State of the art: implantable ventricular assist devices

Candida Infectious Endocarditis and Implantable Cardiac Device Infections

Intravascular diseases due to Candida species, including endocarditis and cardiac device-associated infections, are rare yet devastating manifestations of invasive candidiasis affecting an already vulnerable population. Despite their significant associated morbidity and mortality, limited prospective data exist to inform the optimal diagnostic and therapeutic approaches to these entities. Herein, we review the existing literature pertaining to the epidemiology, diagnosis, and management of infectious endocarditis, rhythm management device infections, and circulatory support device infections caused by Candida species and suggest areas for future research.

Hemocompatibile Thin Films Assessed under Blood Flow Shear Forces

The aim of this study was to minimize the risk of life-threatening thromboembolism in the ventricle through the use of a new biomimetic heart valve based on metal-polymer composites. Finite volume element simulations of blood adhesion to the material were carried out, encompassing radial flow and the cone and plane test together with determination of the effect of boundary conditions. Both tilt-disc and bicuspid valves do not have optimized blood flow due to their design based on rigid valve materials (leaflet made of pyrolytic carbon). The main objective was the development of materials with specific properties dedicated to contact with blood. Materials were evaluated by dynamic tests using blood, concentrates, and whole human blood. Hemostability tests under hydrodynamic conditions were related to the mechanical properties of thin-film materials obtained from tribological tests. The quality of the coatings was high enough to avoid damage to the coating even as they were exposed up to maximum loading. Analysis towards blood concentrates of the hydrogenated carbon sample and the nitrogen-doped hydrogenated carbon sample revealed that the interaction of the coating with erythrocytes was the strongest. Hemocompatibility evaluation under hydrodynamic conditions confirmed very good properties of the developed coatings.

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.

The evolution of long-term pediatric ventricular assistance devices: a critical review

Introduction: The gap between the number of heart failure patients and the number of potential heart donors has never been larger than today, especially among the pediatric population. The use of mechanical circulatory support is seen as a potential alternative for clinicians to treat more patients. This treatment has proven its efficiency on short-term use. However, in order to replace heart transplant, the techniques should be used over longer periods of time.Areas covered: This review aims at furnishing an engineering vision of the evolution of ventricular assistance devices used in pediatrics. A critical analysis of the clinical complications related to devices generation is made to give an overview of the design improvements made since their inception.Expert opinion: The long-term use of a foreign device in the body is not without consequences, especially among fragile pediatric patients. Moreover, the size of their body parts increases the technical difficulties of such procedure. The balance between the living cells of the body is disturbed by the devices, mostly by the shear stress generated. To provide a safe mechanical circulatory support for long-term use, the devices should be more hemocompatible, preserving blood cells, adapted to the patient's systemic grid and miniaturized for pediatric use.

Muscle-Powered Counterpulsation for Untethered, Non-Blood-Contacting Cardiac Support: A Path to Destination Therapy

Conventional long-term ventricular assist devices continue to be extremely problematic due to infections caused by percutaneous drivelines and thrombotic events associated with the use of blood-contacting surfaces. Here we describe a muscle-powered cardiac assist device that avoids both these problems by using an internal muscle energy converter to drive a non-blood-contacting extra-aortic balloon pump. The technology was developed previously in this lab and operates by converting the contractile energy of the latissimus dorsi muscle into hydraulic power that can be used, in principle, to drive any blood pump amenable to pulsatile actuation. The two main advantages of this implantable power source are that it 1) significantly reduces infection risk by avoiding a constant skin wound, and 2) improves patient quality-of-life by eliminating all external hardware components. The counterpulsatile balloon pumps, which compress the external surface of the ascending aorta during the diastolic phase of the cardiac cycle, offer another critical advantage in the setting of long-term circulatory support in that they increase cardiac output and improve coronary perfusion without touching the blood. The goal of this work is to combine these two technologies into a single circulatory support system that eliminates driveline complications and avoids surface-mediated thromboembolic events, thereby providing a safe, tether-free means to support the failing heart over extended - or even indefinite - periods of time.

