The use of muscle flaps to treat left ventricular assist device infections

Left ventricular assist devices have become an important adjunct in the therapeutic armamentarium for patients with end-stage heart failure. Although they may provide a bridge to transplantation, they are prone to certain problems, expecially infection. Because these are life-sustaining devices, changing the device or simple explantation may be a risky, if not impossible, option. Therefore, we evaluated the effectiveness of a surgical alternative, namely, coverage of infected devices with muscle or myocutaneous flaps. Eighty-two consecutive patients who underwent the insertion of 88 left ventricular assist devices at our institution over a 6.5-year period were evaluated. Follow-up was provided for all patients and ranged from 1 to 7.5 years. The duration of ventricular support ranged from 0 to 434 days. All patients who demonstrated clinical evidence of infection were identified. Overall, 54 patients (66 percent) had infections locally at the device site, at distant sites, or systemically during support. Cultured organisms included gram-positive and -negative bacteria, fungi, and viruses. Of the 56 infections in these 54 patients, 21 (38 percent) were device-related, i.e., in the pocket created by the device, in the device itself, or from the driveline. Thus, 24 percent (21 of 88) of all ventricular support devices inserted demonstrated device infection during use. Therapeutic modalities used to combat device-related infection included both nonsurgical management with antibiotics alone and surgical procedures such as device change or relocation, device explant, and flap coverage. Eight of the 20 patients in whom the 21 device-related infections occurred underwent surgical intervention. Four of these eight patients undenwent local flap coverage of their infected left ventricular assist devices. All four patients also had evidence of systemic infection, or "device endocarditis." Coverage was successfully achieved in all cases with pedicled rectus abdominis flaps. There were no perioperative complications. Two patients later underwent successful transplantation; the other two died from causes unrelated to the flap. In conclusion, the treatment of infected left ventricular assist devices currently includes both nonsurgical and surgical alternatives. Of the latter, muscle flaps should be considered a first-line intervention to assist in eradicating infection by providing well-vascularized tissue. Although there were no perioperative complications, the 50 percent mortality rate is consistent with that reported for patients with "device endocarditis." It may be that flap coverage of infected ventricular assist devices, if instituted at an earlier stage in the therapeutic process, could help prevent systemic infection in these patients and, therefore, improve their overall outcome.     

Initial experience with a new blood pump

A new type of blood pump was tested in calves for 6 hours. The pump consists of a rigid housing with a trochoidal internal surface, an inlet and outlet, and two lateral walls. A two-corner piston rotating on an eccentric shaft, describes a trochoidal path, thus creating a gap seal, the gap measuring a constant 10-35 microns. The pump is driven by a watercooled DC motor. For right ventricular assist, a cannula is inserted into the right ventricle through the right atrium, and into the left ventricle for left ventricular assists. From a total of 10 experiments, two left ventricular assists, two right ventricular assists, and three biventricular assists were evaluated. The pump produced a pulsatile flow of 31 at 70 rpm. Energy requirements were 2.19 watts for left, 2.06 for right, and 7.26 for biventricular assists. Plasma hemoglobin remained as low as 10 mg/dl during monoventricular, and increased during biventricular assists to 20 mg/dl after 3 hours, and returned to 16 mg/dl after 6 hours. From these preliminary results it is concluded that this new rotary blood pump may be suitable as a circulatory assist device.     

