HeartMate® VE LVAS design enhancements and its impact on device reliability1

Review of Implantable Left Ventricular Assist Devices

Mechanical circulatory support has been an indispensable treatment for severe heart failure. While the development of a total artificial heart has failed, left ventricular assist devices (LVAD) have evolved from extracorporeal to implantable types. The first generation implantable LVAD (pulsatile device) was used as a bridge to transplantation, and demonstrated improvement in survival rate and activity of daily living. The evolution from the first-generation (pulsatile device) to the second-generation (continuous flow device: axial flow pump and centrifugal pump) has resulted in many clinical benefits by reducing mechanical failures and minimizing device size. Furthermore, third-generation devices, which use a moving impeller suspended by magnetic and/or hydrodynamic forces, have improved overall device reliability and durability. Unfortunately, there are still many device-related complications, and further device development and improvement of patient management methods are required. However, we expect to see further development of implantable VADs, including for destination therapy, in future.

Physiologic effects of continuous-flow left ventricular assist devices

BACKGROUND

Within the past 10 years, continuous-flow left ventricular assist devices (LVADs) have replaced pulsatile-flow LVADs as the standard of care for both destination therapy and bridging patients to heart transplantation. Despite the rapid clinical adoption of continuous-flow LVADs, an understanding of the effects of continuous-flow physiology, as opposed to more natural pulsatile-flow physiology, is still evolving.

MATERIALS AND METHODS

A thorough review of the relevant scientific literature regarding the physiological and clinical effects of continuous-flow physiology was performed. These effects were analyzed on an organ system basis and include an evaluation of the cardiovascular, respiratory, hematologic, gastrointestinal, renal, hepatic, neurologic, immunologic, and endocrine systems.

RESULTS

Continuous-flow physiology is, generally speaking, well tolerated over the long term. However, several changes are manifest at the organ system level. Although many of these changes are without appreciable clinical significance, other changes, such as an increased rate of gastrointestinal bleeding, appear to be associated with continuous-flow physiology.

CONCLUSIONS

Continuous-flow LVADs confer a significant advantage over their pulsatile-flow counterparts with regard to size and durability. From a physiological standpoint, continuous-flow physiology has limited clinical effects at the organ system level. Although improved over previous generations, challenges with this technology remain. Approaching these problems with a combination of clinical and engineering solutions may be needed to achieve continued progression in the field of durable mechanical circulatory support.

Dynamics of device innovation: implications for assessing value

BACKGROUND

In recent years, there has been growing interest in evaluating the health and economic impact of medical devices. Payers increasingly rely on cost-effectiveness analyses in making their coverage decisions, and are adopting value-based purchasing initiatives. These analytic approaches, however, have been shaped heavily by their use in the pharmaceutical realm, and are ill-adapted to the medical device context.

METHODS

This study focuses on the development and evaluation of left ventricular assist devices (LVADs) to highlight the unique challenges involved in the design and conduct of device trials compared with pharmaceuticals.

RESULTS

Devices are moving targets characterized by a much higher degree of post-introduction innovation and "learning by using" than pharmaceuticals. The cost effectiveness ratio of left ventricular assist devices for destination therapy, for example, decreased from around $600,000 per life year saved based on results from the pivotal trial to around $100,000 within a relatively short time period.

CONCLUSIONS

These dynamics pose fundamental challenges to the evaluation enterprise as well as the policy-making world, which this paper addresses.

Devices in heart failure--the new revolution

Heart failure is a growing epidemic, with more patients living longer and suffering from this disease. There is a growing segment of patients who have persistent symptoms despite pharmacologic therapy. In an era when transplants are rare, the need for devices and interventions that can assist ventricular function is paramount. This review goes through the devices used in heart failure, including left ventricular reconstruction, aortic counterpulsation, short-term mechanical circulatory support, long-term mechanical circulatory support, and right heart interventions.

Trends in left ventricular assist device use and outcomes among Medicare beneficiaries, 2004-2011

Objective

To characterise the trends in the left ventricular assist device (LVAD) implantation rates and outcomes between 2004 and 2011 in the Medicare population. Since the approval of the HeartMate II in 2008, the use of LVADs has steadily climbed. Given the increase in LVAD use, issues around discharge disposition, post-implant hospitalisations and costs require further understanding.

