左心室辅助装置研究中的扫描电镜观察

作者运用扫描电镜分别对四只成品左心室辅助泵,和四只动物实验后的左心室辅助泵,以及若干特制标本的表面进行系统的观察。研究发现,血泵内表面的缺陷有气泡突起,气泡开口,入侵异物,和凝胶粒子等。这些表面缺陷是血栓形成的主要原因,但可以通过合理的工艺和严格的质量控制加以防止。经过质量控制后血泵,其内表面未见表面缺陷。动物实验后血泵内有不同程度的白色血栓和纤维旦的沉积。近期实验结果表明,由于表面缺陷得到控制,血泵抗血栓性能有显著提高。     

心室辅助装置的现状及问题

心室辅助装置是用来部分或全部替代心脏的泵血功能，维持良好全身循环状态的机械装置，在近３０年间得到了巨大的发展。本文简介了心室辅助装置的发展历史，主要介绍了心室辅助装置设计中的问题，现有装置的结构和类型及存在的溶血和血栓形成问题。     

心室辅助装置的现状及问题

心室辅助装置是用来部分或全部替代心脏的泵血功能、维持良好全身循环状态的机械装置，在近３０年间得到了巨大的发展。本文简介了心室辅助装置的发展历史，主要介绍了心室辅助装置设计中的问题、现有装置的结构和类型及存在的溶血和血栓形成问题     

采用永磁悬浮的永久性左心室辅助装置

研制出一台采用永磁轴承的左心室辅助装置（LVAD）。该装置包括一个定子和一个转子，采用径向驱动方式；转子包括驱动磁钢和叶轮，电机定子线圈和泵壳组成定子。装置设计采用了一种特殊结构的永磁轴承。转子的位置测量表明，转子稳定悬浮的前提条件是必须有较高的转速（大于3250r／min）且流量大于1L/min。用猪血为介质所做的液动力测试表明，当转速达到3500r／min～4000r／min时，血泵输出流量达到4L/min～6L/min，输出压力达到100mmHg。该装置重200g，最大处直径为40mm。     

基于电机参数的离心式左心室辅助装置流量估算方法

目的 针对苏州同心医疗器械有限公司研制的CH-VAD型血泵进行研究,利用血泵中可获得的电压、电流、转速、占空比以及流体的黏度作为输入,建立实时估算血泵流量的方法.方法 将血泵系统拆解为电机和离心泵两个模块单独进行分析.首先根据电机的电压、电流、转速以及占空比计算得到电机的输出力矩,然后通过实验测试在不同转速和黏度下流量...     

基于集中参数模型的左心室辅助装置血流动力学仿真

目的新一代植入式心室辅助装置(ventricular assist device,VAD)采用旋转式血泵(rotary blood pumps)技术,目前已成为治疗严重心力衰竭的重要手段,因而研究VAD与人体间的生理相互作用机制有着重要的意义。本研究通过在Matlab Simulink环境中建立人体心血管循环系统的集中参数数学模型,模拟左心衰患者在植入左心室辅助装置(left ventricular assist device,LVAD)后,循环系统的血流动力学特性。方法通过弹性腔和电路原理建立集中参数模型,主要包括心脏、肺循环、体循环、冠状动脉循环。调整模型的输入值使得模型的仿真结果符合设定的目标值。结果仿真结果证实LVAD可以使心衰患者的总心排量恢复正常,同时对于心脏有明显的除负荷效果、增加冠脉血流量并降低肺动脉楔压,因此可以缓解心衰末期患者重要器官供血不足、心肌缺氧以及肺水肿等并发症。同时通过改变左心室辅助装置的转速,末期左心衰患者可以恢复一定的运动能力。结论 CAMSIM集中参数模型符合人体血液循环特点。模型仿真结果证实了LVAD对心衰的辅助作用。     

左心室辅助装置技术现状及未来展望

介绍了临床应用的左心室辅助装置的类型和结构特点,分析了基于生理机制的血泵电机参数的血泵控制策略;提出基于多生理信号约束的控制策略控制血泵输出,易满足受体的需求。结合血泵系统现状,从血泵的结构、穿皮能量传递方式和控制策略等方面探讨今后的研究目标。     