Simulation of Dilated Heart Failure with Continuous Flow Circulatory Support

Lumped parameter models have been employed for decades to simulate important hemodynamic couplings between a left ventricular assist device (LVAD) and the native circulation. However, these studies seldom consider the pathological descending limb of the Frank-Starling response of the overloaded ventricle. This study introduces a dilated heart failure model featuring a unimodal end systolic pressure-volume relationship (ESPVR) to address this critical shortcoming. The resulting hemodynamic response to mechanical circulatory support are illustrated through numerical simulations of a rotodynamic, continuous flow ventricular assist device (cfVAD) coupled to systemic and pulmonary circulations with baroreflex control. The model further incorporated septal interaction to capture the influence of left ventricular (LV) unloading on right ventricular function. Four heart failure conditions were simulated (LV and bi-ventricular failure with/without pulmonary hypertension) in addition to normal baseline. Several metrics of LV function, including cardiac output and stroke work, exhibited a unimodal response whereby initial unloading improved function, and further unloading depleted preload reserve thereby reducing ventricular output. The concept of extremal loading was introduced to reflect the loading condition in which the intrinsic LV stroke work is maximized. Simulation of bi-ventricular failure with pulmonary hypertension revealed inadequacy of LV support alone. These simulations motivate the implementation of an extremum tracking feedback controller to potentially optimize ventricular recovery.     

Severe hypoxaemia with a left ventricular assist device in a minipig model with an undiagnosed congenital cardiac disease

We describe the placement of a left ventricular assist device (LVAD) in a pig with spontaneously occurring atrial septal defect (ASD) (incidental finding) that created a right-left cardiac shunt, with subsequent severe hypoxaemia. Early diagnosis was critical in order to prevent end-organ damage due to hypoxaemia. Adequate monitoring alerted us to the deterioration in oxygenation, haemodynamics and cerebral oxygen metabolism. This forced us to change the level of assistance provided by the pump, and thus dramatically correct this impairment. Necropsy revealed an ostium secundum ASD. In conclusion, if hypoxaemia presents after implementation of an LVAD, the presence of a right-left shunt must be ruled out. The first step must be a judicious reduction in assist device flow to minimize intracardiac shunting. Subsequently, atrial septal closure of the defect should be considered. We report an experimental model of severe hypoxaemia after placement of an LVAD as part of a larger research project.     

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.     

The Role of 1.5 Tesla MRI and Anesthetic Regimen Concerning Cardiac Analysis in Mice with Cardiomyopathy

Accurate assessment of left ventricular function in rodent models is essential for the evaluation of new therapeutic approaches for cardiac diseases. In our study, we provide new insights regarding the role of a 1.5 Tesla (T) magnetic resonance imaging (MRI) device and different anesthetic regimens on data validity. As dedicated small animal MRI and echocardiographic devices are not broadly available, we evaluated whether monitoring cardiac function in small rodents with a clinical 1.5 T MRI device is feasible. On a clinical electrocardiogram (ECG) synchronized 1.5 T MRI scanner we therefore studied cardiac function parameters of mice with chronic virus-induced cardiomyopathy. Thus, reduced left ventricular ejection fraction (LVEF) could be verified compared to healthy controls. However, our results showed a high variability. First, anesthesia with medetomidine, midazolam and fentanyl (MMF) led to depressed cardiac function parameters and more variability than isoflurane gas inhalation anesthesia, especially at high concentrations. Furthermore, calculation of an average ejection fraction value from sequenced scans significantly reduced the variance of the results. To sum up, we introduce the clinical 1.5 T MRI device as a new tool for effective analysis of left ventricular function in mice with cardiomyopathy. Besides, we suggest isoflurane gas inhalation anesthesia at high concentrations for variance reduction and recommend calculation of an average ejection fraction value from multiple sequenced MRI scans to provide valid data and a solid basis for further clinical testing.     

Insertion of the Impella 5.0 left ventricular assist device via right anterior mini-thoracotomy: a novel practical approach

The Impella 5.0 microaxial pump is a miniaturized left ventricular assist device commonly used for circulatory support in acute cardiogenic shock. The catheter-based pump is designed to be inserted either into a peripheral artery or directly into the ascending aorta. We report the first case in which the Impella 5.0 device was placed directly into the ascending aorta via a small right anterior thoracotomy in a patient following acute myocardial infarction complicated by cardiogenic shock.     