Methods

We examined LVAD implantation rates and short-term and long-term outcomes among Medicare fee-for-service beneficiaries hospitalised for LVAD implantation. We also conducted analyses among survivors 1-year post-discharge to examine rehospitalisation rates. Lastly, we reported Centers for Medicare & Medicaid Services (CMS) payments for both index hospitalisation and rehospitalisations 1 year post-discharge.

Results

A total of 2152 LVAD implantations were performed with numbers increasing from 107 in 2004 to 612 in 2011. The 30-day mortality rate decreased from 52% to 9%, and 1-year mortality rate decreased from 69% to 31%. We observed no change in overall length of stay, but post-procedure length of stay increased. We also found an increase in home discharge dispositions from 26% to 53%. Between 2004 and 2010, the rehospitalisation rate increased and the number of hospital days decreased. The adjusted CMS payment for the index hospitalisation increased from $188 789 to $225 697 over time but decreased for rehospitalisation from $60 647 to $53 630.

Conclusions

LVAD implantations increased over time. We found decreasing 30-day and 1-year mortality rates and increasing home discharge disposition. The proportion of patients rehospitalised among 1-year survivors remained high with increasing index hospitalisation cost, but decreasing post-implantation costs over time.

Ventricular-assist devices for the treatment of chronic heart failure

The role of ventricular-assist devices in the management of end-stage heart failure is growing. Initially developed as a 'bridge to transplantation', they are now implanted permanently in patients who need cardiac replacement but are not candidates for cardiac transplantation ('destination therapy'). Furthermore, observations from expert centers indicate that a significant proportion of patients under long-term mechanical assistance can be weaned from mechanical circulatory support after significant functional recovery of their native heart ('bridge to recovery'). This review discusses the emerging roles of mechanical circulatory support and their direct implications in clinical practice. Evolution of devices, important aspects of candidate selection, challenging issues in the management of ventricular-assist device patients (infection, device malfunction, anticoagulation-thromboembolic complications, psychosocial issues and cost) and ongoing research targeting sustained myocardial recovery are discussed.

Currently available ventricular-assist devices: capabilities, limitations and future perspectives

The continuous progress in ventricular-assist device (VAD) technology and the management of patients with VADs has broadened the treatment options for end-stage heart failure patients. The available line-up of clinical devices provides the current optimal therapies to meet the specific needs of each patient. The extended durability, safety, efficacy and improved quality of life of the patients provides sufficient proof for the VAD to be a likely alternative therapy to heart transplantation. The sequential progress from the first-, to the second- and to the third-generation VAD technology is expected to bring increasing benefits to clinical outcomes. This article reviews the current status, capabilities, limitations and future perspectives of currently available VADs by generally classifying them via support duration, alignment of pump devices and via pulsatile or nonpulsatile mode of perfusion. Furthermore, the future direction of research and development for next-generation VADs is presented based on the lessons learned from currently available VADs.

Ventricular assist devices: is destination therapy a viable alternative in the non-transplant candidate?

The topic of this article, stated a more familiar way, is whether left ventricular assist devices (LVADs) are ready for 'Primetime' as a therapeutic option in and of themselves. In order to provide an update and insight on this question, we briefly review from where the field has come, and in more detail describe its current state and where we are heading. We believe the short answer to this question is 'Yes', but like many things, a short answer is not adequate. Here we attempt to deliver a more comprehensive answer, providing some historical context, outlining the great achievements that have been made, as well as the many challenges that still remain before LVADs become a truly mainstream therapy.

