小地老虎成虫循环系统形态的初步研究

本文对小地老虎Agrotis ypsilon 成虫循环系统的形态作了初步研究,表明背血管由6个心室的心脏和倒V形的胸部大血管及头部分支的大血管组成.中胸辅搏动器很发达,与大血管的腔直接相连,具有一个小盾片腔前半部的肌肉搏动膜.后胸辅搏动器很小,与背血管无直接通道,具有一个没有肌肉的搏动膜.腹膈显著,具有翼肌.还描述了心脏和辅搏动器的搏动情形.     

电刺激提高骨骼肌微纤维致动器致动性能

生物混合致动器是生物混合机器人的重要部分,该研究利用可光交联水凝胶(GelMA)作为小鼠成肌细胞C2C12细胞的细胞间基质,制作了一种直径为500 μm的微纤维致动器,并探究长时间电刺激对微纤维中C2C12细胞分化及致动能力的影响。该研究利用不同电压的方波脉冲信号在细胞分化期间对细胞进行每天15 min的电刺激,同时利用刚性支架固定微纤维以保持其方向与电场方向一致,并对微纤维施加30%机械拉伸。为表征电刺激对细胞分化的影响,利用ImageJ软件统计肌管长度、宽度与取向角,利用肌球蛋白重链(MHC)荧光染色表征其肌球蛋白重链表达,利用ANSYS有限元仿真计算致动器主动张力。结果表明,该微纤维致动器适合C2C12细胞生长并使其分化形成可收缩的骨骼肌,通过分化期间的长时间电刺激可有效促进C2C12细胞的分化、增大骨骼肌中肌管尺寸并提高微纤维致动器致动性能。其中18 V的电刺激效果最为显著,能使肌管长度有效提高30%,肌管宽度提高24%,肌管主动张力提高198%,使其达到0.21 μN。含有性能增强的骨骼肌的微纤维致动器可进一步应用于生物混合机器人组装领域,在药物筛选和骨骼肌再生等基础研究领域...     

酒石酸锑钾对兔心室神经介质含量的影响

前文报导,在麻醉兎观察酒石酸銻鉀(簡称銻鉀)对电致心室顫动的影响实驗中,发現在实驗后期,大剂量銻鉀本身也能产生心室顫动,而这种銻致性心室顫动能被預先切断交感神經或利血平化所防止。本文采用与前文相同的实驗模型和条件,对家兎心室內儿茶酚胺含量进行了生物测定。发現盐水对照组心室儿茶酚胺含量平均为1.13±0.06微克/克。电刺激对照組为1.72±0.45,虽与盐水对照组相比在統計学上差別不显著,但波动較大。在电刺激加銻鉀组中,銻鉀能显著降低全部动物的电致顫阈,稍加速心率,并使6/11兎出現銻致性心室顫动,心室儿茶酚胺含显著减少至0.65±0.05。单注射銻钾組心肌儿茶酚胺含量平均为0.47±0.08,較盐水对照組显著减少,但与电刺激加銻鉀组差別不显著。利血平化(0.1毫克/公斤/天,共2次)后,兎心儿茶酚胺充份地被耗竭,含量降至0.032±0.003,耗竭程度达97％。利血平化后电刺激加銻鉀组的心室儿茶酚胺含量为0.041±0.010,銻致性心室顫动并不出現。上述資料对前文的推論提出直接証明,卽儿茶酚胺在該种心律紊乱发病机制中具有重要意义。除儿茶酚胺含量外,我們又进行了心室乙酰胆碱含量的测定,发現正常盐水对照家兎心室乙酰胆碱含量平均为0.323±0.013微克/克。銻鉀一次大剂量注射或銻鉀三日給药法均不明显改变其含量。預先切断迷走神經或注射大剂量阿托品后再給大剂量銻鉀,也对心室乙酰胆碱含量无明显影响。因此完全不能証实黄铭新等关于这方面的报导。利血平在对家兎銻致性顫动具有防止作用的剂量下并不影响心室乙酰胆碱含量,較大剂量却能显著提高豚鼠心室乙酰胆碱的含量(P<0.01)。这些資料也完全支持前文所作出的推論,卽迷走神經在这种实驗性心律紊乱发病机制中的意义不大。     

