Publications by authors named "Kiyotaka Fukamachi"

202 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

Ocular surface microcirculation is better preserved with pulsatile versus continuous flow during cardiopulmonary bypass-An experimental pilot.

Artif Organs 2021 Dec 6. Epub 2021 Dec 6.

Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway.

Background: Non-pulsatile cardiopulmonary bypass (CPB) may induce microvascular dysregulation. In piglets, we compared ocular surface microcirculation during pulsatile versus continuous flow (CF) bypass.

Methods: Ocular surface microcirculation in small tissue volumes (~0.1 mm ) at limbus (high metabolic rate) and bulbar conjunctiva (low metabolic rate) was examined in a porcine model using computer assisted video microscopy and diffuse reflectance spectroscopy, before and after 3 and 6 h of pulsatile (n = 5 piglets) or CF (n = 3 piglets) CPB. Functional capillary density, capillary flow velocity and microvascular oxygen saturation were quantified.

Results: At limbus, velocities improved with pulsatility (p < 0.01) and deteriorated with CF (p < 0.01). In bulbar conjunctiva, velocities were severely reduced with CF (p < 0.01), accompanied by an increase in capillary density (p < 0.01). Microvascular oxygen saturation decreased in both groups.

Conclusion: Ocular surface capillary densities and flow patterns are better preserved with pulsatile versus CF during 6 h of CPB in sleeping piglets.
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http://dx.doi.org/10.1111/aor.14137DOI Listing
December 2021

Hemodynamic evaluation of a new pulsatile blood pump during low flow cardiopulmonary bypass support.

Artif Organs 2021 Nov 15. Epub 2021 Nov 15.

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

Background: The VentriFlo True Pulse Pump (VentriFlo, Inc, Pelham, NH, USA) is a new pulsatile blood pump intended for use during short-term circulatory support. The purpose of this study was to evaluate the feasibility of the VentriFlo and compare it to a conventional centrifugal pump (ROTAFLOW, Getinge, Gothenberg, Sweden) in acute pig experiments.

Methods: Pigs (40-45 kg) were supported by cardiopulmonary bypass (CPB) with the VentriFlo (n = 9) or ROTAFLOW (n = 5) for 6 h. Both VentriFlo and ROTAFLOW circuits utilized standard CPB components. We evaluated hemodynamics, blood chemistry, gas analysis, plasma hemoglobin, and microcirculation at the groin skin with computer-assisted video microscopy (Optilia, Sollentuna, Sweden).

Results: Pigs were successfully supported by CPB for 6 h without any pump-related complications in either group. The VentriFlo delivered an average stroke volume of 29.2 ± 4.8 ml. VentriFlo delivered significantly higher pulse pressure (29.1 ± 7.2 mm Hg vs. 4.4 ± 7.0 mm Hg, p < 0.01) as measured in the carotid artery, with mean aortic pressure and pump flow comparable with those in ROTAFLOW. In blood gas analysis, arterial pH was significantly lower after five hours support in the VentriFlo group (7.30 ± 0.07 vs. 7.43 ± 0.03, p = 0.001). There was no significant difference in plasma hemoglobin level in both groups after six hours of CPB support. In microcirculatory assessment, VentriFlo tended to keep normal capillary flow, but it was not statistically significant.

Conclusions: VentriFlo-supported pigs showed comparable hemodynamic parameters with significantly higher pulse pressure compared to ROTAFLOW without hemolysis.
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http://dx.doi.org/10.1111/aor.14119DOI Listing
November 2021

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

Large animal models of heart failure with preserved ejection fraction.

Heart Fail Rev 2021 Nov 9. Epub 2021 Nov 9.

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

Heart failure with preserved ejection fraction (HFpEF) is characterized by diastolic dysfunction and multiple comorbidities. The number of patients is continuously increasing, with no improvement in its unfavorable prognosis, and there is a strong need for novel treatments. New devices and drugs are difficult to assess at the translational preclinical step due to the lack of high-fidelity large animal models of HFpEF. In this review, we describe the summary of historical and evolving techniques for developing large animal models. The representative methods are pressure overload models, including (1) aortic banding, (2) aortic stent, (3) renal hypertension, and (4) mineralocorticoid-induced hypertension. Diet-induced metabolic syndromes are also used. A new technique with an inflatable balloon inside the left ventricle can be used during acute/chronic in vivo surgeries to simulate HFpEF-like hemodynamics for pump-based therapies. Canines and porcine are most widely used, but other non-rodent animals (sheep, non-human primates, felines, or calves) have been used. Feline models present the most well-simulated HFpEF pathology, but small size is a concern, and the information is still very limited. The rapid and reliable establishment of large animal models for HFpEF, and novel methodology based on the past experimental attempts with large animals, are needed.
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http://dx.doi.org/10.1007/s10741-021-10184-9DOI 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 for heart failure with preserved ejection fraction: initial results with torque control mode in diastolic heart failure model.

