Publications by authors named "David J Horvath"

51 Publications

Left Atrial Circulatory Assistance in Simulated Diastolic Heart Failure Model: First in Vitro and in Vivo.

J Card Fail 2022 Jan 10. Epub 2022 Jan 10.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.

Background: We are developing a left atrial assist device (LAAD) that is implanted at the mitral position to treat diastolic heart failure (DHF) represented by heart failure with preserved ejection fraction.

Methods: The LAAD was tested at 3 pump speeds on a pulsatile mock loop with a pneumatic pump that simulated DHF conditions by adjusting the diastolic drive. The LAAD was implanted in 6 calves, and the hemodynamics were assessed. In 3 cases, DHF conditions were induced by using a balloon inserted into the left ventricle, and in 2 cases, mitral valve replacement was also performed after the second aortic cross-clamp.

Results: DHF conditions were successfully induced in the in vitro study. With LAAD support, cardiac output, aortic pressure and left atrial pressure recovered to normal values, whereas pulsatility was maintained for both in vivo and in vitro studies. Echocardiography showed no left ventricular outflow tract obstruction, and the LAAD was successfully replaced by a mechanical prosthetic valve.

Conclusions: These initial in vitro and in vivo results support our hypothesis that use of the LAAD increases cardiac output and aortic pressure and decreases left atrial pressure, while maintaining arterial pulsatility.
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http://dx.doi.org/10.1016/j.cardfail.2021.11.024DOI Listing
January 2022

Characterization and Development of Universal Ventricular Assist Device: Computational Fluid Dynamics Analysis of Advanced Design.

ASAIO J 2021 Nov 10. Epub 2021 Nov 10.

SimuTech Group, Hudson, Ohio SimuTech Group, Huntsville, Alabama R1 Engineering LLC, Euclid Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, USA.

We are developing a universal, advanced ventricular assist device (AVAD) with automatic pressure regulation suitable for both left and right ventricular support. The primary goal of this computational fluid dynamics (CFD) study was to analyze the biventricular performance of the AVAD across its wide range of operating conditions. An AVAD CFD model was created and validated using in vitro hydraulic performance measurements taken over conditions spanning both left ventricular assist device (LVAD) and right ventricular assist device (RVAD) operation. Static pressure taps, placed throughout the pump, were used to validate the CFD results. The CFD model was then used to assess the change in hydraulic performance with varying rotor axial positions and identify potential design improvements. The hydraulic performance was simulated and measured at rotor speeds from 2,300 to 3,600 revolutions/min and flow rates from 2.0 to 8.0 L/min. The CFD-predicted hydraulic pressure rise agreed well with the in vitro measured data, within 6.5% at 2300 rpm and within 3.5% for the higher rotor speeds. The CFD successfully predicted wall static pressures, matching experimental values within 7%. High degree of similarity and circumferential uniformity in the pump's flow fields were observed over the pump operation as an LVAD and an RVAD. A secondary impeller axial clearance reduction resulted in a 10% decrease in peak flow residence time and lower static pressures on the secondary impeller. These lower static pressures suggest a reduction in the upwards rotor forces from the secondary impeller and a desired increase in the pressure sensitivity of the pump. The CFD analyses supported the feasibility of the proposed AVAD's use as an LVAD or an RVAD, over a wide range of operating conditions. The CFD results demonstrated the operability of the pump in providing the desired circumferential flow similarity over the intended range of flow/speed conditions and the intended functionality of the AVAD's automated pressure regulation.
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http://dx.doi.org/10.1097/MAT.0000000000001607DOI Listing
November 2021

Computational Fluid Dynamics Model of Continuous-Flow Total Artificial Heart: Right Pump Impeller Design Changes to Improve Biocompatibility.

ASAIO J 2021 Sep 20. Epub 2021 Sep 20.

From the SimuTech Group, Hudson, Ohio R1 Engineering LLC, Euclid, Ohio Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland Clinic, Cleveland, Ohio.

Cleveland Clinic is developing a continuous-flow total artificial heart (CFTAH). This novel design operates without valves and is suspended both axially and radially through the balancing of the magnetic and hydrodynamic forces. A series of long-term animal studies with no anticoagulation demonstrated good biocompatibility, without any thromboemboli or infarctions in the organs. However, we observed varying degrees of thrombus attached to the right impeller blades following device explant. No thrombus was found attached to the left impeller blades. The goals for this study were: (1) to use computational fluid dynamics (CFD) to gain insight into the differences in the flow fields surrounding both impellers, and (2) to leverage that knowledge in identifying an improved next-generation right impeller design that could reduce the potential for thrombus formation. Transient CFD simulations of the CFTAH at a blood flow rate and impeller rotational speed mimicking in vivo conditions revealed significant blade tip-induced flow separation and clustered regions of low wall shear stress near the right impeller that were not present for the left impeller. Numerous right impeller design variations were modeled, including changes to the impeller cone angle, number of blades, blade pattern, blade shape, and inlet housing design. The preferred, next-generation right impeller design incorporated a steeper cone angle, a primary/splitter blade design similar to the left impeller, and an increased blade curvature to better align the incoming flow with the impeller blade tips. The next-generation impeller design reduced both the extent of low shear regions near the right impeller surface and flow separation from the blade leading edges, while maintaining the desired hydraulic performance of the original CFTAH design.
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http://dx.doi.org/10.1097/MAT.0000000000001581DOI Listing
September 2021

Total Artificial Heart Computational Fluid Dynamics: Modeling of Stator Bore Design Effects on Journal-Bearing Performance.

ASAIO J 2021 Aug 10. Epub 2021 Aug 10.

