Yoshio Ootaki

Lerner Research Institute, Cleveland, Ohio, United States

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Publications (94)213.61 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND: We previously reported renal arterial periarteritis after implantation of a continuous-flow left ventricular assist device in calves. The purpose of the present study was to investigate whether the same periarteritis changes occur in the intrapulmonary arteries after implantation of a continuous-flow right ventricular assist device (CFRVAD) in calves and to determine the mechanism of those histologic changes. METHODS: Ten calves were implanted with a CFRVAD for 29 ± 7 days, and we compared pulmonary artery samples and hemodynamic data before and after CFRVAD implantation prospectively. RESULTS: After implantation, the pulsatility index (pulmonary arterial pulse pressure/pulmonary arterial mean pressure) significantly decreased (0.88 ± 0.40 before vs 0.51 ± 0.22 after; p < 0.05), with severe periarteritis of the intrapulmonary arteries in all animals. Periarterial pathology included hyperplasia and inflammatory cell infiltration. The number of inflammatory cells positive for the angiotensin II type 1 receptor was significantly higher after implantation (7.8 ± 6.5 pre-CFRVAD vs 313.2 ± 145.2 at autopsy; p < 0.01). Serum angiotensin-converting enzyme activity significantly decreased after implantation from 100% to 49.7 ± 17.7% at week 1 (p = 0.01). Tissue levels of angiotensin-converting enzyme also demonstrated a significant reduction (0.381 ± 0.232 before implantation vs 0.123 ± 0.096 at autopsy; p = 0.043). CONCLUSIONS: Periarteritis occurred in the intrapulmonary arteries of calves after CFRVAD implantation. The local renin-angiotensin system (not the angiotensin-converting enzyme pathway) plays an important role in such changes.
    The Annals of thoracic surgery 05/2013; · 3.45 Impact Factor
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    ABSTRACT: Zirconia is a ceramic with material properties ideal for journal bearing applications. The purpose of this study was to evaluate the use of zirconium oxide (zirconia) as a blood journal bearing material in the DexAide right ventricular assist device. Zirconia ceramic was used instead of titanium to manufacture the DexAide stator housing without changing the stator geometry or the remaining pump hardware components. Pump hydraulic performance, journal bearing reliability, biocompatibility, and motor efficiency data of the zirconia stator were evaluated in six chronic bovine experiments for 14-91 days and compared with data from chronic experiments using the titanium stator. Pump performance data including average in vivo pump flows and speeds using a zirconia stator showed no statistically significant difference to the average values for 16 prior titanium stator in vivo studies, with the exception of a 19% reduction in power consumption. Indices of hemolysis were comparable for both stator types. Results of coagulation assays and platelet aggregation tests for the zirconia stator implants showed no device-induced increase in platelet activation. Postexplant evaluation of the zirconia journal bearing surfaces showed no biologic deposition in any of the implants. In conclusion, zirconia ceramic can be used as a hemocompatible material to improve motor efficiency while maintaining hydraulic performance in a blood journal bearing application.
    Artificial Organs 06/2010; 34(6):512-6. · 1.96 Impact Factor
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    ABSTRACT: Our aim was to evaluate the potential use of zirconium oxide (zirconia) as a blood journal bearing material in the DexAide right ventricular assist device. The DexAide titanium stator was replaced by a zirconia stator in several blood pump builds, without changing the remaining pump hardware components. In vitro pump performance and efficiency were evaluated at a predetermined pump speed and flow. Motor power consumption decreased by 20%, and DexAide battery life was extended to over 12 h on two fully charged batteries. The zirconia stator was also successfully evaluated in a severe start/stop test pre- and postexposure of the zirconia to accelerated simulated biologic aging. This study's outcomes indicated the advantages of zirconia as an alternate journal bearing material for the DexAide device.
