Numerical investigation of flow characteristics in the front and rear chambers of centrifugal pump and pump as turbine

To investigate the flow characteristics in front chamber and rear chamber in pump mode and pump as turbine mode, a 3D computational model of a centrifugal pump was established, including the front and rear chamber. Based on Realizable k-ε turbulence model, numerical calculations of incompressible flow were carried out for internal viscous flow in two operating modes. Further analysis was conducted on the flow stability and hydraulic losses under two modes using energy gradient theory and entropy production theory. The numerical simulation results are within reasonable error compared to the experimental results in pump operation mode, which ensures the reliability of the numerical calculation method. The results indicate that the volumetric efficiency in both two modes is on an upward trend with increasing flow, but the volumetric efficiency of the pump mode is more significantly affected by changes in flow; the distribution patterns of dimensionless circumferential velocity and dimensionless radial velocity in the front and rear chambers under two operating modes are similar, but the distribution pattern of dimensionless radial velocity in the front chamber in turbine mode is significantly different from other operating conditions; flow instability is most likely to occur at the outlet of impeller, and the energy loss in clearance of wear-rings is greater than that in the pump chamber.

Optimization of a centrifugal blood pump designed using an industrial method through experimental and numerical study

With improved treatment of coronary artery disease, more patients are surviving until heart failure occurs. This leads to an increase in patients needing devices for struggling with heart failure. Ventricular assist devices are known as the mainstay of these devices. This study aimed to design a centrifugal pump as a ventricular assist device. In order to design the pump, firstly, the geometrical parameters of the pump, including the gap distance, blade height, and position of the outlet relative to the blade, were investigated. Finally, the selected configuration, which had all the appropriate characteristics, both hydraulically and physiologically, was used for the rest of the study. The study of the blade, as the main component in energy transfer to the blood, in a centrifugal pump, has been considered in the present study. In this regard, the point-to-point design method, which is used in industrial applications, was implemented. The designer chooses the relationship between the blade angles at each radius in the point-to-point method. The present study selected logarithmic and second-order relations for designing the blade's profile. In total, 58 blades were examined in this study, which differed regarding blade inlet and outlet angles and the relationship between angle and radial position. ANSYS CFX 17.0 software was utilized to simulate blades' performances, and a benchmark pump provided by the US Food and Drug Administration (FDA) was used to validate the numerical simulations. Then, the selected impeller from the numerical investigation was manufactured, and its performance was compared experimentally with the FDA benchmark pump. A hydraulic test rig was also developed for experimental studies. The results showed that among the blades designed in this study, the blade with an input angle of 45° and an output angle of 55°, which is designed to implement a logarithmic relationship, has the best performance. The selected impeller configuration can increase the total head (at least by 20%) at different flow rates compared to the FDA pump.

Hemodynamic Evaluation of Asynchronous Speed Modulation of a Continuous-Flow Left Ventricular Assist Device in an Acute-Myocardial Injury Sheep Model

Asynchronous rotational-speed modulation of a continuous-flow left ventricular assist device (LVAD) can increase pulsatility; however, the feasibility of hemodynamic modification by asynchronous modulation of an LVAD has not been sufficiently verified. We evaluated the acute effect of an asynchronous-modulation mode under LVAD support and the accumulated effect of 6 consecutive hours of driving by the asynchronous-modulation mode on hemodynamics, including both ventricles, in a coronary microembolization-induced acute-myocardial injury sheep model. We evaluated 5-min LVAD-support hemodynamics, including biventricular parameters, by switching modes from constant-speed to asynchronous-modulation in the same animals ("acute-effect evaluation under LVAD support"). To determine the accumulated effect of a certain driving period, we evaluated hemodynamics including biventricular parameters after weaning from 6-hour (6 h) LVAD support by constant-speed or asynchronous-modulation mode ("6h-effect evaluation"). The acute-effect evaluation under LVAD support revealed that, compared to the constant-speed mode, the asynchronous-modulation mode increased vascular pulsatility but did not have significantly different effects on hemodynamics, including both ventricles. The 6 h-effect evaluation revealed that the hemodynamics did not differ significantly between the two groups except for some biventricular parameters which did not indicate negative effects of the asynchronous-modulation mode on both ventricles. The asynchronous-modulation mode could be feasible to increase vascular pulsatility without causing negative effects on hemodynamics including both ventricles. Compared to the constant-speed mode, the asynchronous-modulation mode increased pulsatility during LVAD support without negative effects on hemodynamics including both ventricles in the acute phase. Six hours of LVAD support with the asynchronous-modulation mode exerted no negative effects on hemodynamics, including both ventricles, after weaning from the LVAD.

