The Effect of Intermittent Low Speed Mode Upon Aortic Valve Opening in Calves Supported With a Jarvik 2000 Axial Flow Device

Aortic Root Thromboembolism and Associated Acute Myocardial Infarction in Patients With Contemporary Durable LVADs

Patients with HeartMate 3 left ventricular assist devices may develop aortic root thrombus, yet its prevalence and associated risks are unknown. We present 2 patients who developed aortic root thromboembolism and acute coronary occlusions. We additionally present heart transplantation as viable treatment for thromboembolic disease and refractory right ventricular failure.

Encouraging Regular Aortic Valve Opening for EVAHEART 2 LVAD Support Using Virtual Patient Hemodynamic Speed Modulation Analysis

This study focuses on investigating the EVAHEART 2 left ventricular assist device (LVAD) toward designing optimal pump speed modulation (PSM) algorithms for encouraging aortic valve (AV) flow. A custom-designed virtual patient hemodynamic model incorporating the EVAHEART 2 pressure-flow curves, cardiac chambers, and the systemic and pulmonary circulations was developed and used in this study. Several PSM waveforms were tested to evaluate their influence on the mean arterial pressure (MAP), cardiac output (CO), and AV flow for representative heart failure patients. Baseline speeds were varied from 1,600 to 2,000 rpm. For each baseline speed, the following parameters were analyzed: 1) PSM ratio (reduced speed/baseline speed), 2) PSM duration (3-7 seconds), 3) native ventricle contractility, and 4) patient MAP of 70 and 80 mm Hg. More than 2,000 rpm virtual patient scenarios were explored. A lower baseline speed (1,600 and 1,700 rpm) produced more opportunities for AV opening and more AV flow. Higher baseline speeds (1,800 and 2,000 rpm) had lower or nonexistent AV flow. When analyzing PSM ratios, a larger reduction in speed (25%) over a longer PSM (5+ seconds) duration produced the most AV flow. Lower patient MAP and increased native ventricle contractility also contributed to improving AV opening frequency and flow. This study of the EVAHEART 2 LVAD is the first to focus on leveraging PSM to enhance pulsatility and encourage AV flow. Increased AV opening frequency can benefit aortic root hemodynamics, thereby improving patient outcomes.

Aortic valve opening in mock-loop with continuous-flow left ventricular assist device

The appropriate opening of aortic valves is crucial for heart failure (HF) patients with left ventricular assist devices (LVADs). Nevertheless, up to the present time, aortic valve monitoring has not been performed in discharged patients. In this study, a mock-loop platform was developed to investigate the aortic valve performance in LVAD patients. An additional sluice valve was placed next to the aortic valve that when the sluice valve is manually closed, the aortic valve will remain closed; when the sluice valve is open, the aortic valve is opened or closed upon the pressures. The results showed that when the LVAD speed was below 2600 rpm, the aortic valve can be intermittently opened, while when the LVAD speed was over 2600 rpm, the aortic valve was persistently closed. The left ventricular end-systolic pressure (LVESP) was found to be an indicator of aortic valve closure that, upon the aortic valve closure LVESP suddenly decreased. The LVESP is suggested for future monitoring the status of the aortic valve for patients with implanted LVADs. The effects of heart failure (HF) degrees, circulation resistance, and aortic compliance on aortic valve closure were further studied. The results revealed that LVAD implantation in patients with early HF degrees will help to avoid persistent aortic valve closure.

Factors influencing the functional status of aortic valve in ovine models supported by continuous-flow left ventricular assist device

Objectives

An acute animal experiment was performed to observe factors influencing the functional status of the aortic valve functional status after continuous‐flow left ventricular assist device (CF‐LVAD) implantation in an ovine model, and a physiologic predictive model was established.

