植入式左心辅助装置

到九十年代以后，非植入式左心辅助装置已逐渐发展成为植入式，且气能驱动已由电能驱动所代替。本文简介了左心辅助装置的发展状况，主要介绍了植入式左心辅助装置的结构及特点、材料及其处理、植入方式和目前存在的问题。     

植入式左心辅助装置

到九十年代以后，非植入式左心辅助装置已逐渐发展成为植入式，且气能驱动已由电能驱动所代替。本文简介了左心辅助装置的发展状况，主要介绍了植入式左心辅助装置的结构及特点、材料及其处理、植入方式和目前存在的问题。     

左心辅助装置中血泵的发展现状

1953年，John Gibbon开发了早期的体外循环机并利用它成功地进行了第一例心脏直视手术，对心脏外科的发展产生了巨大的影响，从此也揭开循环辅助和心室辅助发展的序幕.     

轴流泵在左心辅助装置中的应用

轴流泵在左心辅助装置中的应用北京心肺血管医疗研究中心─安贞医院蔺嫦燕左心辅助循环是通过一种辅助泵的装置，将左心的血液引流到泵内再注入主动脉系统，从而减轻左心室负担。采用这种血泵进行辅助循环时，通过左心室顺应性的改变和射血阻抗的降低，能明显改善左心室的...     

左心辅助泵体外测试的研究

制定系统、全面地评价连续流动式左心辅助泵的体外评价体系,研制用于轴流血泵体外测试的试验台,制定试验方法,使之稳定可靠地评价轴流血泵的设计与加工是否满足性能要求,指导动物实验与临床应用。根据连续流动式左心辅助泵的设计、制造和临床要求制定体外评价内容,按照评价内容设计制作适合于轴流式左心辅助泵结构特点的流体性能试验台、耐压试验台、寿命试验台和溶血试验台。实验分析结果显示,所制定的体外评价体系的评价内容全面,能比较完备地评价连续流动式左心辅助泵,并具有较高的精度与可靠性。     

左心辅助泵的制作及体外模拟实验

本实验表明了用浸渍成型法制作的气动隔膜式血泵工艺简单、易于改型,并对血泵泵壳和隔膜的厚度与强度、刚性之间的关系进行了探讨。由此制作出的血泵体外模拟实验测试结果满意、实验血泵产生的动脉腔压力波形接近生理状态,从而为以后的动物实验和临床使用提供了实验依据。     

Ⅰ型血泵左心辅助循环动物实验研究

为了对Ⅰ型血泵进行深入研究以便在此基础上进行改进，我们选择９只心脏正常犬进行左心辅助动物实验，以验证该泵的血液动力学输出性能、对心脏的辅助功能及对血液的破坏程度。在动物实验中，血泵放入胸腔内，进口通过静脉插管经左心房耳插入左心房，出口经过动脉插管插入升主动脉。输液、测试、辅助管路接通后，控制血泵的辅助流量为心输出量的２５～３０％左右。结果显示：１．辅助流量在５００～６００ｍｌ／ｍｉｎ时，主动脉收缩压可达１３０ｍｍＨｇ，证明Ⅰ型血泵输出性能满足辅助时生理血液动力学要求。２．辅助后，主动脉舒张压和心脏总输出量均升高，提示此血泵对冠状动脉血流量的增加及心脏泵血具有辅助功能。３．辅助４小时后，血浆中游离血红蛋白含量由２．４ｍｇ／ｄｌ升高到３．１ｍｇ／ｄｌ，纤维蛋白未发生明显变化，说明此血泵对血液有较轻的破坏     

成人左心辅助心电触发方式下辅助延迟时间的探讨

本文旨在寻找一个经验公式以有效地指导成人左心辅助装置触发延迟时间.目的:以R Ao代表心电QRS波峰点与主动脉瓣关闭结束的间隔时间,以RR代表RR间期,找出RR与R Ao的相关方程R Ao=A@(RR)n+B.通过加权平均法计算RR的平均值,再求出R Ao预期值,对R Ao做安全较正后,以此做为辅助的延迟时间.方法:选择14岁以上行升主动脉导管的成人患者,经筛选,测量877例心导管记录图中心电部分的RR间期以及与此心电对应的主动脉压力波形,测量主动脉下降波切迹与QRS波起始点间的间隔,以R Ao为因变量,以(RR)n为自变量,绘散点图,找出相关模型,并求出相关方程.结论:当心率小于120次/分时,相关系数为0.5066,回归系数为-0.0948,P值为1.968E 58;截距为0.655,P值为8.097E 109,相关方程为:R Ao=(-0.0948)RR 1/3+0.6551.     

