Pa。通过动态模拟对心脏的仿真研究,为后续心脏的研究提供重要的参考价值。     

人体心脏左心室的超声三维重建及临床意义探讨

目的通过心脏超声心动图检测到的数据,对人体心脏的左心室三维重建技术及其临床教学与应用进行探讨;为心脏疾病的影像学诊断和外科手术提供三维解剖学辅助依据。方法将心脏超声心动图检测到的左心室20个部位心肌厚度所得数据输入ACCESS数据库,经简单统计分析、数据整理,运用AutoCAD 2000 设计软件的VBA二次开发,调用。数据进行建模、构造实体、平滑处理和三维显示等步骤,完成对心脏左心室结构的三维重建。结果本研究较直观地重建出了心脏左心室结构,重建的结构能够以左前半、左后半心室以及左心室的全心室结构模型方式显示,可显示左心室内部结构的空间位置和心室内壁的实际厚度,并可在三维空间位置上绕任意轴旋转任意角度显示。结论重建出的三维图像清晰平滑地显示了左心室内部和整体的结构,在保留二维超声成像所有信息的同时,提供了形象直观的三维立体图像,实现了心脏的三维可视化;并有助于心脏疾病的定性、定位及定量诊断。     

人体左心室复合材料有限元机械模型的建立

人体心脏通过电兴奋引起的心肌收缩实现泵血功能，而心肌的力学特性高度依赖于肌纤维旋向。根据肌纤维结构和复合材料理论建立了人体左心室的三维有限元机械模型，并讨论了心电兴奋力及后负荷的计算问题，最后仿真研究了在正常心脏兴奋传播过程中左心室在载荷作用下的力学响应，并与磁标记的MR成像结果及其他有关模型进行了比较。研究结果表明该模型可用于探讨心脏的机械功能和生理病理机制，为建立具有电生理及力学性能的虚拟心脏奠定了基础。     

用于评价心脏功能的计算生物力学

心脏是维持血液在体内循环的重要器官之一 ,从力学的角度来 ,其泵血功能对定量或客观提供各种心疾患的诊断信息是极为重要的。在这种背景下 ,为了对各种心疾患提供定量且客观的诊断信息 ,开发了采用三维有限元法评价心脏左心室力学功能的数字模拟系统及其图像显示系统。为了能分析三维电刺激传导系统的影响、三维复杂分布的心肌纤维的构造及由此而产生的三维应力及变形分布等 ,系统引入了三维有限元法。研究所采用的数字模拟器由左心室有限元模型及与此相关的循环系统模型构成。在左心室三维有限元模型中引入了心肌的力学特性模型、电刺激传…     

013 用于评价心脏功能的计算生物力学

[日]/Sawaki K…∥BME.－2000，14(10).－28～30 心脏是维持血液在体内循环的重要器官之一，从力学的角度来，其泵血功能对定量或客观提供各种心疾患的诊断信息是极为重要的。在这种背景下，为了对各种心疾患提供定量且客观的诊断信息，开发了采用三维有限元法评价心脏左心室力学功能的数字模拟系统及其图像显示系统。为了能分析三维电刺激传导系统的影响、三维复杂分布的心肌纤维的构造及由此而产生的三维应力及变形分布等，系统引入了三维有限元法。研究所采用的数字模拟器由左心室有限元模型及与此相关的循环系统模型构成。在左心室三维有限元模型中引入了心肌的力学特性模型、电刺激传导路径及心肌纤维的分布模型。在进行模拟时，首先要确定循环系统的参数及心肌的杨氏模量和泊松比等材料特性，并将这些值参照以往研究中所使用的参数调整到正常心脏的心内压-容积关系。为了能得到更接近实际心脏的变形情况，应在健康志愿者心脏的短轴断面MRI图像的基础上加以重叠，作成左心室实际形状数据。此外，由于在分析中是以舒张末期为计算的始点，因此，在制作左心室实际形状数据时，应使用舒张末期的MRI图像。应用这一系统可替代部分基础医学中的动物实验等多种实验，且可预测假设疾患心尤其是心肌肥大(HCM)的人类心脏左心室壁内应力及变形分布，并通过与MR tagging法获得的室壁变形信息进行比较，定量评价疾患心的心肌纤维收缩功能。 (刘士新摘)     

