用于心室辅助装置血流动力学性能评价的体外模拟循环系统技术进展

体外模拟循环系统(mock circulatory systems,MCS)是一个模拟人体循环系统血流动力学状态的试验平台,被广泛用于心室辅助装置和人工瓣膜等心血管人工器官的体外性能评价和生机电系统中的血流动力学响应研究。通过调整模拟心脏的驱动元件和模拟血管系统的集中参数元件,MCS可以模拟人体健康、运动、心力衰竭等不同生理状态的血流动力学特性。自1960年代至今,MCS研发目标从满足最基本的心室辅助装置或机械瓣膜的系统性能评价要求,已发展到能够复现局部重要器官的血流动力学状态。总结MCS目前的设计原则、系统搭建以及研究进展和未来展望。     

一种模拟血液循环系统实验研究

目的 研究一种能够准确复现人体血流动力学环境的模拟血液循环系统（mock circulation system,MCS）用于心室辅助装置（ventricular assist device, VAD）、人工心肺机等人工器官研发过程中的体外测试。方法 建立一套包括体肺循环的双心驱动MCS,基本涵盖心血管系统的主要生理特征及功能,其中对瓣膜和动脉的模拟提出采用硅胶材料制作的新方式。该系统可以通过调整控制系统参数或结构参数来模拟正常人体、心衰、瓣膜疾病、动脉硬化以及外周阻性变化等多种生理环境,并利用传感器与控制系统实现压力、流量的实时显示、控制和数据保存。结果 该MCS模拟正常人体和多种病症下的血流动力学环境均与人体实际情况基本一致。并且新的瓣膜和动脉模拟方式减小了压力波动,使模拟效果更好。在模拟心衰病症下使用航天泰心HeartCon型VAD接入系统,可以看到其血流动力学环境（主动脉压力、左心室压力、心排量等）均能恢复到正常范围。结论 该MCS能够准确复现多种生理状态下体肺循环的血流动力学环境,为VAD等人工器官的性能测试和控制策略的设计提供有效的实验平台。同时,采用硅胶材料制作瓣膜和动脉的模拟方式也可以作为MCS研究中的新思路进一步完善。     

心室辅助装置延时模式对心血管系统血流动力学的影响EI北大核心CSCD

双心室辅助装置(BiVAD)因多输入输出过程的相互作用,其植入相比左心室辅助装置更具挑战性。同时,因心室辅助装置(VAD)在临床上常工作于定转速(CS)模式,BiVAD面临由此引起的系统搏动性低及体循环与肺循环血容量不平衡等问题。本文提出一种缩短VAD支持时间的延时辅助方案,应用数值方法观察延时模式对心输出量、血流搏动性以及动脉瓣生理状态的影响,揭示系统的血液动力学变化规律。研究表明:与CS模式相比,本文提出的辅助方案通过延时设置可满足收缩期和舒张期内的最低灌注量要求,并能使保持关闭的动脉瓣恢复正常功能。主动脉瓣(AV)和肺动脉瓣(PV)开放比例随延时增长而上升,且流经AV/PV的血流量有助于左、右心血容量的平衡。此外,延时模式还可以提高动脉血流的搏动指数,有助于患者心室搏动功能的恢复。     

体外模拟心血管系统血液动力学性能分析

为研究人工心脏和心血管系统之间的血液动力学作用机制．根据弹性腔模型建立了一套能反映血液动力学特性的体外血液循环模拟实验装置，测试血液动力学参量与心室后负荷（即外周力R和动脉顺应性C）以及每搏心输出量Vs，心动周期T和心室收缩时间间隔Ts，前负荷等六个参量之间的相互关系．通过改变六个参量中的某一个参量而固定其余参量，测试这个参量对动脉血压及流量的影响情况。实验结果与生理情况和数学模型分析相符合。压力和流量波呈脉动性，与真实生理波形相似。整个模拟装置能够反映血液动力学特性。     

新型左室辅助装置——脉动导管式血泵

机械循环辅助装置是一种挽救生命的方法,严重心室衰竭而须手术的患者有必要进行短期机械循环辅助,以利于患者缓解病情而过渡到心脏手术。同时机械循环辅助也是药物治疗心衰的一种辅助治疗。由于此种心室辅助装置常用于心脏急救,所以要求此种装置的使用应简便省时,最低限度地减少手术操作。基于此种设想,最近研制了一种脉动导管或血泵(PUCA)。此种新型血泵由一个体外膜式泵与一个植入体内的带有活瓣的导管相连。导管经一个最易接近的动脉插入,其尖端可经主动脉置入左心室。膜式泵为气动或电液压驱动,将左室血液吸出,对心室进行去负荷,并将…     

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。     

模拟心血管系统装置的研制及其在血液动力学测试中的应用

为研究心血管系统血液动力学特性和评测人工心脏,本文根据弹性腔模型建立了一套能反映血液动力学特性的体外血液循环模拟实验装置,测试血液动力学参量与心室后负荷(即外周阻力R和动脉顺应性C)以及每搏心输出量Vs,心动周期T,心室收缩时间间隔Ts和前负荷等六个参量之间的相互关系,通过改变六个参量的某一个参量而固定其余参量,测试这个参量对动脉血压及流量的影响情况.实验结果与生理情况和数学模型分析相符合,整个模拟装置能够反映血液动力学特性.     