Estimating flow fields with reduced order models

The estimation of fluid flows inside a centrifugal pump in realtime is a challenging task that cannot be achieved with long-established methods like CFD due to their computational demands. We use a projection-based reduced order model (ROM) instead. Based on this ROM, a realtime observer can be devised that estimates the temporally and spatially resolved velocity and pressure fields inside the pump. The entire fluid-solid domain is treated as a fluid in order to be able to consider moving rigid bodies in the reduction method. A greedy algorithm is introduced for finding suitable and as few measurement locations as possible. Robust observability is ensured with an extended Kalman filter, which is based on a time-variant observability matrix obtained from the nonlinear velocity ROM. We present the results of the velocity and pressure ROMs based on a unsteady Reynolds-averaged Navier-Stokes CFD simulation of a 2D centrifugal pump, as well as the results for the extended Kalman filter.

Numerical simulation of the leakage flow of the hydrodynamically levitated centrifugal blood pump for extracorporeal mechanical circulatory support systems

Extracorporeal centrifugal pumps are widely used in various forms of mechanical circulatory support, including extracorporeal membrane oxygenation and ventricular assist device. A durable centrifugal pump was developed by implementing a new hydrodynamic bearing design that prevents the impeller from touching to the casing wall and provides sufficient washout through the pump to prevent thrombus formation in the pump. The hydrodynamic bearings of the pump are composed of dual annular paths located on both sides of the impeller. Computational fluid dynamics analyses were performed on the flow field inside the pump to estimate the leakage flow through the gap and its impact on the pump efficiency and biocompatibility. The calculations were performed for motor speeds from 3000 to 5000 rpm and flow rates from 1.0 to 9.0 L/min. The leakage flow increased linearly with increasing pressure head of the pump, and the total leakage flow ranged from 2.0 to 27.3% of the total flow. The average wall shear stresses in the casing bottom ranged from 10.6 to 40.9 Pa. The leakage flow of the centrifugal pump with the hydrodynamically levitated impeller had a measurable impact on hydraulic energy losses while enhancing the washout flow to achieve good anti-thrombogenicity.

Development of Inspired Therapeutics Pediatric VAD: Benchtop Evaluation of Impeller Performance and Torques for MagLev Motor Design

PURPOSE

Despite the availability of first-generation extracorporeal mechanical circulatory support (MCS) systems that are widely used throughout the world, there is a need for the next generation of smaller, more portable devices (designed without cables and a minimal number of connectors) that can be used in all in-hospital and transport settings to support patients in heart failure. Moreover, a system that can be universally used for all indications for use including cardiopulmonary bypass (CPB), uni- or biventricular support (VAD), extracorporeal membrane oxygenation (ECMO) and respiratory assist that is suitable for use for adult, neonate, and pediatric patients is desirable. Providing a single, well designed, universal technology could reduce the incidence of human errors by limiting the need for training of hospital staff on a single system for a variety of indications throughout the hospital rather than having to train on multiple complex systems. The objective of this manuscript is to describe preliminary research to develop the first prototype pump for use as a ventricular assist device for pediatric patients with the Inspired Universal MCS technology. The Inspired VAD Universal System is an innovative extracorporeal blood pumping system utilizing novel MagLev technology in a single portable integrated motor/controller unit which can power a variety of different disposable pump modules intended for neonate, pediatric, and adult ventricular and respiratory assistance.

METHODS

A prototype of the Inspired Pediatric VAD was constructed to determine the hemodynamic requirements for pediatric applications. The magnitude/range of hydraulic torque of the internal impeller was quantified. The hydrodynamic performance of the prototype pump was benchmarked using a static mock flow loop model containing a heated blood analogue solution to test the pump over a range of rotational speeds (500-6000 RPM), flow rates (0-3.5 L/min), and pressures (0 to ~ 420 mmHg). The device was initially powered by a shaft-driven DC motor in lieu of a full MagLev design, which was also used to calculate the fluid torque acting on the impeller.

RESULTS

The pediatric VAD produced flows as high as 4.27 L/min against a pressure of 127 mmHg at 6000 RPM and the generated pressure and flow values fell within the desired design specifications.

CONCLUSIONS

The empirically determined performance and torque values establish the requirements for the magnetically levitated motor design to be used in the Inspired Universal MagLev System. This next step in our research and development is to fabricate a fully integrated and functional magnetically levitated pump, motor and controller system that meets the product requirement specifications and achieves a state of readiness for acute ovine animal studies to verify safety and performance of the system.