Perioperative management of patients with undergoing durable mechanical circulatory support

Durable mechanical circulatory support (MCS) devices revolutionized the treatment options for patients with end-stage heart failure (HF). Implantation of durable mechanical support has become an integral treatment modality in end-stage HF patients and it is associated with improved quality of life and survival. There is no doubt that this needs an interdisciplinary and interprofessional approach of cardiac surgeons, cardiologists, cardiac anesthesiologists, perfusionists, intensivists, psychologists, assist device coordinators as well as physiotherapists and intensive care. Implantation of durable MCS is a challenging procedure for the anesthesiologist due to the patient’s characteristics and comorbid diseases. It demands comprehensive training, high vigilance and quick response during the acute hemodynamic changes occurring during the surgery. Preoperative risk stratification is of major importance to guide perioperative medical treatment strategies. Most of these patients have several comorbidities and multiple medications. Therefore, to anticipate postoperative end-organ dysfunction such as cognitive dysfunction, pulmonary or renal failure, an interdisciplinary approach is necessary to optimize patient’s prior surgery. Transthoracic and transesophageal echocardiography (TTE and TEE), both play an invaluable role in diagnosing the cause and guiding the management in different unstable clinical situations. Especially prevention of postoperative right HF with subsequent necessity of temporary MCS is important as it is associated with higher mortality. The aim of this review is to provide an overview about the current concepts of perioperative management for durable MCS. A multimodal standard operating procedure supports early recovery after surgery and intensive care stay. Standardized perioperative care helps to ensure optimal medical treatment. This review focusses on several major skills of perioperative management of these high-risk surgical patients.

Cardiac Assist Devices: Early Concepts, Current Technologies, and Future Innovations

Congestive heart failure (CHF) is a debilitating condition that afflicts tens of millions of people worldwide and is responsible for more deaths each year than all cancers combined. Because donor hearts for transplantation are in short supply, a safe and durable means of mechanical circulatory support could extend the lives and reduce the suffering of millions. But while the profusion of blood pumps available to clinicians in 2019 tend to work extremely well in the short term (hours to weeks/months), every long-term cardiac assist device on the market today is limited by the same two problems: infections caused by percutaneous drivelines and thrombotic events associated with the use of blood-contacting surfaces. A fundamental change in device design is needed to address both these problems and ultimately make a device that can support the heart indefinitely. Toward that end, several groups are currently developing devices without blood-contacting surfaces and/or extracorporeal power sources with the aim of providing a safe, tether-free means to support the failing heart over extended periods of time.

Preclinical performance of a pediatric mechanical circulatory support device: The PediaFlow ventricular assist device

OBJECTIVES

The PediaFlow (HeartWare International, Inc, Framingham, Mass) is a miniature, implantable, rotodynamic, fully magnetically levitated, continuous-flow pediatric ventricular assist device. The fourth-generation PediaFlow was evaluated in vitro and in vivo to characterize performance and biocompatibility.

METHODS

Supported by 2 National Heart, Lung, and Blood Institute contract initiatives to address the limited options available for pediatric patients with congenital or acquired cardiac disease, the PediaFlow was developed with the intent to provide chronic cardiac support for infants as small as 3 kg. The University of Pittsburgh-led Consortium evaluated fourth-generation PediaFlow prototypes both in vitro and within a preclinical ovine model (n = 11). The latter experiments led to multiple redesigns of the inflow cannula and outflow graft, resulting in the implantable design represented in the most recent implants (n = 2).

RESULTS

With more than a decade of extensive computational and experimental efforts spanning 4 device iterations, the AA battery-sized fourth-generation PediaFlow has an operating range of 0.5 to 1.5 L/min with minimal hemolysis in vitro and excellent hemocompatibility (eg, minimal hemolysis and platelet activation) in vivo. The pump and finalized accompanying implantable components demonstrated preclinical hemodynamics suitable for the intended pediatric application for up to 60 days.

CONCLUSIONS

Designated a Humanitarian Use Device for "mechanical circulatory support in neonates, infants, and toddlers weighing up to 20 kg as a bridge to transplant, a bridge to other therapeutic intervention such as surgery, or as a bridge to recovery" by the Food and Drug Administration, these initial results document the biocompatibility and potential of the fourth-generation PediaFlow design to provide chronic pediatric cardiac support.

