Assist Device System Research Articles

Outcomes in Patients With HeartMate3 Versus HeartWare Ventricular Assist Device Implanted as Destination Therapy

Donor organ shortage caused a growing interest in mechanical circulatory support not only as a bridge to transplant but also as a destination therapy. Improved results and increased applicability and durability of left ventricular assist devices (LVADs) have established this treatment option as an alternative for patients with end-stage heart failure. The aim of the study was to compare the early results, major complications, and the follow up of all patients undergoing HeartMate3 (HM3) LVAD and HeartWare Ventricular Assist Device (HVAD) system implantation in one of the most experienced Clinic in Poland between 2015 and 2020. There were 78 individuals (72 male, 92%; 6 female, 8%), with median age 57 years (range, 50-62 years). Until 2020 we implanted 47 (60%) HVADs and 31 (40%) HM3 LVADs. Patient characteristics were comparable between both groups apart from median left ventricle diameter (8.2 cm [range, 7.4-8.4 cm] in HM3 group vs 7.2 cm [range, 6.7-7.9 cm] in HVAD group; P < .01) The overall survival was 53.2% in the HVAD group and 77.4% in the HM3 group (P =.03). Mean survival time was higher in HM3 group (2.97 years [range, 2.43-3.5 years] vs 2.51 years [range, 1.94-3.08 years]; P < .05). Mean complication-free survival time was also higher in the HM3 group (2.16 years [range, 1.55-2.76] vs 1.61 [range, 1.16-2.06 years]; P < .05), with overall complication-free rate of 54.8% for HM3 vs 29.8% for HVAD (P=.27). Median hospitalization time was comparable (31 days [range, 25-39 days] in the HM3 group vs 32 days [range, 24-38 days] in the HVAD group; P=.49). Patients supported with the HM3 had significantly fewer major complications than HVAD. Moreover, the HVAD was associated with higher mortality.

Continuous-flow left ventricular assist device systems infections: current outcomes and management strategies

Continuous-flow left ventricular assist device systems infections: current outcomes and management strategies

Continuous-flow left ventricular assist device systems infections: current outcomes and management strategies.

Left ventricular assisted devices (LVADs) are increasingly used for management of patients with advanced heart failure. However, infection remains one of the most commonly reported complications. Diagnosis, as well as treatment of LVAD infections is challenging. There are multiple diagnostic modalities that have been used to assist with accurate diagnosis of LVAD infections. Treatment of the infection can be especially challenging in these patients, given the presence of the implantable device that cannot be easily replaced or removed. There are no clinical trials assessing the best approach to diagnosis, treatment or long-term management of LVAD infections. In this article we review the most recent diagnostic modalities and treatment approaches, as well as offer our guidance on diagnosis and treatment of LVAD infections.

Comparing short‐term outcome after implantation of the HeartWare® HVAD® and the Abbott® HeartMate 3®

AimsCentrifugal continuous flow pumps are currently the state of the art in left ventricular assist device therapy. This study was conducted to compare the results after implantation of the HVAD® and the HeartMate 3®.Methods and resultsWe retrospectively analysed preoperative and post‐operative patient data of all 106 patients, who received a HeartMate 3 (HM3) at our centre between 2014 and 2018. A total of 392 patients receiving a sintered HVAD® served as controls. Patient matching was performed for age, sex, Interagency Registry for Mechanically Assisted Circulatory Support level at the time of implant, perioperative right heart failure, and implantation strategy, that is, bridge to transplant or destination therapy, as well as preoperative renal function, that is, as indicated by serum creatinine levels. A total of 79 matched pairs could be identified. During a median follow‐up of 15.3 months (range: 0–30 months), 23 (29.1%) and 19 (24.1%) patients died in the HVAD and HM3 groups, respectively, with a hazard ratio for mortality of 0.84 [95% confidence interval (CI): 0.46–1.54; P = 0.568]. Freedom from cerebrovascular events did not differ significantly between study groups, with a hazard ratio of 0.57 (95% CI: 0.23–1.45; P = 0.241). The risk of driveline infection was significantly lower in the HM3 (n = 33) than in the HVAD (n = 55) group (hazard ratio = 0.54; 95% CI: 0.35–0.84; P = 0.006). Eight HVAD, but no HM3, patients developed a pump thrombosis during follow‐up (P = 0.148).ConclusionsPerformance of both currently used centrifugal left ventricular assist device systems is comparable in terms of short‐term patient survival and freedom from cerebrovascular events. In our single‐centre experience, HM3 patients less frequently develop driveline infections and no pump thrombosis, which requires further evaluation.