Methods

A CF‐LVAD model was established in Small Tail Han sheep. The initial heart rate (HR) was set to 60 beats/min, and grouping was performed at an interval of 20 beats/min. In all groups, the pump speed was started from 2000 rpm and was gradually increased by 50–100 rpm. A multi‐channel physiological recorder recorded the HR, aortic pressure, central venous pressure, and left ventricular systolic pressure (LVSP). A double‐channel ultrasonic flowmeter was used to obtain real‐time artificial vascular blood flow (ABF). A color Doppler ultrasound device was applied to assess the aortic valve functional status. Multivariate dichotomous logistic regression was used to screen significant variables for predicting the functional status of the aortic valve.

Results

Observational studies showed that ABF and the risk of aortic valve closure (AVC) were positively correlated with pump speed at the same HR. Meanwhile, the mean arterial pressure (MAP) was unaltered or slightly increased with increased pump speed. When the pump speed was constant, an increase in HR was associated with a decrease in the size of the aortic valve opening. This phenomenon was accompanied by an initial transient increase in the ABF and MAP, which subsequently decreased. Statistical analysis showed that the AVC was associated with increased pump speed (OR = 1.02, 95% CI = 1.01–1.04, p = 0.001), decreased LVSP (OR = 0.95, 95% CI = 0.91–0.98, p = 0.003), and decreased pulse pressure (OR = 0.82, 95% CI = 0.68–0.96, p = 0.026). ABF or MAP was negatively associated with the risk of AVC (OR < 1). The prediction model of AVC after CF‐LVAD implantation exhibited good differentiation (AUC = 0.973, 95% CI = 0.978–0.995) and calibration performance (Hosmer–Lemeshow χ² = 9.834, p = 0.277 > 0.05).

Conclusions

The pump speed, LVSP, ABF, MAP, and pulse pressure are significant predictors of the risk of AVC. Predictive models built from these predictors yielded good performance in differentiating aortic valve opening and closure after CF‐LVAD implantation.

Performance of the Jarvik 2000 left ventricular assist device on mid-term hemodynamics and exercise capacity

The hemodynamic and exercise capacity performance of the Jarvik 2000 left ventricular assist device (LVAD), which is generally used in patients with small body size and relatively preserved cardiac function, is not well understood. We retrospectively examined 18 patients implanted with the Jarvik 2000 LVAD. Pump rotation speed was optimized by the hemodynamic ramp test one year after implantation based on the criteria of mean pulmonary capillary wedge pressure (PCWP) < 18 mmHg, mean right atrial pressure (RAP) < 12 mmHg, and cardiac index (CI) > 2.2 L/min/m² as well as echocardiographic parameters. Exercise capacity was assessed by cardiopulmonary exercise test in an optimized setting. To investigate the impacts of larger body surface area (BSA) and extremely impaired pre-implantation cardiac function on hemodynamics and exercise capacity, two correlation analyses based on BSA and original CI were performed. At a pump speed of 9500 ± 707 rpm, the mean pulmonary artery pressure, PCWP, RAP, and CI were 17 ± 5 mmHg, 9 ± 5 mmHg, 6 ± 4 mmHg, and 2.82 ± 0.54 L/min/m², respectively. Only one patient failed to achieve the hemodynamic criteria. The peak VO₂ and VE/VCO₂ slope were 12.9 ± 3.1 mL/min/kg and 37.7 ± 15.0, respectively. There was an inverse correlation between original CI and heart rate (r = -0.60, p  =  0.01), and a weak correlation between BSA and PCWP (r  =  0.43, p  =  0.08). Based on this study, the overall performance of the Jarvik 2000 device was acceptable, and the patients' body size and original cardiac function had minimum effect on the performance of this device.

Prediction of aortic valve regurgitation after continuous-flow left ventricular assist device implantation using artificial intelligence trained on acoustic spectra