Devices in the management of advanced, chronic heart failure

Heart failure (HF) is a global phenomenon, and the overall incidence and prevalence of the condition are steadily increasing. Medical therapies have proven efficacious, but only a small number of pharmacological options are in development. When patients cease to respond adequately to optimal medical therapy, cardiac resynchronization therapy has been shown to improve symptoms, reduce hospitalizations, promote reverse remodelling, and decrease mortality. However, challenges remain in identifying the ideal recipients for this therapy. The field of mechanical circulatory support has seen immense growth since the early 2000s, and left ventricular assist devices (LVADs) have transitioned over the past decade from large, pulsatile devices to smaller, more-compact, continuous-flow devices. Infections and haematological issues are still important areas that need to be addressed. Whereas LVADs were once approved only for 'bridge to transplantation', these devices are now used as destination therapy for critically ill patients with HF, allowing these individuals to return to the community. A host of novel strategies, including cardiac contractility modulation, implantable haemodynamic-monitoring devices, and phrenic and vagus nerve stimulation, are under investigation and might have an impact on the future care of patients with chronic HF.

Device exchange after primary left ventricular assist device implantation: indications and outcomes

BACKGROUND

Patients are being supported for longer periods with implantable left ventricular assist devices (LVADs) owing to longer transplantation wait times and approval of LVADs for destination therapy. This comes with an increased potential need for device exchange when complications arise. There are few data examining this patient population.

METHODS

Between August 1998 and January 2012, 45 patients (34 men) underwent 57 device exchanges after primary pulsatile or continuous-flow LVAD implantation. The median age at the initial LVAD implantation was 58 years (range, 28-78 years) and the median time to first device exchange was 15 months (range, immediate-56 months). Indications for primary LVAD included bridge to transplantation in all but 10 patients, and devices included the HeartMate I (Thoratec, Pleasanton, CA) in 16 patients, the HeartMate II (Thoratec) in 21 patients, the HeartWare HVAD (HeartWare, Framingham, MA) in 2 patients, the DuraHeart I (Terumo Heart, Ann Arbor, MI) in 1 patient, and other devices in 5 patients. Indications for reoperation included device/component failure (n=24), major driveline infection (n=15), pump thrombus (n=15), and other indications (n=2).

RESULTS

Pumps implanted in 57 reoperations included the HeartMate I in 15 patients, the HeartMate II in 35 patients, the HeartWare HVAD in 2 patients, the DuraHeart I in 2 patients, and other devices in 3 patients. Early mortality occurred in 2/57 (3.5%) patients. Median follow-up was 18 months (range, 1-113 months); median length of LVAD therapy after the first device exchange was 13 months (range, 1-59 months). Actuarial 1-year survival and freedom from repeated device exchange after the first exchange was 89% and 79%, respectively.

CONCLUSIONS

Device exchange may be required after LVAD implantation. This can be performed with low early mortality and no adverse effect on late survival. Multiple reoperations may be required in some patients.

Current technology: devices available for destination therapy

Left ventricular assist device therapy as a destination therapy for end-stage heart failure has made a large leap with continuous flow devices. Continuous flow does not seem to have a detrimental effect on end-organ function, at least in the midterm. Various expected and unexpected complications have been reported associated with this technology. More experience and research are warranted.

Current trends in implantable left ventricular assist devices

The shortage of appropriate donor organs and the expanding pool of patients waiting for heart transplantation have led to growing interest in alternative strategies, particularly in mechanical circulatory support. Improved results and the increased applicability and durability with left ventricular assist devices (LVADs) have enhanced this treatment option available for end-stage heart failure patients. Moreover, outcome with newer pumps have evolved to destination therapy for such patients. Currently, results using nonpulsatile continuous flow pumps document the evolution in outcomes following destination therapy achieved subsequent to the landmark Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure Trial (REMATCH), as well as the outcome of pulsatile designed second-generation LVADs. This review describes the currently available types of LVADs, their clinical use and outcomes, and focuses on the patient selection process.

A durability study of a paracorporeal pulsatile electro-mechanical pneumatic biventricular assist device

In 2002, the paracorporeal pulsatile electro-mechanical pneumatic ventricular assist device (VAD) began to be developed by the Korea Artificial Organ Center at Korea University under a Health & Medical Technology Research and Development program which finished in 2008. In vitro durability testing was conducted on the paracorporeal pulsatile pneumatic VAD to determine device durability and to evaluate device failures. The 1- and 2-year reliability of the paracorporeal pulsatile pneumatic VAD was shown to be 91.2% and 54.9%, respectively, with an 80% confidence level. Failure modes were analyzed using fault tree analysis, with customized software continuously acquiring data during the test period. After this period, 21 in vivo animal tests were done, with 14 cases of left atrium to left ventricle (LV) inflow cannulation (36Fr)/outflow grafting to descending aorta, and seven cases of apex cannulation of LV to descending aorta (12 mm). The longest postoperative day (182 days) in Korea was recently recorded in in vivo animal testing (bovine, 90 kg, male, 3.5-4.0 L/min flow rate, and 55 bpm).