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。     

三维重构展示类胚体样结构

背景：干细胞因其具有增殖能力及分化潜能,被认为是实施细胞治疗的重要细胞而被广泛研究。实现干细胞与组织三维结构的展示与分析,对阐明干细胞增殖与分化的机制有重要意义。 目的：探讨实现对经分化的类胚体样组织结构进行三维重构展示的方法。 方法：以来源于骨骼肌干细胞经诱导具有三维立体结构的类胚体作为实验对象,利用多色免疫荧光染色结合Z轴连续图像采集和三维重构技术,对经分化的类胚体样组织结构进行三维重构展示。 结果与结论：利用实验方法可实现对类胚体样组织结构进行三维重构,经重构的三维模型可实现任意角度旋转,利用不同荧光通道iso-surface处理后,选择分别显示不同颜色功能或任意横断面展示功能,即可展示心脏特异性肌钙蛋白Ⅰ阳性组织结构与细胞核的空间位置关系,并清晰展示在经分化形成类心肌组织的结构中存在细胞核。提示利用该技术,可对经分化的类胚体样组织结构进行三维重构展示及测量。     

人体左心室三维有限元模型构建及流-固耦合动力学分析

有限元分析是研究心血管动力学问题的重要手段。本文基于中国数字人体心脏断层解剖图像,采用Visu-al C++可视化工具包对心脏外形及内腔结构进行三维重建,进一步基于结构模型构建了左心室、血液耦合有限元模型。在通用有限元分析软件ANSYS环境下使用双向流-固耦合方法对心脏灌注期心室壁受力与血液流动过程进行了动力学仿真。仿真结果成功实现了对心脏灌注期心室两阶段充盈过程中室壁应力与血液流体动态特性的定量分析。本研究提供了一种基于二维医学图像信息构建心室有限元模型,并进行心室血液流体力学模拟的新方法,为心脏生理及病理过程的定量有限元分析提供了一套可行的技术方案。     

心梗患者血流动力学改变对左室重构的影响

目的和方法 :左心室重构是慢性心肌缺血 ,特别是心肌梗塞后 ,心肌发生的进行性病理生理学过程。这一变化不仅导致心室构型、容积及心肌舒缩功能的改变 ,同时也引起心腔内血流动力学的异常 ,而血流的严重紊乱又会促进左心室重构而使心功能恶化 ,既往文献对此涉猎较少 ,本文通过采用彩色多普勒血流显像 (ＣＤＦＩ)联合脉搏多普勒超声心动图 (ＰＤＥ)技术 ,对 2 2例陈旧性心肌梗塞 (ＯＭＩ)患者和 2 0例正常人左心腔内不同部位血流状态及其速度分布进行了定性和半定量分析 ,探讨心肌梗塞后左心室腔内血流动力学的改变及其对左心室重构的影响。…     