From the SimuTech Group, Montreal, Quebec, Canada SimuTech Group, Hudson, Ohio Yaksh Magnetic Solutions, Lilburn, Georgia R1 Engineering, LLC, Euclid, Ohio Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland Clinic, Cleveland, Ohio.

Cleveland Clinic's continuous-flow total artificial heart (CFTAH) is a double-ended centrifugal blood pump that has a single rotating assembly with an embedded magnet, which is axially and radially suspended by a balance of magnetic and hydrodynamic forces. The key to the radial suspension is a radial offset between the stator bearing bore and the magnet's steel laminations. This offset applies a radial magnetic force, which is balanced by a hydrodynamic force as the rotating assembly moves to a "force-balanced" radial position. The journal-bearing blood passage is a narrow flow path between the left and right impellers. The intent of this study was to determine the impact of the stator-bearing bore radius on the journal-bearing hydraulic performance while satisfying the geometric design constraints imposed by the pump and motor configuration. Electromagnetic forces on the journal bearing were calculated using the ANSYS EMAG program, Version 18 (ANSYS, Canonsburg, PA). ANSYS CFX Version 19.2 was then used to model the journal-bearing flow paths of the most recent design of the CFTAH. A transient, moving mesh approach was used to locate the steady state, force-balanced position of the rotating assembly. The blood was modeled as a non-Newtonian fluid. The computational fluid dynamics simulations showed that by increasing stator bore radius, rotor power, stator wall average shear stress, and blood residence time in journal-bearing decrease, while blood net flow rate through the bearing increases. The results were used to select a new bearing design that provides an improved performance compared with the baseline design. The performance of the new CFTAH-bearing design will be confirmed through upcoming in vitro and in vivo testing.
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http://dx.doi.org/10.1097/MAT.0000000000001556DOI Listing
August 2021

Left atrial assist device function at various heart rates using a mock circulation loop.

Int J Artif Organs 2021 Jul 1;44(7):465-470. Epub 2020 Dec 1.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.

We are developing a new left atrial assist device (LAAD) for patients who have heart failure with preserved ejection fraction (HFpEF). This study aimed to assess the hemodynamic effects of the LAAD under both normal heart conditions and various diastolic heart failure (DHF) conditions using a mock circulatory loop. A continuous-flow pump that simulates LAAD, was placed between the left atrial (LA) reservoir and a pneumatic ventricle that simulated a native left ventricle on a pulsatile mock loop. Normal heart (NH) and mild, moderate, and severe DHF conditions were simulated by adjusting the diastolic drive pressures of the pneumatic ventricle. With the LAAD running at 3200 rpm, data were collected at 60, 80, and 120 bpm of the pneumatic ventricle. Cardiac output (CO), mean aortic pressure (AoP), and mean LA pressure (LAP) were compared to evaluate the LAAD performance. With LAAD support, the CO and AoP rose to a sufficient level at all heart rates and DHF conditions (CO; 3.4-3.8 L/min, AoP; 90-105 mm Hg). Each difference in the CO and the AoP among various heart rates was minuscule compared with non-pump support. The LAP decreased from 21-23 to 17-19 mm Hg in all DHF conditions (difference not significant). Furthermore, hemodynamic parameters improved for all DHF conditions, independent of heart rate. The LAAD can provide adequate flow to maintain the circulation status at various heart rates in an in vitro mock circulatory loop.
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http://dx.doi.org/10.1177/0391398820977508DOI Listing
July 2021

Modeling of Virtual Mechanical Circulatory Hemodynamics for Biventricular Heart Failure Support.

Cardiovasc Eng Technol 2020 12 19;11(6):699-707. Epub 2020 Nov 19.

Department of Biomedical Engineering/ND20, Lerner Research Institute, Cleveland Clinic, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, 9500 Euclid Avenue, ND20, Cleveland, OH, 44195, USA.

Objective: In this study, a mechanical circulatory support simulation tool was used to investigate the application of a unique device with two centrifugal pumps and one motor for the biventricular assist device (BVAD) support application. Several conditions-including a range of combined left and right systolic heart failure severities, aortic and pulmonary valve regurgitation, and combinations of high and low systemic and pulmonary vascular resistances-were considered in the simulation matrix. Relative advantages and limitations of using the device in BVAD applications are discussed.

Methods: The simulated BVAD pump was based on the Cleveland Clinic pediatric continuous-flow total artificial heart (P-CFTAH), which is currently under development. Different combined disease states (n = 10) were evaluated to model the interaction with the BVAD, considering combinations of normal heart, moderate failure and severe systolic failure of the left and right ventricles, regurgitation of the aortic and pulmonary valves and combinations of vascular resistance. The virtual mock loop simulation tool (MATLAB; MathWorks®, Natick, MA) simulates the hemodynamics at the pump ports using a lumped-parameter model for systemic/pulmonary circulation characteristic inputs (values for impedance, systolic and diastolic ventricular compliance, beat rate, and blood volume), and characteristics of the cardiac chambers and valves.

Results: Simulation results showed that this single-pump BVAD can provide regulated support of up to 5 L/min over a range of combined heart failure states and is suitable for smaller adult and pediatric support. However, good self-regulation of the atrial pressure difference was not maintained with the introduction of aortic valve regurgitation or high systemic vascular resistance when combined with low pulmonary vascular resistance.

Conclusions: This initial in silico study demonstrated that use of the P-CFTAH as a BVAD supports cardiac output and arterial pressure in biventricular heart failure conditions. A similar but larger device would be required for a large adult patient who needs more than 5 L/min of support.
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http://dx.doi.org/10.1007/s13239-020-00501-yDOI Listing
December 2020

The Effects of Preserving Mitral Valve Function on a Left Atrial Assist Device: An In Vitro Mock Circulation Loop Study.

