Publications by authors named "Takuma Miyamoto"

33 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

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

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

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

Ultrasonographic test for detecting the chiasma plantare formation between the flexor hallucis longus and flexor digitorum longus.

Surg Radiol Anat 2021 Jul 4;43(7):1061-1065. Epub 2021 Jan 4.

Graduate School of Medicine, Musculoskeletal Reconstructive Surgery, Nara Medical University, Kashihara, Nara, Japan.

Purpose: Flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendons are frequently used in surgery. Therefore, it is necessary to evaluate the chiasma plantare formation preoperatively. The development of ultrasonography (US) may help the chiasma plantare formation evaluation. The purpose of this study is to prove the usefulness of the US method using cadavers.

Methods: Eleven cases (twenty-two ankles) were obtained from Asian adult cadavers. At first, we evaluated and compared the chiasma plantare formation using US. Later, we evaluated that using the findings after dissection as type A (connection from FHL to FDL of the second toe), type B (connection from FHL to the second and third toes), type C (connection from FHL to the second through fourth toes), or type D (connection from FHL to all lesser toes).

Results: Chiasma plantare formation was classified as types A and B in fifteen and seven ankles, respectively. After dissection, chiasma plantare formation was classified as types A, B, and C in fourteen, six, and two ankles, respectively. Therefore, there was an 86% similarity between the two methods.

Conclusions: Chiasma plantare formation can be reliably and noninvasively evaluated using US. This may be useful for preoperative rehabilitation or surgical procedure planning.
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http://dx.doi.org/10.1007/s00276-020-02630-4DOI Listing
July 2021

Application of a Customized Total Talar Prosthesis for Revision Total Ankle Arthroplasty.

JB JS Open Access 2020 Oct-Dec;5(4). Epub 2020 Oct 28.

Department of Orthopedic Surgery, Nara Medical University, Nara, Japan.

Background: The rate of revision surgery for total ankle arthroplasty (TAA) is higher than for hip and knee arthroplasties. Tibiotalocalcaneal arthrodesis is widely used; however, it requires a large allograft. Thus, the use of a customized total talar prosthesis in combination with the tibial component of TAA (combined TAA) may be an effective strategy for talar component subsidence. This study aimed to evaluate the clinical and radiographic effectiveness of the combined TAA in such revision cases.

Methods: Between 2000 and 2015, 10 patients (10 women; 10 ankles) were treated using the combined TAA for revision after standard TAA or combined procedures that included the use of a talar body prosthesis. In 6 patients, the tibial component was concurrently replaced. The median follow-up period was 49 months (interquartile range [IQR], 24.5 to 90 months). The Japanese Society for Surgery of the Foot (JSSF) ankle-hindfoot scale score, a numerical rating scale (NRS) pain score, passive range of motion of the ankle, and the presence of osteophytes and degenerative changes in the adjacent joints were assessed preoperatively and at final postoperative follow-up.

Results: The median NRS pain score improved significantly, from 7 (IQR, 6.25 to 8.75) to 2 (IQR, 1 to 3). The median JSSF ankle-hindfoot scale total score improved significantly, from 64 (IQR, 56.25 to 71.5) to 88.5 (IQR, 79.75 to 96). In the subcategories of this scale, the median pain score improved from 20 (IQR, 20 to 27.5) to 35 (IQR, 30 to 40), and the median function score improved from 34 (IQR, 26.5 to 37) to 43.5 (IQR, 39.75 to 46). The median range of motion improved from 29° (IQR, 25.5° to 35°) to 35° (IQR, 31.25° to 43.75°). No significant difference in osteophyte formation was found. Degenerative changes in the adjacent joint were found only in the talonavicular joint.

Conclusions: The combined TAA, used in revision for postoperative complications after standard TAA or combined procedures including the use of a talar body prosthesis, was associated with improved objective JSSF ankle-hindfoot scale scores, subjective pain assessment, and range of motion in the ankle.