Influence of dilated cardiomyopathy and a left ventricular assist device on vortex dynamics in the left ventricle

Together with new developments in mechanical cardiac support, the analysis of vortex dynamics in the left ventricle has become an increasingly important topic in literature. The aim of this study was to develop a method to investigate the influence of a left ventricular assist device (LVAD) on vortex dynamics in a failing ventricle. An axisymmetric fluid dynamics model of the left ventricle was developed and coupled to a lumped parameter model of the complete circulation. Simulations were performed for healthy conditions and dilated cardiomyopathy (DCM). Vortex structures in these simulations were analysed by means of automated detection. Results show that the strength of the leading vortex ring is lower in a DCM ventricle than in a healthy ventricle. The LVAD further influences the maximum strength of the vortex and also causes the vortex to disappear earlier in time with increasing LVAD flows. Understanding these phenomena by means of the method proposed in this study will contribute to enhanced diagnostics and monitoring during cardiac support.     

How the Electronic Health Record Will Change the Future of Health Care

Genetic testing is expected to play a critical role in patient care in the near future. Advances in genomic research have the potential to impact medicine in very tangible and direct ways, from carrier screening to disease diagnosis and prognosis to targeted treatments and personalized medicine. However, numerous barriers to widespread adoption of genetic testing continue to exist, and health information technology will be a critical means of addressing these challenges. Electronic health records (EHRs) are a digital replacement for the traditional paper-based patient chart designed to improve the quality of patient care. EHRs have become increasingly essential to managing the wealth of existing clinical information that now includes genetic information extracted from the patient genome. The EHR is capable of changing health care in the future by transforming the way physicians use genomic information in the practice of medicine.     

Influence of dilated cardiomyopathy and a left ventricular assist device on vortex dynamics in the left ventricle

Together with new developments in mechanical cardiac support, the analysis of vortex dynamics in the left ventricle has become an increasingly important topic in literature. The aim of this study was to develop a method to investigate the influence of a left ventricular assist device (LVAD) on vortex dynamics in a failing ventricle. An axisymmetric fluid dynamics model of the left ventricle was developed and coupled to a lumped parameter model of the complete circulation. Simulations were performed for healthy conditions and dilated cardiomyopathy (DCM). Vortex structures in these simulations were analysed by means of automated detection. Results show that the strength of the leading vortex ring is lower in a DCM ventricle than in a healthy ventricle. The LVAD further influences the maximum strength of the vortex and also causes the vortex to disappear earlier in time with increasing LVAD flows. Understanding these phenomena by means of the method proposed in this study will contribute to enhanced diagnostics and monitoring during cardiac support.     

Méthodologie d’évaluation de l’impact d’une formation sur la qualité de l’utilisation d’une nouvelle technologie

For health care professionals, training is critical to assure the patient safety. This paper is interested in the nurses training when a new technology is introduced in their work environment, and more particularly in the impact of the type of training on the quality of the new device use. This means that both the learned knowledge and their integration in the work environment have to be evaluated. Two types of training were compared through qualitative and quantitative indicators of the device used in the work situation. The results highlight a better satisfaction of learners and more effective results on the practice with one of the two trainings.     

左心室脱血回注循环辅助法对急性心肌梗死血流动力学的改善作用

目的:实验观察左心室脱血回注循环辅助法对急性心肌梗死血流动力学的改善作用.方法:18只杂种犬分两组制作急性心肌梗死泵衰竭模型,治疗组给予左心室脱血回注循环辅助,对照组不进行治疗.观察比较两组间心律失常、死亡率、外周动脉压、肺动脉毛细血管楔嵌压(PCWP)、左心室舒张末期压(LVEDP)、左心室内径的变化.结果:治疗组室性期外收缩、心室纤颤发生率和死亡率显著低于对照组;对照组的外周动脉收缩压低于80 mmHg以下,治疗组维持在100mmHg以上(P＜0.01);治疗组PCWP和LVEDP值在45 min以后的各时段低于对照组(P＜0.01);治疗组的左室舒张末期内径小于对照组(P＜0.01).结论:左心室脱血回注循环辅助法能够减少急性心肌梗死泵衰竭的心室纤颤发生率和死亡率,有显著改善血流动力学、防止梗死后心肌扩张和有效的左心室辅助作用.     