Long-Term Survival of Patients With Advanced Heart Failure Receiving an Left Ventricular Assist Device Intended as a Bridge to Transplantation: The Registry to Evaluate the HeartWare Left Ventricular Assist System.

The paucity of available hearts for transplantation means that more patients remain on durable left ventricular support for longer periods of time. The Registry to Evaluate the HeartWare Left Ventricular Assist System was an investigator-initiated multicenter, prospective, single-arm database established to collect post-Conformité Européene mark clinical information on patients receiving the HeartWare ventricular assist device system as a bridge to transplantation. This registry represents the longest multicenter follow-up of primary left ventricular assist device outcomes. Data were collected on 254 commercial implants performed between February 2009 and March 2012 from 9 centers in Europe (7) and Australia (2). Patients were followed to device explant, heart transplantation, or death. The outcomes of patients through July/August 2018 were analyzed. Summary statistics were used to describe patient demographics, adverse events, length of support, and outcomes for this extended-term cohort. A total of 122 patients were on support for >2 years, and 34 patients were on support for >5 years. Twenty nine patients are still alive on support (support ranging from 1213 to 3396 days), and 23 of those are on their original HeartWare ventricular assist device system. Kaplan-Meier survival through 7 years was 51%. Through 6 years, freedom from any stroke was 82%, while freedom from severely disabling stroke was 89%. Low rates of heart transplant now require longer periods of left ventricular assist device support in patients. This analysis demonstrates that long-term support using a HeartWare ventricular assist device system offers survival of 51% through 7 years.

A Comparative Study of Hyperelastic Constitutive Models to Characterize the Behaviour of a Biopolymer Material for Diaphragm of Blood Pump Manufacturing

This article presents the results of the stress-strain state modelling of a blood pump diaphragm manufacturing from polyurethane ‘Vitur’ T-1413-85 for pulsatile type Ventricle Assist Device systems. Based on the analysis of the most distributed models of hyperelasticity, a model which most accurately describes the behaviour of the specified material has been determined (R2 = 0.9999 between numerical simulation and experimental uniaxial tensile tests data). Experimental studies have been carried out to determine the displacement of the diaphragm with a thickness of 0.3 mm and 0.5mm under the influence of control pressure. A comparison of the modelling results of the blood pump diaphragm stress-strain state and the conducted experimental studies on the determination of displacements confirmed the adequacy of the chosen model (R2 = 0.96 between numerical simulation and experiment) for both of the studied diaphragm thickness.

Risk Factors Associated with In-Hospital Mortality for Patients with Acute Abdomen After Cardiac Surgery.

Management of acute abdomen (AA) differs due to the heterogeneity of underlying pathophysiology. Complications of AA and its overall outcome after cardiac surgery are known to be associated with poor results. The aim of this retrospective analysis was to evaluate risk factors for AA in patients undergoing cardiac surgery. Between December 2011 and December 2014, a total of 131 patients with AA after cardiac surgery were identified and retrospectively analyzed using our institutional database. Statistical analysis of risk factors concerning in-hospital mortality of mentioned patient cohort was performed using IBM SPSS Statistics. Overall in-hospital mortality was 54.2% (71/131). Analyzing in-hospital non-survivors (NS) versus in-hospital survivors (S) peripheral artery disease (28.2% vs. 11.7%; p = 0.03), the need for assist device therapy (33.8% vs. 16.7%; p = 0.03) and the requirement of hemodialysis (67.6% vs. 23.3%; p < 0.01) were significantly higher in NS. Furthermore, lactic acid values at onset of symptoms were shown to be significantly higher in NS (5.7 ± 5.7mmol/L vs. 2.8 ± 2.9mmol/L; p < 0.01). Assured diagnosis of mesenterial ischemia was strongly associated with worse outcome (odds ratio 10.800, 95% confidence interval 2.003-58.224; p = 0.006). In conclusion, in critically ill patients after performed cardiac surgery peripheral vascular disease, need for supportive hemodynamic assist device systems and occurrence of renal failure are risk factors associated with worsen outcome. Additionally, rise of lactic acid could potentially be associated with onset of intestinal malperfusion and should be taken into account in therapeutic decisions preventing fatal mesenterial ischemia.