    Artificial Organs 10/2009; 34(2):146-9. · 1.96 Impact Factor
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    ABSTRACT: The DexAide right ventricular assist device (RVAD) has been developed as an implantable RVAD. The purpose of this study was to determine the final design and optimal anatomical placement of the DexAide RVAD when implanted simultaneously with either of two commercially available left ventricular assist devices (LVADs) in patients. A mock-up DexAide RVAD was used to assess configuration with each of two types of commercially available LVADs at the time of LVAD implantation in three human clinical cases. The pump body of the DexAide RVAD was placed either in the preperitoneal space or in the right thoracic cavity. The DexAide RVAD placed into the right thoracic cavity is suitable for use with the Novacor or HeartMate II LVADs. The results of this study will guide the finalization of the inflow cannula and optimal placement of the DexAide RVAD for human clinical trials.
    Artificial Organs 08/2009; 33(7):558-61. · 1.96 Impact Factor
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    ABSTRACT: A right ventricular assist device is a treatment option for patients with severe right ventricular failure after left ventricular assist device (LVAD) implantation. Recognition of risk factors for mortality after biventricular assist device (BiVAD) implantation is important for patient selection and optimal outcomes. We reviewed our experiences between 1991 and 2005 in 44 patients who were supported by both an LVAD and a right ventricular assist device. Thirteen patients (30%) survived until heart transplantation, and 31 patients (70%) died while on support. The multivariate analysis shows that post-LVAD extracorporeal membrane oxygenation and worsening renal function are associated with the highest postoperative mortality. The univariate analysis also included previous thoracic surgery and ischemic cardiomyopathy as potential preoperative indicators for poor outcome after BiVAD implants. No differences were observed in the rates for the need of preoperative support with a ventilator, an intra-aortic balloon pump, or extracorporeal membrane oxygenation, or in the rates of postoperative complications between survivors and nonsurvivors. BiVAD implantation remains one of the challenges in treating severe heart failure. Previous cardiac surgery, elevated creatinine, and post-LVAD extracorporeal membrane oxygenation were risk factors for mortality after BiVAD implantation. Dialated Cardiomyopathy on the other hand was associated with a more favorable outcome.
    Journal of cardiac failure 01/2009; 14(10):844-9. · 3.25 Impact Factor
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    ABSTRACT: Canine and porcine hearts have been widely used to investigate diagnoses, interventions, and surgical therapies for ischemic heart disease. Dogs and pigs are known to vary with regard to the anatomic distribution of their coronary arteries. However, the mechanisms of these differences and the differing phasic coronary blood flow patterns between the two species are not well characterized. Phasic coronary blood flow patterns and hemodynamic data were analyzed using three flow probes placed around the left anterior descending (LAD), left circumflex (LCX), and right coronary (RCA) arteries in both canine and porcine models. Systolic left ventricular pressure, arterial pressure, and systemic vascular resistance in dogs were higher than in pigs. Likewise, total coronary blood flow, LAD flow, and LCX flow were higher in dogs than in pigs. LCX flow was higher in dogs, but RCA flow was higher in pigs. Diastolic fraction and diastolic/systolic peak velocity ratio of the LAD, LCX, and RCA showed no significant differences at baseline between dogs and pigs. Systolic LAD flow in dogs decreased after the creation of an LAD stenosis, whereas systolic LAD flow in pigs increased. Coronary blood flow patterns in dogs and pigs are quite different. These findings are potentially relevant to understanding the physiology of myocardial blood perfusion in dogs and pigs with ischemic heart disease.