End-stage heart failure and mechanical circulatory support: feasibility of discharge from hospital

Background. Due to the shortage of donor hearts, mechanical circulatory support is increasingly being used as a bridge to transplantation. In order to allow for more widespread use of ventricular assist devices it is mandatory that patients are not continuously hospitalised. We present the results of our experience with patients with end-stage heart failure, discharged from hospital after implantation of a ventricular assist device and followed in an outpatient setting. Methods. After an intensive training and education programme, focusing on the management of the percutaneous driveline and instructions on how to handle in case of an alarm or malfunction of the device, patients were discharged. They were followed in the outpatient department. All regular and unplanned visits were registered, including readmissions. Results. Twenty-seven patients treated with a ventricular assist device were discharged from hospital. There were 37 extra visits, of these, 27 were device related resulting in 21 readmissions (0.78/patient). We treated eight infectious episodes in four patients, all device related. Furthermore seven thromboembolic episodes occurred in four patients. One patient died because of multiorgan failure seven weeks after he was readmitted with an urosepsis. In our experience of 11.4 patient years at home while on the device, only 5% of the time was spent in hospital for complications. In comparison with patients on an assist device who stayed in hospital until transplantation, there were no more complications. Conclusion. This study demonstrates that patients with end-stage heart failure, treated with a ventricular assist device, can be safely discharged from hospital, with an acceptable rate of readmissions. It results in a fair quality of life, with a high degree of independence of the patient. (Neth Heart J 2007; 15:45-50.)     

CLINICAL TRIALS OF THE ABDOMINAL LEFT VENTRICULAR ASSIST DEVICE (ALVAD): PROGRESS REPORT

An abdominal left ventricular assist device (ALVAD) is undergoing controlled clinical trials in our institution. The ALVAD is pneumatically-actuated, synchronously or asynchronously with an external console and is interposed between the apex of the left ventricle and the infrarenal abdominal aorta. It is an order of magnitude more effective than conventional intraaortic balloon pumping. Thus far, we have implanted this pump in 21 patients (15 males and six females). The average age has been 50. The duration of cardiopulmonary bypass with intensive pharmacologic support and IABP until ALVAD implantation has been nearly 4 hours. The plasma hemoglobins prior to ALVAD implantation have averaged 168 mg%. The platelet counts at implantation have averaged 68,000 mm(3). The average duration of ALVAD support has been in excess of one day and the longest trial extended for one week. We have been able to remove the pump after ventricular recovery in two instances and effected cardiac allografting in one instance of ALVAD dependency. We have found that (1) the profoundly depressed left (and right) ventricles can recover if totally supported with this device; (2) the device can function in the presence of ventricular fibrillation and/or standstill; (3) the device can effectively replace both left and right ventricular function in the presence of normal pulmonary vascular resistance and microcirculatory hemodynamics; and (4) in the presence of impending multiple organ failure, procrastination in use is to be avoided.     

ONTOLOGY OR PHENOMENOLOGY? HOW THE LVAD CHALLENGES THE EUTHANASIA DEBATE

This article deals with the euthanasia debate in light of new life‐sustaining technologies such as the left ventricular assist device (LVAD). The question arises: does the switching off of a LVAD by a doctor upon the request of a patient amount to active or passive euthanasia, i.e. to ‘killing’ or to ‘letting die’? The answer hinges on whether the device is to be regarded as a proper part of the patient's body or as something external. We usually regard the switching off of an internal device as killing, whereas the deactivation of an external device is seen as ‘letting die’. The case is notoriously difficult to decide for hybrid devices such as LVADs, which are partly inside and partly outside the patient's body. Additionally, on a methodological level, I will argue that the ‘ontological’ arguments from analogy given for both sides are problematic. Given the impasse facing the ontological arguments, complementary phenomenological arguments deserve closer inspection. In particular, we should consider whether phenomenologically the LVAD is perceived as a body part or as an external device. I will support the thesis that the deactivation of a LVAD is to be regarded as passive euthanasia if the device is not perceived by the patient as a part of the body proper.     