美采用激光穿心室壁血管再造术

激光穿心室壁血管再造术(TMR Tra-nsmyocardial Revascularization),是治疗冠状动脉堵塞引起心肌缺血及心绞痛的新疗法。手术采用胸廊切开术,暴露心脏,将激光探头置于跳动心脏上的左心室部位,高能脉冲激光由R波峰触发,能量直接穿透心室壁,在左心室壁建立数十个直径约1mm的血管通道,让左心室内富氧血液直接流入新建通道内,改善缺血区的供血不足。传统治疗缺血性心脏病的方法有:内科药物治疗及经皮穿刺冠状动脉成形术(PTCA);外科方法中最经典的是冠状动     

神经中枢在停止血液循环后的生存和复活

循环停止以后,神經組織尤其是神經中枢的继續生存以及其功能停止以后的恢复的問題,仍旧是有兴趣的問題。因为这問題直接地牵涉到一些临床上的問題,例如在急性缺氧或窒息或由于麻醉以及主要是在心脏本身的手术所引起的心搏停止以后,神經系統功能的恢复与复活等等問題。心脏发生突然传导阻滞(Stokcs-Adams綜合病征),或心室纤維性顫动的时候,循环也是会停止的。     

一套研究机械电反馈的心室压力钳系统

在心脏机械电反馈的研究中准确控制机械刺激是非常重要的。本研究室构建了一套适用于离体家兔心脏的心室压力钳系统。该系统通过计算机控制压力钳,不仅能模拟正常生理条件下左心室的压力波形,还能在心室活动周期的特定时相、以适当波形对心室施加机械刺激。该系统集心脏灌流与起搏、表面心电图记录、单相动作电位记录、心室压力钳制与测定等多种功能于一体,特别适用于器官水平上观察机械电反馈现象并探讨其机制。     

基于进化思想和科学思维的“心脏”（第1课时）教学设计

在"输送血液的泵——心脏"一节的教学中,基于进化思想,通过对不同类型动物心脏由简单到复杂的演化过程的分析,帮助学生更好地理解人体四腔心脏的由来,以及心房、心室、瓣膜等结构的与其功能相适应的特点。同时,结合心脏模型观察、猪心解剖、资料阅读与分析、人体血液循环模式图的构建与修正等方式,培养学生科学思维与自主学习能力,为"人体血液循环路径"的学习做铺垫。     

小型人工心脏在上海诞生

人工心脏可分全人工心脏和心室辅助泵。置换全人工心脏不多见,目前为止,仅美国置换过五例。而心室辅助泵应用较为普遍。上海第二医科大学人工心脏研究室研制成一种带电机和电池重800g的左心辅助泵,替代山羊心脏实验,存活了32小时,目前即将从动物实验向临床试用过渡。这种小型左心辅助泵为电动叶轮式,能植入体内,病人活动自如,生活正常。流量大于10升压力150 mmHg,溶血发生率仅为目前使用的人工心肺机的三分之一。特别是采用国际上尚     

牵张家兔左心室所致的心律失常及链霉素的阻断作用

目的:研究复极末期牵张家兔左心室对心脏电活动的影响及其机制.方法:应用心室压力钳技术观察复极末期牵张刺激(120 mmHg,50 ms)对家兔心脏节律的影响,并用链霉素(500 μmol/L)对其机制进行探讨.结果:复极末期牵张刺激引起心律失常的发生(P<0.05),链霉素则抑制复极末期牵张的致心律失常作用(P<0.05).结论:利用心室压力钳技术对家兔左心室施加复极末期牵张刺激可导致心律失常的发生,而链霉素可抑制这种致心律失常作用,说明牵张激活离子通道在牵张刺激引起的心律失常中可能发挥作用.     

