Initial experiences with the HeartMate vented electric left ventricular assist system in Japan

We report three consecutive cases of long-term circulatory support using the HeartMate vented electric (VE) left ventricular assist system (LVAS). The HeartMate VE LVAS dramatically improved the functional status and quality of life of these three patients with end-stage heart failure, and all were successfully bridged to transplantation after 659, 995, and 1055 days of support on the device. Only an antiplatelet agent was used for anticoagulation therapy, and no cerebrovascular event occurred. Although the pump stopped in two of these three patients 665 days and 491 days after implantation, both were supported by the backup pneumatic driver thereafter. The drive-line exit site became infected in one patient and thinning of the left ventricular wall due to an unknown cause occurred in one patient.     

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.     

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.     

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.     

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     

Long-term medical control of inflow cuff infection in a patient with a left ventricular assist system

We report on a patient fitted with a Toyobo left ventricular assist system who developed inflow cannula exit-site infection. Although the exit-site infection seemed to be overcome by local irrigation and intravenous antibiotic therapy, repeated attempts at discontinuation of the intravenous antibiotic therapy resulted in bacteremia, and long-term administration of intravenous antibiotics was required. At the time of heart transplantation, it was noticed that the exit-site infection had caused ascending infection via the cannula and resulted in abscess formation around the left ventricular apical cuff. The infection was successfully controlled by heart transplantation and prophylactic omentopexy.     

左心室辅助装置控制模式影响双心室搏动同步性的数值研究

右心室(RV)衰竭已成为左心室辅助装置(LVAD)治疗的一种致命并发症。由LVAD引起的双心室搏动的不同步是引发RV功能障碍的重要因素。本文采用数值方法研究LVAD的控制模式对左、右心室搏动同步性的影响。数值结果表明:左心室(LV)与RV的收缩持续时间在无泵模式下没有显著差异(分别为48.52%和51.77%)。连续模式下,LV收缩期明显短于RV收缩期(LV vs.RV:24.38%vs.49.16%)和无泵模式的LV收缩期。搏动模式下,LV收缩期明显短于RV收缩期(LV vs.RV:28.38%vs.50.41%)但长于连续模式的LV收缩期。反搏动模式中的LV、RV收缩期差异较小(LV vs.RV:43.13%vs.49.23%),而LV收缩期短于无泵模式,并且长于连续模式。与连续和搏动模式相比,由反搏动模式提供的收缩期转速(RS)降低显著地校正了LV收缩持续时间,连续模式下缩短的收缩持续时间在反搏动模式下被校正为LV和RV之间的重新同步。因此,本文认为LV和RV收缩的再同步有助于预防RV功能障碍。总之,使用在收缩期间降低RS的反搏动模式有望用于由LVAD引起的双心室搏动不同步的临床校正。     

Advancements in left ventricular assist devices to prevent pump thrombosis and blood coagulopathy

Mechanical circulatory support (MCS) devices, such as left ventricular assist devices (LVADs) are very useful in improving outcomes in patients with advanced-stage heart failure. Despite recent advances in LVAD development, pump thrombosis is one of the most severe adverse events caused by LVADs. The contact of blood with artificial materials of LVAD pumps and cannulas triggers the coagulation cascade. Heat spots, for example, produced by mechanical bearings are often subjected to thrombus build-up when low-flow situations impair washout and thus the necessary cooling does not happen. The formation of thrombus in an LVAD may compromise its function, causing a drop in flow and pumping power leading to failure of the LVAD, if left unattended. If a clot becomes dislodged and circulates in the bloodstream, it may disturb the flow or occlude the blood vessels in vital organs and cause internal damage that could be fatal, for example, ischemic stroke. That is why patients with LVADs are on anti-coagulant medication. However, the anti-coagulants can cause a set of issues for the patient—an example of gastrointestinal (GI) bleeding is given in illustration. On account of this, these devices are only used as a last resort in clinical practice. It is, therefore, necessary to develop devices with better mechanics of blood flow, performance and hemocompatibility. This paper discusses the development of LVADs through landmark clinical trials in detail and describes the evolution of device design to reduce the risk of pump thrombosis and achieve better hemocompatibility. Whilst driveline infection, right heart failure and arrhythmias have been recognised as LVAD-related complications, this paper focuses on complications related to pump thrombosis, especially blood coagulopathy in detail and potential strategies to mitigate this complication. Furthermore, it also discusses the LVAD implantation techniques and their anatomical challenges.     

Current status of left ventricular assist devices: the role in bridge to heart transplantation and future perspectives

Increasing numbers of patients with end-stage heart failure are awaiting heart transplantation worldwide. Left ventricular assist systems have been applied to these patients with increasing frequency and support duration. This situation calls for more reliably applied long-term support devices and is also stimulating the investigation of destination therapy or bridge to recovery use of the device. This is particularly relevant in countries where organ shortages are crucial. However, reports in this area are still limited, and there exist several problems to be solved before wider application of these strategies is possible in clinical practice. We review currently available devices with special reference to their respective roles and limitations quoting our own experiences over the past several years, and discuss future perspectives of ventricular assist devices.     

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.     