Prevention and Infection Management in Mechanical Circulatory Support Device Recipients

There are currently no guidelines for the management of infection and its prevention in mechanical circulatory support (MCS) device recipients. The International Society of Heart and Lung Transplantation (ISHLT) has initiated a multidisciplinary collaboration for the creation of a consensus document to guide clinicians in infection prevention and management in MCS patients. Most medical centers use local protocols that are based on expert opinion. MCS recipients are debilitated and have some immunological dysfunction. Over the years there have been technical advancements with smaller devices and drivelines with improved durability. The pulsatile devices have been replaced with newer-generation continuous-flow devices. Patient are living longer with MCSs for bridge to transplant (BTT) and destination therapy (DT). MCS centers have improved patient management by introducing standardized driveline protocols, leading to reduced infection rates among MCS recipients.

Left ventricular assist device: a bridge to transplant or destination therapy?

Heart failure is a major problem worldwide; it is the leading cause of hospitalisation and is posing a huge financial burden. Advances in healthcare have contributed to increased life expectancy, with a resultant increase in the number of patients with chronic heart failure. For many patients who are still severely symptomatic despite optimal medical therapy and cardiac resynchronisation therapy, cardiac transplantation would be the preferred treatment option. However, hopes are cut short with a limited donor pool of hearts for the increasing number of patients requiring cardiac transplantation. One uprising method to fill this treatment void for patients with advanced end-stage heart failure (ESHF) is the Left Ventricular Assist Device (LVAD). Although traditionally used as a bridge to transplantation, owing to limitation of suitable donors, evidence suggests increasing potential for the use of LVAD as destination therapy (DT), that is, lifelong permanent support. Exploration of DT is a promising avenue to many patients suffering with ESHF who may never be fortunate enough to receive a heart transplant, but not without reservations of its efficacy, safety, effects on quality-adjusted life years and cost-effectiveness, especially in comparison to heart transplantation.

Minimally invasive ventricular assist device surgery

The use of mechanical circulatory support to treat patients with congestive heart failure has grown enormously, recently surpassing the number of annual heart transplants worldwide. The current generation of left ventricular assist devices (LVADs), as compared with older devices, is characterized by improved technologies and reduced size. The result is that minimally invasive surgery is now possible for the implantation, explantation, and exchange of LVADs. Minimally invasive procedures improve surgical outcome; for example, they lower the rates of operative complications (such as bleeding or wound infection). The miniaturization of LVADs will continue, so that minimally invasive techniques will be used for most implantations in the future. In this article, we summarize and describe minimally invasive state-of-the-art implantation techniques, with a focus on the most common LVAD systems in adults.

Thromboresistance comparison of the HeartMate II ventricular assist device with the device thrombogenicity emulation- optimized HeartAssist 5 VAD

Approximately 7.5 × 106 patients in the US currently suffer from end-stage heart failure. The FDA has recently approved the designations of the Thoratec HeartMate II ventricular assist device (VAD) for both bridge-to-transplant and destination therapy (DT) due to its mechanical durability and improved hemodynamics. However, incidence of pump thrombosis and thromboembolic events remains high, and the life-long complex pharmacological regimens are mandatory in its VAD recipients. We have previously successfully applied our device thrombogenicity emulation (DTE) methodology for optimizing device thromboresistance to the Micromed Debakey VAD, and demonstrated that optimizing device features implicated in exposing blood to elevated shear stresses and exposure times significantly reduces shear-induced platelet activation and significantly improves the device thromboresistance. In the present study, we compared the thrombogenicity of the FDA-approved HeartMate II VAD with the DTE-optimized Debakey VAD (now labeled HeartAssist 5). With quantitative probability density functions of the stress accumulation along large number of platelet trajectories within each device which were extracted from numerical flow simulations in each device, and through measurements of platelet activation rates in recirculation flow loops, we specifically show that: (a) Platelets flowing through the HeartAssist 5 are exposed to significantly lower stress accumulation that lead to platelet activation than the HeartMate II, especially at the impeller-shroud gap regions (b) Thrombus formation patterns observed in the HeartMate II are absent in the HeartAssist 5 (c) Platelet activation rates (PAR) measured in vitro with the VADs mounted in recirculation flow-loops show a 2.5-fold significantly higher PAR value for the HeartMate II. This head to head thrombogenic performance comparative study of the two VADs, one optimized with the DTE methodology and one FDA-approved, demonstrates the efficacy of the DTE methodology for drastically reducing the device thrombogenic potential, validating the need for a robust in silico/in vitro optimization methodology for improving cardiovascular devices thromboresistance.