Pharmacotherapy for Mechanical Circulatory Support: A Comprehensive Review

Objective

To provide a comprehensive review of the pharmacotherapy associated with the provision of mechanical circulatory support (MCS) to patients with end-stage heart failure and guidance regarding the selection, assessment, and optimization of drug therapy for this population.

Data Sources:

The MEDLINE/PubMed, EMBASE, and Cochrane databases were searched from 1960 to July 2010 for articles published in English using the search terms mechanical circulatory support, ventricular assist system, ventricular assist device, left ventricular assist device, right ventricular assist device, biventricular assist device, total artificial heart, pulsatile, positive displacement, axial, centrifugal, hemostasis, bleeding, hemodynamic, blood pressure, thrombosis, antithrombotic therapy, anticoagulant, antiplatelet, right ventricular failure, ventricular arrhythmia, anemia, arteriovenous malformation, stroke, infection, and clinical pharmacist.

Study Selection And Data Extraction:

All relevant original studies, metaanalyses, systematic reviews, guidelines, and reviews were assessed for inclusion. References from pertinent articles were examined for content not found during the initial search.

Data Synthesis:

MCS has advanced significantly since the first left ventricular assist device was implanted in 1966. Further advancements in MCS technology that occurred in the tatter decade are changing the overall management of end-stage heart failure care and cardiac transplantation. These pumps allow for improved bridge-to-transplant rates, enhanced survival, and quality of life. Pharmacotherapy associated with MCS devices may optimize the performance of the pumps and improve patient outcomes, as well as minimize morbidity related to their adverse effects. This review highlights the knowledge needed to provide appropriate clinical pharmacy services for patients supported by MCS devices.

Conclusions:

The HeartMate II clinical investigators called for the involvement of pharmacists in MCS patient assessment and optimization. Pharmacotherapeutic management of patients supported with MCS devices requires individualized care, with pharmacists as part of the team, based on the characteristics of each pump and recipient.

Noninvasive predictor of HeartMate XVE pump failure by neural network and waveform analysis

Patients increasingly require longer durations of left ventricular assist device (LVAD) therapy. Despite a recent trend toward continuous flow VADs, the HeartMate XVE is still commonly used, but its longevity remains a significant limitation. Existing surveillance methods of pump failure often give inconclusive results. XVE electrical current waveforms were collected regularly (2001-2008) and sorted into quartiles according to number of days until pump failure (Q1, 0-34; Q2, 34-160; Q3, 160-300; and Q4, 300-390 days). Thoratec waveform files were converted into text files. The 10-second electrical current, voltage waveform was identified and isolated for analysis. Waveforms were analyzed by principal component analysis (PCA) and with a fast Fourier transform. Quartiles were compared with analysis of variance (ANOVA). Waveforms (n = 454) were collected for 21 patients with failed pumps. An artificial neural network was used to predict pump failure within 30 days from the waveform characteristics identified though signal processing.

Extended mechanical circulatory support with a continuous-flow rotary left ventricular assist device

OBJECTIVES

This study sought to evaluate the use of a continuous-flow rotary left ventricular assist device (LVAD) as a bridge to heart transplantation.

BACKGROUND

LVAD therapy is an established treatment modality for patients with advanced heart failure. Pulsatile LVADs have limitations in design precluding their use for extended support. Continuous-flow rotary LVADs represent an innovative design with potential for small size and greater reliability by simplification of the pumping mechanism.

METHODS

In a prospective, multicenter study, 281 patients urgently listed (United Network of Organ Sharing status 1A or 1B) for heart transplantation underwent implantation of a continuous-flow LVAD. Survival and transplantation rates were assessed at 18 months. Patients were assessed for adverse events throughout the study and for quality of life, functional status, and organ function for 6 months.