ASAIO J 2021 05;67(5):567-572

From the Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.

We are developing a left atrial assist device (LAAD) to pump blood from the left atrium to the left ventricle for patients who have heart failure with preserved ejection fraction (HFpEF). This study aimed to assess the hemodynamics with the LAAD implanted at two different levels: the mitral valve (MV) level, after removing the MV; and the supravalvular level, preserving MV function conditions using an in vitro mock circulatory loop. Normal heart and mild, moderate, and severe diastolic heart failure conditions were simulated, and the LAAD was set at three different speeds. Without the LAAD support, cardiac output (CO) decreased from 3.7 to 1.1 L/min, aortic pressure (AoP) decreased from 100 to 33 mm Hg, and left atrial pressure (LAP) increased from 16 to 23 mm Hg as the diastolic function became impaired. With high pump support after removing the MV, CO and AoP readings were comparable with those for preserved MV function (CO reached 3.9-4.1 L/min, AoP reached more than 110 mm Hg, and LAP dropped to 16-17 mm Hg under both conditions at high pump speeds). In the mock circulatory loop, our LAAD appeared to have sufficient ability to maintain the hemodynamic status at both positions.
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http://dx.doi.org/10.1097/MAT.0000000000001257DOI Listing
May 2021

Anti-clogging mechanisms of a motion-activated chest tube patency maintenance system: Histology and high-speed camera assessment.

Artif Organs 2020 Nov 5;44(11):1162-1170. Epub 2020 Jul 5.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.

The motion-activated system (MAS) employs vibration to prevent intraluminal chest tube clogging. We evaluated the intraluminal clot formation inside chest tubes using high-speed camera imaging and postexplant histology analysis of thrombus. The chest tube clogging was tested (MAS vs. control) in acute hemothorax porcine models (n = 5). The whole tubes with blood clots were fixed with formalin-acetic acid solution and cut into cross-sections, proceeded for H&E-stained paraffin-embedded tissue sections (MAS sections, n = 11; control sections, n = 11), and analyzed. As a separate effort, a high-speed camera (FASTCAM Mini AX200, 100-mm Zeiss lens) was used to visualize the whole blood clogging pattern inside the chest tube cross-sectional view. Histology revealed a thin string-like fibrin deposition, which showed spiral eddy or aggregate within the blood clots in most sections of Group MAS, but not in those of the control group. Histology findings were compatible with high-speed camera views. The high-speed camera images showed a device-specific intraluminal blood "swirling" pattern. Our findings suggest that a continuous spiral flow in blood within the chest tube (MAS vs. static control) contributes to the formation of a spiral string-like fibrin network during consumption of coagulation factors. As a result, the spiral flow may prevent formation of thick band-like fibrin deposits sticking to the inner tube surface and causing tube clogging, and thus may positively affect chest tube patency and drainage.
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http://dx.doi.org/10.1111/aor.13740DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7679276PMC
November 2020

First In Vivo Experience With Biventricular Circulatory Assistance Using a Single Continuous Flow Pump.

Semin Thorac Cardiovasc Surg 2020 Autumn;32(3):456-465. Epub 2020 May 1.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.

Biventricular assist device (BVAD) implantation is the treatment of choice in patients with severe biventricular heart failure and cardiogenic shock. Our team has developed a miniaturized continuous flow, double-ended centrifugal pump intended for total artificial heart implant (CFTAH). The purpose of this initial in vivo study was to demonstrate that the scaled-down CFTAH (P-CFTAH) can be appropriate for BVAD support. The P-CFTAH was implanted in 4 acute lambs (average weight, 41.5 ± 2.8 kg) through a median sternotomy. The cannulation was performed through the left and right atria, and cannulae length adjustment was performed for atrial and ventricular cannulation. The BVAD system was tested at 3 pump speeds (3000, 4500, and 6000 rpm). The BVAD performed very well for both atrial and ventricular cannulation within the 3000-6000 rpm range. Stable hemodynamics were maintained after implantation of the P-CFTAH. The self-regulating performance of the system in vivo was demonstrated by the left (LAP) and right (RAP) pressure difference (LAP-RAP) falling predominantly within the range of -5 to 10 mm Hg with variation, in addition to in vitro assessment of left and right heart failure conditions. Left and right pump flows and total flow increased as the BVAD speed was increased. This initial in vivo testing of the BVAD system demonstrated satisfactory device performance and self-regulation for biventricular heart failure support over a wide range of conditions. The BVAD system keeps the atrial pressure difference within bounds and maintains acceptable cardiac output over a wide range of hemodynamic conditions.
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http://dx.doi.org/10.1053/j.semtcvs.2020.03.006DOI Listing
October 2020

Effects of blood pump orientation on performance: In vitro assessment of universal advanced ventricular assist device.

Artif Organs 2020 Oct 20;44(10):1055-1060. Epub 2020 Apr 20.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.

An advanced ventricular assist device (VAD), which is under development in our institution, has specific features that allow changes in the axial rotor position and pump performance by intrapump pressure difference. However, performance could be influenced by the pump orientation because of the effect of gravity on the rotor position. The purpose of this study was to evaluate the effects of pump orientation on the pump performance, including pulse pressure and regurgitant flow through the pump when the pump was stopped. Bench testing of the VAD was performed on a static or pulsatile mock loop with a pneumatic device to simulate the native ventricle. The pump performance, including pressure-flow curve, pulsatility, and regurgitant flow, was evaluated at several angles, ranging from -90° (inlet pointed upward) to +90° (inlet pointed downward) at pump speeds of 2000, 2500, 3000, and 3500 rpm. The pump performance was slightly lower at +90° at all rotational speeds, compared with -90°. The pulse pressure on the pulsatile mock loop (80 bpm) was 50 mm Hg without pump support, remained at 50 mm Hg during pump support, and was not changed by orientation (-90°, 0°, and +90°). When the pump was stopped, the regurgitant flow was near 0 L/min at all angles. Pump orientation had a minor effect on pump performance, with no effect on pulse pressure or regurgitant flow when the pump was stopped. This indicates that the effect of gravity on the rotor assembly is insignificant.
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http://dx.doi.org/10.1111/aor.13690DOI Listing
October 2020

Left atrial assist device to treat patients with heart failure with preserved ejection fraction: Initial in vitro study.