Monitoring of adult patient on venoarterial extracorporeal membrane oxygenation in intensive care medicine.

Nowadays high-tech medical assist device therapy is a crucial part of intensive care medicine. Especially, management of circulatory assist device systems poses an increasing challenge for intensive care medicine. So far, autonomous recommendations for monitoring of extracorporeal life support systems in the form of guidelines or position papers are lacking. The purpose of this paper was to present an orientation guide on this important topic.

Blood damage in Left Ventricular Assist Devices: Pump thrombosis or system thrombosis?

Despite significant technical advancements in the design and manufacture of Left Ventricular Assist Devices, post-implant thrombotic and thromboembolic complications continue to affect long-term outcomes. Previous efforts, aimed at optimizing pump design as a means of reducing supraphysiologic shear stresses generated within the pump and associated prothrombotic shear-mediated platelet injury, have only partially altered the device hemocompatibility. We examined hemodynamic mechanisms that synergize with hypershear within the pump to contribute to the thrombogenic potential of the overall Left Ventricular Assist Device system. Numerical simulations of blood flow in differing regions of the Left Ventricular Assist Device system, that is the diseased native left ventricle, the pump inflow cannula, the impeller, the outflow graft and the anastomosed downstream aorta, reveal that prothrombotic hemodynamic conditions might occur at these specific sites. Furthermore, we show that beyond hypershear, additional hemodynamic abnormalities exist within the pump, which may elicit platelet activation, such as recirculation zones and stagnant platelet trajectories. We also provide evidences that particular Left Ventricular Assist Device implantation configurations and specific post-implant patient management strategies, such as those allowing aortic valve opening, are more hemodynamically favorable and reduce the thrombotic risk. We extend the perspective of pump thrombosis secondary to the supraphysiologic shear stress environment of the pump to one of Left Ventricular Assist Device system thrombosis, raising the importance of comprehensive characterization of the different prothrombotic risk factors of the total system as the target to achieve enhanced hemocompatibility and improved clinical outcomes.

Right Ventricular Failure Post LVAD Implantation Corrected with Biventricular Support: An In Vitro Model

Right ventricular failure after left ventricular assist device (LVAD) implantation is associated with high mortality. Management remains limited to pharmacologic therapy and temporary mechanical support. Delayed right ventricular assist device (RVAD) support after LVAD implantation is associated with poorer outcomes. With the advent of miniaturized, durable, continuous flow ventricular assist device systems, chronic RVAD and biventricular assist device (BiVAD) support has been used with some success. The purpose of this study was to assess combined BiVAD and LVAD with delayed RVAD support within a four-elemental mock circulatory loop (MCL) simulating the human cardiovascular system. Our hypothesis was that delayed continuous flow RVAD (RVAD) would produce similar hemodynamic and flow parameters to those of initial BiVAD support. Using the MCL, baseline biventricular heart failure with elevated right and left filling pressures with low cardiac output was simulated. The addition of LVAD within a biventricular configuration improved cardiac output somewhat, but was associated with persistent right heart failure with elevated right-sided filling pressures. The addition of an RVAD significantly improved LVAD outputs and returned filling pressures to normal throughout the circulation. In conclusion, RVAD support successfully restored hemodynamics and flow parameters of biventricular failure supported with isolated LVAD with persistent elevated right atrial pressure.