Significant aortic regurgitation (AR) is a common complication after continuous-flow left ventricular assist device (LVAD) implantation. Using machine-learning algorithms, this study was designed to examine valuable predictors obtained from LVAD sound and to provide models for identifying AR. During a 2-year follow-up period of 13 patients with Jarvik2000 LVAD, sound signals were serially obtained from the chest wall above the LVAD using an electronic stethoscope for 1 min at 40,000 Hz, and echocardiography was simultaneously performed to confirm the presence of AR. Among the 245 echocardiographic and acoustic data collected, we found 26 episodes of significant AR, which we categorized as “present”; the other 219 episodes were characterized as “none”. Wavelet (time–frequency) analysis was applied to the LVAD sound and 19 feature vectors of instantaneous spectral components were extracted. Important variables for predicting AR were searched using an iterative forward selection method. Seventy-five percent of 245 episodes were randomly assigned as training data and the remaining as test data. Supervised machine learning for predicting concomitant AR involved an ensemble classifier and tenfold stratified cross-validation. Of the 19 features, the most useful variables for predicting concomitant AR were the amplitude of the first harmonic, LVAD rotational speed during intermittent low speed (ILS), and the variation in the amplitude during normal rotation and ILS. The predictive accuracy and area under the curve were 91% and 0.73, respectively. Machine learning, trained on the time–frequency acoustic spectra, provides a novel modality for detecting concomitant AR during follow-up after LVAD.

Evolutionary Improvements in the Jarvik 2000 Left Ventricular Assist Device

Mechanical circulatory support devices experience a wide range of operating conditions during patient use. Since its first implant in June 2000, the Jarvik 2000 left ventricular assist device has witnessed systematic stepwise modifications to reduce the risk of serious adverse events and improve patient outcomes. Over time, clinical experience revealed a number of low-incidence failure modes that presented opportunities for improvement. Design changes have included, but are not limited to, a Y cable to permit battery changes without pump stoppage, increased pull strength of external cables from 35 to 200 lbs, an intermittent low-speed controller to improve aortic root washout, sintered titanium microsphere surface on the pump housing to prevent apical thrombus, and novel cone bearings to reduce thrombus formation. In summary, real world conditions challenge devices in ways that laboratory or animal experiments do not. Thorough case reviews have led to many improvements as the Jarvik 2000 continues through its second decade of implants.

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

Introduction:

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.

Methods:

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.

Results:

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.

Conclusion:

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.

The Influence of Rotary Blood Pump Speed Modulation on the Risk of Intraventricular Thrombosis

Rotary left ventricular assist devices (LVADs) are commonly operated at a constant speed, attenuating blood flow pulsatility. Speed modulation of rotary LVADs has been demonstrated to improve vascular pulsatility and pump washout. The effect of LVAD speed modulation on intraventricular flow dynamics is not well understood, which may have an influence on thromboembolic events. This study aimed to numerically evaluate intraventricular flow characteristics with a speed modulated LVAD. A severely dilated anatomical left ventricle was supported by a HeartWare HVAD in a three-dimensional multiscale computational fluid dynamics model. Three LVAD operating scenarios were evaluated: constant speed and sinusoidal co- and counter-pulsation. In all operating scenarios, the mean pump speed was set to restore the cardiac output to 5.0 L/min. Co- and counter-pulsation was speed modulated with an amplitude of 750 rpm. The risk of thrombosis was evaluated based on blood residence time, ventricular washout, kinetic energy densities, and a pulsatility index map. Blood residence time for co-pulsation was on average 1.8 and 3.7% lower than constant speed and counter-pulsation mode, respectively. After introducing fresh blood to displace preexisting blood for 10 cardiac cycles, co-pulsation had 1.5% less old blood in comparison to counter-pulsation. Apical energy densities were 84 and 27% higher for co-pulsation in comparison to counter-pulsation and constant speed mode, respectively. Co-pulsation had an increased pulsatility index around the left ventricular outflow tract and mid-ventricle. Improved flow dynamics with co-pulsation was caused by increased E-wave velocities which minimized blood stasis. In the studied scenario and from the perspective of intraventricular flow dynamics, co-pulsation of rotary LVADs could minimize the risk of intraventricular thrombosis.