Development of Inspired Therapeutics Pediatric VAD: Computational Analysis and Characterization of VAD V3

PURPOSE

Pediatric heart failure patients remain in critical need of a dedicated mechanical circulatory support (MCS) solution as development efforts for specific pediatric devices continue to fall behind those for the adult population. The Inspired Pediatric VAD is being developed as a pediatric specific MCS solution to provide up to 30-days of circulatory or respiratory support in a compact modular package that could allow for patient ambulation during treatment.

METHODS

Hydrodynamic performance (flows, pressures), impeller/rotor mechanical properties (torques, forces), and flow shear stress and residence time distributions of the latest design version, Inspired Pediatric VAD V3, were numerically predicted and investigated using computational fluid dynamics (CFD) software (SolidWorks Flow Simulator).

RESULTS

Hydrodynamic performance was numerically predicted, indicating no change in flow and pressure head compared to the previous device design (V2), while displaying increased impeller/rotor torques and translation forces enabled by improved geometry. Shear stress and flow residence time volumetric distributions are presented over a range of pump rotational speeds and flow rates. At the lowest pump operating point (3000 RPM, 0.50 L/min, 75 mmHg), 79% of the pump volume was in the shear stress range of 0-10 Pa with < 1% of the volume in the critical range of 150-1000 Pa for blood damage. At higher speed and flow (5000 RPM, 3.50 L/min, 176 mmHg), 65% of the volume resided in the 0-10 Pa range compared to 2.3% at 150-1000 Pa.

CONCLUSIONS

The initial computational characterization of the Inspired Pediatric VAD V3 is encouraging and future work will include device prototype testing in a mock circulatory loop and acute large animal model.

The optimization of centrifugal pump driving horizontal tubular photobioreactor for enhancing astaxanthin production using heterotrophic Haematococcus pluvialis

Haematococcus pluvialis is the prime source of natural astaxanthin for commercial exploitation. The large-scale cultivation of H. pluvialis is one of the key technologies for the development of natural astaxanthin industry. So far, horizontal tubular photobioreactor (HTPBR) circulated by a centrifugal pump has been the main PBR for the large-scale cultivation of H. pluvialis. Shear stress is a negative factor in microalgal cultivation at different scales, particularly for large-scale cultivation. To reduce the adverse impact of shear stress, the tolerance of H. pluvialis to the shear stress during the induction stage was first investigated in this study. H. pluvialis aplanospore was not sensitive to stresses between 19.18 and 27.32 Pa, but was resulted in about 30% cell death under shear stress between 27.32 and 63.84 Pa. Accordingly, two centrifugal pumps with different impellers was selected in 400 L HTPBRs to study the outdoor photoinduction for astaxanthin accumulation. The highest astaxanthin productivity and astaxanthin concentration were obtained in HTPBRs using a centrifugal pump equipped with three unshrouded backward-bladed impellers. The HTPBR was then successfully scaled up to 800 L with a similar performance, showing good scalability.

Coagulation complications after conversion from roller to centrifugal pump in neonatal and pediatric extracorporeal membrane oxygenation

BACKGROUND/PURPOSE

Coagulation complications are frequent, unwanted occurrences in extracorporeal membrane oxygenation (ECMO) treatment, possibly influenced by the pump in the ECMO-circuit. We hypothesized that fewer complications would occur with a smaller, heparin-coated ECMO system with a centrifugal pump (CP) than with one with a roller pump (RP) and that after conversion, complication rates would decrease over time.

METHODS

This single-center, retrospective chart study included all first neonatal and pediatric ECMO runs between 2009 and 2015. Differences between groups were assessed with Mann-Whitney U tests and Kruskal-Wallis tests. Determinants of complication rates were evaluated through Poisson regression models. The CP group was divided into three consecutive groups to assess whether complication rates decreased over time.

RESULTS

The RP group comprised 90 ECMO runs and the CP group 82. Hemorrhagic complication rates were significantly higher with the CP than with the RP, without serious therapeutic consequences, while thrombotic complications rates were unaffected. Intracranial hemorrhage rates and coagulation-related mortality rates were similar. Gained experience with the CP did not improve complication rates or survival over time.

CONCLUSIONS

Although the CP seems safe, it does not seem beneficial over the RP. Further research is warranted on how pump type affects coagulation, taking into account the severity and implications of coagulation complications.

LEVEL OF EVIDENCE

Level III.