左心室辅助装置与主动脉吻合角度对主动脉瓣膜影响的血流动力学研究

目的 探究左心室辅助装置(left ventricular assist device, LVAD)与主动脉吻合角度对主动脉瓣膜的血流动力学影响。方法 分别构建LVAD与主动脉吻合角度为45°、60°、90°的3个主动脉模型和主动脉瓣膜模型,搭建体外搏动台用于体外实验。运用粒子图像测速(particle image velocimetry, PIV)系统,选取心动周期中的3个时刻(T₁收缩峰值期,T₂瓣膜快速闭合时期和T₃舒张峰值期)探究主动脉瓣膜处血流动力学状态。结果 采用速度矢量、涡量、黏性剪切力指标评价LVAD吻合角度对主动脉瓣膜血流动力学的影响。瓣膜快速闭合时期,吻合角度增大时,瓣膜近壁面血流速度、平均涡量和最大黏性剪切力均增大。结论 吻合角度较低时,血流对主动脉瓣膜的冲击速度较小,瓣膜受到较小的剪切力,使瓣膜处于较好的血流动力学环境。研究结果为临床手术中吻合角度的选择提供参考。     

心室辅助装置的内皮化

由于供心的短缺及心脏移植的长期生存率并不理想，长期心室辅助成为终末期心衰病人的最好选择。然而，血栓栓塞仍然是长期心室辅助最主要的并发症之一。如何控制长期辅助循环过程中血液的激活，提高辅助循环装置的生物相容性是辅助循环装置发展需要解决的重要课题。本对心室辅助装置内皮化的提出、目前进展、理论基础、方法及其存在的问题作一综述。     

左心辅助循环后心肌功能恢复的预测研究

左心辅助装置 (left ventricular assist device,L VAD)作为一种重度心衰的抢救措施及等待心脏移植阶段的过渡支持 ,近年来已取得长足进步 ,临床应用的病例数不断增加 ,抢救了许多濒死患者的生命。患者是否可以撤离 L VAD,何时撤离 L VAD,目前主要依据患者心功能的恢复情况而定。能否在用 L VAD前通过测定一些简单的、无创伤的指标来预测患者的愈后 ,该用什么指标 ,这对于临床有着重要意义 ,然而这些问题尚未弄清楚。本文就该方面研究的近况作一综述     

心室辅助装置的内皮化

由于供心的短缺及心脏移植的长期生存率并不理想 ,长期心室辅助成为终末期心衰病人的最好选择。然而 ,血栓栓塞仍然是长期心室辅助最主要的并发症之一。如何控制长期辅助循环过程中血液的激活 ,提高辅助循环装置的生物相容性是辅助循环装置发展需要解决的重要课题。本文对心室辅助装置内皮化的提出、目前进展、理论基础、方法及其存在的问题作一综述     

一种经皮植入式左心辅助装置的泵流量测试

目的 研究设计一种能用于心血管急危重症的经皮植入式左心辅助装置（血泵）。方法 根据机翼理论,设计一种经皮植入的左心辅助装置,通过测量3种不同参数（叶片旋转角度、血泵出水口距离、血泵出水口长度）的血泵所能产生的流量,最终选择最优化的血泵设计。结果 经过简易流量测定装置测量,当血泵采取单叶设计,血泵叶片的旋转角度为720°时,或血泵出水口与叶片的距离为0 mm时,血泵出水口长度为4 mm时,血泵流量最大。结论 选择能产生最大流量的参数值,研制出一种可在体外正常运转的经皮植入式左心辅助装置,为最终研制一种可用于临床的经皮植入式左心辅助装置提供理论和数据支持。     

Importance of luxury flow for critically ill patients receiving a left ventricular assist system

The presence of a significant organ dysfunction does not immediately exclude patients from consideration for treatment with a left ventricular assist system (LVAS). However, in treating morbid circulatory shock patients with multiple organ failure, it is important to know the preoperative and postoperative factor or factors related to the recovery of the damaged organ function. In this study, we retrospectively analyzed patients receiving a LVAS at our institution and tried to determine the important factors related to the survival of patients with multisystem failure. Twenty-seven patients who underwent LVAS placement at Saitama Medical School Hospital between 1993 and 2003 were included in this study. The preoperative risk factors analyzed were renal dysfunction, respiratory dysfunction, hepatic dysfunction, the existence of active infection, and the combination of all four factors. As a postoperative factor, the pump flow index (mean LVAS pump flow during the first 2 weeks after LVAS surgery divided by the body surface area) was analyzed. None of the analyzed preoperative factors could predict survival after LVAS surgery, but a pump flow index of less than 2.5 l/min/m² had a significant relationship with death after LVAS surgery. Further analysis revealed that all the patients with a pump flow index of 3.0 l/min/m² or more could overcome preoperative organ dysfunction. Congestive heart failure patients with multisystem failure need luxury pump flow for successful LVAS surgery; this factor could be especially important in device selection and postoperative management.     