Intermittent Aortic Valve Opening and Risk of Thrombosis in Ventricular Assist Device Patients

The current study evaluates quantitatively the impact that intermittent aortic valve (AV) opening has on the thrombogenicity in the aortic arch region for patients under left ventricular assist device (LVAD) therapy. The influence of flow through the AV, opening once every five cardiac cycles, on the flow patterns in the ascending aortic is measured in a patient-derived computed tomography image-based model, after LVAD implantation. The mechanical environment of flowing platelets is investigated, by statistical treatment of outliers in Lagrangian particle tracking, and thrombogenesis metrics (platelet residence times and activation state characterized by shear stress accumulation) are compared for the cases of closed AV versus intermittent AV opening. All hemodynamics metrics are improved by AV opening, even at a reduced frequency and flow rate. Residence times of platelets or microthrombi are reduced significantly by transvalvular flow, as are the shear stress history experienced and the shear stress magnitude and gradients on the aortic root endothelium. The findings of this device-neutral study support the multiple advantages of management that enables AV opening, providing a rationale for establishing this as a standard in long-term treatment and care for advanced heart failure patients.

Late de Novo Aortic Regurgitation with the Jarvik 2000 Flowmaker® left ventricular assist device

Introduction

There is a worldwide trend towards a more liberal use of ventricular assist devices (VADs) as a definitive treatment for patients in end-stage heart failure. This has also led to a new set of complications related to the prolonged interaction between the native heart and the device.

Methods

We report a case of, late, de novo aortic regurgitation (AR), leading to acute pulmonary edema in a 56-year-old man, 20 months after the implantation of a left ventricular assist device (LVAD), the Jarvik 2000 Flowmaker®, as destination therapy for end-stage heart failure.

Results

The Jarvik 2000 was working well at check up at level 3 of assistance, i.e. generating a flow between 3–5 l/min at 10,000 rpm. The only new finding was a moderate, de novo, AR at trans-thoracic echocardiogram (TTE). The patient was assisted in intensive care with inotropic and diuretic support and made a good recovery. He remains under close follow up in NYHA class II with the same level of mechanical assistance and a more intensive diuretic therapy.

Conclusions

This case shows how dramatic the onset of de novo AR in patients with LVAD can be. The AR occurred despite the presence of the ILS (intermittent low speed) that allows the opening of the native aortic valve for 8 seconds every 64 and should, theoretically, preserve the native aortic valve. To our knowledge, this is the first report of de novo AR in a patient with the Jarvik 2000 axial flow device.

Exertional Angina Due To Fused Aortic Bioprosthesis During Left Ventricular Assist Device Support: Two Cases and Review of the Literature

We present the case of two patients with idiopathic dilated cardiomyopathy and moderate aortic valve regurgitation that were treated with a bioprosthetic valve at the time of the left ventricular assist device (LVAD) implantation. A few months later, patients revealed partial recovery in the left ventricle systolic function. Both patients, during the LVAD turndown protocol, reported the onset of chest pain. The transthoracic echocardiography revealed the presence of a new transaortic pressure gradient. We confirmed the presence of a fused bioprosthetic valve by further performing a transesophageal echocardiogram and a left and right heart catheterization. Replacement of aortic valve at the time of an LVAD implantation constitutes a challenging case. Although a mechanical valve is contraindicated due to the increased thromboembolic risk, selecting a bioprosthetic valve increases the risk of valve leaflets fusion. The consequences of this phenomenon should be acknowledged in LVAD patients undergoing aortic valve replacement with a bioprosthetic, especially under the view of LVAD explantation for those revealing myocardial recovery under mechanical unloading.

Mitral Valve Regurgitation with a Rotary Left Ventricular Assist Device: The Haemodynamic Effect of Inlet Cannulation Site and Speed Modulation

Mitral valve regurgitation (MVR) is common in patients receiving left ventricular assist device (LVAD) support, however the haemodynamic effect of MVR is not entirely clear. This study evaluated the haemodynamic effect of MVR with LVAD support and the influence of inflow cannulation site and LVAD speed modulation. Left atrial (LAC) and ventricular (LVC) cannulation was evaluated in a mock circulation loop with no, mild, moderate and severe MVR with constant speed and speed modulation (±600 RPM) modes. The use of an LVAD relieved pulmonary congestion during severe MVR, by reducing left atrial pressure from 20.5 to 10.8 (LAC) and 11.5 (LVC) mmHg. However, LAC resulted in decreased left ventricular stroke work (-0.08 J), ejection fraction (-7.9%) and higher MVR volume (+12.7 mL) and pump speed (+100 RPM) compared to LVC. This suggests that LVC, in addition to reducing MVR severity, also improves ventricular washout over LAC. LVAD speed modulation in synchrony with ventricular systole reduced MVR volume and increased ejection fraction with LAC and LVC, thus demonstrating the potential benefits of this mode, despite a reduction in cardiac output.