J Thorac Cardiovasc Surg 2021 07 25;162(1):120-126. Epub 2020 Jan 25.

Department of Cardiovascular Medicine, Miller Family Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio; Kaufman Center for Heart Failure, Cleveland Clinic, Cleveland, Ohio.

Objectives: Many patients with heart failure have preserved ejection fraction but also diastolic dysfunction, with no effective therapy. We are developing a new pump (left atrial assist device, LAAD) for implantation at the mitral position to pump blood from the left atrium to sufficiently fill the left ventricle. The purpose of the initial in vitro study was to demonstrate that the LAAD can reduce left atrial pressure (LAP) and increase cardiac output (CO) while maintaining arterial pulsatility and normal aortic valve function using a proof-of-concept device.

Methods: The LAAD concept was tested at 3 pump speeds on a pulsatile mock loop with a pneumatic pump that simulated the normal function of the native ventricle as well as 3 levels of diastolic heart failure (DHF 1, 2, and 3) by adjusting the diastolic drive pressure to limit diastolic filling of the ventricle.

Results: Without the LAAD, CO and aortic pressure (AoP) decreased dramatically from 3.8 L/min and 100 mm Hg at normal heart condition to 1.2 L/min and 35 mm Hg at DHF 3, respectively. With LAAD support, both CO and AoP recovered to normal heart values at 3200 rpm and surpassed normal heart values at 3800 rpm. Furthermore, with LAAD support, LAP recovered to almost that of the normal heart condition at 3800 rpm.

Conclusions: These initial in vitro results support our hypothesis that use of the LAAD increases CO and AoP and decreases LAP under DHF conditions while maintaining arterial pulsatility and full function of the aortic valve.
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http://dx.doi.org/10.1016/j.jtcvs.2019.12.110DOI Listing
July 2021

Use of a Virtual Mock Loop model to evaluate a new left ventricular assist device for transapical insertion.

Int J Artif Organs 2020 Oct 22;43(10):677-683. Epub 2020 Feb 22.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.

We are developing a novel type of miniaturized left ventricular assist device that is configured for transapical insertion. The aim of this study was to assess the performance and function of a new pump by using a Virtual Mock Loop system for device characterization and mapping. The results, such as pressure-flow performance curves, from pump testing in a physical mock circulatory loop were used to analyze its function as a left ventricular assist device. The Virtual Mock Loop system was programmed to mimic the normal heart condition, systolic heart failure, diastolic heart failure, and both systolic and diastolic heart failure, and to provide hemodynamic pressure values before and after the activation of several left ventricular assist device pump speeds (12,000, 14,000, and 16,000 r/min). With pump support, systemic flow and mean aortic pressure increased, and mean left atrial pressure and pulmonary artery pressure decreased for all heart conditions. Regarding high pump-speed support, the systemic flow, aortic pressure, left atrial pressure, and pulmonary artery pressure returned to the level of the normal heart condition. Based on the test results from the Virtual Mock Loop system, the new left ventricular assist device for transapical insertion may be able to ease the symptoms of patients with various types of heart failure. The Virtual Mock Loop system could be helpful to assess pump performance before in vitro bench testing.
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http://dx.doi.org/10.1177/0391398820907104DOI Listing
October 2020

A simulation tool for mechanical circulatory support device interaction with diseased states.

J Artif Organs 2020 Jun 14;23(2):124-132. Epub 2020 Feb 14.

Department of Biomedical Engineering/ND20, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, 44195, USA.

We have created a simulation model to investigate the interactions between a variety of mechanical circulatory support (MCS) devices and the circulatory system with various simulated patient conditions and disease states. The present simulation accommodates a family of continuous-flow MCS devices under various stages of consideration or development at our institution. This article describes the mathematical core of the in silico simulation system and shows examples of simulation output imitating various disease states and of selected in vitro and clinical data from the literature.
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http://dx.doi.org/10.1007/s10047-020-01155-2DOI Listing
June 2020

Development of a circulatory mock loop for biventricular device testing with various heart conditions.

Int J Artif Organs 2020 Sep 4;43(9):600-605. Epub 2020 Feb 4.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.

This study aimed to evaluate a newly designed circulatory mock loop intended to model cardiac and circulatory hemodynamics for mechanical circulatory support device testing. The mock loop was built with dedicated ports suitable for attaching assist devices in various configurations. This biventricular mock loop uses two pneumatic pumps (Abiomed AB5000, Danvers, MA, USA) driven by a dual-output driver (Thoratec Model 2600, Pleasanton, CA, USA). The drive pressures can be individually modified to simulate a healthy heart and left and/or right heart failure conditions, and variable compliance and fluid volume allow for additional customization. The loop output for a healthy heart was tested at 4.2 L/min with left and right atrial pressures of 1 and 5 mm Hg, respectively; a mean aortic pressure of 93 mm Hg; and pulmonary artery pressure of 17 mm Hg. Under conditions of left heart failure, these values were reduced to 2.1 L/min output, left atrial pressure = 28 mm Hg, right atrial pressure = 3 mm Hg, aortic pressure = 58 mm Hg, and pulmonary artery pressure = 35 mm Hg. Right heart failure resulted in the reverse balance: left atrial pressure = 0 mm Hg, right atrial pressure = 30 mm Hg, aortic pressure = 100 mm Hg, and pulmonary artery pressure = 13 mm Hg with a flow of 3.9 L/min. For biventricular heart failure, flow was decreased to 1.6 L/min, left atrial pressure = 13 mm Hg, right atrial pressure = 13 mm Hg, aortic pressure = 52 mm Hg, and pulmonary artery pressure = 18 mm Hg. This mock loop could become a reliable bench tool to simulate a range of heart failure conditions.
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http://dx.doi.org/10.1177/0391398820903316DOI Listing
September 2020

Analysis of Cleveland Clinic continuous-flow total artificial heart performance using the Virtual Mock Loop: Comparison with an in vivo study.