Hemodynamic evaluation and in vitro hemolysis evaluation of a novel centrifugal pump for extracorporeal membrane oxygenation

Background

The STM CP-24 I centrifugal pump is a newly developed centrifugal pump for extracorporeal membrane oxygenation equipment. This study aimed to combine hydraulic experiments, hemodynamic numerical simulations, and standard in vitro hemolysis experiments to investigate the comprehensive performance of this centrifugal pump.

Methods

In vitro experiments were first done to obtain the pressure-flow data of the centrifugal pump in its working range to evaluate its hydraulic performance. Next, the commonly used clinical working points were selected as boundary conditions, and a computational fluid dynamics method was applied to evaluate its hemodynamic performance. The blood pressure distribution, blood flow fields, and high-wall-shear-stress zones in the centrifugal pump were determined as indicators for hemodynamic evaluation. Finally, standard in vitro hemolysis experiments were performed to test the blood compatibility of this centrifugal pump (n=3 blood samples). In addition, its blood compatibility was evaluated in the form of the normalized index of hemolysis (NIH).

Results

The pressure-flow curve of the centrifugal pump showed that the head pressure and flow of the centrifugal pump showed a mostly linear relationship within the whole working range. When the rotation speed of the centrifugal pump was 5,500 rpm, it achieved a hydraulic performance of 550 mmHg head pressure and 8 L/min output flow, which could meet the clinical needs of extracorporeal membrane oxygenation. Analysis of computational fluid dynamics data indicated that the centrifugal pump had excellent hemodynamic performance: even distribution of blood pressure in the pump, no blood flow stagnation zone or dead zone in the overall flow field, and secondary flows in the gap between the rotor and the volute that significantly reduced the volume of the low-blood-flow zone close to the impeller. There was no obvious high-shear-stress zone on the surface of the volute or the impeller, which will effectively reduce the risk of thrombosis. In vitro hemolysis experiments indicated that the centrifugal pump had excellent blood biocompatibility, with a NIH =0.0125±0.0022 g/100 L.

Conclusions

The STM CP-24 I centrifugal pump has excellent hydraulic performance, a reasonable design of the hemodynamic structure of the blood pump, and excellent blood compatibility. Therefore, it can meet clinical needs.

Suitable hemolysis index for low-flow rotary blood pumps

A suitable index is needed for hemolysis tests that use low-flow pumps, such as pediatric blood pumps or blood purification pumps. To create such an index, the present study investigates the change of plasma-free hemoglobin in the pump circuit with time and the change of the hemolysis rate with flow rate and impeller rotational speed. The results show that the hemolysis rate or the increase rate of the total free hemoglobin are suitable measures for hemolysis evaluation for low-flow pumps.

Preclinical biocompatibility study of ultra-compact durable ECMO system in chronic animal experiments for 2 weeks

Although the innovation has come in ECMO field, many problems remain unresolved. One of the main problems is about long-term durability and biocompatibility. Another is the system's size, weight, and its complicated equipment. For the former problem, we have previously developed ECMO system which consists of a tiny, hydrodynamically levitated centrifugal pump (BIOFLOAT-NCVC), a membrane oxygenator with hollow polyolefin fibers (BIOCUBE-NCVC), and the circuit treated with a heparin-bonding material (T-NCVC coating), and reported three cases of animal experiments for 30-day heparin-free drive. For the latter problem, we have integrated these elements to the compact system with sensors of temperature, pressure, and SvO₂, and blood flow. Its installation area is 595 cm², weighs 8.9 kg with attachable oxygen cassette, and battery which could last an hour at least. To evaluate the biocompatibility of this system, this ECMO was installed in four goats. Scheduled duration was 14 days. Heparin was continuously infused to control their ACT between 150 and 200 s except one 2-week experiment without systemic heparinization. All of the four goats survived till the scheduled termination. Function of the pump and the oxygenator during ECMO was stable. No obvious adverse events were observed. All lab data were of normal range after 1 week. Small infarctions were found at kidneys, but they were not clinically significant. No thrombus was found in the pump system. The oxygenators were extremely clean except a little thrombus formation; while, the heparin-free examination revealed acceptable cleanliness. The present study revealed good anti-thrombogenicity of this ultra-compact durable ECMO system with heparinization. Our system encourages awake and extubated management, rehabilitation, inter-hospital transfer, and prehospital initiation of ECMO.