First Biventricular Jarvik 2000 Implants (Retroauricular Version) Via a Median Sternotomy

OBJECTIVES

Organ shortages and increased numbers of nontransplant older patients have necessitated a search for alternatives to heart transplants. The Jarvik 2000 assist device (Jarvik Heart, Inc., Manhattan, NY, USA), as a small long-term axial flow pump, offers many advantages, such as retroauricular power supply, which minimizes driveline infection risks. When implanted biventricularly, the device may offer support for patients with biventricular heart failure, especially for nontransplant patients as a destination therapy.

MATERIALS AND METHODS

We implanted biventricular Jarvik 2000 systems into 3 men (aged, 65.3 ± 5.0 y; ejection fraction, 24.7% ± 1.5% for left ventricle and 17.7% ± 5.0% for right ventricle). These were the first patients worldwide to receive a biventricular Jarvik 2000 device with retroauricular power supply via a median sternotomy and with additional cardiac surgical procedures.

RESULTS

No technical problems were noted during biventricular assist device implant. Mean support time on the device was 224 ± 198 days. All 3 patients showed sufficient cardiac support; 2 patients died from noncardiac complications. Patient 1 died on day 3 as a result of postoperative hepatic failure after preoperative reanimation, and patient 3 died as a result of an ileus and colon perforation after 50 days. Patient 2 died of ventricular fibrillation (after 1.5 y), which occurred 1 year after right ventricular pump shutdown, although significant improvement of right ventricle function was shown (ejection fraction increased by 48%).

CONCLUSIONS

Our 3 patients were old, had multiple comorbidities, and needed further cardiac surgery. None of the patients died as a result of technical failure of the device but because of complications accompanying their morbidities. If complication rates can be reduced, a biventricular assist device implant could and should be considered as a potential alternative for nontransplant patients.

Aortic Valve Function Under Support of a Left Ventricular Assist Device: Continuous vs. Dynamic Speed Support

Continuous flow left ventricular devices (CF-LVADs) support the failing heart at a constant speed and alters the loads on the aortic valve. This may cause insufficiency in the aortic valve under long-term CF-LVAD support. The aim of this study is to assess the aortic valve function under varying speed CF-LVAD support. A Medtronic freestyle valve and a Micromed DeBakey CF-LVAD were tested in a mock circulatory system. First, the CF-LVAD was operated at constant speeds between 7500 and 11,500 rpm with 1000 rpm intervals. The mean pump outputs obtained from these tests were applied in varying speed CF-LVAD support mode using a reference model for the pump flow. The peak of the instantaneous pump flow was applied at peak systole and mid-diastole, respectively. Ejection durations and in the aortic valve were the longest when the peak pump flow was applied at mid-diastole among the CF-LVAD operating modes. Furthermore, mean aortic valve area over a cardiac cycle was highest when the peak pump flow was applied at mid-diastole. The results show that changing phase of the reference flow rate signal may reduce the effects of the CF-LVADs on altered aortic valve closing behavior, without compromising the overall pump support level.

Physiologic and hematologic concerns of rotary blood pumps: what needs to be improved?

Over the past few decades, advances in ventricular assist device (VAD) technology have provided a promising therapeutic strategy to treat heart failure patients. Despite the improved performance and encouraging clinical outcomes of the new generation of VADs based on rotary blood pumps (RBPs), their physiologic and hematologic effects are controversial. Currently, clinically available RBPs run at constant speed, which results in limited control over cardiac workload and introduces blood flow with reduced pulsatility into the circulation. In this review, we first provide an update on the new challenges of mechanical circulatory support using rotary pumps including blood trauma, increased non-surgical bleeding rate, limited cardiac unloading, vascular malformations, end-organ function, and aortic valve insufficiency. Since the non-physiologic flow characteristic of these devices is one of the main subjects of scientific debate in the literature, we next emphasize the latest research regarding the development of a pulsatile RBP. Finally, we offer an outlook for future research in the field.