Artif Organs 2020 Apr 10;44(4):375-383. Epub 2019 Nov 10.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.

The Virtual Mock Loop (VML) is a mathematical model designed to simulate mechanism of the human cardiovascular system interacting with mechanical circulatory support devices. Here, we aimed to mimic the hemodynamic performance of Cleveland Clinic's self-regulating continuous-flow total artificial heart (CFTAH) via VML and evaluate the accuracy of the VML compared with an in vivo acute animal study. The VML reproduced 124 hemodynamic conditions from three acute in vivo experiments in calves. Systemic/pulmonary vascular resistances, pump rotational speed, pulsatility, and pulse rate were set for the VML from in vivo data. We compared outputs (pump flow, left and right pump pressure rises, and atrial pressure difference) between the two systems. The pump performance curves all fell in the designed range. There was a strong correlation between the VML and the in vivo study in the left pump flow (r = 0.84) and pressure rise (r = 0.80), and a moderate correlation in right pressure rise (r = 0.52) and atrial pressure difference (r = 0.59). Although there is room for improvement in simulating right-sided pump performance of self-regulating CFTAH, the VML acceptably simulated the hemodynamics observed in an in vivo study. These results indicate that pump flow and pressure rise can be estimated from vascular resistances and pump settings.
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http://dx.doi.org/10.1111/aor.13574DOI Listing
April 2020

Continuous-flow total artificial heart: hemodynamic and pump-related changes associated with posture in a chronic calf model.

J Artif Organs 2019 Sep 10;22(3):256-259. Epub 2019 May 10.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, 44195, USA.

This study aimed to evaluate the effects of posture (sitting [lying down]/standing) on hemodynamic and pump-related parameters in calves implanted with our institution's continuous-flow total artificial heart (CFTAH). These parameters were analyzed with posture information in four calves that had achieved the intended 14-, 30-, or 90-day durations of implantation. In each animal, postoperative hourly data gathered throughout the study were used to compare average values with the animal sitting vs. standing. Pump flow became significantly higher in the standing than sitting position at the same pump speed (standing 7.9 ± 0.8, sitting 7.4 ± 1.0 L/min, p = 0.028). Systemic vascular resistance (SVR) and aortic pressure (AoP) were significantly lower in the standing than sitting position (SVR standing 779 ± 145, sitting 929 ± 206 dyne s/cm, p = 0.027; AoP standing 93 ± 7, sitting 103 ± 7 mm Hg, p < 0.001). No substantial change occurred in pulmonary vascular resistance (PVR) or pulmonary arterial pressure (PAP) with posture (PVR standing 161 ± 39, sitting 164 ± 48 dyne s/cm, p = 0.639; PAP standing 32 ± 3, sitting 33 ± 4 mm Hg, p = 0.340). Posture affected some hemodynamic and pump-related parameters in calves with CFTAH, with implications for patients with implanted pumps.
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http://dx.doi.org/10.1007/s10047-019-01105-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6687532PMC
September 2019

The design modification of advanced ventricular assist device to enhance pulse augmentation and regurgitant flow shut-off.

Artif Organs 2019 Oct 18;43(10):961-965. Epub 2019 Jun 18.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.

The new Advanced ventricular assist device (Advanced VAD) has many features such as improving pulsatility and preventing regurgitant flow during pump stoppage. The purpose of this study was to evaluate the effects of design modifications of the Advanced VAD on these features in vitro. Bench testing of four versions of the Advanced VAD was performed on a static or pulsatile mock loop with a pneumatic device. After pump performance was evaluated, each pump was run at 3000 rpm to evaluate pulse augmentation, then was stopped to assess regurgitant flow through the pump. There was no significant difference in pump performance between the pump models. The average pulse pressure in the pulsatile mock loop was 23.0, 34.0, 39.3, 33.8, and 37.3 mm Hg without pump, with AV010, AV020 3S, AV020 6S, and AV020 RC, respectively. The pulse augmentation factor was 48%, 71%, 47%, and 62% with AV010, AV020 3S, AV020 6S, and AV020 RC, respectively. In the pump stop test, regurgitant flow was -0.60 ± 0.70, -0.13 ± 0.57, -0.14 ± 0.09, and -0.18 ± 0.06 L/min in AV010, AV020 3S, AV020 6S, and AV020 RC, respectively. In conclusion, by modifying the design of the Advanced VAD, we successfully showed the improved pulsatility augmentation and regurgitant flow shut-off features.
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http://dx.doi.org/10.1111/aor.13484DOI Listing
October 2019

Use of a Mechanical Circulatory Support Simulation to Study Pump Interactions With the Variable Hemodynamic Environment.

Artif Organs 2018 Dec 4;42(12):E420-E427. Epub 2018 Nov 4.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland, Ohio, USA.