Application of CAD/CFD/RP-technologies for development of LVAD systems

The important problem of new Left Ventricle Assist Device (LVAD) systems development is to determine their hemodynamic and functional characteristics and reduce the design time. An effective method for achieving this is the use of approaches based on the application of CAD/CFD/PR-technologies. Methods of computer modelling were applied to determine the geometrical parameters of the blood pump, and methods of finite element analysis were used for the optimization of hemodynamic parameters of the LVAD system. The geometrical modelling was carried out in the Pro/Engineer WF5. The CAE-system Ansys was used to analyze the blood flow in the chamber of the pump. The motion of the flexible walls was simulated by normal flow through rigid walls. At the final stage some models were prepared for prototyping. The critical parameters of hemodynamic gave the possibility to optimize the shape of the blood pump. The LVAD system and its components were made using various RP-technologies. The hydraulic tests for the performance investigation and the analysis of implantability for implantable systems were carried out for manufactured prototypes of LVAD systems. The manufactured components of the LVAD system are completely operability and give the possibility to estimate the critical hemodynamic and functional parameters of the LVAD system.

Identification and Management of Pump Thrombus in the HeartWare Left Ventricular Assist Device System: A Novel Approach Using Log File Analysis

ObjectivesThe study sought to characterize patterns in the HeartWare (HeartWare Inc., Framingham, Massachusetts) ventricular assist device (HVAD) log files associated with successful medical treatment of device thrombosis. BackgroundDevice thrombosis is a serious adverse event for mechanical circulatory support devices and is often preceded by increased power consumption. Log files of the pump power are easily accessible on the bedside monitor of HVAD patients and may allow early diagnosis of device thrombosis. Furthermore, analysis of the log files may be able to predict the success rate of thrombolysis or the need for pump exchange. MethodsThe log files of 15 ADVANCE trial patients (algorithm derivation cohort) with 16 pump thrombus events treated with tissue plasminogen activator (tPA) were assessed for changes in the absolute and rate of increase in power consumption. Successful thrombolysis was defined as a clinical resolution of pump thrombus including normalization of power consumption and improvement in biochemical markers of hemolysis. Significant differences in log file patterns between successful and unsuccessful thrombolysis treatments were verified in 43 patients with 53 pump thrombus events implanted outside of clinical trials (validation cohort). ResultsThe overall success rate of tPA therapy was 57%. Successful treatments had significantly lower measures of percent of expected power (130.9% vs. 196.1%, p = 0.016) and rate of increase in power (0.61 vs. 2.87, p < 0.0001). Medical therapy was successful in 77.7% of the algorithm development cohort and 81.3% of the validation cohort when the rate of power increase and percent of expected power values were <1.25% and 200%, respectively. ConclusionsLog file parameters can potentially predict the likelihood of successful tPA treatments and if validated prospectively, could substantially alter the approach to thrombus management.

Gastrointestinal Bleeding in Recipients of the HeartWare Ventricular Assist System

ObjectivesThis study evaluated gastrointestinal bleeding (GIB) in patients receiving the HeartWare HVAD System (HeartWare Inc., Framingham, Massachusetts) in the pivotal BTT (Bridge to Transplant) trial and under the continued access protocol (CAP). BackgroundGIB has become a significant problem for recipients of continuous flow device left ventricular assist devices (CF-LVAD). The need for anticoagulation and antiplatelet therapies complicates the management of GIB. MethodsBleeding events from 382 patients with advanced heart failure (140 patients enrolled in the BTT trial, and an additional 242 CAP patients) were analyzed. Post-implant anticoagulation consisted of heparin followed by warfarin at a target international normalized ratio of 2 to 3. Acetylsalicylic acid was recommended at 81 to 325 mg. ResultsOverall, 59 of 382 (15.4%) patients experienced 108 GIB events (0.27 events per patient year). Mean time to first bleed was 273.1 days and 86.1% of events occurred beyond 30 days. Freedom from GIB was 84.1% at 1 year. Median international normalized ratio at the time of first bleed was 2.4 ± 1.4. The most common etiology of bleeding identified was arteriovenous malformation and the most common site was the small intestine. Repeat bleeding was infrequent, though GIB patients required more readmissions and developed nondevice infections more frequently. No patients required surgical intervention and no deaths directly related to GIB occurred. ConclusionsRecipients of the HeartWare Ventricular Assist Device System had an incidence of 0.27 GIB/patient year with a freedom from GIB of 84.1% at 1 year. All patients with GIB events were managed with medical and endoscopic therapies, although 31% of patients experienced a recurrence of GIB. No surgical intervention was required. GIB did not impact survival. (Evaluation of the HeartWare Left Ventricular Assist Device for the Treatment of Advanced Heart Failure [ADVANCE]; NCT00751972)