Assessment of aortic valve opening during rotary blood pump support using pump signals

During left ventricular support by rotary blood pumps (RBPs), the biomechanics of the aortic valve (AV) are altered, potentially leading to adverse events like commissural fusion, valve insufficiency, or thrombus formation. To avoid these events, assessment of AV opening and consequent adaptation of pump speed seem important. Additionally, this information provides insight into the heart-pump interaction. The aim of this study was to develop a method to assess AV opening from the pump flow signal. Data from a numerical model of the cardiovascular system and animal experiments with an RBP were employed to detect the AV opening from the flow waveform under different hemodynamic conditions. Three features calculated from the pump flow waveform were used to classify the state of the AV: skewness, kurtosis, and crest factor. Three different classification algorithms were applied to determine the state of the AV based on these features. In the model data, the best classifier resulted in a percentage of correctly identified beats with a closed AV (specificity) of 99.9%. The percentage of correctly identified beats with an open AV (sensitivity) was 99.5%. In the animal experiments, specificity was 86.8% and sensitivity reached 96.5%. In conclusion, a method to detect AV opening independently from preload, afterload, heart rate, contractility, and degree of support was developed. This algorithm makes the evaluation of the state of the AV possible from pump data only, allowing pump speed adjustment for a frequent opening of the AV and providing information about the interaction of the native heart with the RBP.

In vitro hydrodynamic analysis of pin and cone bearing designs of the Jarvik 2000 adult ventricular assist device

The Jarvik 2000 adult ventricular assist device (VAD) is a second-generation blood pump with mechanical contact bearings. The original configuration of the pump employed a pin bearing and a more recent configuration uses a cone bearing. We compare the hydrodynamic performance of the two designs under steady-state and pulsatile flow conditions in vitro. Furthermore, we employ the Intermittent Low Speed (ILS) Flowmaker Controller to demonstrate the effect on pulsatility index (PI) performance of both device configurations. We use an open-loop flow system in both steady-state and pulsatile arrangements, complete with pressure transducers and flow probes. Working fluid was a 3.6 cP blood-analog, glycerin-water solution. Steady-state flow tests were carried out to determine pressure-flow (H-Q) performance curves. Pulsatile tests under normotensive, hypertensive, and hypotensive conditions were executed with controller speed 3 (10710 ± 250 rpm) at 100 beats per minute. Steady-state tests show greater capacity for pressure and flow with the cone bearing, compared with pin bearing, with best efficiency point (BEP) 68% greater for cone bearing. Pulsatile tests show the cone bearing design to yield a 20% increase in Qavg , a 17% decrease in pulsatility index (PIQ ), and a qualitative increase in pressure responsivity. The ILS mode (for both bearing designs) decreases Qavg by 68% and likewise increases PIQ by 360% and pulsatility ratio (Rpul ) by 200%. The ILS controller regularly reduces the flow, increasing pulsatility index during device operation. The Jarvik 2000 continuous-flow VAD can sustain pulsatile flow under pulsating pressure conditions. The new cone bearing design yields increased flow rates over the earlier pin bearing design.

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.

Newer-generation ventricular assist devices

The latest generation of ventricular assist devices has evolved from the pulsatile, volume-displacement pumps of the 1990s to today's non-pulsatile, constant pressure-generating rotary pumps. These pumps include both centrifugal and axial flow devices that are currently being used or are in advanced development. Rotary pumps have the advantage of a much longer and more reliable duty life than pulsatile pumps. They are also considerably smaller than pulsatile pumps, requiring less invasive surgery for implantation and smaller transcutaneous (electrical rather than pneumatic) drivelines. Most of these devices have been approved as a bridge to transplant (BTT) while some are currently in trials for destination therapy (DT) in Europe (Conformité Européenne (CE) mark) or the United States (Food and Drug Administration (FDA)). This article discusses the current generation of pumps, examining particular design features as highlighted by the designers as well as the current approval status of each device in the United States and Europe.