RESULTS

Of 281 patients, 222 (79%) underwent transplantation, LVAD removal for cardiac recovery, or had ongoing LVAD support at 18-month follow-up. Actuarial survival on support was 72% (95% confidence interval: 65% to 79%) at 18 months. At 6 months, there were significant improvements in functional status and 6-min walk test (from 0% to 83% of patients in New York Heart Association functional class I or II and from 13% to 89% of patients completing a 6-min walk test) and in quality of life (mean values improved 41% with Minnesota Living With Heart Failure and 75% with Kansas City Cardiomyopathy questionnaires). Major adverse events included bleeding, stroke, right heart failure, and percutaneous lead infection. Pump thrombosis occurred in 4 patients.

CONCLUSIONS

A continuous-flow LVAD provides effective hemodynamic support for at least 18 months in patients awaiting transplantation, with improved functional status and quality of life. (Thoratec HeartMate II Left Ventricular Assist System [LVAS] for Bridge to Cardiac Transplantation; NCT00121472).

Destination therapy: current results and future promise

The landmark Randomized Evaluation of Mechanical Assistance in the Treatment of Congestive Heart Failure (REMATCH) trial demonstrated that the implantation of left ventricular assist devices (LVADs) as an alternative to heart transplantation, or destination therapy (DT) is superior to any known medical therapy in patients with end-stage heart failure who are not eligible for transplantation. In this article, we review results of the first United States and European clinical trials of DT, including the REMATCH, the Investigation of the Non-Transplant Eligible Patients who are Inotrope Dependent (INTREPID), and the Clinical Utility Baseline Study (CUBS) trials, as well as the outcomes of the first DT implantations in the post-REMATCH era in the United States. The article summarizes the current state of knowledge and future directions in the field of permanent mechanical circulatory support therapy as an alternative to heart transplantation.

Mechanical circulatory support: a clinical reality

Mechanical circulatory support is becoming an alternative therapeutic option for patients in cardiogenic shock or advanced cardiac failure who cannot be improved by maximal medical therapy. More than 30 years of engineering development and clinical research have led to a level of efficacy and reliability of ventricular assist devices, which allows promotion of this approach for the most difficult patients. Uses include a gaining-time strategy as a bridge to cardiac transplantation or recovery of native cardiac function, as well as permanent support with the device. The large variety of devices permits every cardiac surgical unit, even those not used to cardiac transplantation, to propose this option to the patient. Recent experience with small silent implantable pumps suggests that the pioneering period of mechanical circulatory support is probably over, and the time has come for precise prospective trials to optimize both patient selection and the timing for utilization. In countries where cardiac transplantation has not developed, there is now an easily accessible technique for management of patients with cardiac failure.

Pressures generated within the chambers of the MagScrew TAH: an in vitro study

Incompetent inflow valves have been reported with clinical pulsatile left ventricular assist devices that use bioprosthetic valves. Suspected as the cause of premature valve failure within these devices, absolute pressures and instantaneous pressure changes were evaluated in the MagScrew total artificial heart (TAH). The MagScrew TAH is a passively filling pulsatile pump which uses a reciprocating magnetic actuating mechanism under various control modes to propel blood into circulation. Both right and left ejection speeds were modulated and optimized at the onset of hydraulic eject. These various speed profiles were evaluated in vitro at 220 beats per minute (bpm), 100% pump fill, mean aortic pressure of 100 mm Hg and mean pulmonary artery pressure of 20 mm Hg. The pressure inside the left and right pump chambers was measured with Millar Mikro-Tip catheter and captured using Power Lab at a rate of 40 kHz. The pump chamber peak pressure, operating with unmodified eject speeds, measured on average 183 mm Hg for the left and 133 mm Hg for the right. Eject speed profiling for both pumps reduced the peak pressure by 10% and 28% for the left and right pump, respectively. Future studies will assess software controlled optimization of the eject speed profiles under any operating condition and how effective it is in vivo.