Outcomes after implantation of 139 full-support continuous-flow left ventricular assist devices as a bridge to transplantation

OBJECTIVES

Left ventricular assist devices (LVADs) are a routine treatment for patients with advanced heart failure as a bridge to transplantation. The aim of this study was to present our institutional experience and mid-term outcomes after implantation of 139 continuous-flow (cf) LVADs as a bridge to transplantation.

METHODS

One hundred and thirty-nine consecutive LVAD implantations were performed in our institution between July 2007 and August 2013. The mean age of the population was 44.0 ± 13.7 years and 24 (17%) of the patients were female. A substantial number of the patients were on preoperative mechanical support: 35 (25%) with an intra-aortic balloon pump, 9 (6.5%) with an extracorporeal membrane oxygenator and 25 (18%) with previous LVAD, for LVAD exchange.

RESULTS

The mean support duration was 514 ± 481 days, whereas the longest support duration was 2493 days (>6 years). The overall cumulative survival rate following cfLVAD implantation was 89% at 30 days, 76% at 1 year and 66% at 2 years (Fig. 1). There was a statistically significant difference in survival in favour of first LVAD implantation compared with VAD exchange: 91 vs 80% at 30 days, 79 vs 57% at 1 year and 70 vs 43% at 2 years (log-rank P = 0.010). Postoperatively, patients had a significant improvement in end-organ function 1 month after LVAD implantation. In addition, comparison of two different devices [HeartMate II (HM II) and HeartWare] using propensity score matching showed no significant differences in survival and most postoperative adverse events. However, patients supported with HM II required significantly more units of fresh frozen plasma (P = 0.020) with a trend towards a higher use of red blood cells (P = 0.094), and were also more likely to develop percutaneous site infections (P = 0.022).

CONCLUSIONS

HM II and HeartWare cfLVADs have excellent early postoperative outcomes and good mid-term survival, despite a considerable number of patients needing VAD exchange.

Outcomes after implantation of partial-support left ventricular assist devices in inotropic-dependent patients: Do we still need full-support assist devices?

OBJECTIVES

Partial-support left ventricular assist devices (LVADs) represent a novel strategy for heart failure treatment. The Synergy Pocket Micro-pump (HeartWare Inc, Framingham, Mass), the smallest surgically implanted long-term LVAD, provides partial flow up to 4.25 L/min and was primarily designed for "less sick" patients with severe heart failure. This device is implanted minimally invasively without sternotomy or cardiopulmonary bypass. Early implantation in patients with Interagency Registry for Mechanically Assisted Circulatory Support class 4 and higher was shown to be feasible and associated with significantly improved hemodynamics and quality of life. The aim of this study was to present our experience with implementation of long-term partial circulatory support as a bridge to transplantation in patients with more advanced heart failure who were dependent preoperatively on inotropic support or intra-aortic balloon pump.

METHODS

In this observational study, only inotropic or intra-aortic balloon pump-dependent patients with end-stage heart failure were included (n = 12). These patients underwent Synergy device implantation between February 2012 and August 2013.