Fifteen-year experience with Toyobo paracorporeal left ventricular assist system

Our 15-year experience of the Toyobo paracorporeal left ventricular assist system (LVAS) at Osaka University Hospital was reviewed. In total, 61 patients underwent Toyobo LVAS implantation from January 1992 to August 2007. Their mean age was 38.1 ± 16.9 years. The etiologies of heart failure were idiopathic dilated cardiomyopathy in 35 patients, ischemic cardiomyopathy in 15, myocarditis in 5, secondary cardiomyopathy in 4, and others in 2. Preoperatively, intubation was required in 41 patients (67.3%), an intra-aortic balloon pump was required in 38 (62.3%), and extracorporeal membrane oxygenation was required in 30 (49.2%). Four patients underwent heart transplantation and 11 underwent LVAS removal. Of those 11 patients, 4 were subjected to emergent removal because of device complications and all of them died. Of the 7 patients that underwent scheduled LVAS removal, heart failure recurred in 2 patients and reimplantation was required. In terms of major device-related complications, cerebral hemorrhage occurred in 16 patients (26.2%), cerebral infarction in 19 (31.1%), mediastinitis in 10 (16.4%), and inflow/outflow cannula exit site infection in 19 patients (31.1%). The actuarial survival rate of the patients operated on in the last 5 years of this study was 66.3% at 6 months and 45.9% at 1 year. Although the survival rate of patients supported by the Toyobo LVAS has recently improved, the morbidity rate is significant. Considering the current severe shortage of heart donors in Japan, it is important to introduce more durable devices with fewer complications and to establish the strategies for using the LVAS as a bridge to recovery.     

Flow study on a newly developed impeller for a left ventricular assist device

 Nowadays, left ventricular assist devices are usually designed as high-speed, electric, rotary blood pumps. The pump drains blood from the left ventricular apex via an inlet cannula and ejects into the aortic root via an outlet conduit. To develop a high-performance pump, the present study utilizes partial differential equations to generate a surface representation of the impeller of the blood pump. Flow analysis around the impeller is performed by using the finite volume method to solve the fully incompressible three-dimensional Navier–Stokes equations along with the k-ε turbulence model. The numerical results highlight flow features in the end-wall region of the pump, namely the clearance leakage cross-flow, and the vortex associated with this leakage. These secondary flows induce major energy losses in the pumping device. On the test study, a test loop was proposed to measure the performance characteristics. It was shown that the design would provide a flow rate of 4.4 l/min with a pressure head of 122 mmHg. The DC motor power under these conditions was about 6 W and the rotational speed was 4500 rpm. Both the flow rate and head can satisfy the demand for the left artificial heart to work normally. Received: September 25, 2002 / Accepted: January 23, 2003 Acknowledgments National Science Council, R.O.C., grant number NSC 91-2213-E-218-018 supported this work.     

Effects of implantation on the mechanical properties of the polyurethane diaphragm of left ventricular assist devices

Tensile properties of blood pump diaphragms made from a segmented polyether polyurethane (Toyobo TM5) were studied after implanting in goats for variable periods of time up to 72 days. The implantation decreased the tensile strength and ultimate elongation at break, while the elastic modulus increased very slightly. These changes in the strength and ductility were primarily caused by the contact of material with blood rather than by the mechanical fatigue of material. Mechanical stability was greatly improved by removing residual oligomers from the material by a refining procedure. The refined polyurethane has characteristics favourable for blood pump applications.     

心室辅助装置引发血管性血友病因子损伤的检测方法研究

目的由于血液成分血管性血友病因子(von Willebrand factor,vWF)的机械损伤现象发现和研究较晚,至今仍然定义模糊且缺乏相关的评价标准,非常不利于心室辅助装置(ventricular assist device,VAD)的创新设计与发展。本文通过研究分析,提出检测vWF受高剪切应力损伤的实验方法。方法人血作为基础血样,离心式血泵BPX-80剪切前后的猪血作为测试血样,通过免疫印迹法,将电泳分离的vWF转移到膜上,然后用特异性抗体检测膜上vWF多聚体的分子量分布情况,根据vWF分子量的灰度值比值,定量分析vWF多聚体的机械损伤,整个实验过程包括制胶、电泳、转印、免疫反应和显色5部分。结果得到条带清晰完整且容易区分的vWF分子量分布图。其中健康人血vWF高分子量、中分子量、低分子量区域的灰度值比值与文献中健康人血vWF的实际比值相一致。BPX-80血泵剪切猪血中高分子量vWF与未经剪切的猪血高分子量vWF灰度值的比值随时间呈下降趋势,表明BPX-80血泵剪切对猪血中vWF的降解情况。结论成功设计并建立了vWF多聚体分析实验方法,为此后制定vWF机械损伤的标准化体外评价方案提供重要参考。