人工心脏泵辅助对左心室血流动力学影响的数值研究

目的采用数值模拟方法研究人工心脏辅助装置植入对左心室内血流动力学的影响。方法首先利用心血管集中参数模型获取了健康状态、心衰状态以及人工心脏泵辅助状态下收缩末期左心室三维几何模型,其中选取超弹性材料Ogden为心肌材料,以左心房压力,主动脉压力以及通过左心室容积计算获取的左心室壁面位移作为边界条件,利用CFD方法对上述三种情况进行左心室的数值模拟。同时对比了健康时的模拟结果和生理状态下的左心室压力,以及心衰和人工心脏泵辅助两种状态下的血流动力学指标的差别。通过左心室压力和流速等评价灌注和负荷的情况,通过壁面切应力和涡流,评价人工心脏泵辅助后的左心室血流动力学变化规律。结果健康状态下模拟的左心室压力与生理指标相符合。在心衰和人工心脏泵辅助状态下,收缩期内左心室压力与健康状态比分别降低了1718 Pa和8455 Pa,辅助后左心室最大压力下降速度高于心衰时。人工心脏泵辅助后,舒张期壁面切应力峰值由4.3 Pa降低至3.8 Pa,收缩期壁面切应力峰值由4.1 Pa降低至1.3 Pa,射血速度峰值由1.61 m/s降低至0.68 m/s,主动脉瓣开放时间由0.25 s增加至0.65 s,左室射血分数由43.6%增加至52.7%,心室底端漩涡持续时间由0.35 s增加至0.51 s,顶端漩涡出现血流分离。结论左心室压力对比表明本研究方法可以用来模拟左心室的行为。人工心脏泵辅助能够快速降低心室内压力和心室负荷,增加灌注时间,提高器官灌注,降低左心室壁面切应力以及提高左心室内血液流场的涡流强度,延长涡流持续时间。     

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     

各种辅助泵对心室功能恢复的影响

应用自制隔膜泵、非捕动流叶轮泵和捕动流叶轮泵,以及临床应用的美国Ｓａｒｎｓ转子泵分别在迷你猪和小公牛身上做左心室或双心室辅助试验。结果显示搏动流泵在自然心脏衰竭时能维持动物主动脉压的搏动特性,从而降低周身而增加血流循环流量,而叶轮泵及转子泵因没有瓣膜返流能提高动物主动脉舒张压,增加自 脏冠状动脉灌注,因此搏动流叶轮泵对于衰竭心脏功能的恢复,最为有利。     

A pulsatile control algorithm of continuous-flow pump for heart recovery

The intra-aorta pump is a novel continuous flow (CF) left ventricular (LV) device. According to literatures, the pulsatile flow LV device can provide superior LV unloading and circulatory support compared with CF LV assist devices at the same level of ventricular assist device flow. Therefore, a pulsatile control algorithm for the intra-aorta pump is designed. It can regulate the pump to generate pulsatile arterial pressure (AP) and blood flow. A mathematic model of the cardiovascular-pump system is used to verify the feasibility of the control strategy in the presence of LV failure. The surplus hemodynamic energy (SHE), pulsatile ratio (PR), and pulsatile attenuation index (PAI) are used to evaluate the pulsatility of AP and blood flow. The SHE is 8,012.0 ergs/cm(3) by using the pulsatile control strategy (PCS) compared with 5,630.0 ergs/cm(3) by failing heart without support. The PR is 0.302 in the PCS vs. 0.315 in failing heart without support. Meanwhile, the PAI is 85.9% in the PCS compared with 69.7% in failing heart without support. The results demonstrate that the presented control strategy can maintain the pulsatility of AP and blood flow. Moreover, the pulsatile controller provides notably LV unloading. To test the response of the controller to the change of blood demand of patients, another simulation is conducted. In this simulation, the peripheral resistance is reduced to mimic the status of a slight physical active; the Emax is increased to simulate the ventricular contractility recovery. The simulation results demonstrate that the proposed control strategy can automatically regulate the pump in response to the change of the parameters of the circulatory system. To test the dynamic character of the intra-aorta pump, an in vitro experiment is conducted on an in vitro experiment rig. The experimental results demonstrate that the intra-aorta pump can achieve the pulsatile pump speed calculated by the pulsatile controller. The PCS is feasible for the intra-aorta pump. As a key feature, the proposed control strategy provides adequate perfusion in response to the change of blood demands of patients, while restoring the pulsatility of AP and blood flow.     