RESULTS

The mean preoperative Interagency Registry for Mechanically Assisted Circulatory Support class was 2.17 ± 0.84 (class 1, 25%; class 2, 33%; class 3, 42%). The mean age was 46 ± 15 years, and 33% were female. Preoperatively, 4 patients (33%) had at least 1 previous sternotomy, 3 patients (25%) were supported with a balloon pump, 1 patient (8%) had a previous full-support LVAD, and 4 patients (33%) had cerebrovascular events in the past. After device implantation, there were no right ventricular failures, device-related infections, hemorrhagic strokes, arterial or venous thromboembolisms, or worsenings of aortic and mitral regurgitation observed over the follow-up. The mean follow up was 174 ± 171 days (range, 5-764 days; cumulative, 3199 days). One patient (8%) died, 3 patients (25%) successfully underwent transplantation, 1 device (8%) was explanted after myocardial recovery, and 5 patients (42%) are still on ongoing support. Two patients (17%) were upgraded to a full-support LVAD after 65 days of mean support. A total of 11 of 12 patients (92%) were discharged from the hospital and are presently alive. Left ventricular end-diastolic diameter was significantly reduced 3 months after device implantation.

CONCLUSIONS

Partial LVAD support may be clinically efficacious in inotropic and intra-aortic balloon pump-dependent patients. On the basis of our experience and evidence of previous research, such patients may benefit from minimally invasive access, no need for sternotomy and cardiopulmonary bypass, a short implantation time, an easy exchange if necessary, and a lower risk of subsequent heart transplantation. Because the implantation is performed without sternotomy, device upgrade is feasible with a comparatively low operative risk and good clinical outcome. Our preliminary results show that partial-support devices may have the potential to replace full-support LVADs in the near future.

Organ donation following brain stem death after ventricular assist device implantation

The availability of donor organs is the biggest limitation for lung transplantation, and a significant proportion of patients die on the waiting list. We describe a case of a 44-year-old lady who developed subarachnoid hemorrhage and cerebral edema on second postoperative day after left ventricular assist device implantation. She was declared brain stem dead 2 days later, and her organs were transplanted to suitable recipients on the waiting list for lung, liver and kidney transplantation.

Analysis of aortic valve commissural fusion after support with continuous-flow left ventricular assist device

OBJECTIVES

Continuous-flow left ventricular assist devices (cf-LVADs) may induce commissural fusion of the aortic valve leaflets. Factors associated with this occurrence of commissural fusion are unknown. The aim of this study was to examine histological characteristics of cf-LVAD-induced commissural fusion in relation to clinical variables.

METHODS

Gross and histopathological examinations were performed on 19 hearts from patients supported by either HeartMate II (n = 17) or HeartWare (n = 2) cf-LVADs and related to clinical characteristics (14 heart transplantation, 5 autopsy).

RESULTS

Eleven of the 19 (58%) aortic valves showed fusion of single or multiple commissures (total fusion length 11 mm [4-20] (median [interquartile range]) per valve), some leading to noticeable nodular displacements or considerable lumen diameter narrowing. Multiple fenestrations were observed in one valve. Histopathological examination confirmed commissural fusion, with varying changes in valve layer structure without evidence of inflammatory infiltration at the site of fusion. Commissural fusion was associated with continuous aortic valve closure during cf-LVAD support (P = 0.03). LVAD-induced aortic valve insufficiency developed in all patients with commissural fusion and in 67% of patients without fusion. Age, duration of cf-LVAD support and aetiology of heart failure (ischaemic vs dilated cardiomyopathy) were not associated with the degree of fusion.

CONCLUSIONS

Aortic valve commissural fusion after support with cf-LVADs is a non-inflammatory process leading to changes in valve layer structure that can be observed in >50% of cf-LVAD patients. This is the first study showing that patients receiving full cf-LVAD support without opening of the valve have a significantly higher risk of developing commissural fusion than patients on partial support.

Comparison of left ventricular geometry after HeartMate II and HeartWare left ventricular assist device implantation

Background

HeartMate II (HM II) and HeartWare (HW) Left Ventricular Assist Devices have been successfully used in end-stage heart failure patients as a bridge to transplantation, recovery, or decision. We set out to compare their effect in off-loading the left ventricle and its geometry.

Methods

The left ventricular end diastolic (LVEDD) and end systolic (LVESD) diameters were compared between first time HM II (n = 25) and HW implantations (n = 24) before and after the operation at 1, 3, and 6 months. A p value of less than 0.05 was considered as significant.

Results

Post-operative LVEDD and LVESD at 1, 3, and 6 months were significantly reduced in comparison with pre-operative values in both HM II and HW groups. No significant difference was found comparing HM II and HW groups together before and after the operation.