Late aortic insufficiency related to poor prognosis during left ventricular assist device support

BACKGROUND

Management of native aortic insufficiency (AI) during left ventricular assist device (LVAD) support is challenging. We investigated the occurrence of de novo AI during long-term LVAD support to identify its effect on late clinical and echocardiographic outcomes.

METHODS

Left ventricular assist devices were implanted in 99 patients with dilated cardiomyopathy, of whom 47 without preoperative AI were investigated using serial echocardiography examinations for more than 1 year after the operation.

RESULTS

The mean duration of LVAD support was 838±327 days, and 26 patients (55%) were supported for more than 2 years. Twenty-nine patients (62%) had no AI (group A), whereas de novo AI developed in the remaining 18 (38%; group B) at 1 year after LVAD implantation (≥grade 2 in 5, grade 1 in 13). The LV end-diastolic diameter was significantly reduced after LVAD implantation in both groups, with no significant difference between them. Overall survival was better in group A (p=0.0195). Multivariate analysis revealed that preoperative mitral regurgitation of more than grade 2 (odds ratio, 7.8; 95% confidence interval, 1.2 to 48.6; p=0.028) and an aortic valve that remained closed at 1 month after implantation (odds ratio, 6.7; 95% confidence interval, 1.0 to 43.9; p=0.048) were significant independent predictors of de novo AI at 1 year after LVAD implantation.

CONCLUSIONS

Survival was significantly worse when de novo AI developed in patients during long-term LVAD. Our findings indicate that preoperative functional mitral regurgitation and postoperative aortic valve opening are related to the progression of AI during long-term LVAD support.

Biventricular support using implantable continuous-flow ventricular assist devices

A 34-year-old woman with fulminant myocarditis underwent emergent implant with the Toyobo (Nipro, Osaka, Japan) paracorporeal biventricular assist device (BiVAD). The patient had been stable for 6 months, until she started to develop heart failure symptoms due to severe pulmonary insufficiency. Pulmonary valve closure and BiVAD conversion to implantable rotary pumps was performed. A DuraHeart centrifugal pump (Terumo Heart Inc., Ann Arbor, MI) was used for left ventricular assist, and a Jarvik 2000 axial-flow pump (Jarvik Heart Inc., New York, NY) was used for right ventricular assist. Although strict management was required to balance the flow rates of the two different types of devices, her postoperative course was uneventful and she was discharged home.

Aortic valve pathophysiology during left ventricular assist device support

The increased applicability and excellent results with left ventricular assist devices (LVADs) have revolutionized the available treatment options for patients with advanced heart failure. Pre-existing valve abnormalities are common in this population, and subsequent development of valve abnormalities after LVAD placement is also often noted. Although native mitral and tricuspid valve disease is more common in heart failure patients before LVAD placement, aortic valves are much more likely to generate abnormal pathophysiology in the LVAD patient during as well as after LVAD placement. The aim of this comprehensive review is to review aortic valve function in LVAD patients and highlight the consideration of pre-existing valve disease on patient treatment at the time of LVAD implant. The basis for structural changes leading to valve pathophysiology during and after LVAD placement will be described, providing a basis for improved clinical understanding and new strategies to prevent these conditions.

Ventricular assist device outflow-graft site: effect on myocardial blood flow

BACKGROUND

Recent advances in left ventricular assist device (LVAD) technology have resulted in small, durable, energy-efficient, continuous-flow blood pumps that can support patients with end-stage heart failure. However, the effects of reduced or nonpulsatile flow on end-organ function are unclear. We performed a pilot study in calves with a continuous-flow LVAD to assess the effects of the pump's outflow-graft location (ascending versus descending aorta) on myocardial blood flow.