Physical and computer modelling of blood flow in a systemic-to-pulmonary shunt

The aim of this work was the application of computer and physical in vitro simulation methods for estimating surgery procedure hemodynamics. The modified Blalock-Taussig (mB-T) palliative surgical procedure is performed to increase the pulmonary blood flow in children with congenital heart defects. Such a systemic-to-pulmonary shunt yields substantial modification in the blood flow within the large blood vessels. The objective of the present study was to investigate basic characteristics of the flow, flow pattern and pressure-flow efficiency, before and after opening of the mB-T graft. Methods: The model was based on the vessel geometry obtained from the Visible Human Project and included the arch of aorta, the three arteries branching from the arch, the pulmonary trunck, and the left and right pulmonary arteries. The graft was added between the left subclavian artery and the left pulmonary artery. The glass model of the vessels was produced and investigated in a physical model of the cardiovascular system with an artificial ventricular device as the blood pump. Flow rate and hydrostatic pressure were measured at the inlet to and outlets from the glass model and in a few points within the system. Laser flow visualization was also performed. Computer simulations were done using the boundary conditions from the physical model. Results: The opening of the mB-T graft changed flow distribution in all branches (including inflow). A complex flow pattern with large eddies and channelling of the flow in the vicinity of the graft and within it was observed in flow visualization and in computer simulations. Because of that complexity the local measurements of hydrostatic pressure at the vessel wall could not predict the average flow rate. The reversed flow in the graft was observed during the systole. Conclusions: The complex flow pattern developed in the physical model of the mB-T graft. The channelling of the flow and the formation of large eddies may yield high shear stress and modify blood properties. The rigid wall model can describe only some flow characteristics observed in vivo. Computer simulation is a very fast and accurate method which permits earlier qualification of cardiac surgeons on how to change cardiac vascular blood flow after operations.     

应用CT评价急性肺栓塞对家兔心功能的影响*

 [摘要] 目的:建立家兔急性肺栓塞（APE）模型,应用64排心电门控CT评价APE对心脏功能及结构的影响并探讨其机制。方法: 7只健康日本大耳白兔通过自体血栓注入法复制APE模型,分别于APE前及APE后2 h、4 h、8 h行64排双源心电门控CT肺动脉造影（CTPA）,通过CT图像重建,应用Volume 及View软件计算出APE前后左心室和右心室收缩末期容积（LVESV和 RVESV）、舒张末期容积（LVEDV和 RVEDV）、收缩末期内径（LVESD和 RVESD）及舒张末期内径（LVEDD和 RVEDD）,CT图像寻找肺动脉血栓并与解剖观察对比分析。结果: APE后2 h、4 h及8 h各时点RVEDV、RVESV、RVEDD及RVESD明显增加（P<0.01）,LVEDV及LVEDD明显减少（P<0.05）,左、右心室每搏输出量（LVSV 和RVSV）减少（P<0.05）。64排CT肺动脉成像显示较大的肺动脉血栓表现为偏心充盈缺损,而较小的动脉血栓为肺动脉分支缺损;与解剖比较,发现较大动脉血栓的准确率达100%。结论: 家兔APE后右心室明显扩大,左、右心功能均受损,2 h后维持相对稳定。64排双源心电门控CT扫描对于判断APE后心功能障碍具有重要价值。     

Measurement of QRS duration for biventricular pacing optimization

Optimization of left ventricular pacing site or interventricular pacing delay improves the efficacy of biventricular pacing (BiVP). Cardiac output (CO) based optimization, however, is invasive and slow. QRS duration (QRSd) is noninvasive and responds rapidly. Accordingly, we investigated the utility of QRSd for BiVP optimization in a model of acute right ventricular (RV) pressure overload. In seven anesthetized open-chest pigs, BiVP was implemented with right atrial and RV pacing wires. A 6-electrode array was placed behind the LV. Heart block was established by alcohol ablation. The pulmonary artery was snared to double peak RV pressure. Fifty-four combinations of left ventricular pacing site and interventricular pacing delay were tested in random order over 30-second intervals. QRSd was assessed from electrocardiogram lead II, CO from aortic flow probe, and ventricular function from micromanometers. Comparisons were made with the Pearson's correlation coefficient (r). QRSd narrowing was associated with improved RV function and transseptal synchrony, but correlation with CO was poor. Additionally, QRSd averaged over the last 20 cardiac cycles in each interval was compared with values averaged over successive cardiac cycles following each reprogramming. Seven cardiac cycles after reprogramming, the average r-value went above 0.90 and plateaued. QRSd-based optimization merits further study during BiVP in patients with congestive heart failure.     