Medical simulation: the new tool for training and skill assessment

Medical simulation is a new method to facilitate skill training and assessment. Simulation has achieved a high degree of sophistication in aviation and other fields. However, the complexity of health care, the numerous stakeholders, and the lack of central control of medical education have been barriers to the development and broad implementation of medical simulation. Acceptance by the medical community is growing, with the publication of scientific validation studies, the development of economic models and funding, and the integration of simulation into existing curricula and training programs. The major forces for implementing simulation will most likely come from the medical device industry and from institutions with mandates to improve the quality of health care and enhance patient safety. Certification boards are expected to increase their utilization of simulation technology to objectively assess proficiency of skills relevant to physicians and the health care system. Medical simulation has made the transition from an experimental technology to the clinical world, and the next five to 10 years may be viewed as the golden age of medical simulation.     

可植入式心室辅助装置动物模型的建立

目的探讨建立可植入式心室辅助装置研究的实验动物模型。方法选取体质量120-180 kg小公牛7只,常规全麻后左侧第4肋间开胸,建立体外循环,体外循环辅助下诱颤后,植入自主研发的国产可植入式心室辅助装置（DIVAD,domestic-made implantable ventricular assist device）,DIVAD机械性能参数接近国际同类产品,泵尺寸29.5mm×72 mm,重量158 g,体外转速可达9000 r/min,流量可达8 L/min,整合流量计,并可通过体外控制器监测控制。DIVAD连接左室及降主动脉,转速3500-8000 r/min左右,行左室辅助。术后撤除体外循环,持续监测动物生命体征及DIVAD运转情况。肝素静滴维持ACT在正常值1.5-2倍之间。结果7只小牛术后全部复跳,均能成功撤离体外循环辅助,最长存活时间超过93 h,最短存活时间0.5 h,平均存活时间20.28 h。结论小牛可以作为DIVAD研究的合适动物模型,其围手术期处理有相应特点,小牛DIVAD实验模型的建立对于进一步研究改进DIVAD有重要作用。     

Impact of left ventricular assist device (LVAD) support on the cardiac reverse remodeling process

With improved technology and expanding indications for use, left ventricular assist devices (LVADs) are assuming a greater role in the care of patients with end-stage heart failure. Following LVAD implantation with the intention of bridge to transplant, it became evident that some patients exhibit substantial recovery of ventricular function. This prompted explantation of some devices in lieu of transplantation, the so-called bridge-to-recovery (BTR) therapy. However, clinical outcomes following these experiences are not always successful. Patients treated in this fashion have often progressed rapidly back to heart failure. Special knowledge has emerged from studies of hearts supported by LVADs that provides insights into the basic mechanisms of ventricular remodeling and possible limits of ventricular recovery. In general, it was these studies that spawned the concept of reverse remodeling now recognized as an important goal of many heart failure treatments. Important examples of myocardial and/or ventricular properties that do not regress towards normal during LVAD support include abnormal extracellular matrix metabolism, increased tissue angiotensin levels, myocardial stiffening and partial recovery of gene expression involved with metabolism. Nevertheless, studies of LVAD-heart interactions have led to the understanding that although we once considered the end-stage failing heart of patients near death to be irreversibly diseased, an unprecedented degree of myocardial recovery is possible, when given sufficient mechanical unloading and restoration of more normal neurohormonal milieu. Evidence supporting and unsupporting the notion of reverse remodeling and clinical implications of this process will be reviewed.     

Percutaneous left ventricular partitioning device for chronic heart failure

We report the first implantation of a percutaneous left ventricular partitioning device in the Netherlands. This device is developed for patients with chronic heart failure due to a left ventricular apical aneurysm caused by an anterior myocardial infarction.     

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.