Conclusions

Our study shows that both HM II and HW can significantly reduce the left ventricular systolic and diastolic dimensions and off-load the left ventricle. The miniaturized nature of HW does not affect its performance and it could be as effective as HM II.

Clinical xenotransplantation: the next medical revolution?

The shortage of organs and cells from deceased individuals continues to restrict allotransplantation. Pigs could provide an alternative source of tissue and cells but the immunological challenges and other barriers associated with xenotransplantation need to be overcome. Transplantation of organs from genetically modified pigs into non-human primates is now not substantially limited by hyperacute, acute antibody-mediated, or cellular rejection, but other issues have become more prominent, such as development of thrombotic microangiopathy in the graft or systemic consumptive coagulopathy in the recipient. To address these problems, pigs that express one or more human thromboregulatory or anti-inflammatory genes are being developed. The results of preclinical transplantation of pig cells--eg, islets, neuronal cells, hepatocytes, or corneas--are much more encouraging than they are for organ transplantation, with survival times greater than 1 year in all cases. Risk of transfer of an infectious microorganism to the recipient is small.

Intraoperative transesophageal echocardiography and ventricular assist device insertion

A decade after cardiac surgery was established, transesophageal echocardiography (TEE) was developed and used to evaluate perioperative cardiac performance. It has become an invaluable tool to provide real-time information in the cardiac operating room. TEE provides practical and useful information prior to insertion as well as after placement of the device. Additionally, during episodes of device malfunction or hemodynamic instability, TEE can be extremely useful in defining the etiology of the problem. As ventricular assist devices (VADs) have undergone evolution in design and as more VADs are being implanted, the development of specific indications for TEE use during device placement is a relevant issue. Formal guidelines for use of TEE during VAD insertion are yet to be adopted or implemented, but for now TEE remains an essential tool for managing this patient population.

The use of computational fluid dynamics in the development of ventricular assist devices

Progress in the field of prosthetic cardiovascular devices has significantly contributed to the rapid advancements in cardiac therapy during the last four decades. The concept of mechanical circulatory assistance was established with the first successful clinical use of heart-lung machines for cardiopulmonary bypass. Since then a variety of devices have been developed to replace or assist diseased components of the cardiovascular system. Ventricular assist devices (VADs) are basically mechanical pumps designed to augment or replace the function of one or more chambers of the failing heart. Computational Fluid Dynamics (CFD) is an attractive tool in the development process of VADs, allowing numerous different designs to be characterized for their functional performance virtually, for a wide range of operating conditions, without the physical device being fabricated. However, VADs operate in a flow regime which is traditionally difficult to simulate; the transitional region at the boundary of laminar and turbulent flow. Hence different methods have been used and the best approach is debatable. In addition to these fundamental fluid dynamic issues, blood consists of biological cells. Device-induced biological complications are a serious consequence of VAD use. The complications include blood damage (haemolysis, blood cell activation), thrombosis and emboli. Patients are required to take anticoagulation medication constantly which may cause bleeding. Despite many efforts blood damage models have still not been implemented satisfactorily into numerical analysis of VADs, which severely undermines the full potential of CFD. This paper reviews the current state of the art CFD for analysis of blood pumps, including a practical critical review of the studies to date, which should help device designers choose the most appropriate methods; a summary of blood damage models and the difficulties in implementing them into CFD; and current gaps in knowledge and areas for future work.

NHLBI's program for VAD therapy for moderately advanced heart failure: the REVIVE-IT pilot trial

BACKGROUND

Ventricular assist devices (VADs) are used to bridge heart failure patients to transplantation, to allow their own hearts to recover, or as permanent ("destination") therapy. To date, the use of VADs has been limited to late-stage heart failure patients because of the associated device risks. In 2008, a National Heart, Lung, and Blood Institute (NHLBI) working group met to evaluate the treatment of heart failure using VADs and to advise the institute on how therapy for heart failure may be best advanced by clinical trials involving the devices.