Heart Fail Rev 2021 May 1. Epub 2021 May 1.

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

A novel pump, the left atrial assist device (LAAD), is a device specifically for the treatment of heart failure with preserved ejection fraction (HFpEF). The LAAD is a mixed-flow pump that is implanted in the mitral position and delivers blood from the left atrium to the left ventricle. During the development process, we aimed to explore whether device activation in torque control (TC) mode would improve the function of the LAAD. The TC mode causes adjustment of the pump speed automatically during each cardiac cycle in order to maintain a specified torque. In this study, we tested four different TC settings (TC modes 0.9, 1.0, 1.25, and 1.5) using an in vitro mock circulatory loop. Mild, moderate, and severe diastolic heart failure (DHF) conditions, as well as normal heart condition, were simulated with the four TC modes. Also, we evaluated the LAAD in vivo with three calves. The LAAD was implanted at the mitral position with four TC settings (TC modes 0.9, 1.0, 1.1, 1.2). With LAAD support, the in vitro cardiac output and aortic pressure recovered to normal heart levels at TC 1.25 and 1.5 even under severe DHF conditions with little pump regurgitation. The TC mode tested in vivo with three calves, and it also showed favorable result without elevating the left ventricular end-diastolic pressure. These initial in vitro and in vivo results suggest that the TC mode could be potentially effective, and the LAAD could be a treatment option for HFpEF patients.
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http://dx.doi.org/10.1007/s10741-021-10117-6DOI Listing
May 2021

Universal ventricular assist device for right and left circulatory support: the Cleveland Clinic concept.

Ann Cardiothorac Surg 2021 Mar;10(2):271-273

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, USA.

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http://dx.doi.org/10.21037/acs-2020-cfmcs-22DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8033260PMC
March 2021

Acute Response of Human Aortic Endothelial Cells to Loss of Pulsatility as Seen during Cardiopulmonary Bypass.

Cells Tissues Organs 2021 Feb 25:1-11. Epub 2021 Feb 25.

Division of Cardiovascular Disease, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA,

Cardiopulmonary bypass (CPB) results in short-term (3-5 h) exposure to flow with diminished pulsatility often referred to as "continuous flow". It is unclear if short-term exposure to continuous flow influences endothelial function, particularly, changes in levels of pro-inflammatory and pro-angiogenic cytokines. In this study, we used the endothelial cell culture model (ECCM) to evaluate if short-term (≤5 h) reduction in pulsatility alters levels of pro-inflammatory/pro-angiogenic cytokine levels. Human aortic endothelial cells (HAECs) cultured within the ECCM provide a simple model to evaluate endothelial cell function in the absence of confounding factors. HAECs were maintained under normal pulsatile flow for 24 h and then subjected to continuous flow (diminished pulsatile pressure and flow) as observed during CPB for 5 h. The ECCM replicated pulsatility and flow morphologies associated with normal hemodynamic status and CPB as seen with clinically used roller pumps. Levels of angiopoietin-2 (ANG-2), vascular endothelial growth factor-A (VEGF-A), and hepatocyte growth factor were lower in the continuous flow group in comparison to the pulsatile flow group whereas the levels of endothelin-1 (ET-1), granulocyte colony stimulating factor, interleukin-8 (IL-8) and placental growth factor were higher in the continuous flow group in comparison to the pulsatile flow group. Immunolabelling of HAECs subjected to continuous flow showed a decrease in expression of ANG-2 and VEGF-A surface receptors, tyrosine protein kinase-2 and Fms-related receptor tyrosine kinase-1, respectively. Given that the 5 h exposure to continuous flow is insufficient for transcriptional regulation, it is likely that pro-inflammatory/pro-angiogenic signaling observed was due to signaling molecules stored in Weible-Palade bodies (ET-1, IL-8, ANG-2) and via HAEC binding/uptake of soluble factors in media. These results suggest that even short-term exposure to continuous flow can potentially activate pro-inflammatory/pro-angiogenic signaling in cultured HAECs and pulsatile flow may be a successful strategy in reducing the undesirable sequalae following continuous flow CPB.
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http://dx.doi.org/10.1159/000512558DOI Listing
February 2021

Device-based treatment options for heart failure with preserved ejection fraction.

Heart Fail Rev 2021 07 12;26(4):749-762. Epub 2021 Jan 12.