The Virtual Mock Loop, a versatile virtual mock circulation loop, was developed using a lumped-parameter model of the mechanically assisted human circulatory system. Inputs allow specification of a variety of continuous-flow pumps (left, right, or biventricular assist devices) and a total artificial heart that can self-regulate between left and right pump outputs. Hemodynamic inputs were simplified using a disease-based input panel, allowing selection of a combination of cardiovascular disease states, including systolic and diastolic heart failure, stenosis, and/or regurgitation in each of the four valves, and high to low systemic and pulmonary vascular resistance values. The menu-driven output includes a summary of hemodynamic parameters and graphical output of selected flows, pressures, and volumes in the heart's four chambers as well as in the pulmonary artery and aorta. New tools to augment experimental research on implantable heart-assist devices and to increase our understanding of patient-specific pump interactions are in high demand. The purpose of this ongoing study is to demonstrate the use of a system analysis computer simulation to explore and better comprehend the interactions of mechanical circulatory support pumps with a more extensive combination of patient-specific or simulation conditions than can be established by practical experimentation. Usability is an important factor in constructing computer models for research purposes, and among our primary objectives in creating this simulation model were to make it as portable and useful as possible outside the lab environment, by people not involved in the creation of its operational software.
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http://dx.doi.org/10.1111/aor.13287DOI Listing
December 2018

Simulated Performance of the Cleveland Clinic Continuous-Flow Total Artificial Heart Using the Virtual Mock Loop.

ASAIO J 2019 08;65(6):565-572

From the Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.

Our new Virtual Mock Loop (VML) is a mathematical model designed to simulate the human cardiovascular system and gauge performance of mechanical circulatory support devices. We aimed to mimic the hemodynamic performance of Cleveland Clinic's self-regulating continuous-flow total artificial heart (CFTAH) via VML and evaluate VML's accuracy versus bench data from our standard mock circulatory loop. The VML reproduced 23 hemodynamic conditions. Systemic/pulmonary vascular resistances and pump rotational speed were set for VML from bench test data. We compared outputs (pump flow, left/right pump pressure rise, normalized pump performance, and atrial pressure difference) of the two methods. Data from pump flow and left pump pressure rise were similar, but right pump pressure rise slightly differed. Left pump normalized pump performance curves were similar. Right pump VML results were within the same performance range indicated by bench tests. The plots of atrial pressure differences of VML versus bench-test data were similar, but slightly differed in the midrange of systemic/pulmonary gradients. Virtual Mock Loop successfully reproduced results from our mock circulatory loop of CFTAH test conditions. The CFTAH's self-regulation feature of right pump performance was also calculated effectively. We foresee using versions of the VML for training, simulating physiologic cardiac conditions, and patient monitoring.
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http://dx.doi.org/10.1097/MAT.0000000000000857DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6359994PMC
August 2019

Early in vivo experience with the pediatric continuous-flow total artificial heart.

J Heart Lung Transplant 2018 08 30;37(8):1029-1034. Epub 2018 Mar 30.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA. Electronic address:

Background: Heart transplantation in infants and children is an accepted therapy for end-stage heart failure, but donor organ availability is low and always uncertain. Mechanical circulatory support is another standard option, but there is a lack of intracorporeal devices due to size and functional range. The purpose of this study was to evaluate the in vivo performance of our initial prototype of a pediatric continuous-flow total artificial heart (P-CFTAH), comprising a dual pump with one motor and one rotating assembly, supported by a hydrodynamic bearing.

Methods: In acute studies, the P-CFTAH was implanted in 4 lambs (average weight: 28.7 ± 2.3 kg) via a median sternotomy under cardiopulmonary bypass. Pulmonary and systemic pump performance parameters were recorded.

Results: The experiments showed good anatomical fit and easy implantation, with an average aortic cross-clamp time of 98 ± 18 minutes. Baseline hemodynamics were stable in all 4 animals (pump speed: 3.4 ± 0.2 krpm; pump flow: 2.1 ± 0.9 liters/min; power: 3.0 ± 0.8 W; arterial pressure: 68 ± 10 mm Hg; left and right atrial pressures: 6 ± 1 mm Hg, for both). Any differences between left and right atrial pressures were maintained within the intended limit of ±5 mm Hg over a wide range of ratios of systemic-to-pulmonary vascular resistance (0.7 to 12), with and without pump-speed modulation. Pump-speed modulation was successfully performed to create arterial pulsation.

Conclusion: This initial P-CFTAH prototype met the proposed requirements for self-regulation, performance, and pulse modulation.
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http://dx.doi.org/10.1016/j.healun.2018.03.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6647019PMC
August 2018

Anatomical study of the Cleveland Clinic continuous-flow total artificial heart in adult and pediatric configurations.

J Artif Organs 2018 Sep 3;21(3):383-386. Epub 2018 Apr 3.

R1 Engineering, Euclid, OH, USA.

The purpose of this study was to assess the smallest possible body sizes of patients in whom the Cleveland Clinic continuous-flow total artificial heart for adult (CFTAH) and pediatric configurations (P-CFTAH) can fit. One of the most critical dimensions is the vertebra-to-sternum distance at the junction of the right atrium to the inferior vena cava (V-S distance). Our previous CFTAH anatomical fitting study suggested that the CFTAH would fit patients of V-S distance ≥ 7.5 cm and the P-CFTAH of V-S distance ≥ 5.25 cm (70% of 7.5 cm). To confirm this, we assessed the relationship between body surface area (BSA) and V-S distance in 15 adult patients (BSA 1.86-2.62 m) and 31 pediatric patients (BSA 0.17-1.80 m) whose computed tomography scans were available. We found a highly significant correlation between BSA and V-S distance (p < 1.0 × 10). It appears that the CFTAH will fit in most patients with BSA ≥ 1.0 m (corresponding height of ≥ 130 cm and age of 9 years) and the P-CFTAH in patients with BSA ≥ 0.3 m (corresponding height of ≥ 55 cm and age of 1 month). Further anatomical fitting studies are needed to evaluate the two pump models inside human chests to determine the smallest patient size/critical dimensions and device port configurations.
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http://dx.doi.org/10.1007/s10047-018-1039-0DOI Listing
September 2018

Advantages of Integrating Pressure-Regulating Devices Into Mechanical Circulatory Support Pumps.