搏动型心室辅助装置大动物模型的建立

目的建立可用于搏动型心室辅助装置动物实验的大动物模型。方法选取实验动物小尾寒羊3只,麻醉后建立动静脉通路,左侧开胸建立体外循环,心脏诱颤,心尖部打孔缝合心尖插管,降主动脉缝合主动脉插管,连接DPVAD,启动驱动器,观察血泵运转情况和实验动物情况。结果血泵运转良好,血泵随驱动器正压负压驱动血液单向流动。同时动物左心室负荷减轻,动脉血压升高。结论建立搏动型心室辅助装置的大动物模型对于进行国产化心室辅助装置的研发具有重要意义。     

The Sequential External Counter Pulsator: A New Circulatory Assist Device

The three goals of cardiac assistance are: (1) To maintain systemic blood flow; (2) To reduce cardiac work and tension development; and (3) To increase oxygen availability to the heart. Toward these ends, various devices and techniques have been developed, including several different types of vascular shunts in combination with or without extracorporeal oxygenation of blood, implantable auxiliary ventricle and augmentation of diastolic pressure by direct counter pulsation of blood through femoral cannulae or intra-aortic balloon.The sequenced counter pulsator is an external cardiac assist device being developed for the therapy of low output syndromes. Investigation in the laboratory has shown that it is capable of increasing cardiac output and diastolic systemic pressure with concomitant reduction in left ventricular end-diastolic pressure. Therefore, it appears to be clinically useful in patients with low cardiac output syndromes.     

Three-Dimensional Computational Modeling of an Extra-Descending Aortic Assist Device Using Fluid-Structure Interaction

BackgroundThe incidence of heart failure is anticipated to rise by 2030, resulting in more than 8 million adults with this condition in US. Despite the advancement in pharmacological and surgical treatments, some patients progress to severe forms of cardiac dysfunction requiring cardiac transplantation as a last-resort treatment. Cardiac assist devices play an essential role in the recovery of normal cardiac performance through reversible remodeling or in assisting the weak organ to prolong survival rate. However, these devices need to be monitored carefully, as prolonged use may lead to physiological maladaptation and further cardiac complications. The optimization of such devices has done through the development and use of numerical simulations that allow the analysis of in-vivo hemodynamic patterns of blood flow. This study aims to investigate the performance of a model of extra-aortic assist device surrounding the descending aorta through three-dimensional patient-specific modeling.MethodsA three-dimensional model of the aorta was constructed from patient-specific cardiac CT images of a 60-year-old male diagnosed with left ventricular failure at the Tehran Heart Center (THC). Numerical simulation was conducted for two complete cardiac cycles using fluid-structure interaction (FSI) analysis under the assumption that the balloon and the aortic vessel behave as linear elastic materials, and that blood is a Newtonian and incompressible fluid.ResultsThe numerical simulation demonstrated a high correlation between the FSI analysis and clinical data of the patient-specific anatomical and physiological conditions. Blood velocity, pressure, deformation, and strain contours were simulated and analyzed through three-dimensional modeling. Compared to the unassisted aorta, the device provided an increase in blood flow displacement of an additional 15 ml of blood in the descending aorta, brachiocephalic, carotid, and subclavian arteries. The maximum von Mises stress distribution across the aortic vessel was higher than the stress imposed on the system in the unassisted heart, with values of 3.3 MPa and 0.28 MPa, respectively. Numerical investigation of structural responses revealed that no remarkable force was exerted on the aortic valve by the device at the descending aorta.ConclusionWe present the numerical investigation of a counterpulsation device around the descending aorta that has not previously been tested on human or animal models. While this extra-aortic balloon pump (EABP) did not show a significant improvement in coronary perfusion, there is room for improvement in further studies to optimize the geometry of the balloon. Additional investigations are required to determine the efficacy of this device and its safety before in-vivo experimental studies are pursued. This simulation has clinical relevance when choosing an appropriate cardiac assist device to address patient-specific physiological and pathological conditions.     