Outpatient Management of Intra-Corporeal Left Ventricular Assist Device System in Children: A Multi-Center Experience

Little is known about the outcomes of children supported on intracorporeal left ventricular assist device (HVAD), and the feasibility of outpatient management. All centers with pediatric patients discharged from the hospital on the device were identified using company database. A total of 14 centers were contacted, with 9 centers, contributing data retrospectively. From 2011 to 2013, 12 pediatric patients (7 females), mean aged 11.9 ± 2.3 years (range 8-15), mean weight 43 ± 19 kg (range 18-81), mean body surface area 1.3 ± 0.3 m(2) (range 0.76-1.96) were identified. Diagnosis included: dilated cardiomyopathy (CMP) (n = 5), noncompaction CMP (n = 4), toxic CMP (n = 2) and viral CMP (n = 1). Indications for support were permanent support (n = 1), bridge to recovery (n = 1) and bridge to transplantation (n = 10). Prior to HVAD implantation, all patients received intravenous inotropes and two patients were on temporary mechanical support. Overall mortality was 0%. Mean duration of inpatient and outpatient support were 56 (range: 19-95 days) and 290 days (range: 42-790), respectively. Mean readmission rate was 0.02 per patient month (2.1 per patient). No adverse events involving emergency department occurred. Eight children resumed local schooling. Home discharge of children supported on HVAD is feasible and safe. School integration can be achieved. There is wide center variability to discharge practice for children.

Cannulation in aortic surgery: subclavian and axillary cannulation.

Cannulation of peripheral vessels is being frequently used as a standard access for establishing cardiopulmonary bypass (CPB) in recent times. Apart from an increased use in patients requiring left ventricular circulatory support, i.e. either extracorporeal membrane oxygenation or long-term ventricular assist device systems, peripheral vessel cannulation is also beneficial in aortic surgery. The subclavian and axillary arteries are commonly used as sites for arterial cannulation to establish CPB during aortic surgery in many centres. Both cannulation sites enable safe implementation of CPB in patients requiring complex and difficult reoperations and those undergoing aortic surgery for acute type A aortic dissections or artherosclerotic aortic disease, in which cerebral perfusion is required. Here, we describe our techniques of direct cannulation of the subclavian and axillary artery for aortic arch surgery.

Hemodynamic Evaluation of HeartWare MVAD in Normal and Infarct Swine Models

Purpose The HeartWare MVAD is a novel ventricular assist device* that utilizes a magnetically-levitated, axial flow system. The hemodynamic effects of the MVAD have not yet been fully elucidated. We sought to evaluate the hemodynamic effects of the MVAD in normal and infarct swine models. Methods and Materials We implanted the MVAD as a left ventricular assist device in 2 healthy adult male swines and 1 adult male swine subjected to 30 minutes of left circumflex artery occlusion followed by reperfusion. All 3 animals had the MVAD implanted via median sternotomy, using cardiopulmonary bypass, and a standard apical-to-aorta implantation technique. Following implantation, hemodynamic measurements were obtained using a left-ventricular conductance catheter with MVAD settings at low, medium, and high speeds. Results In the uninjured animal, mean MVAD flow (diamond line) across increasing speed settings did not change significantly, while both dP/dt-Max and LV stroke work (LVSW) showed significant LV unloading ( Figure 1A and 1C ) In the infarcted animal, mean MVAD flow increased directly with increasing speed settings and showed a trend towards a significant reduction in dP/dt-Max and LVSW (Figure 1B and 1D). Conclusions The HeartWare MVAD is a novel miniaturized ventricular assist device system that provides significant hemodynamic support. We observed that at low, medium and high speeds, the MVAD significantly reduced ventricular volume, pressure, and stroke work. * for investigational use only.