Tei指数评价卡维地洛治疗充血性心力衰竭患者左心室功能的变化

目的与传统评价心功能指标比较，探讨多普勒超声左心室Tei指数在评价充血性心力衰竭患者治疗前后心功能的临床意义。方法60例充血性心力衰竭患者随机分为卡维地洛组和对照组（各30例），治疗前和治疗后3、6个月时分别用彩色多普勒超声测量左心室Tei指数、左心室射血分数（EF）、二尖瓣血流频谱舒张早期和晚期血流峰值之比（E，A）、E峰减速时间（Dn、等容舒张时间0VRT）、肺静脉血流频谱收缩波和舒张波峰值之比（S／D）及反向波（ARW）。结果两组EF在治疗后3个月及6个月逐渐增大（P＜0．01～0．05），卡维地洛组EF在治疗后6个月较对照组同期增大（P＜0．05）。两组治疗后舒张功能指标E／A先减小后增大，DT、IVRT及ARW逐渐减小，S，D逐渐增大（P＜0．01～0．05），组间差异未见有统计学意义（P＞0．05）。两组Tei指数在治疗后逐渐减低，组内比较差异均有显著统计学意义（P＜0．01），卡维地洛组减低更明显，与对照组同期比较差异有统计学意义（P＜0．01～0．05）。结论Tei指数可简便、敏感地评价心脏的整体收缩舒张功能。充血性心力衰竭患者卡维地洛治疗后左心室功能得到改善。     

Isolated non-compaction of the left ventricular myocardium in an adult treated with heart transplantation

Isolated left ventricular non-compaction is a rare unclassified cardiomyopathy characterized by arrest of normal embryogenesis that results in the persistence of intertrabecular recesses and the development of a spongy myocardium. The pathological diagnosis is often first established at autopsy. Described herein is the case of a 57-year-old man with isolated non-compaction of the left ventricle who had a 17 year history of worsening heart failure and was successfully treated with heart transplantation. To the authors' knowledge only seven adult patients with non-compaction cardiomyopathy have been reported to have undergone heart transplantation. Including the present case the mean age of the adult patients at transplantation was 39.5 years (range, 18-60 years). The male : female ratio was 3:1. Both ventricles were involved in 37.5% of cases. The mean follow up was 6.3 years (range, 2 months-17 years). One patient died because of a malignant tumor 9 years after transplantation. The morphological pattern of the isolated ventricular non-compaction represents a pathological entity discernible from other cardiomyopathies and should be classified as a specific cardiomyopathy. It is likely that surgical pathologists will encounter this entity more frequently due to involvement in transplantation teams.     

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.     

Sympathoadrenal system under conditions of increased left and right ventricular afterload

Adrenergic plexuses in the myocardium and adrenal medulla were studied histochemically under conditions of increased left or right ventricular afterload. Under conditions of high afterload not accompanied by heart failure the density of sympathetic myocardial innervation remained unchanged in the loaded ventricle, but increased in the intact ventricle. Comparison of the state of the sympathoadrenal system under conditions of increased afterload complicated or uncomplicated by heart failure revealed common prognostically unfavorable changes: sharp decrease in the density of adrenergic nerve plexuses in the ventricular myocardium and activation of adrenal chromaffin cells.Translated from Byulleten Eksperimentalnoi Biologii i Meditsiny, Vol. 138, No. 11, pp. 597–600, November, 2004     

Experimental evaluation of the hemodynamic efficiency of dynamic cardiomyoplasty in the surgical treatment of severe left ventricular failure

A. N. Bakulev Institute of Cardiovascular Surgery, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. I. Burakovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 12, pp. 584–588, December, 1991.     

Analysis of the relationship between left ventricular pressure and motor current for evaluation of native cardiac function during left ventricular support with a centrifugal blood pump

Control of the ventricular assist device (VAD) for native heart preservation should be attempted, and the VAD could be one strategy for dealing with the shortage of donors in the future. In the application of nonpulsatile blood pumps for ventricular assistance from the ventricular apex to the aorta, bypass flow and hence the motor current of the pumps change in response to the ventricular pressure change. Utilizing these intrinsic characteristics of the continuous-flow pumps, in this study we investigated whether motor current could be used as an index for continuous monitoring of native cardiac function. In study 1, a centrifugal blood pump (CFP) VAD was installed between the apex and descending aorta of a mock circulatory loop. In this model, a baseline with a preload of 10 mmHg, afterload of 40 mmHg, and LV systolic pressure of 40 mmHg was used. The pump speed was fixed at 1300, 1500, and 1700 rpm, and LV systolic pressure was increased up to 140 mmHg by steps of 20 mmHg while the changes in LV pressure, motor current, pump flow, and aortic pressure were observed. In study 2, an in vivo experiment was performed using three sheep. A left heart bypass model was created using a centrifugal pump from the ventricular apex to the descending aorta. The LVP was varied through administration of dopamine while the changes in LV pressure, pump flow, and motor current at 1500 and 1700 rpm were observed. An excellent correlation was observed in both in vitro and in vivo studies in the relationship between motor current and LV pressure. In study 1, the correlation coefficients were 0.77, 0.92, and 0.99 for 1300, 1500, and 1700 rpm, respectively. In study 2, they were 0.88 (animal no. 1), 0.83 (animal no. 2), and 0.88 (animal no. 3) for 1500 rpm, and 0.95 (animal no. 2) and 0.93 (animal no. 3) for 1700 rpm. These results suggest that motor current amplitude monitoring could be useful as an index for the control of VAD for native heart preservation.     

The severe end of the spectrum: Hypoplastic left heart in Potocki-Lupski syndrome

Potocki-Lupski syndrome (PTLS) is a recently described microduplication syndrome associated with duplication 17p11.2, including the RAI1 gene. Features of PTLS include hypotonia, feeding difficulties, failure to thrive, developmental delay and behavioral abnormalities including autistic spectrum disorder, anxiety, and inattention. Cardiovascular anomalies were not recognized as a feature of duplication 17p11.2 until 2007 when noted in over 50% of a clinically characterized cohort. We report a patient with hypoplastic left heart syndrome whose diagnosis of PTLS was delayed until a genetic evaluation at age 4 years because of severe expressive language impairment. We suggest that array comparative genomic hybridization be performed in infants with severe congenital heart defects.