Beta-adrenoceptor inhibition for induction of acute cardiac failure in pigs

For the testing of heart assist devices most animal models of acute cardiac failure that are usually used show certain disadvantages. We therefore developed a new method using the beta-adrenoceptor antagonist carazolol. We administered a bolus injection of 1 mg/kg followed by a continuous infusion of 1 mg/kg/h in adult German 'Landrasse' pigs. Blood pressure, heart rate, cardiac output and maximum left ventricular pressure rise time showed a significant (P < 0.05) reduction of the control value varying between 40% and 59%. The method is suitable for the testing of surgical approaches in heart failure.     

Intraventricular flow patterns and stasis in the LVAD-assisted heart

Left ventricular assist device (LVAD) support disrupts the natural blood flow path through the heart, introducing flow patterns associated with thrombosis, especially in the presence of medical devices. The aim of this study was to quantitatively evaluate the flow patterns in the left ventricle (LV) of the LVAD-assisted heart, with a focus on alterations in vortex development and stasis. Particle image velocimetry of a LVAD-supported LV model was performed in a mock circulatory loop. In the Pre-LVAD flow condition, a vortex ring initiating from the LV base migrated toward the apex during diastole and remained in the LV by the end of ejection. During LVAD support, vortex formation was relatively unchanged although vortex circulation and kinetic energy increased with LVAD speed, particularly in systole. However, as pulsatility decreased and aortic valve opening ceased, a region of fluid stasis formed near the left ventricular outflow tract. These findings suggest that LVAD support does not substantially alter vortex dynamics unless cardiac function is minimal. The altered blood flow introduced by the LVAD results in stasis adjacent to the LV outflow tract, which increases the risk of thrombus formation in the heart.     

Third-generation continuous flow left ventricular assist devices

Tremendous advances have been made in the treatment of end-stage heart failure patients with left ventricular assist devices (LVADs). An important factor playing a role in the improved clinical outcomes is the development of continuous flow, rotary LVADs. New technology using magnetic levitation and hydrodynamic suspension to eliminate contact bearings offers the potential of more durable and efficacious mechanical circulatory blood pumps. Clinical trials evaluating these novel "third-generation" LVADs are in progress.     

Treatment options in end-stage heart failure: where to go from here?

Chronic heart failure is a major healthcare problem associated with high morbidity and mortality. Despite significant progress in treatment strategies, the prognosis of heart failure patients remains poor. The golden standard treatment for heart failure is heart transplantation after failure of medical therapy, surgery and/or cardiac resynchronisation therapy. In order to improve patients' outcome and quality of life, new emerging treatment modalities are currently being investigated, including mechanical cardiac support devices, of which the left ventricular assist device is the most promising treatment option. Structured care for heart failure patients according to the most recent international heart failure guidelines may further contribute to optimal decision-making. This article will review the conventional and novel treatment modalities of heart failure.     

Left ventricular assist device as a bridge to recovery in a young woman admitted with peripartum cardiomyopathy

Left ventricular assist devices (LVAD) are an effective therapeutic option for end-stage heart failure patients as a bridge to cardiac transplantation in those who deteriorate despite maximal therapy and when a donor heart is not ready available. In some patients, cardiac recovery has been reported while supported by an LVAD. In this case report, we describe a 29-year-old female who was admitted to our centre because of peripartum cardiomyopathy (PPCM). Despite intensive treatment with intravenous inotropes and intra-aortic balloon counter-pulsation she had a persisting low cardiac index and an LVAD was implanted. In the months following implantation the left ventricular systolic function improved and the left ventricular dimensions normalised. Eventually the LVAD could be ex-planted nine months after implantation. At this moment, three years after explantation, echo-cardiography shows a normal-sized left ventricle and almost completely recovered systolic function. (Neth Heart J 2008;16:426-8).     