    Medical science monitor: international medical journal of experimental and clinical research 11/2008; 14(10):BR193-7. · 1.22 Impact Factor
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    ABSTRACT: Occlusion of the left atrial appendage is proposed to reduce the risk of stroke in patients with atrial fibrillation. The third-generation atrial exclusion device, modified to provide uniform distribution of pressure at appendage exclusion, was assessed for safety and effectiveness in a canine model and compared with a surgical stapler. The atrial exclusion device consists of 2 parallel, straight, rigid titanium tubes and 2 nitinol springs with a knit-braided polyester fabric. Fourteen mongrel dogs were implanted with the device at the base of the left atrial appendage via a median sternotomy. In each dog, the right atrial appendage was stapled with a commercial apparatus for comparison. The animals were evaluated at 7 days (n = 3), 30 days (n = 5), and 90 days (n = 6) after implantation by epicardial echocardiography, left atrial and coronary angiography, gross pathology, and histology. Left atrial appendage exclusion was complete and achieved without hemodynamic instability, and coronary angiography revealed that the left circumflex artery was patent in all cases. A new endothelial tissue layer developed on the occluded orifice of the left atrium 90 days after implantation. This endothelial layer was not evident on the stapled right atrial appendage. In dogs, the third-generation atrial exclusion device achieved easy, reliable, and safe exclusion of the left atrial appendage with favorable histologic results. Clinical application could provide a new therapeutic option for reducing the risk of stroke in patients with atrial fibrillation.
    The Journal of thoracic and cardiovascular surgery 11/2008; 136(4):1019-27. · 3.41 Impact Factor
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    ABSTRACT: Several studies have been performed to assess heart rate variability (HRV) in several species such as humans, dogs, pigs, calves, rabbits and rats. However, haemodynamic parameters are totally different in each animal, and optimal animal models for studying HRV corresponding to human HRV are still unclear. The purpose of this study was to assess HRV in human subjects and to compare those HRV data with canine, bovine and rabbit HRV data. The heart rate in the human subjects (62.8 +/- 7.4 bpm) was significantly lower than that in dogs (124.2 +/- 18.8 bpm, P < 0.001), calves (73.4 +/- 10.5 bpm, P < 0.05), and rabbits (217.3 +/- 21.5 bpm, P < 0.001). The low-frequency waves (LF) (57.9 +/- 65.8 ms(2)/Hz) and high-frequency waves (HF) (33.8 +/- 49.1 ms(2)/Hz) in rabbits were significantly lower than human LF (1216.3 +/- 1220.7 ms(2)/Hz, P < 0.05) and HF (570.9 +/- 581.3 ms(2)/Hz, P < 0.05). Dogs and calves showed similar LF (991.1 +/- 646.1 ms(2)/Hz and 547.0 +/- 256.9 ms(2)/Hz, respectively), HF (702.1 +/- 394.1 ms(2)/Hz and 601.0 +/- 666.6 ms(2)/Hz, respectively) and LF/HF (2.0 +/- 1.3 and 2.5 +/- 1.9, respectively) when compared with the human data. The present study shows that dogs and calves revealed similar HRV values as those which relate to humans. Large deviation of the HRV values in rabbits compared with humans might be considered when conducting animal studies using those animals to reflect human clinical situations.
    Laboratory Animals 11/2008; 43(1):41-5. · 1.26 Impact Factor
  • The Annals of thoracic surgery 08/2008; 86(2):694. · 3.45 Impact Factor
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    ABSTRACT: The need for pulsatility in the circulation during long-term mechanical support has been a subject of debate. We compared histologic changes in calf renal arteries subjected to various degrees of pulsatile circulation in vivo. We addressed the hypothesis that the local renin-angiotensin system may be implicated in these histologic changes. Sixteen calves were implanted with devices giving differing degrees of pulsatile circulation: 6 had a continuous flow left ventricular assist device (LVAD); 6 had a continuous flow right ventricular assist device (RVAD); and 4 had a pulsatile total artificial heart (TAH). Six other calves were histologic and immunohistochemical controls. In the LVAD group, the pulsatility index was significantly lower (0.28 +/- 0.07 LVAD vs 0.56 +/- 0.08 RVAD, vs 0.53 +/- 0.10 TAH; P < 0.01), and we observed severe periarteritis in all cases in the LVAD group. The number of angiotensin II type 1 receptor-positive cells and angiotensin converting enzyme-positive cells in periarterial areas was significantly higher in the LVAD group (angiotensin II type 1 receptor: 350 +/- 139 LVAD vs 8 +/- 6 RVAD, vs 3 +/- 2 TAH, vs 3 +/- 2 control; P < .001; angiotensin-converting enzyme: 325 +/- 59 LVAD vs 6 +/- 4 RVAD, vs 6 +/- 5 TAH, vs 3 +/- 1 control; P < .001). The reduced pulsatility produced by a continuous flow LVAD implantation induced severe periarteritis in the kidneys. The local renin-angiotensin system was up-regulated in the inflammatory cells only in the continuous flow LVAD group.