ASAIO J 2019 01;65(1):e1-e3

Department of Biomedical Engineering, Lerner Research Institute (LRI), Cleveland Clinic, Cleveland, Ohio.

Control of mechanical circulatory support pump output typically requires that pressure-regulating functions be accomplished by active control of the speed or geometry of the device, with feedback from pressure or flow sensors. This article presents a different design approach, with a pressure-regulating device as the core design feature, allowing the essential control function of regulating pressure to be directly programmed into the hydromechanical design. We show the step-by-step transformation of a pressure-regulating device into a continuous-flow total artificial heart that passively balances left and right circulations without the need for pressure and flow sensors. In addition, we discuss a ventricular assist device that prevents backflow in the event of power interruption and also dynamically interacts with residual ventricle function to preserve pulsatility.
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http://dx.doi.org/10.1097/MAT.0000000000000772DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6128778PMC
January 2019

Initial in vitro testing of a paediatric continuous-flow total artificial heart.

Interact Cardiovasc Thorac Surg 2018 06;26(6):897-901

Department of Thoracic and Cardiovascular Surgery, Kaufman Center for Heart Failure, Miller Family Heart and Vascular Institute, Cleveland Clinic, Cleveland, OH, USA.

Objectives: Mechanical circulatory support has become standard therapy for adult patients with end-stage heart failure; however, in paediatric patients with congenital heart disease, the options for chronic mechanical circulatory support are limited to paracorporeal devices or off-label use of devices intended for implantation in adults. Congenital heart disease and cardiomyopathy often involve both the left and right ventricles; in such cases, heart transplantation, a biventricular assist device or a total artificial heart is needed to adequately sustain both pulmonary and systemic circulations. We aimed to evaluate the in vitro performance of the initial prototype of our paediatric continuous-flow total artificial heart.

Methods: The paediatric continuous-flow total artificial heart pump was downsized from the adult continuous-flow total artificial heart configuration by a scale factor of 0.70 (1/3 of total volume) to enable implantation in infants. System performance of this prototype was evaluated using the continuous-flow total artificial heart mock loop set to mimic paediatric circulation. We generated maps of pump performance and atrial pressure differences over a wide range of systemic vascular resistance/pulmonary vascular resistance and pump speeds.

Results: Performance data indicated left pump flow range of 0.4-4.7 l/min at 100 mmHg delta pressure. The left/right atrial pressure difference was maintained within ±5 mmHg with systemic vascular resistance/pulmonary vascular resistance ratios between 1.4 and 35, with/without pump speed modulation, verifying expected passive self-regulation of atrial pressure balance.

Conclusions: The paediatric continuous-flow total artificial heart prototype met design requirements for self-regulation and performance; in vivo pump performance studies are ongoing.
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http://dx.doi.org/10.1093/icvts/ivx429DOI Listing
June 2018

Unlocking the box: basic requirements for an ideal ventricular assist device controller.

Expert Rev Med Devices 2017 May 19;14(5):393-400. Epub 2017 Apr 19.

b Department of Biomedical Engineering, Lerner Research Institute , Cleveland Clinic , Cleveland , OH , USA.

Introduction: A modern ventricular assist device (VAD) system comprises an implantable rotary blood pump and external components located outside the patient's body: a wearable controller connected to the pump via a percutaneous cable, wearable rechargeable batteries, battery charger, alternating- and direct-current power supplies, and a hospital device to control and monitor the system. If the blood pump is the 'heart' of a VAD system, the controller is its 'brain.' The controller drives the pump's electrical motor; varies the pump speed or flow based on user commands or feedback signals; collects, processes, and stores data; performs self-diagnostics; transmits to and receives data from other system components, i.e., hospital monitor and batteries; and provides various types of user interface - audible, visual, and tactile. Areas covered: Here we describe the essential functions and basic design of the VAD external controller and give our views on the future of this technology. Expert commentary: Controllers for VAD systems are crucial to their successful operation. The current clinically available system comprises an external power supply and patient-friendly controller unit. Future controller solutions may enable remote hospital monitoring, more intuitive system interface, and the potential to use a single controller to automatically control a biventricular assist device configuration.
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http://dx.doi.org/10.1080/17434440.2017.1318059DOI Listing
May 2017

Generating pulsatility by pump speed modulation with continuous-flow total artificial heart in awake calves.

J Artif Organs 2017 Dec 8;20(4):381-385. Epub 2017 Apr 8.

Cardiovascular Dynamics Laboratory, Department of Biomedical Engineering/ND20, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, 44195, USA.

The purpose of this study was to evaluate the effects of sinusoidal pump speed modulation of the Cleveland Clinic continuous-flow total artificial heart (CFTAH) on hemodynamics and pump flow in an awake chronic calf model. The sinusoidal pump speed modulations, performed on the day of elective sacrifice, were set at ±15 and ± 25% of mean pump speed at 80 bpm in four awake calves with a CFTAH. The systemic and pulmonary arterial pulse pressures increased to 12.0 and 12.3 mmHg (±15% modulation) and to 15.9 and 15.7 mmHg (±25% modulation), respectively. The pulsatility index and surplus hemodynamic energy significantly increased, respectively, to 1.05 and 1346 ergs/cm at ±15% speed modulation and to 1.51 and 3381 ergs/cm at ±25% speed modulation. This study showed that it is feasible to generate pressure pulsatility with pump speed modulation; the platform is suitable for evaluating the physiologic impact of pulsatility and allows determination of the best speed modulations in terms of magnitude, frequency, and profiles.
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http://dx.doi.org/10.1007/s10047-017-0958-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5632582PMC
December 2017

Thrombotic Depositions on Right Impeller of Double-Ended Centrifugal Total Artificial Heart In Vivo.