METHODS AND RESULTS

Recognizing the improvements in VAD technology and in patient care and selection over the past decade, the working group recommended that a trial be performed to assess the use of chronic VAD therapy in patients who are less ill than those currently eligible for destination therapy. The hypothesis proposed for the trial is that VAD therapy may improve both survival and quality of life in moderately advanced heart failure patients who are neither inotrope-dependent nor exercise-intolerant and have not yet developed serious consequences such as malnourishment, end-organ damage, and immobility.

CONCLUSION

Based on the group's recommendations, NHLBI issued an RFP in 2009 for the REVIVE-IT Pilot Trail, which will serve to test the hypothesis and inform the pivotal trial.

Novel therapies in childhood heart failure: today and tomorrow

Heart failure is an important cause of morbidity and mortality in individuals of all ages. The many-faceted nature of the clinical heart failure syndrome has historically frustrated attempts to develop an overarching explanative theory. However, much useful information has been gained by basic and clinical investigation, even though a comprehensive understanding of heart failure has been elusive. Heart failure is a growing problem, in both adult and pediatric populations, for which standard medical therapy, as of 2010, can have positive effects, but these are usually limited and progressively diminish with time in most patients. If we want curative or near-curative therapy that will return patients to a normal state of health at a feasible cost, much better diagnostic and therapeutic technologies need to be developed. This review addresses the vexing group of heart failure etiologies that include cardiomyopathies and other ventricular dysfunctions of various types, for which current therapy is only modestly effective. Although there are many unique aspects to heart failure in patients with pediatric and congenital heart disease, many of the innovative approaches that are being developed for the care of adults with heart failure will be applicable to heart failure in childhood.

Hematologic effects of continuous flow left ventricular assist devices

The extent of hematologic effects of the new continuous flow left ventricular assist devices (CF-LVAD) has not been studied. Recent clinical studies have demonstrated that hemolysis and thrombosis are not common during CF-LVAD support, however, the incidence of bleeding remains a concern. The rate of postoperative bleeding is similar to that of the prior generation pulsatile LVAD, but gastrointestinal bleeding due to angiodysplasia and arteriovenous malformations is more common and appears to be related to the blood flow rheology of these devices. New evidence suggests that acquired von Willebrand's disease develops in some patients due to the reduction in high molecular weight (HMW) multimers of von Willebrand's factor (vWF). Similar to acquired von Willebrand's disease seen in patients with aortic stenosis, the shear stress of the CF-LVAD may cause proteolysis of the HMW multimers of vWF. In addition to acquired von Willebrand's disease, there is activation of the fibrinolytic system and a loss of platelet numbers and function during CF-LVAD support. The hematologic responses during CF-LVAD support are constantly changing, and antiplatelet therapy may need to be adjusted accordingly. Considerable research is needed to better define the complex hematologic effects during CF-LVAD support. Screening of patients for angiodysplasia and von Willebrand's disease before CF-LVAD implant may allow for effective preemptive treatment. Because bleeding causes significant morbidity for this population, more effective treatment strategies need to be developed.

Design Improvements and In Vitro Testing of an Implantable Muscle Energy Converter for Powering Pulsatile Cardiac Assist Devices

Harnessing skeletal muscle for circulatory support would improve on current blood pump technologies by eliminating infection-prone drivelines and cumbersome transcutaneous energy transmission systems. Toward that end, we have built and tested an implantable muscle energy converter (MEC) designed to transmit the contractile energy of the latissimus dorsi muscle in hydraulic form. The MEC weighs less than 300 g and comprises a metallic bellows formed from AM350 stainless steel actuated by a rotary cam (440C) attached to a titanium rocker arm (Ti–6Al–4V). The rocker arm is fixed to the humeral insertion of the muscle via a looped artificial tendon developed specifically for this purpose. The device housing (Ti–6Al–4V) is anchored to the ribcage using a perforated mounting ring and a wire suture. Lessons learned through seven previous design iterations have produced an eighth-generation pump with excellent durability, energy transfer efficiency, anatomic fit, and tissue interface characteristics. This report describes recent improvements in MEC design and summarizes results from in silico and in vitro testing. Long-term implant studies will be needed to confirm these findings prior to clinical testing.