VentrAssist™ left ventricular assist device: clinical trial results and Clinical Development Plan update

OBJECTIVES

To summarise the primary efficacy and safety results from the first international clinical trial with the VentrAssist left ventricular assist device and to provide an update on the VentrAssisttrade mark Clinical Development Plan.

METHODS

The first prospective, single-arm, multicentre international clinical trial with the VentrAssist in bridge-to-transplant patients (CE Mark trial) was conducted in Australia, UK and Norway between 2004 and 2006. The primary outcome measure was survival until transplant or being transplant-eligible at postoperative day 154. The number and status of other clinical trials in the VentrAssist Clinical Development Plan are also described.

RESULTS

At the completion of the CE Mark trial, 25 of the 30 patients (83%) were transplanted or transplant-eligible. There were no unexpected safety issues and no reported uncontrolled stops of the VentrAssist pump. The Clinical Development Plan for the VentrAssist currently comprises seven clinical trials: two are completed, three are ongoing and two are ready for initiation. As of January 30th, 2007, a total of 87 patients have been implanted with the VentrAssist at 14 centres worldwide, yielding a total exposure time of more than 43 patient-years and a maximum implant duration of 2.7 years.

CONCLUSIONS

The efficacy and safety data from a clinical trial of the VentrAssist were favourable and resulted in gaining European regulatory approval for this indication. Notably, the survival success rate for the VentrAssist was higher than that reported for other left ventricular assist devices. The overall number of implants with the VentrAssist has now surpassed that of any other third-generation centrifugal device.

Cadaver fitting study of the DexAide right ventricular assist device

The DexAide right ventricular assist device (RVAD) has been developed to provide an implantable RVAD option to surgeons. The aim of this study was to determine the optimal cannula design and optimal implantation location of the DexAide RVAD in preparation for its clinical use. Separately, a HeartMate XVE left ventricular assist device (LVAD) and CorAide LVAD models were implanted into the preperitoneal and right thoracic space, and the anatomical fit of the DexAide RVAD was evaluated in five preserved human cadavers. The DexAide RVAD inflow cannula was inserted through the diaphragmatic surface of the right ventricle and the outflow was directed to the pulmonary artery. Right thoracic implantation of the DexAide RVAD provided an excellent fit with either the HeartMate or CorAide LVAD in all cadavers. The results of this study will guide improvements in the designs of cannulae and implantation of the DexAide RVAD in future clinical applications.

Destination therapy: does progress depend on left ventricular assist device development?

The role of therapy using mechanical circulatory support devices has evolved rapidly over the last two decades. New developments in the field achieved smaller adverse events, but, currently, only minor improvements in survival were observed in published observational data. The authors discuss the development of mechanical circulatory support devices as a "destination therapy" option for patients who have end-stage heart failure and are ineligible for heart transplantation as it relates to left ventricular assist device development.

Perioperative echocardiographic examination for ventricular assist device implantation

Ventricular assist devices (VADs) are systems for mechanical circulatory support of the patient with severe heart failure. Perioperative transesophageal echocardiography is a major component of patient management, and important for surgical and anesthetic decision making. In this review we present the rationale and available data for a comprehensive echocardiographic assessment of patients receiving a VAD. In addition to the standard examination, device-specific pre-, intra-, and postoperative considerations are essential to the echocardiographic evaluation. These include: (a) the pre-VAD insertion examination of the heart and large vessels to exclude significant aortic regurgitation, tricuspid regurgitation, mitral stenosis, patent foramen ovale, or other cardiac abnormality that could lead to right-to-left shunt after left VAD placement, intracardiac thrombi, ventricular scars, pulmonic regurgitation, pulmonary hypertension, pulmonary embolism, and atherosclerotic disease in the ascending aorta; and to assess right ventricular function; and (b) the post-VAD insertion examination of the device and reassessment of the heart and large vessels. The examination of the device aims to confirm completeness of device and heart deairing, cannulas alignment and patency, and competency of device valves using two-dimensional, and color, continuous and pulsed wave Doppler modalities. The goal for the heart examination after implantation should be to exclude aortic regurgitation, or an uncovered right-to-left shunt; and to assess right ventricular function, left ventricular unloading, and the effect of device settings on global heart function. The variety of VAD models with different basic and operation principles requires specific echocardiographic assessment targeted to the characteristics of the implanted device.