    The Journal of thoracic and cardiovascular surgery 07/2008; 136(1):150-8. · 3.41 Impact Factor
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    ABSTRACT: This study evaluated the short-term feasibility of a novel epicardial device that treats functional mitral regurgitation by simultaneously changing the mitral and the left ventricular geometry. We implanted a prototype device that consists of 2 tissue anchors, a deflector, and a flexible tightening chord in 7 mongrel dogs with heart failure and functional mitral regurgitation induced by rapid ventricular pacing. Hemodynamic and echocardiographic data were obtained before and after device implantation. The device acutely reduced the mitral regurgitation grade from 3.2 +/- 0.3 to 0.9 +/- 0.5 (p < 0.001). Left ventricular end-diastolic volume (79.6 +/- 23.6 to 61.2 +/- 16.9 mL; p = 0.004) and end-systolic volume (63.1 +/- 17.3 to 49.2 +/- 12.3 mL; p = 0.006) decreased substantially. End-systolic elastance significantly increased from 1.9 +/- 1.0 to 2.6 +/- 1.4 mm Hg/mL (p = 0.02). Device implantation did not alter coronary perfusion. The epicardial device acutely reduced functional mitral regurgitation and improved left ventricular geometry. Further studies are required to demonstrate the long-term safety and efficacy of this concept.
    The Annals of thoracic surgery 06/2008; 85(5):1771-5. · 3.45 Impact Factor
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    ABSTRACT: The purpose of this study was to develop a method for real-time, fiberoptic, intracardiac imaging to serve as a platform for closed-chest, intracardiac surgery on the beating heart. Fiberoptic cardioscopy of the left and right heart was conducted in a porcine model. A cardiopulmonary bypass circuit maintained systemic organ perfusion and a separate circuit replaced intracardiac blood with oxygenated, modified Krebs-Henseleit perfusate. Video images of structures in the left and right sides of an in vivo beating heart were obtained, including the inner surface of the left and right atria and ventricles, the mitral and aortic valves, the Thebesian veins, and the coronary sinus. Effective isolation of the heart from systemic and intracardiac blood flow and control of perfusion rates were important factors for successful image acquisition. Fiberoptic cardioscopy is a novel approach that allows for visualization of the structures within a nonarrested heart on bypass. It lays the groundwork for a platform that could lead to more successful percutaneous valvular and intracardiac procedures in a stable hemodynamic environment.
    The Annals of thoracic surgery 04/2008; 85(3):1061-5. · 3.45 Impact Factor
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    ABSTRACT: The purpose of this study was to evaluate the feasibility of our innovative, replaceable heart valves that can be easily detached from the sewing ring at the time of repeat replacement. The prototype devices consist of the base magnet ring assembly and the valve magnet ring assembly that utilize magnetic coupling force for the locking mechanism. Magnetic coupling strength was evaluated in vitro. Prototype bioprosthetic valves were implanted acutely in three sheep to confirm the feasibility of the replaceable mitral valve. The static separation force of prototype size #25 was 12.5 lb, meeting the design goal. In situ attachment and detachment of the valve magnet ring assembly from the base magnet ring assembly were very easily accomplished in all animals. The magnetic coupling did not decouple even under extremely high left ventricular pressures. We have demonstrated the feasibility of this innovative concept of a replaceable mitral valve.