气动式左心辅助泵气室密封工艺的改进

空气驱动式左心辅助泵血泵部分与气室部分之间的密封方法,一直是泵研制者关注的问题.广东省心血管病研究所研制的左心辅助泵(罗叶泵)由原来设计的螺栓密封改进为树脂螺纹套密封,泵体积在有效容积不变的情况下,外尺寸大大缩小,密封性能也大幅度提高.改进后的左心辅助泵通过了200多天的体外模拟试验及活体动物试验,结果显示泵的血流动力学性能良好、气动驱动性能也正常,性能达到设计要求.     

新型推板式左心辅助血泵的流场试验

报告了Z-4型推板式左心辅助血泵的结构以及进行流场试验的方法。试验结果表明，在充盈期，流体在心室内形成一个大旋涡，这个旋涡形成是以切线方向流入的模拟液与圆形血室内壁相互作用的结果，最大线速度(125cm／s)产生在进口管内瓣膜的大口一侧。在排血期，旋涡中心往出口管方向偏移，最大线速度(120cm／s)出现在出口管内。血室内流动状况良好，无滞流，无紊流，血液对血室内壁有良好的洗刷效应，血室内壁不易形成血栓，该血泵形状设计是比较合理的。     

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.     

Numerical simulation of left ventricular assist device implantations: Comparing the ascending and the descending aorta cannulations

In this work we present numerical simulations of continuous flow left ventricle assist device implantation with the aim of comparing difference in flow rates and pressure patterns depending on the location of the anastomosis and the rotational speed of the device. Despite the fact that the descending aorta anastomosis approach is less invasive, since it does not require a sternotomy and a cardiopulmonary bypass, its benefits are still controversial. Moreover, the device rotational speed should be correctly chosen to avoid anomalous flow rates and pressure distribution in specific location of the cardiovascular tree. With the aim of assessing the differences between these two approaches and device rotational speed in terms of flow rate and pressure waveforms, we set up numerical simulations of network of one-dimensional models where we account for the presence of an outflow cannula anastomosed to different locations of the aorta. Then, we use the resulting network to compare the results of the two different cannulations for several stages of heart failure and different rotational speed of the device. The inflow boundary data for the heart and the cannulas are obtained from a lumped parameters model of the entire circulatory system with an assist device, which is validated with clinical data. The results show that ascending and descending aorta cannulations lead to similar waveforms and mean flow rate in all the considered cases. Moreover, regardless of the anastomosis region, the rotational speed of the device has an important impact on wave profiles; this effect is more pronounced at high RPM.     

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     

主动脉内经皮左心室辅助泵出口处流场非定常模拟分析及其影响

目的:分析主动脉内经皮左心室辅助泵出口处的径向血流及其对主动脉内皮细胞造成损伤的可能性。方法:运用计算流体力学（CFD）对一款经皮左心室辅助泵在主动脉直径分别为20、30、40 mm 3种情况下进行非定常数值仿真,分析血泵出口处的流场分布。通过研究其速度、压力和剪切应力分布情况来分析血泵径向血流对主动脉血管内皮细胞的影响。结果:数据结果显示,血泵出口处的径向血流对3个模型额外增加的正应力分别为24、17、8 mmHg,近壁面剪切应力大于25 Pa的比例分别为19.3%、13.6%、3.0%。结论:实验表明,经皮左心室辅助泵的植入会增大主动脉压和近壁面剪切应力,而且主动脉直径越小,其效果越明显,因此对于主动脉直径偏小、患有高血压或动脉病变的患者应谨慎使用。     

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.     