Artif Organs 2017 May 23;41(5):476-481. Epub 2016 Nov 23.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic.

The development of total artificial heart devices is a complex undertaking that includes chronic biocompatibility assessment of the device. It is considered particularly important to assess whether device design and features can be compatible long term in a biological environment. As part of the development program for the Cleveland Clinic continuous-flow total artificial heart (CFTAH), we evaluated the device for signs of thrombosis and biological material deposition in four animals that had achieved the intended 14-, 30-, or 90-day durations in each respective experiment. Explanted CFTAHs were analyzed for possible clot buildup at "susceptible" areas inside the pump, particularly the right pump impeller. Depositions of various consistency and shapes were observed. We here report our findings, along with macroscopic and microscopic analysis post explant, and provide computational fluid dynamics data with its potential implications for thrombus formation.
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http://dx.doi.org/10.1111/aor.12778DOI Listing
May 2017

Deairing Techniques for Double-Ended Centrifugal Total Artificial Heart Implantation.

Artif Organs 2017 Jun 22;41(6):568-572. Epub 2016 Sep 22.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic.

The unique device architecture of the Cleveland Clinic continuous-flow total artificial heart (CFTAH) requires dedicated and specific air-removal techniques during device implantation in vivo. These procedures comprise special surgical techniques and intraoperative manipulations, as well as engineering design changes and optimizations to the device itself. The current study evaluated the optimal air-removal techniques during the Cleveland Clinic double-ended centrifugal CFTAH in vivo implants (n = 17). Techniques and pump design iterations consisted of developing a priming method for the device and the use of built-in deairing ports in the early cases (n = 5). In the remaining cases (n = 12), deairing ports were not used. Dedicated air-removal ports were not considered an essential design requirement, and such ports may represent an additional risk for pump thrombosis. Careful passive deairing was found to be an effective measure with a centrifugal pump of this design. In this report, the techniques and design changes that were made during this CFTAH development program to enable effective residual air removal and prevention of air embolism during in vivo device implantation are explained.
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http://dx.doi.org/10.1111/aor.12775DOI Listing
June 2017

Advanced ventricular assist device with pulse augmentation and automatic regurgitant-flow shut-off.

J Heart Lung Transplant 2016 12 27;35(12):1519-1521. Epub 2016 Jul 27.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; Department of Thoracic and Cardiovascular Surgery, Kaufman Center for Heart Failure, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio, USA.

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http://dx.doi.org/10.1016/j.healun.2016.07.019DOI Listing
December 2016

The Contribution to Hemodynamics Even at Very Low Pump Speeds in the HVAD.

Ann Thorac Surg 2016 Jun 22;101(6):2260-4. Epub 2016 Feb 22.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio. Electronic address:

Background: We recently reported using bench testing that the Thoratec HeartMate II at 6,000 rpm contributed to hemodynamics when the heart had not recovered well, making weaning assessment questionable. In this bench study, we characterized hemodynamics and pump flow of the HeartWare HVAD at 1,800 rpm, the lowest speed commonly used to assess clinical recovery.

Methods: The HVAD was operated in a mock loop at 1,800, 2,400, and 3,000 rpm. We acquired pressure-flow curves in each steady state. In pulsatile mode with the pneumatic ventricle (heart simulator) activated, pump flow, total flow, and aortic pressure (AoP) data were obtained under conditions simulating normal heart function or heart failure.

Results: A large regurgitant flow during diastole was confirmed during normal heart function at 1,800 rpm support; however, the net flow was zero, and there was no difference in mean AoP between 1,800 rpm support and no HVAD support. In contrast, in the heart failure condition, HVAD flow at 1,800 rpm significantly contributed to mean AoP and total flow, because there was less regurgitant flow.

Conclusions: Similar to the results for the HeartMate II at 6,000 rpm, we found that the net pump flow generated by the HeartWare HVAD at 1,800 rpm depends on the degree of residual left ventricular (LV) function. In the setting of improved LV function, at 1,800 rpm we noted a large regurgitant flow. Although this "marker" can serve as a useful indicator for recovery, assessing recovery at this speed is flawed unless measures are taken to prevent regurgitant flow.
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http://dx.doi.org/10.1016/j.athoracsur.2015.12.002DOI Listing
June 2016

Future Prospects for the Total Artificial Heart.

Expert Rev Med Devices 2016 6;13(2):191-201. Epub 2016 Feb 6.

a Department of Biomedical Engineering , Lerner Research Institute, Cleveland Clinic , Cleveland , OH , USA.

A total artificial heart (TAH) is the sole remaining option for patients with biventricular failure who cannot be rescued by left ventricular assist devices (LVADs) alone. However, the pulsatile TAH in clinical use today has limitations: large pump size, unknown durability, required complex anticoagulation regimen, and association with significant postsurgical complications. That pump is noisy; its large pneumatic driving lines traverse the body, with bulky external components for its drivers. Continuous-flow pumps, which caused a paradigm shift in the LVAD field, have already contributed to the rapidly evolving development of TAHs. Novel continuous-flow TAHs are only in preclinical testing or developmental stages. We here review the current state of TAHs, with recommended requirements for the TAH of the future.
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http://dx.doi.org/10.1586/17434440.2016.1136212DOI Listing
October 2016
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