Investigation of effect of pump rotational speed on performance and detection of cavitation within a centrifugal pump using vibration analysis

Cavitation is an essential problem that occurs in any pump. It highly contributes to deteriorating the performance of the pump. In industrial applications, it is important to detect and decrease the effect of the cavitation in pumps. In this work, detecting and diagnosing the cavitation phenomenon within centrifugal pumps using vibration technique was investigated. The results obtained for vibration signal in both time and frequency domains were analysed in order to gain a better understanding about the detection of cavitation in the pumps in question. The effect of different operating conditions including various flow rates and pump rotational speeds related to the cavitation were measured. Different statistical features in time domain analysis (TDA) and also the Fast Fourier Transform (FFT) technique for frequency domain analysis (FDA) were applied.

Perception and adoption of a new agricultural technology: Evidence from a developing country

Adoption of new agricultural technologies is always at the center of policy interest in developing countries. In reality, despite the visible benefits of many of the new agricultural technologies, including machinery and management practices, farmers either do not adopt them or it takes a long time to begin the adoption process and scaling up. To enhance the provision of irrigation using surface water and to enhance irrigation efficiency, Bangladesh has been trying to introduce the axial-flow-pump (AFP) appropriate for surface water irrigation, which can lift up to 55% more water, conditional on the water head, than a conventional centrifugal pump. Despite the visible benefits of the AFP, the uptake of the AFP for irrigation is low in the targeted zone of Bangladesh. The present study demonstrates that the new technology must be modified to adapt to local demand and specifications. Most importantly, the price of the new technology must be competitive with the prices of the existing available substitute technologies to ensure a rapid uptake and scaling up of this new agricultural technology.

The momentum of HeartMate 3: a novel active magnetically levitated centrifugal left ventricular assist device (LVAD)

Left ventricular assist devices (LVADs) are emerging as the treatment of choice for advanced heart failure due to the dearth of healthy donor hearts for cardiac transplantation. The HeartMate 3 LVAD is a novel centrifugal pump which was developed to provide hemodynamic support in heart failure patients, either as a bridge to transplant (BTT), myocardial recovery, or as destination therapy (DT). Technological and clinical advancements have led to optimized hemocompatibility and development of less invasive surgical procedures for the implantation of this pump. The worldwide first implantation of the HeartMate 3 was performed by Prof. Schmitto and his team at Hannover Medical School, Germany in 2014, paving the way for subsequent surgical developments. This article summarizes the advanced technological and clinical aspects of the HeartMate 3 and outlines future technical developments for safe and effective treatment of advanced heart failure.

Clinical overview of the HVAD: a centrifugal continuous-flow ventricular assist device with magnetic and hydrodynamic bearings including lateral implantation strategies

Growing worldwide incidences of end-stage heart failure and declining rates of cardiac transplants have given rise to the need for alternative treatment options, based on mechanical circulatory support (MCS) devices such as left ventricular assist devices (LVADs). Technologically advanced LVADs such as the HVAD^® (HeartWare^®, Medtronic) facilitate safe and efficient treatment of heart failure patients with reduced post-operative complications, which is attributed to their considerably miniaturized size. This also facilitates the development and implementation of novel, minimally-invasive surgical techniques. The HVAD is a centrifugal pump, manufactured by HeartWare Inc., (Framingham, MA, USA) and subsequently by Medtronic Inc., (Minnesota, MN, USA), and has been approved for clinical application after receiving the CE Mark approval in 2008 and the FDA approval in 2012. Current research efforts are focused on further miniaturization alongside optimization of electronic and software controllers as well as implementation of the transcutaneous energy transfer (TET) technology. Salient features of the HVAD pump technology, clinical applications and future optimization strategies have been discussed in this article.

Principle and basic property of the sequential flow pump

In the emergency care field, early treatment of acute heart or respiratory failure has been a global concern. In severe cases, patients are frequently required to be on an extracorporeal membrane oxygenator (ECMO) life support. To make the ECMO system more compact and portable, we proposed a sequential flow-type centrifugal pump named the sequential flow pump (SFP). In this study, principle and basic properties of this novel blood pump were examined by computational fluid dynamic (CFD) analysis and an experimental model. In the SFP, fluid is given centrifugal force sequentially twice with a single closed impeller. This sequential pressurization mechanism enables high-pressure output without high impeller speed. To realize easy integration of a blood pump with an artificial lung, the inlet and outlet ports are located at lateral side and center of the pump, respectively, which is the reverse configuration of conventional centrifugal pumps. The computational model was composed for CFD analysis and the experimental model was developed for the experiment of the actual pump. For both models, dimension of the impeller and volute was designed to be equal. In the CFD analysis, the SFP could generate higher performance than the single pressurization model with the same rotational speed of the impeller. Basic property of the experimental model was very similar to that of the computational model. The results showed the possibility that the SFP would be more suitable for the compact ECMO system than conventional centrifugal pumps.