Resting values of left ventricular work to coronary blood flow ratio in rats exposed to intermittent high altitude hypoxia and swimming

Summary Total hemodynamic values and left ventricular blood flow were studied using Sapirstein's method of ⁸⁶Rb uptake in female rats 24 h after a last exposure to high altitude. A simulated altitude of 1350 m was used, initial exposure being for 30 min, gradually increased by 30 min daily up to 330 min daily for 5 days a week; the total number of exposures was 32. In another animal group the hypobaric exposure was combined with swimming in water at 37 C.In both experimental groups the cardiac output and stroke volume increased, and in rats undergoing swimming the total peripheral resistance decreased as well.In the rats exposed to intermittent hypoxia only, left ventricular blood flow increased by about the same proportion as the cardiac output. The ratio of left ventricular work to coronary blood flow was significantly increased.In rats exposed to the combined influence of hypoxia and swimming, the increase in left ventricular blood flow did not match either the increase in cardiac output, or the weight gain of the left ventricle. The ventricular work to coronary blod flow ratio was the same as in controls.     

Large-Scale 3-D Geometric Reconstruction of the Porcine Coronary Arterial Vasculature Based on Detailed Anatomical Data

The temporal and spatial distribution of coronary blood flow, pressure, and volume are determined by the branching pattern and three-dimensional (3-D) geometry of the coronary vasculature, and by the mechanics of heart wall and vascular tone. Consequently, a realistic simulation of coronary blood flow requires, as a first step, an accurate representation of the coronary vasculature in a 3-D model of the beating heart. In the present study, a large-scale stochastic reconstruction of the asymmetric coronary arterial trees (right coronary artery, RCA; left anterior descending, LAD; and left circumflex, LCx) of the porcine heart has been carried out to set the stage for future hemodynamic analysis. The model spans the entire coronary arterial tree down to the capillary vessels. The 3-D tree structure was reconstructed initially in rectangular slab geometry by means of global geometrical optimization using parallel simulated annealing (SA) algorithm. The SA optimization was subject to constraints prescribed by previously measured morphometric features of the coronary arterial trees. Subsequently, the reconstructed trees were mapped onto a prolate spheroid geometry of the heart. The transformed geometry was determined through least squares minimization of the related changes in both segments lengths and their angular characteristics. Vessel diameters were assigned based on a novel representation of diameter asymmetry along bifurcations. The reconstructed RCA, LAD and LCx arterial trees show qualitative resemblance to native coronary networks, and their morphological statistics are consistent with the measured data. The present model constitutes the first most extensive reconstruction of the entire coronary arterial system which will serve as a geometric foundation for future studies of flow in an anatomically accurate 3-D coronary vascular model.     

Computer-controlledin vitro model of the human left heart

The decision for surgical intervention in the treatment of stenosis and for regurgitation of the mitral valve demands an objective and quantitative evaluation of the severity of mitral valve disease. The availability of ultrasound techniques capable of analysing flow velocities across valves and to produce representative images of valve orifices has increased the interest in the hydraulics of cardiac valves. To isolate and study the determinants of transmitral flow, an in vitro model of the human left heart was built. From the model it is possible to differentiate the influence of the different determinants of left heart performance on transmitral flow: preload, compliance of the left atrium and ventricle, peripheral resistance (afterload) and heart rate. The mechanical part of the model consists of a reservoir connected to an elastic closed circuit (Latex pulmonary veins, left atrium, left ventricle and aortic arch) with replaceable mitral and aortic valves. The electronic part of the model drives and controls the hydraulic part, allowing the independent regulation and monitoring of left atrial and left ventricular pressures p, volumes V and 'pV-loops' throughout the cardiac cycle at different cardiac rhythms. Left atrial filling pressure and aortic resistance are variable in a controlled fashion. Echo-Doppler study of the mitral valve and the transmitral valve flow is possible both from an atrial and a ventricular window in the model. This technical note describes the model.     