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。     

20mL小儿罗叶泵的动物存活实验

目的 采用自行研制的20 mL小儿罗叶泵行动物存活实验,明确其对血细胞和重要器官的影响,探讨临床应用的可行性.方法 健康山羊6只,体重（18±3.3）kg.经左侧第5肋间进胸,以左室心尖及降主动脉的插管方式建立左心辅助循环.止血关胸,清醒后拔除气管插管,动物置于专用饲养笼内.辅助期间持续静脉给予肝素抗凝,维持激活全血凝固时间（activated clotting time,ACT）在180～250 s.经颈动、静脉置管监测中心静脉压和血压.在辅助前,辅助后1 h、3h、6 h、10 h、16 h、24 h及存活期间每24 h监测血浆游离血红蛋白,在辅助前及存活期间每24 h检测血常规、肝肾功能、凝血指标.实验结束时取动物心、肝、肾、肺观察病理变化.结果 开胸后插管时发生顽固性室颤死亡1只,其余5只成功进行存活实验,平均存活时间（79.8±60）h.其中因栓塞死亡1只,胸腔出血、肺部感染死亡1只,肝素连接管脱落出血致失血性休克1只,反复气胸、ACT过高致脏器出血1只.1只山羊在存活至预定的7 d时,再次麻醉插管,开胸撤离辅助装置,关胸后顺利拔除气管插管,动物存活.辅助过程中肝素抗凝剂量25～35u/（kg＊h）,所维持的ACT具足够的抗凝效果.中心静脉压、平均动脉压、肝肾功能在辅助前后无明显变化.血浆游离血红蛋白由辅助前的（2.227±1.321）mg/dL升高到辅助72h的（8.873±2.510）mg/dL,二者相比有统计学差异,但在正常生理值范围内.除第1例因抗凝不足产生肾栓塞外,其余4例心、肝、肾、肺的病理检查均无栓塞.结论 20mL小儿罗叶泵血液相容性好,对肝肾功能无不良影响,具备用于临床的条件.     

Long-distance transportation of patients with a paracorporeal left ventricular assist system

In Japan, the heart transplantation program is specialized in only three institutions in Osaka and Tokyo. Therefore, a patient must be transferred to these hospitals for extended treatment, regardless of the distance. Trans-portation of the patient with a paracorporeal left ventricular assist system (Toyobo LVAS) is difficult because of its extremely large consumption of electric power. We planned to transfer a patient with a Toyobo LVAS for 600 km, but the patient was not transferred because he had a stroke. In order to find the best transportation method, various possi-bilities are evaluated; special ambulance car, Shinkansen (Super express train), fiexed-wing aircraft, medium-sized helicopter (belonging to private company or public aviation corps), and large helicopter (belonging to the Self-Defense Force). The special ambulance car the medium-sized helicopter may not be able to provide a stable electric power supply. There is a connecting traffic problem with the Shinkansen and the aircraft, depsite their sufficient electric power supply. The large Self-Defense Force helicopter seems to be the best option for us. Some aspects of the logistics and complexity of long-distance transportationare also commented on.     

Development of Terumo implantable left ventricular assist system (T-ILVAS) with a magnetically suspended centrifugal pump

The research group of Terumo, NTN, and the Setsunan University have been developing an implantable left ventricular assist system (T-ILVAS) featuring a centrifugal blood pump with a magnetically suspended impeller (MSCP). The present study describes recent progress in the development of the T-ILVAS, focusing on ex vivo and in vivo evaluations of the prototype MSCP. The MSCP is composed of four parts: a magnetic bearing, an impeller, a housing, and a DC burshless motor. The impeller is suspended by a magnetic bearing, thus providing contact-free rotation of the impeller inside the pump. The prototype MSCP was placed paracorporeally in three sheep and implanted intrathoracically in two sheep to evaluate its long-term durability and nonthrombogenicity. One sheep implanted ex vivo with the paracorporeal MSCP (Model I) survived for 864 days without any mechanical failure or thromboembolic complications, and with negligible hemolysis. The implantable Model II pump was evaluated ex vivo in two sheep and intrathoracically implanted in one sheep. These experiments were terminated 70, 79, and 17 days after implantation due to mechanical failure caused by blood leakage through the intrahousing connector of the Model II pump. However, there was no intradevice thrombus formation in any of the retrieved pumps. The dual connector system was then introduced to the Model II pump (the modified Model II), and the pump was intrathoracically implanted in a sheep. The sheep survived for more than 14 months without major complications, and the study is being continued. The preliminary chronic animal experiments demonstrated improved durability and nonthrombogenicity of the MSCP, with a low hemolysis rate for up to 864 days. Thus, the MSCP has significant potential for longterm application as an implantable circulatory assist system. Further developments toward a totally implantable system, including an implantable controller and a transcutaneous energy/information transfer system, are under way.