Outcomes of left ventricular assist device implantation as destination therapy in the post-REMATCH era: implications for patient selection

BACKGROUND

The landmark Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure (REMATCH) trial first demonstrated that implantation of left ventricular assist devices (LVADs) as destination therapy (DT) can provide survival superior to any known medical treatment in patients with end-stage heart failure who are ineligible for transplantation. In the present study, we describe outcomes of DT in the post-REMATCH era in the United States.

METHODS AND RESULTS

The present study included 280 patients who underwent HeartMate XVE LVAD implantation between November 2001 and December 2005. A preoperative risk score for in-hospital mortality after LVAD implantation was established in 222 patients with complete data. All patients were followed up until death or December 2006. The 1-year survival after LVAD implantation was 56%. The in-hospital mortality after LVAD surgery was 27%. The main causes of death included sepsis, right heart failure, and multiorgan failure. The most important determinants of in-hospital mortality were poor nutrition, hematological abnormalities, markers of end-organ or right ventricular dysfunction, and lack of inotropic support. Stratification of DT candidates into low (n=65), medium (n=111), high (n=28), and very high (n=18) risk on the basis of the risk score calculated from these predictors corresponded with 1-year survival rates of 81%, 62%, 28%, and 11%, respectively.

CONCLUSIONS

Appropriate selection of candidates and timing of LVAD implantation are critical for improved outcomes of DT. Patients with advanced heart failure who are referred for DT before major complications of heart failure develop have the best chance of achieving an excellent 1-year survival with LVAD therapy.

Cardiac Transplantation: Any Role Left?

The authors analyze the question of whether heart transplantation still has a role in the current era of complex technologies. To achieve this objective, the authors first discuss the known benefits of different therapeutic modalities currently available for patients who have end-stage heart failure, including pharmacologic management, electrophysiologic therapies, high-risk surgical strategies, implantation of mechanical circulatory support device therapy, and heart transplantation. The authors then evaluate the current developments and future perspectives in the field that may influence the likelihood of heart transplantation to remain the therapeutic modality of choice for end-stage heart failure.

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.

Utilization of Acoustic Signatures to Identify HeartMate XVE Device End-of-Life

BACKGROUND

As outcomes for destination therapy continue to improve, many patients are requiring left ventricular assist device (LVAD) exchange due to end-of-life of their LVAD. Current techniques to identify and diagnose device end-of-life issues usually require invasive testing or off-site filter dust analysis. In this study we assess a non-invasive technique using acoustic signals generated from the HeartMate XVE LVAD to potentially identify impending device end-of-life issues.

METHODS

Nine patients were prospectively followed after implantation of the HeartMate XVE LVAD as destination therapy between May 2004 and July 2006. Acoustic signals were collected using an aquatic hydrophone system interfaced with a data acquisition system and a standard laptop computer. Data were collected at pre-set intervals. All data/acoustic signals were prospectively interpreted by a blinded independent reviewer skilled at interpreting acoustic signals. Acoustic data suggesting possible device failure were then correlated with clinical findings and LVAD examination at the time of device removal.

RESULTS

All patients survived long enough to develop signs of impending device end-of-life. Four of 9 (44%) patients developed inflow valve incompetence, 4 (44%) were identified as having significant bearing wear, and 1 (12%) had both. All acoustically identified device issues were confirmed by standard clinical examinations and testing (echocardiography, angiography, laboratory tests and filter dust analysis). The acoustic findings were subsequently confirmed at time of device exchange. All patients ultimately had their device successfully exchanged and have continued to live with their new apparatus.

CONCLUSIONS

Acoustic signal monitoring can successfully identify HeartMate XVE device end-of-life. This new method provides a low-cost, reproducible, non-invasive technique that may be used to identify possible impending device failure.