Biventricular support using a centrifugal pump in a 6 year old with fulminant myocarditis

We experienced a case of ventricular assist with both a pulsatile-flow and a continuous-flow pump in a pediatric patient, and herein report the clinical course and characteristics of the pumps. A 6-year-old female was diagnosed with fulminant myocarditis and transferred to our hospital for mechanical support. After 12 days of extracorporeal membrane oxygenation, we implanted a left ventricular assist device (LVAD) and a right ventricular assist device (RVAD) using centrifugal Gyro pumps with a membrane oxygenator in a paracorporeal fashion. The membrane oxygenator was removed on postoperative day (POD) 4, and the patient was weaned from the respirator on POD 6. The LVAD was exchanged on POD 13 and 17, and the RVAD was exchanged on POD 14 because of thrombus formation inside the pumps. The RVAD was removed on POD 25. On POD 32, the patient experienced cerebral infarction and the centrifugal Gyro pump was switched to an extracorporeal pulsatile pump. No thromboembolic event occurred after pump conversion, although continuous administration of vasodilators was required to avoid hypertension. She underwent successfully heart transplantation in the USA after 8 months of ventricular support. A centrifugal pump is considered useful for pediatric patients, as pump flow and blood pressure can be relatively easily controlled in the postoperative acute phase compared with the pulsatile pump. However, special care should be taken to monitor for thrombus formation when support length becomes longer than 13 days, and a switch to a pulsatile pump should be considered once the hemodynamic status stabilizes.

Detection of Thrombosis in the Extracorporeal Membrane Oxygenation Circuit by Infrasound: Proof of Concept

As of today, there exist no reliable, objective methods for early detection of thrombi in the extracorporeal membrane oxygenators (ECMO) system. Within the ECMO system, thrombi are not always fixed to a certain component or location in the circuit. Thus, clot fragments of different shapes and consistencies may circulate and give rise to vibrations and sound generation. By bedside sound measurements and additional laboratory experiments (although not detailed herein), we found that the presence of particles (clots or aggregates and fragments of clots) can be detected by analyzing the strength of infra-sound (< 20 Hz) modes of the spectrum near the inlet and outlet of the centrifugal pump in the ECMO circuit. For the few patients that were considered in this study, no clear false positive or negative examples were found when comparing the spectral approach with clinical observations. A laboratory setup provided insight to the flow in and out of the pump, confirming that in the presence of particles a low-amplitude low-frequency signal is strongly amplified, enabling the identification of a clot.

Open-heart surgery using a centrifugal pump: a case of hereditary spherocytosis

Background

Hereditary spherocytosis is a genetic, frequently familial hemolytic blood disease characterized by varying degrees of hemolytic anemia, splenomegaly, and jaundice. There are few reports on adult open-heart surgery for patients with hereditary spherocytosis.

Case presentation

We report a rare case of an adult open-heart surgery associated with hereditary spherocytosis. A 63-year-old man was admitted for congestive heart failure due to bicuspid aortic valve, aortic valve regurgitation, and sinus of subaortic aneurysm. The family history, the microscopic findings of the blood smear, and the characteristic osmotic fragility confirmed the diagnosis of hereditary spherocytosis. Furthermore, splenectomy had not been undertaken preoperatively.

The patient underwent a successful operation by means of a centrifugal pump. Haptoglobin was used during the cardiopulmonary bypass, and a biological valve was selected to prevent hemolysis. No significant hemolysis occurred intraoperatively or postoperatively.

Conclusion

There are no previous reports of patients with hereditary spherocytosis, and bicuspid aortic valve. We have successfully performed an adult open-heart surgery using a centrifugal pump in an adult patient suffering from hereditary spherocytosis and bicuspid aortic valve.

Usefulness of extracorporeal membrane oxygenation using double roller pumps in a low body weight newborn: A novel strategy for mechanical circulatory support in an infant

Extracorporeal membrane oxygenation (ECMO) with a centrifugal pump requires a certain flow rate; therefore, its application for low body weight infants is frequently accompanied by oxygenator membrane malfunction and/or inadequate perfusion. To prevent low-flow associated complications, we report a case in which a novel system of dual roller pumps was used. A baby girl with a body mass index 0.25 m², who experienced difficulty weaning from cardiopulmonary bypass after a Norwood-like operation, required an ECMO. Concerns for the tube lifespan reduction due to roller pump friction led to the use of a double roller pump circulation. The termination of ECMO during tube exchange is not needed, because circulation is maintained by another roller pump. The novel strategy of ECMO with double roller pumps will allow low perfusion rate to provide adequate circulatory support for low body weight patients.