Level Of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
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http://dx.doi.org/10.2106/JBJS.OA.20.00034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7593043PMC
October 2020

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

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

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

Challenges in pediatric mechanical circulatory support devices.

Artif Organs 2019 May 22;43(5):441-443. Epub 2019 Mar 22.

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

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http://dx.doi.org/10.1111/aor.13447DOI Listing
May 2019

Acute and chronic effects of continuous-flow support and pulsatile-flow support.

Artif Organs 2019 Jul 22;43(7):618-623. Epub 2019 Mar 22.

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

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http://dx.doi.org/10.1111/aor.13446DOI Listing
July 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

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

Effects of continuous and pulsatile flows generated by ventricular assist devices on renal function and pathology.

Expert Rev Med Devices 2018 03 9;15(3):171-182. Epub 2018 Feb 9.

a Department of Biomedical Engineering , Lerner Research Institute, Cleveland Clinic , Cleveland , OH , U.S.A.

Introduction: Continuous-flow (CF) left ventricular assist devices (LVADs) are widely used to treat end-stage heart failure. Despite substantial improvement in clinical results, numerous complications remain associated with this technology. Worsening renal function is one, associated with morbidity and mortality in patients supported by CF LVADs. The effects of CF LVAD support on renal function have been investigated since the mid-1990s by many research groups.

Areas Covered: We review the current status of LVAD therapy, experimental results regarding the effects of types of flow generated by LVADs on renal function and pathology, changes in renal function after LVAD implant, the influence of renal function on outcomes, and risk factors for renal dysfunction post implant. This information was obtained through online databases and direct extraction of single studies.

Expert Commentary: Immediately after CF LVAD implantation, renal function improves temporarily as patients recover from the kidneys' previously low perfusion and congestive state. However, many studies have shown that this initially recovered renal function gradually declines during long-term CF LVAD support. Although it is known that CF LVAD support adversely affects renal function over the long term, just how it does has not yet been clearly defined in terms of clinical symptoms or signs.
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http://dx.doi.org/10.1080/17434440.2018.1437346DOI Listing
March 2018

Outflow graft anastomosis site design could be correlated to aortic valve regurgitation under left ventricular assist device support.

J Artif Organs 2018 Jun 21;21(2):150-155. Epub 2017 Nov 21.

Department of Cardiovascular Surgery, Tokyo Women's Medical University, 8-1, Kawadacho, Shinjuku-ku, Tokyo, Japan.

Aortic valve regurgitation (AR) is a critical complication during circulatory support with a left ventricular assist device (LVAD). The time-course of AR and related factors, including outflow graft anastomosis site design, were investigated. Twenty-three patients who had continuous-flow LVAD implantation and were supported for more than 6 months were investigated. AR grade (none, 0; trivial, 0.5; mild, 1; mild-moderate, 1.5; moderate, 2; moderate-severe, 2.5; severe, 3) and aortic valve opening were evaluated with echocardiography. Computed tomography was performed to all the patients postoperatively. The angle of the outflow graft to the aorta (O-A angle, parallel 0; tangent 90°, 0-180°), aortic diameter at the anastomosis site, sino-tubular junction (STJ) diameter, distance between the STJ and the anastomosis site, and distance between the anastomosis site and the brachiocephalic artery were measured. The patients' age was 38 ± 11 years. Support duration was 686 ± 354 days. Mean AR grade after continuous-flow LVAD implantation was increased to around mild and was maintained thereafter. No patient needed any intervention to the aortic valve. The aortic valves of 82.6% of patients were closed continuously. The O-A angle (83 ± 14) was positively correlated with maximum AR grade (p = 0.0095). The O-A angle was significantly smaller in patients with maximum AR grade of 1 or less (77 ± 9°) than in those with 1.5 or greater (94 ± 15°, p = 0.021). The other CT measurements had no correlation with AR grade. In conclusion, the O-A angle was correlated with AR grade progression. The O-A angle appears to be one of the important factors related to AR under continuous-flow LVAD support.
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http://dx.doi.org/10.1007/s10047-017-1006-1DOI Listing
June 2018
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