Urgent Pump Exchange for Stroke Resulting From a Distorted HeartMate XVE Inflow Conduit

Long-term left ventricular assist device (LVAD) implantation is associated with an inherent risk of transient ischemic attacks (TIAs). When TIAs occur in patients who have undergone placement of a HeartMate XVE LVAD, the pump must be assumed to be the likely source of the TIA. The HeartMate XVE is unique in that it has a pumping surface of flocked Biomer and a pump housing and inlet cannula coated with sintered titanium. This design facilitates coating of the surfaces with the patient's own cells, usually within 48 hours of implantation, effectively eliminating the pumping surface as a source of thromboemboli. Similarly, neither the outflow conduit nor the porcine outflow valve have been shown to be sources of thromboemboli, as they are both subjected to the wash-out of pulsatile systolic pressure. In our experience, the only components vulnerable to pannus formation are the inflow conduit and its associated valve, and then only when the inflow conduit is distorted at implantation. We describe an illustrative case of a patient supported with a HeartMate XVE LVAD who suffered a device-related stroke that was attributed to the inflow conduit, which was distorted during implantation to configure the pump for the patient's narrow body habitus. The resultant disruption in laminar flow was the most likely cause of the TIAs and stroke. Therefore, documented TIAs in patients with an implanted HeartMate XVE are an indication for urgent pump replacement, even if pump performance is otherwise normal. In this case, the pump was exchanged for a smaller, continuous-flow HeartMate II LVAD.

Identification of Device Malfunction in Patients Supported With the HeartMate XVE Left Ventricular Assist System

Predicting end-of-life for left ventricular assist devices is important to determine timing of device removal. A retrospective analysis was performed on 46 patients undergoing implantation of the latest HeartMate XVE from July 1, 2003, through March 31, 2006. Devices were assessed by analysis of motor current waveforms and quantification of the titanium or copper particles within dust localized to the driveline vent filter by optical, polarized light, scanning electron microscopy, and energy dispersive x-ray spectroscopy. Assessments were performed monthly for patients supported > or =330 days or for unexpected device alarms. Thirty-one (67%) patients were supported for <330 days and 15 (33%) were supported for > or =330 days. No malfunctions occurred in patients supported <330 days. For patients supported > or =330 days, five had abnormal current waveforms or copper and titanium dust localized to the vent filter. One underwent urgent transplantation, three underwent device replacement (one death; two ongoing), and one is with ongoing support. Of the remaining 10 patients, seven underwent transplantation; two remain on device; and one died while on left ventricular assist device support. There were no unexpected device failures. Bearing wear of the HeartMate XVE is predictable by analysis of current waveforms or titanium and copper dust within the vent filter.

Clinical comparison between HeartMate VE auto-mode and HeartMate XVE auto-mode with Opti-Fill and the effect of stroke volume on blood chamber and inflow valve peak pressures

We determined the difference between HeartMate (HM) VE auto mode, average filling 76 mL, and HM XVE Opti-Fill, average filling 79 mL, regarding blood chamber and inflow valve peak pressure pulses (BCPP and IVPP). The relation between stroke volume (SV) and peak pressures was investigated by using a circulatory mock loop. At high SVs, 79 to 83 mL, BCPP and IVPP never exceeded 400 mm Hg. For lower SVs, down to 50 mL, the peak pressures increased to 788 mm Hg for BCPP and 416 mm Hg for IVPP. Distribution of SV was measured in 2 VE and 6 XVE patients during rest and activities of daily living (ADL). For clinical comparison, percentages of SV >78 mL were determined. At rest, 2190 (VE) and 5772 (XVE) pump beats were registered and 4511 (VE) and 8713 (XVE) during ADL. Percentages of "SV >78 mL" at rest, respectively, were 42.5 +/- 3.5 and 78.2 +/- 4.7 (p < 0.01) and during ADL, respectively, 48.7 +/- 7.4 and 73.5 +/- 5.3 (p < 0.01). The Opti-Fill software shows a significant increase in percentage SV >78 mL and makes an important contribution to reducing the incidence of high peak pressures in the clinical setting.

Management of Multiple Left Ventricular Assist Device Failures in a Patient

Device failure is a rare but life-threatening complication in patients receiving mechanical circulatory support. Because patients are supported by these devices for longer periods, the incidence of device failure has increased. We report 3 instances of device failure and successful surgical management in a single patient.