Evaluation of a Ventricular Assist Device System

Inadequate research exists regarding testing of a ventricular assist device (VAD) for susceptibility to radiation damage. Specifically, minimal data are available to radiation oncologists prescribing treatment plans for patients with an implanted VAD. As the number of implanted devices increases, patients requiring radiation at tissue sites near or at the device will increase. The purpose of this study is to provide the first analysis of radiation effects of proton beams on VADs. Five left VAD (LVAD) pumps (HeartWare Inc., Miami Lakes, FL) were exposed to proton beam radiation at a calibrated dose rate of 5 Gy/min up to a cumulative dose of 70 Gy. The Heartware LVAD pump recorded parameters including power (W), speed (revolutions/min), and estimated flow (L/min). Analysis of collected data after each irradiation found no deviation in pump parameters from baseline values. The Heartware LVAD pump exhibited no change in device function when directly irradiated by a high energy proton beam. Secondary neutron fluence created in the proton beam during irradiation had no effect on external components including the system controller and batteries powering the Heartware LVAD.

Hearts From the Deep Freezer? Novel Concept to Increase Safe Cardiac Preservation Times

Heart transplantation is still the gold standard to treat terminal heart insufficiency. A major limitation is donor shortage: the discrepancy between available organs and patients on the waiting lists increases continuously during the last two decades. Even the increasing use of assist device systems could not lead to lesser demand of donor hearts. Various efforts may increase the donor pool, which include the optimizing of brain-dead donors, increased used of marginal donors, and the extension of donor criteria as well as the increase of safe cardiac preservation times. It was shown that donor brain death significantly impairs cardiac function, which may lead to exclusion of organs from transplantation. Improved management strategies including adequate volume substitution and hormone replacement therapy can retrieve at least some of these organs for cardiac transplantation (1). In the last years, accumulating evidence shows that the transplantation of so-called marginal organs is feasible with acceptable to good clinical outcomes (2). Especially these groups of potential donor hearts, which are the majority of the offered organs in certain regions, would profit from improved cardiac preservation strategies. Therefore, recent research activities focus on the improvement of existing cardiac preservation solutions or the development of novel preservation strategies. Currently, it was shown that the modification of one of the most commonly used cardiac preservation solution histidine-tryptophan-ketoglurate (Custodiol; Dr F. Köhler Chemie GmbH, Bensheim, Germany) improves postischemic cardiac and vascular function (3) and may eligible for longer preservation times up to 12 hr. This solution is currently under clinical investigation. A complete different concept of cardiac preservation is continuous blood perfusion of donor organs. Some years ago, the company Transmedics introduced the Organ Care System. First clinical experience showed that continuous blood perfusion of donor hearts with subsequent successful transplantation is feasible. Although currently a clinical trial (PROCEED II) is under way, until now, no scientific data have been published, which showed a superiority of this concept in comparison to standard care or any additional advantage. Furthermore, the Organ Care System is extremely expensive (ca. (euro)200,000 [U.S. $252,080] device costs plus ca. (euro)40,000 [U.S. $37,812] material costs per each heart procurement) and needs significantly more human resources, which—in my opinion—precludes the use of this system in the clinical routine. Under these circumstances, alternative cardiac preservation strategies may significantly contribute to the improvement of graft quality and outcomes after heart transplantation. In the present article of Kato et al. (4), a novel method of subzero storage is described. The idea to preserve organs at subzero temperatures has been already discussed in the mid seventies (5). Nevertheless, for 40 years, less then a dozen scientific reports have been published in this topic. Although the advantages of supercooling are obvious, as we also know from the food industry, some adverse effects and technical issues precluded this concept from being used clinically. Freeze temperatures may destroy the tissue of the donor organs; therefore, different cryoprotectants such as polyethylene glycol or antifreeze protein had to be used to protect donor tissue, which in turn may have adverse effects during rewarming and after transplantation. The novel supercooling system, which is described in the present study, uses variable magnetic field to prevent crystallization of water and thereby tissue damage. In this system, the use of cryoprotectants is not necessary, and therefore, related adverse effects can be excluded. The application of this system led to an improved functional recovery and better preserved high-energy phosphate contents in a Langendorff model. Whether the donor hearts can be taken from the deep freezer in the near future remains unclear. Nevertheless, this promising new technology deserves further evaluation in more clinically relevant models.