Repair of an acute Type A aortic dissection with LVAD patient after failed mitral and tricuspid operation

An acute type A dissection in a patient with a left ventricular assist device was treated by replacement of the ascending aorta and the proximal arch using a prosthesis with a side branch which was connected to the left ventricular assist device outflow branch, greatly simplifying the procedure.

Hemodynamics of a functional centrifugal-flow total artificial heart with functional atrial contraction in goats

Implantation of a total artificial heart (TAH) is one of the therapeutic options for the treatment of patients with end-stage biventricular heart failure. There is no report on the hemodynamics of the functional centrifugal-flow TAH with functional atrial contraction (fCFTAH). We evaluated the effects of pulsatile flow by atrial contraction in acute animal models. The goats received fCFTAH that we created from two centrifugal-flow ventricular assist devices. Some hemodynamic parameters maintained acceptable levels: heart rate 115.5 ± 26.3 bpm, aortic pressure 83.5 ± 10.1 mmHg, left atrial pressure 18.0 ± 5.9 mmHg, pulmonary pressure 28.5 ± 9.7 mmHg, right atrial pressure 13.6 ± 5.2 mmHg, pump flow 4.0 ± 1.1 L/min (left) 3.9 ± 1.1 L/min (right), and cardiac index 2.13 ± 0.14 L/min/m(2). fCFTAH with atrial contraction was able to maintain the TAH circulation by forming a pulsatile flow in acute animal experiments. Taking the left and right flow rate balance using the low internal pressure loss of the VAD pumps may be easier than by other pumps having considerable internal pressure loss. We showed that the remnant atrial contraction effected the flow rate change of the centrifugal pump, and the atrial contraction waves reflected the heart rate. These results indicate that remnant atria had the possibility to preserve autonomic function in fCFTAH. We may control fCFTAH by reflecting the autonomic function, which is estimated with the flow rate change of the centrifugal pump.

Potential Danger of Pre-Pump Clamping on Negative Pressure-Associated Gaseous Microemboli Generation During Extracorporeal Life Support--An In Vitro Study

The objectives of this study were to investigate the relationship between revolution speed of a conventional centrifugal pump and negative pressure at the inlet of the pump by clamping the tubing upstream of the pump, and to verify whether negative pressure leads to gaseous microemboli (GME) production in a simulated adult extracorporeal life support (ECLS) system. The experimental circuit, including a Maquet Rotaflow centrifugal pump and a Medos Hilite 7000 LT polymethyl-pentene membrane oxygenator, was primed with packed red blood cells (hematocrit 35%). Negative pressure was created in the circuit by clamping the tubing upstream of the pump for 10 s, and then releasing the clamp. An emboli detection and classification quantifier was used to record GME volume and count at pre-oxygenator and post-oxygenator sites, and pressure and flow rate data were collected using a custom-based data acquisition system. All trials were conducted at 36°C at revolution speeds of 2000-4000 rpm (500 rpm increment). The flow rates were 1092.5-4708.4 mL/min at the revolution speeds of 2000-4000 rpm. Higher revolution speed generated higher negative pressure at the pre-pump site when clamping the tubing upstream of the pump (-108.3 ± 0.1 to -462.0 ± 0.5 mm Hg at 2000-4000 rpm). Moreover, higher negative pressure was associated with a larger number and volume of GME at pre-oxygenator site after de-clamp (GME count 10,573 ± 271 at pre-oxygenator site at 4000 rpm). The results showed that there was a potential danger of delivering GME to the patient when clamping pre-pump tubing during ECLS using a centrifugal pump. Our results warrant further clinical studies to investigate this phenomenon.

Preclinical study of a novel hydrodynamically levitated centrifugal pump for long-term cardiopulmonary support : In vivo performance during percutaneous cardiopulmonary support

An extracorporeal centrifugal blood pump with a hydrodynamically levitated impeller was developed for use in a durable extracorporeal membrane oxygenation (ECMO) system. The present study examined the biocompatibility of the blood pump during long-term use by conducting a series of 30-day chronic animal experiments. The ECMO system was used to produce a percutaneous venoarterial bypass between the venae cavae and carotid artery in adult goats. No anticoagulation or antiplatelet therapy was administered during the experiments. Three out of four animals survived for the scheduled 30-day period, and the blood pumps and membrane oxygenators both exhibited sufficient hydrodynamic performance and good antithrombogenicity, while one animal died of massive bleeding from the outflow cannulation site. The animals' plasma free hemoglobin had returned to within the normal range by 1 week after the surgical intervention, and their hemodynamic and biochemistry parameters remained within their normal ranges throughout the experiment. The explanted centrifugal blood pumps did not display any trace of thrombus formation. Based on the biocompatibility demonstrated in this study, the examined centrifugal blood pump, which includes a hydrodynamically levitated impeller, is suitable for use in durable ECMO systems.