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

Heart failure with preserved ejection fraction (HFpEF) is a syndrome with an unfavorable prognosis, and the number of the patients continues to grow. Because there is no effective therapy established as a standard, including pharmacological treatments, a movement to develop and evaluate device-based therapies is an important emerging area in the treatment of HFpEF patients. Many devices have set their target to reduce the left atrial pressure or pulmonary capillary wedge pressure because they are strongly related to the symptoms and prognosis of HFpEF, but the methodology to achieve it varies based on the devices. In this review, we summarize and categorize these devices into the following: (1) interatrial shunt devices, (2) left ventricle expander, (3) electrical therapy, (4) left ventricular assist devices, and (5) mechanical circulatory support devices under development. Here, we describe the features and specifications of device-based therapies currently under development and those at more advanced stages of preclinical testing. Advantages and limitations of these technologies, with insights on their safety and feasibility for HFpEF patients, are described.
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http://dx.doi.org/10.1007/s10741-020-10067-5DOI Listing
July 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

Quantification of ocular surface microcirculation by computer assisted video microscopy and diffuse reflectance spectroscopy.

Exp Eye Res 2020 12 22;201:108312. Epub 2020 Oct 22.

Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, P.O. Box 1171 Blindern, 0318, Oslo, Norway; The Circulation Laboratory, Department of Cardiothoracic Surgery, Oslo University Hospital HF, Postboks 4950 Nydalen, 0424, Oslo, Norway. Electronic address:

In piglets we tested the applicability of digital video microscopy and diffuse reflectance spectroscopy for non-invasive assessments of limbal and bulbar conjunctival microcirculation. A priori we postulated that the metabolic rate is higher in limbal as compared to bulbar conjunctiva, and that this difference is reflected in microvascular structure or function between the two locations. Two study sites, Oslo University Hospital (OUH), Norway and Cleveland Clinic (CC), USA, used the same video microscopy and spectroscopy techniques to record limbal and bulbar microcirculation in sleeping piglets. Recordings were analyzed with custom-made software to quantify functional capillary density, capillary flow velocity and microvascular oxygen saturation in measuring volumes of approximately 0.1 mm. The functional capillary density was higher in limbus than in bulbar conjunctiva at both study sites (OUH: 18.1 ± 2.9 versus 12.2 ± 2.9 crossings per mm line, p < 0.01; CC: 11.3 ± 3.0 versus 7.1 ± 2.8 crossings per mm line, p < 0.01). Median categorial capillary blood flow velocity was higher in bulbar as compared with limbal recordings (CC: 3 (1-3) versus 1 (0-3), p < 0.01). Conjunctival microvascular oxygen saturation was 88 ± 5.9% in OUH versus 94 ± 7.5% in CC piglets. Non-invasive digital video microscopy and diffuse reflectance spectroscopy can be used to obtain data from conjunctival microcirculation in piglets. Limbal conjunctival microcirculation has a larger capacity for oxygen delivery as compared with bulbar conjunctiva.
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http://dx.doi.org/10.1016/j.exer.2020.108312DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7581323PMC
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

Postimplant Phosphodiesterase Type 5 Inhibitors Use Is Associated With Lower Rates of Thrombotic Events After Left Ventricular Assist Device Implantation.

J Am Heart Assoc 2020 07 10;9(14):e015897. Epub 2020 Jul 10.

Kaufman Center for Heart Failure, Heart and Vascular Institute Cleveland Clinic Cleveland OH.

Background Left ventricular assist device (LVAD) thrombosis is clinically devastating and impacts the cost effectiveness of LVAD therapy for advanced heart failure. Anticoagulation and antiplatelet therapies represent the standard of care to mitigate LVAD thrombosis. Phosphodiesterase type 5 inhibitors (PDE-5is) exhibit hemodynamic, antiplatelet, and antithrombotic effects. Using a national registry, we examined the relationship of PDE-5i use on thrombotic events in patients with continuous-flow LVADs. Methods and Results We obtained data from 13 772 patients with continuous flow LVADs participating in a national registry. Patients implanted with primary LVADs from 2012 to 2017 were included in the analysis. The primary end point was a composite of LVAD thrombosis and ischemic stroke. Patients were analyzed according to any use of PDE-5i after LVAD implantation (PDE-5i group) versus no use after LVAD implantation (no PDE-5i group). The primary end point was significantly lower in the PDE-5i group compared with the no PDE-5i group (hazard ratio [HR], 0.84; 95% CI, 0.77-0.91; <0.001) at 48 months. The components of the primary end point (LVAD thrombosis: HR, 0.82; 95% CI, 0.74-0.90; <0.001; and ischemic stroke: HR, 0.85; 95% CI, 0.75-0.97; =0.019), as well as the secondary end point all-cause mortality (HR, 0.86; 95% CI, 0.79-0.93; <0.001) were lower in the PDE-5i group versus the no PDE-5i at 48 months post LVAD. The favorable results observed with postimplant PDE-5i use were consistent with both axial and centrifugal flow devices. Conclusions The postimplant use of PDE-5i was associated with fewer thrombotic events and improved survival in LVAD patients. A randomized clinical trial is warranted to confirm these findings.
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http://dx.doi.org/10.1161/JAHA.119.015897DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7660717PMC
July 2020

Development and Evaluation of Motion-activated System for Improved Chest Drainage: Bench, In Vivo Results, and Pilot Clinical Use of Technology.