Numerical Modeling of Hemodynamics with Pulsatile Impeller Pump Support

There is significant interest in the development and application of variable speed impeller-pump type ventricular assist devices designed to generate pulsatile blood flow. However, no study has so far been carried out to investigate the systemic cardiovascular response to various aspects of pump motion. In this article, a numerical model is constructed for the simulation of the cardiovascular response in the heart failure condition under representative cases of pulsatile impeller pump support. The native cardiovascular model is based on a previously validated model, and the impeller pump is modeled by directly fitting the pressure–flow curves that describe the pump characteristics. The model developed is applied to study circulatory dynamics under different degrees of phase shift and pulsation ratio in the pump motion profile. The characteristic variables are discussed as criteria for the evaluation of system response for comparison of the pulsatile flows. Simulation results show that a constant pump speed is the most efficient work mode for the rotary pump, and with the application of either a phase shift of 75% and a pulsation ratio of 0.5, or a phase shift of 42% and a pulsation ratio of 0.55, it is possible to generate arterial pulse pressure with the maximal magnitude of about 28 mmHg. However, this is achieved at the cost of reduced cardiac output and pump efficiency.     

The enabler cannula pump: a novel circulatory support system.

BACKGROUND: The enabler circulatory support system is a catheter pump which expels blood from the left or right ventricular cavity and provides pulsatile flow in the ascending aorta or pulmonary artery. It is driven by a bedside installed pulsatile driving console. The device can easily be implanted by a minimal invasive approach, similar to the Hemopump. PURPOSE: To demonstrate the hemodynamic performance of this new intracardiac support system. METHODS: In a series of 9 sheep, hemodynamic evolutions were recorded in various conditions of myocardial contractility (the non-failing, the moderately failing and the severely failing heart). Heart failure was induced by injection of microspheres in the coronary arteries. RESULTS: Introduction of the cannula through the aortic valve was feasible in all cases. Pump flow by the enabler was gradually increased to a maximum of 3.5 L/min. Diastolic (and mean) aortic blood pressure is significantly increased in the non-failing and moderately failing condition (counterpulsation mode). In heart failure, cardiac output is significantly increased by the pump (p < 0.0001). A drop in left atrial pressure (indicating unloading) is achieved in all conditions but reaches significant levels only during heart failure (p=0.0068). CONCLUSIONS: This new circulatory support system contributes to stabilization of the circulation in the presence of cardiac unloading. In heart failure it actually supports the circulation by increasing cardiac output and perfusion pressure.     

Hemodynamic modes of ventricular assist with a rotary blood pump: continuous, pulsatile, and failure

Pulsatile operation of rotary blood pumps (RBPs) has received interest due to potential concern with nonphysiological hemodynamics. This study aimed to gain insight to the effects of various RBP modes on the heart-device interaction. A Deltastream diagonal pump (Medos Medizintechnik GmbH) was inserted in a cardiovascular simulator with apical-to-ascending aorta cannulation. The pump was run in continuous mode with incrementally increasing rotating speed (0-5000 rpm). This was repeated for three heart rates (50-100-150 bpm) and three levels of left ventricular (LV) contractility. Subsequently, the Deltastream was run in pulsatile mode to elucidate the effect of (de)synchronization between heart and pump. LV volume and pressure, arterial pressure, flows, and energetic parameters were used to evaluate the interaction. Pump failure (0 rpm) resulted in aortic pressure drops (17-46 mm Hg) from baseline. In continuous mode, pump flow compensated by diminished aortic flow, thus yielding constant total flow. High continuous rotating speed resulted in acute hypertension (mean aortic pressure up to 178 mm Hg). In pulsatile mode, unmatched heart and pulsatile pump rates yielded unphysiologic pressure and flow patterns and LV unloading was found to be highly dependent on synchronization phase. Optimal unloading was achieved when the minimum rotating speed occurred at end-systole. We conclude that, in continuous mode, a perfusion benefit can only be achieved if the continuous pump flow exceeds the preimplant (baseline) cardiac output. Pulsatile mode of support results in complex pressure and volume variations and requires accurate triggering to achieve optimal unloading.     