Development of ventricular assist devices in China: present status, opportunities and challenges

The growing number of heart failure patients and the scarcity of organ donors account for the huge need for the development of mechanical circulatory systems, including ventricular assist devices (VADs) and artificial hearts, in China. Several research programmes on blood pumps have been under way for the last three decades. However, unlike in other countries, the development of VADs has been extremely slow, and no system is currently approved and available for clinical application. There are many reasons for this situation. This article provides an overview of the present development of experimental and clinical research on VADs in China. In addition, the challenges for the clinical development of mechanical circulatory support in China are discussed.

Centrifugal blood pump for temporary ventricular assist devices with low priming and ceramic bearings

A new model of centrifugal blood pump for temporary ventricular assist devices has been developed and evaluated. The design of the device is based on centrifugal pumping principles and the usage of ceramic bearings, resulting in a pump with reduced priming (35 ± 2 mL) that can be applied for up to 30 days. Computational fluid dynamic (CFD) analysis is an efficient tool to optimize flow path geometry, maximize hydraulic performance, and minimize shear stress, consequently decreasing hemolysis. Initial studies were conducted by analyzing flow behavior with different impellers, aiming to determine the best impeller design. After CFD studies, rapid prototyping technology was used for production of pump prototypes with three different impellers. In vitro experiments were performed with those prototypes, using a mock loop system composed of Tygon tubes, oxygenator, digital flow meter, pressure monitor, electronic driver, and adjustable clamp for flow control, filled with a solution (1/3 water, 1/3 glycerin, 1/3 alcohol) simulating blood viscosity and density. Flow-versus-pressure curves were obtained for rotational speeds of 1000, 1500, 2000, 2500, and 3000 rpm. As the next step, the CFD analysis and hydrodynamic performance results will be compared with the results of flow visualization studies and hemolysis tests.

Preliminary validation of a new magnetic wireless blood pump

In general, a blood pump must be small, have a simple configuration, and have sufficient hydrodynamic performance. Herein, we introduce new mechanisms for a wireless blood pump that is small and simple and provides wireless and battery-free operation. To achieve wireless and battery-free operation, we implement magnetic torque and force control methods that use two external drivers: an external coil and a permanent magnet with a DC-motor, respectively. Power harvesting can be used to drive an electronic circuit for wireless monitoring (the observation of the pump conditions and temperature) without the use of an internal battery. The power harvesting will be used as a power source to drive other electronic devices, such as various biosensors with their driving circuits. To have both a compact size and sufficient pumping capability, the fully magnetic impeller has five stages and each stage includes four backward-curved blades. The pump has total and inner volumes of 20 and 9.8 cc, respectively, and weighs 52 g. The pump produces a flow rate of approximately 8 L/min at 80 mm Hg and the power generator produces 0.3 W of electrical power at 120 Ω. The pump also produces a minimum flow rate of 1.5 L/min and a pressure of 30 mm Hg for circulation at a maximum distance of 7.5 cm.

Ventricular assist devices in pediatrics

The implantation of a mechanical circulatory device for end-stage ventricular failure is a possible therapeutic approach in adult and pediatric cardiac surgery and cardiology. The aim of this article is to present mechanical circulatory assist devices used in infants and children with special emphasis on extracorporeal membrane oxygenation, Berlin Heart assist device, centrifugal pump and Medos assist device. The success of long-term support with implantable ventricular assist devices in adults and children has led to their increasing use as a bridge to transplantation in patients with otherwise non-treatable left ventricular failure, by transforming a terminal phase heart condition into a treatable cardiopathy. Such therapy allows rehabilitation of patients before elective cardiac transplantation (by removing contraindications to transplantation mainly represented by organ impairment) or acting as a bridge to recovery of the native left ventricular function (depending on underlying cardiac disease). Treatment may also involve permanent device implantation when cardiac transplantation is contraindicated. Indications for the implantation of assisted circulation include all states of cardiac failure that are reversible within a variable period of time or that require heart transplantation. This article will address the current status of ventricular assist devices by examining historical aspects of its development, current technical issues and clinical features of pediatric ventricular assist devices, including indications and contraindications for support.