Surg Innov 2020 Oct 3;27(5):507-514. Epub 2020 Jun 3.

R1 Engineering, OH, USA.

. The aim of this study was to evaluate a motion-activated system (MAS) that applies motion-activated energy (vibration) to prevent chest tube clogging and maintain tube patency. We performed chest tube blood flow analysis in vitro, studied MAS effects on intraluminal clot deposition in vivo, and conducted a pilot clinical test. . Chest tube clogging is known to adversely contribute to postoperative cardiac surgery outcomes. . The MAS was tested in vitro with a blood-filled chest tube model for device acceleration and performance. In vivo acute hemothorax studies (n = 5) were performed in healthy pigs (48.0 ± 2 kg) to evaluate the drainage in MAS versus control (no device) groups. Using a high-speed camera (FASTCAM Mini AX200, 100 mm Zeiss lens) in an additional animal study (n = 1), intraluminal whole-blood activation imaging of the chest tube (32 Fr) was made. The pilot clinical study (n = 12) consisted of up to a 30 minutes device tolerance test. . In vitro MAS testing suggested optimal device performance. The 2-hour in vivo evaluation showed a longer incremental drainage in the MAS group versus control. The total drainage in the MAS group was significantly higher than that in the control group (379 ± 144 mL vs 143 ± 40 mL; = .0097), indicating tube patency. The high-speed camera images showed a characteristic intraluminal blood "swirling" pattern. Clinical data showed no discomfort with the MAS use (pleural = 4; mediastinal = 8). . The MAS showed optimal performance at bench and better drainage profile in vivo. The clinical trial showed patients' tolerance to the MAS and device safety.
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http://dx.doi.org/10.1177/1553350620927579DOI Listing
October 2020

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

Continuous-flow total artificial heart port-to-port connection technique using dedicated de-airing sleeve.

Perfusion 2020 11 7;35(8):861-864. Epub 2020 May 7.

Perfusion Services, Miller Family Heart and Vascular Institute, Cleveland Clinic, Cleveland, OH, USA.

Preventing the introduction of air while a mechanical circulatory support device is being implanted is critical for successful outcomes. A substantial amount of air may be introduced into the circulation during the pump-to-outflow and/or pump-to-inflow port connection, which can be detrimental to optimal pump function and long-term survival. We have developed a novel connecting sleeve that enables an airless connection of the continuous-flow total artificial heart to the conduits. Herein, we describe the device design and surgical techniques evaluated in vivo.
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http://dx.doi.org/10.1177/0267659120917862DOI Listing
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

Progress in mechanical circulatory support: Challenges and opportunities.

Artif Organs 2019 Sep 18;43(9):818-820. Epub 2019 Jun 18.

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

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http://dx.doi.org/10.1111/aor.13500DOI Listing
September 2019

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

Update on the management and associated challenges of adult patients treated with veno-arterial extracorporeal membrane oxygenation.

Expert Rev Med Devices 2019 06 9;16(6):483-491. Epub 2019 May 9.

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

Introduction: Currently, veno-arterial extracorporeal membrane oxygenation (VA ECMO) represents a valuable treatment option for patients presenting with severe cardiogenic shock. Although the overall usage of VA ECMO in experienced centers is expanding, some management aspects remain challenging, with no consensus among centers on well-defined assessment criteria, duration, and, particularly, weaning strategies.

Areas Covered: This article aims to provide a review and evaluation of strategies reported in the literature to wean patients from VA ECMO, with a special emphasis on weaning protocols. A selected successful weaning protocol and rate of removal of adult patients from VA ECMO from recent reports will be also discussed.

Expert Commentary: To improve patient outcome, it is essential to remove patients from VA ECMO without weaning failure. Furthermore, the accurate evaluation of the patient's condition must be principal. However, as technology advances, the strategy of weaning patients from VA ECMO or drug therapies is changing, and we must periodically update our knowledge and use of VA ECMO.
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http://dx.doi.org/10.1080/17434440.2019.1614439DOI Listing
June 2019
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