A computer model of the pediatric circulatory system for testing pediatric assist devices

Lumped parameter computer models of the pediatric circulatory systems for 1- and 4-year-olds were developed to predict hemodynamic responses to mechanical circulatory support devices. Model parameters, including resistance, compliance and volume, were adjusted to match hemodynamic pressure and flow waveforms, pressure-volume loops, percent systole, and heart rate of pediatric patients (n = 6) with normal ventricles. Left ventricular failure was modeled by adjusting the time-varying compliance curve of the left heart to produce aortic pressures and cardiac outputs consistent with those observed clinically. Models of pediatric continuous flow (CF) and pulsatile flow (PF) ventricular assist devices (VAD) and intraaortic balloon pump (IABP) were developed and integrated into the heart failure pediatric circulatory system models. Computer simulations were conducted to predict acute hemodynamic responses to PF and CF VAD operating at 50%, 75% and 100% support and 2.5 and 5 ml IABP operating at 1:1 and 1:2 support modes. The computer model of the pediatric circulation matched the human pediatric hemodynamic waveform morphology to within 90% and cardiac function parameters with 95% accuracy. The computer model predicted PF VAD and IABP restore aortic pressure pulsatility and variation in end-systolic and end-diastolic volume, but diminish with increasing CF VAD support.     

Effective ventricular unloading by left ventricular assist device varies with stage of heart failure: cardiac simulator study

Although the use of left ventricular assist devices (LVADs) as a bridge-to-recovery (BTR) has shown promise, clinical success has been limited due to the lack of understanding the timing of implantation, acute/chronic device setting, and explantation. This study investigated the effective ventricular unloading at different heart conditions by using a mock circulatory system (MCS) to provide a tool for pump parameter adjustments. We tested the hypothesis that effective unloading by LVAD at a given speed varies with the stage of heart failure. By using a MCS, systematic depression of cardiac performance was obtained. Five different stages of heart failure from control were achieved by adjusting the pneumatic systolic/diastolic pressure, filling pressure, and systemic resistance. The Heart Mate II? (Thoratec Corp., Pleasanton, CA) was used for volumetric and pressure unloading at different heart conditions over a given LVAD speed. The effective unloading at a given LVAD speed was greater in more depressed heart condition. The rate of unloading over LVAD speed was also greater in more depressed heart condition. In conclusion, to get continuous and optimal cardiac recovery, timely increase in LVAD speed over a period of support is needed while avoiding the akinesis of aortic valve.     

Computational analysis of the effect of the control model of intraaorta pump on ventricular unloading and vessel response

The intraaorta pump is a novel left ventricular assist device (LVAD) whose hemodynamic effects on the circulatory system is unknown. This article aims to evaluate the different effects on the circulatory system supported by the intraaorta pump. In this article, the pump is controlled by three control strategies, including the continuous flow method, the constant rotational speed, and the constant pressure head. A cardiovascular pump system, which includes cardiovascular circulation, intraaorta pump, and regulating mechanisms of systemic circulation, has been proposed. Left ventricle pressure (LVP), end-diastolic volume (EDV), and left ventricular external work (LVEW) were used to evaluate the degree of ventricular unloading. The pulsatile index (PI), which is defined as a ratio of pulse pressure and mean arterial pressure (MAP), was used to evaluate the effect of the vessel response by three control strategies. The comparison results showed that LVP and EDV were lower than those measured before the intraaorta pump was implanted. For LVEW, the constant pressure head strategy provided a superior ventricular unloading compared with other strategies. Support of the pump led to the lower pulsatility by the three models. However, the PI of the constant pressure head was the most at 0.37. In conclusion, these results indicate that the intraaorta pump controlled by constant pressure head strategy provides superior ventricular unloading and pulsatility of the vessel.     

Computational analysis of the effect of the type of LVAD flow on coronary perfusion and ventricular afterload

We developed a computational model to investigate the hemodynamic effects of a pulsatile left ventricular assist device (LVAD) on the cardiovascular system. The model consisted of 16 compartments for the cardiovascular system, including coronary circulation and LVAD, and autonomic nervous system control. A failed heart was modeled by decreasing the end-systolic elastance of the ventricle and blocking the mechanism controlling heart contractility. We assessed the physiological effect of the LVAD on the cardiovascular system for three types of LVAD flow: co-pulsation, counter-pulsation, and continuous flow modes. The results indicated that the pulsatile LVAD with counter-pulsation mode gave the most physiological coronary blood perfusion. In addition, the counter-pulsation mode resulted in a lower peak pressure of the left ventricle than the other modes, aiding cardiac recovery by reducing the ventricular afterload. In conclusion, these results indicate that, from the perspective of cardiovascular physiology, a pulsatile LVAD with counter-pulsation operation is a plausible alternative to the existing LVAD with continuous flow mode. An erratum to this article can be found at