Three-dimensional flow characteristics in ventricular assist devices: Impact of valve design and operating conditions

The use of paracorporeal ventricular assist devices has become a well-established procedure for patients with cardiogenic shock. However, implantation of ventricular assist devices is often associated with severe complications, such as thrombosis inside the ventricular assist device and subsequent embolic events. It was the purpose of this study to use flow-sensitive 4-dimensional magnetic resonance imaging for a detailed analysis of the 3-dimensional (3D) flow dynamics inside a clinical routine ventricular assist device and to study the effect of different system adjustments and a new valve design on flow patterns. A routinely used clinical paracorporeal ventricular assist device was integrated into a magnetic resonance-compatible mock loop. Flow-sensitive 3D magnetic resonance imaging was performed to measure time-resolved 3-directional flow velocities (spatial resolution ∼ 1.2 mm, temporal resolution = 42.4 ms) in the entire device under ideal conditions (full fill, full empty, ejection fraction = 88%), insufficient filling (ejection fraction = 81%), and insufficient emptying (ejection fraction = 67%) of the pump chamber. In addition, a new valve design was evaluated. Flexible control and monitoring of pressures at inlet and outlet were used to generate realistic boundary conditions. Flow pattern changes for different operating conditions were clearly identified and included reduced velocities during systolic outflow for impaired filling (78% reduction in pump flow compared with optimal operating conditions) and impaired clearing of the pump chamber for insufficient emptying (52% reduction). For all operating conditions, 3D visualization revealed vortex flow inside the ventricular assist device at typical locations of thrombus formation near the valve systems. Most noticeably, the new valve design provided similar global ventricular assist device function (pump flow 3.6 L/min), but vortex formation was eliminated. The results of this study provide insight into the mechanisms underlying possible thrombus formation inside a ventricular assist device and the effect of different system adjustments. The presented methods may permit the optimization of future ventricular assist device systems with respect to optimal flow conditions.

Left ventricular assist devices decrease fixed pulmonary hypertension in cardiac transplant candidates

Fixed pulmonary hypertension is a contraindication for cardiac transplantation because of the increased risk of donor heart failure. We sought to determine whether left ventricular assist devices improve fixed pulmonary hypertension in cardiac transplant candidates to enable safe cardiac transplantation. Thirty-five consecutive cardiac transplant candidates (age 56 +/- 6 years, 88.5% were men) with fixed pulmonary hypertension (5.1 +/- 2.6 Wood units) resistant to medical treatment received a left ventricular assist device as a bridge to transplantation. Three left ventricular assist device systems were used (pulsatile blood flow: Novacor [World Heart Inc, Oakland, Calif] n = 8; continuous blood flow: MicroMed DeBakey [MicroMed Technology Inc, Houston, Tex] n = 24, DuraHeart [Terumo Heart Inc, Ann Arbor, Mich] n = 3). Right-sided heart catheter data were obtained before left ventricular assist device implantation at 3-day and 6-week follow-ups. Clinical data and complications were recorded. Before left ventricular assist device implantation, the pulmonary vascular resistance was 5.1 +/- 2.8 Wood units. Values were comparable in patients receiving pulsatile (5.1 +/- 3.4 Wood units) or continuous blood flow left ventricular assist devices (5.1 +/- 2.7 Wood units, P = .976). Left ventricular assist device implantation decreased pulmonary vascular resistance at 3-day (2.9 +/- 1.3 Wood units, P < .0001) and 6-week (2.0 +/- 0.8 Wood units, P < .0001) follow-ups compared with before implantation. This effect was independent of the type of left ventricular assist device system used (3-day follow-up: pulsatile flow: 3.2 +/- 1.3 Wood units vs continuous flow: 2.7 +/- 1.2 Wood units; P = .310 and 6-week follow-up: pulsatile flow: 1.9 +/- 0.9 Wood units vs continuous flow: 2.1 +/- 0.8 Wood units; P = .905). Twenty-four patients had successful bridges to transplantation (69%, mean time on left ventricular assist device 210 +/- 83 days), and 11 patients died before transplantation (31%, mean time on left ventricular assist device 67 +/- 30 days). The 1-year survival after transplantation was 95%. Left ventricular assist devices decrease fixed pulmonary hypertension in cardiac transplant candidates and allow patients to overcome a contraindication for cardiac transplantation. Therefore, left ventricular assist devices should be considered in all cardiac transplant candidates with fixed pulmonary hypertension.