Myocardial hemodynamics, physiology, and perfusion with an axial flow left ventricular assist device in the calf

The Jarvik 2000 axial flow left ventricular assist device (LVAD) is used clinically as a bridge to transplantation or as destination therapy in end-stage heart disease. The effect of the pump's continuous flow output on myocardial and end-organ blood flow has not been studied experimentally. To address this, the Jarvik 2000 pump was implanted in eight calves and then operated at speeds ranging from 8,000 to 12,000 rpm. Micromanometry, echocardiography, and blood oxygenation measurements were used to assess changes in hemodynamics, cardiac dimensions, and myocardial metabolism, respectively, at different speeds as compared with baseline (pump off, 0 rpm) in this experimental model. Microsphere studies were performed to assess the effects on heart, kidney, and brain perfusion at different speeds. The Jarvik 2000 pump unloaded the left ventricle and reduced end-diastolic pressures and left ventricular dimensions, particularly at higher pump speeds. The ratio of myocardial oxygen consumption to coronary blood flow and the ratio of subendocardial to subepicardial blood flow remained constant. Optimal adjustment of pump speed and volume status allowed opening of the aortic valve and contribution of the native left ventricle to cardiac output, even at the maximum pump speed. Neither brain nor kidney microcirculation was adversely affected at any pump speed. We conclude that the Jarvik 2000 pump adequately unloads the left ventricle without compromising myocardial metabolism or end-organ perfusion.     

缬沙坦治疗高血压病并逆转左心室肥厚改善心功能的临床研究

目的评估缬沙坦治疗高血压病的降压效果、安全性与逆转高血压心肌肥厚和改善心功能的疗效。方法以氨氯地平为对照药物，在老年性轻、中度高血压患者中进行随机、平行对照的临床研究。结果缬沙坦组患者治疗4周总有效率为60．8％（45／74），降压幅度15．6／10．9mmHg；治疗24周后总有效率为78．4％（54／74）．降压幅度21．1／17．9mmHg。缬沙坦组治疗24周后在逆转高血压心肌肥厚中取得满意的疗效，能显著逆转左室肥厚（LVH），左室后壁厚度（PWT），室间隔厚度（IVST），降低左室重量指数（LVMI），且缬沙坦组能有效地改善心功能．经治疗后患者的心脏每分输出量（CO）、左室射血分数（LVEF）、舒张早期与舒张晚期峰值流速的比值（E／A）、E峰减速度（Ede）均不同程度得到改善；缬沙坦组患者血尿酸、C-反应蛋白较治疗前明显下降，不良反应率为8．1％．主要是面红、头昏及心悸。心率、血生化、肝肾功能无明显变化。结论缬沙坦降压疗效好，且能逆转左心室肥厚，改善心功能，不良反应少，可作为治疗老年性轻、中度高血压伴左心室肥厚的一线药物。     

Numerical comparison of hemodynamics with atrium to aorta and ventricular apex to aorta VAD support

We report the first attempt to study with numerical methods ventricular assist device (VAD) models and the effects of various inlet VAD cannulations, coupling physical explanations and numerical investigation conclusions with clinical research results. We compared the hemodynamic response with VAD support by using two distinct VAD-inlet cannulation configurations: left atrium to aorta and left ventricular apex to aorta. Impeller pump and displacement pump VADs are considered. Constant VAD flow rate and counterpulsation motion models are simulated. The native cardiovascular system is modeled using the concentrated-parameter method by considering the flow resistance, vessel elasticity, and inertial effect of blood flow in cardiovascular system individual segments. Impeller and displacement pump dynamic models are represented by corresponding inlet and outlet flow rate changes in the VADs. Results show that the two VAD inlet cannulation configurations produce similar cardiac response (flows, pressures, volumes), except that when the VAD flow approaches the 100% assisting condition, the peak left ventricular systolic pressure and diastolic volume increase slightly in the left atrial cannulation, whereas they drop markedly in the left ventricular apex cannulation, suggesting increased ventricular wall tension and ventricular dilatation in the left atrial cannulation and that hemodynamically the left ventricular apex cannulation is more advantageous.