MATERIALS AND METHODS

In 8 healthy calves, we implanted the Jarvik 2000 LVAD in the left ventricular apex without the use of cardiopulmonary bypass. We anastomosed the outflow graft to either the ascending aorta (group 1; n = 4) or the descending aorta (group 2; n = 4). Hemodynamic parameters, myocardial oxygen consumption, and regional myocardial blood flow (analyzed with colored microspheres) were assessed at baseline (pump off) and during pump operation at 8000, 10,000, and 12,000 rpm.

RESULTS

No intergroup differences were found in the aortic pressure, heart rate, central venous pressure, pump-flow to total-cardiac-flow ratio, or blood flow in the left anterior descending and right posterior descending coronary arteries at increasing pump speeds. Neither myocardial oxygen consumption nor myocardial tissue perfusion differed significantly between the two groups.

CONCLUSIONS

Regardless of the outflow-graft location (ascending versus descending aorta), the continuous-flow LVAD unloaded the left ventricle and did not adversely affect myocardial perfusion in either the right or left ventricle. Owing to the small number of animals studied, however, the most we can conclude is that neither outflow-graft location appeared to be inferior to the other.

Midterm experience with the Jarvik 2000 axial flow left ventricular assist device

OBJECTIVE

Rotary axial flow pumps have several potential advantages and disadvantages over pulsatile pumps. The Jarvik 2000 is distinctive in being intracardiac. We report our experience in 22 patients.

METHODS

The Jarvik 2000 was implanted in 15 men and 7 women. Mean age was 38.8 (range 23-59) years, preoperative diagnosis was dilated cardiomyopathy in 16, postpartum cardiomyopathy in 3, ischemic heart disease in 2, and chronic allograft failure in 1. Twenty-one patients were in New York Heart Association class IV, and 1 patient was in class III. Nineteen patients were on inotropic support, 6 were supported with an intra-aortic balloon pump, and 2 patients had been salvaged with a Centrimag (Levitronix) ventricular assist device. The median pulmonary vascular resistance was 3 Wood units; median pulmonary capillary wedge pressure was 26.6 mm Hg; and mean Cardiac Index was 1.5 L/min/m2.

RESULTS

There were 2 early deaths and 6 late deaths. The average postoperative ventilation time and Intensive Treatment Unit stay was 2.2 and 10 days, respectively. One patient required a right ventricular assist device for short-term support and another for medium-term support. Seven patients were bridged to transplant, 3 had myocardial recovery, and 4 are ongoing. Mean and total duration of support was 280.5 and 6172 days, respectively. Driveline failures were noted in 3, but there were no pump infections or failure.

CONCLUSION

The Jarvik 2000 provides satisfactory intermediate-term results as a bridge to transplant or recovery. It appears to be associated with a low rate of serious driveline or pump infections and technical failure. However, bleeding complications due to the required anticoagulation treatment frequently occurred.

Total heart replacement using dual intracorporeal continuous-flow pumps in a chronic bovine model: a feasibility study

Continuous-flow pumps are small, simple, and respond physiologically to input variations, making them potentially ideal for total heart replacement. However, the physiological effects of complete pulseless flow during long-term circulatory support without a cardiac interface or with complete cardiac exclusion have not been well studied. We evaluated the feasibility of dual continuous-flow pumps as a total artificial heart (TAH) in a chronic bovine model. Both ventricles of a 6-month-old Corriente crossbred calf were excised and sewing rings attached to the reinforced atrioventricular junctions. The inlet portions of 2 Jarvik 2000 pumps were positioned through their respective sewing rings at the mid-atrial level and the pulseless atrial reservoir connected end-to-end to the pulmonary artery and aorta. Pulseless systemic and pulmonary circulations were thereby achieved. Volume status was controlled, and systemic and pulmonary resistance were managed pharmacologically to keep mean arterial pressures at 100+/-10 mmHg (systemic) and 20+/-5 mmHg (pulmonary) and both left and right atrial pressures at 15+/-5 mmHg. The left pump speed was maintained at 14,000 rpm and its output autoregulated in response to variations in right pump flow, systemic and pulmonary pressures, fluid status, and activity level. Hemodynamics, end-organ function, and neurohormonal status remained normal. These results suggest the feasibility of using dual continuous-flow pumps as a TAH.