Implantation of the Syncardia Total Artificial Heart

With advances in technology, the use of mechanical circulatory support devices for end stage heart failure has rapidly increased. The vast majority of such patients are generally well served by left ventricular assist devices (LVADs). However, a subset of patients with late stage biventricular failure or other significant anatomic lesions are not adequately treated by isolated left ventricular mechanical support. Examples of concomitant cardiac pathology that may be better treated by resection and TAH replacement includes: post infarction ventricular septal defect, aortic root aneurysm / dissection, cardiac allograft failure, massive ventricular thrombus, refractory malignant arrhythmias (independent of filling pressures), hypertrophic / restrictive cardiomyopathy, and complex congenital heart disease. Patients often present with cardiogenic shock and multi system organ dysfunction. Excision of both ventricles and orthotopic replacement with a total artificial heart (TAH) is an effective, albeit extreme, therapy for rapid restoration of blood flow and resuscitation. Perioperative management is focused on end organ resuscitation and physical rehabilitation. In addition to the usual concerns of infection, bleeding, and thromboembolism common to all mechanically supported patients, TAH patients face unique risks with regard to renal failure and anemia. Supplementation of the abrupt decrease in brain natriuretic peptide following ventriculectomy appears to have protective renal effects. Anemia following TAH implantation can be profound and persistent. Nonetheless, the anemia is generally well tolerated and transfusion are limited to avoid HLA sensitization. Until recently, TAH patients were confined as inpatients tethered to a 500 lb pneumatic console driver. Recent introduction of a backpack sized portable driver (currently under clinical trial) has enabled patients to be discharged home and even return to work. Despite the profound presentation of these sick patients, there is a 79-87% success in bridge to transplantation.     

An in vitro fluid dynamic study of pediatric cannulae: the value of animal studies to predict human flow

A challenge to the development of pediatric ventricular assist devices (PVADs) is the use of the aortic cannulae attached to the devices. Cannulae used for pediatric application have small diameters and large pressure drops. Furthermore, during the development of the 12cc Penn State pediatric PVAD, particle image velocimetry (PIV) illustrated that hematocrit levels, through changes in blood viscoelasticity, affected the fluid dynamics. The objective of this study is to compare the fluid dynamics of a pediatric viscoelastic blood analog and a goat viscoelastic blood analog within the PVAD aortic cannula. Two acrylic models were manufactured to model the aortic cannula (6 mm and 8 mm diameters). PIV data was collected to examine the flow at the outlet of the VAD and in the aortic cannula at heart rates of 50 and 75 beats per minute (bpm). Three planes of data were taken, one at the centerline and two 1.5 mm above and below the centerline. Three more planes of data were taken orthogonal to the original planes. While a 75 bpm heart rate was used to represent normal operating conditions, a 50 bpm heart rate represented use of the PVAD during weaning. At 75 bpm, differences were evident between the two different fluids and the two models. Separation zones developed in the plane below the centerline for the higher hematocrit pediatric blood analog. This study raises question to the usefulness of animal testing results in regard to how well they predict the outcome of pediatric patients.     

Hemocompatibility and hemodynamic comparison of two centrifugal LVADs: HVAD and HeartMate3

Mechanical circulatory support using ventricular assist devices is a common technique for treating patients suffering from advanced heart failure. The latest generation of devices is characterized by centrifugal turbopumps which employ magnetic levitation bearings to ensure a gap clearance between moving and static parts. Despite the increasing use of these devices as a destination therapy, several long-term complications still exist regarding their hemocompatibility. The blood damage associated with different pump designs has been investigated profoundly in the literature, while the hemodynamic performance has been hardly considered. This work presents a novel comparison between the two main devices of the latest generation–HVAD and HM3–from both perspectives, hemodynamic performance and blood damage. Computational fluid dynamics simulations are performed to model the considered LVADs, and computational results are compared to experimental measurements of pressure head to validate the model. Enhanced performance and hemocompatibility are detected for HM3 owing to its design incorporating more conventional blades and larger gap clearances.