    Artificial Organs 04/2008; 32(3):226-9. · 1.96 Impact Factor
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    ABSTRACT: An implantable biventricular assist device offers a considerable opportunity to save the lives of patients with combined irreversible right and left ventricular failure. The purpose of this study was to evaluate the hemodynamic and physiologic performance of the combined implantation of the CorAide left ventricular assist device (LVAD) and the DexAide right ventricular assist device (RVAD). Acute hemodynamic responses were evaluated after simulating seven different physiological conditions in two calves. Evaluation was performed by fixing the speed of one individual pump and increasing the speed of the other. Under all conditions, increased LVAD or RVAD speed resulted in increased pump flow. The predominant pathophysiologic effect of independently varying DexAide and CorAide pump speeds was that the left atrial pressure was very sensitive to increasing RVAD speed above 2,400 rpm, whereas the right atrial pressure demonstrated much less sensitivity to increasing LVAD speed. An increase in aortic pressure and RVAD flow was observed while increasing LVAD speed, especially under low contractility, ventricular fibrillation, high pulmonary artery pressure, and low circulatory blood volume conditions. In conclusion, a proper RVAD-LVAD balance should be maintained by avoiding RVAD overdrive. Additional studies will further investigate the performance of these pumps in chronic animal models.
    ASAIO journal (American Society for Artificial Internal Organs: 1992) 01/2008; 54(1):20-4. · 1.39 Impact Factor
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    ABSTRACT: The fitting of implantable ventricular assist devices (VADs) is a particular challenge for pediatric patients and patients with small body surface area. The purpose of this study was to determine optimal placement of the PediPump, a pediatric VAD currently under development at the Cleveland Clinic, using virtual three-dimensional (3D) on-screen models. Digital models were created from computed tomographic datasets of pediatric hearts using commercially available 3D image processing software. Pixels representing the myocardium, great vessels, sternum, and rib cage were selected and rendered as on-screen models (n = 13) from pediatric patients with or without congenital heart disease (median age 42 months; range 2 days to 13 years 11 months). Using 3D model manipulation software, virtual models of the PediPump (70 x 10 mm) were combined on-screen with the anatomic models. A variety of virtual fitting options were created, which allowed easy detection of device interference with surrounding tissues. Generation of 3D on-screen models of cardiac structures in relation to PediPump placement has provided useful preliminary fitting information, which is being used to guide further development of this device.
    ASAIO journal (American Society for Artificial Internal Organs: 1992) 01/2008; 54(1):133-7. · 1.39 Impact Factor
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    ABSTRACT: Heart rate variability (HRV) is an indicator of autonomic nervous system functionality and a recognized predictor of cardiac death; however, the changes in HRV occurring in progressive heart failure are not fully understood. The purpose of this study was to evaluate the progressive changes of autonomic system activity in progressive heart failure by rapid ventricular pacing in an animal model. Heart failure was induced in 13 mongrel dogs (27.8 +/- 3.7 kg) by rapid ventricular pacing (230 beats/min) for 4 weeks and maintenance of pacing at a reduced rate (190 beats/min) for 2 weeks. Time domain analysis and spectral analysis of HRV were performed with the MemCalc system after 30 minutes of pacing cessation every week. Hemodynamic and echocardiographic data were obtained before and after induction of heart failure. Cardiac output decreased significantly (3.6 L/min versus 1.6 L/min, P < .001) after 6 weeks of ventricular pacing. Significantly increased were the heart rate (126 beats/min versus 138 beats/min, P < .05), left ventricular end-diastolic pressure (9.1 mm Hg versus 30.9 mm Hg, P < .001), and pulmonary capillary wedge pressure (8.0 mm Hg versus 18.7 mm Hg, P < .001). High-frequency components progressively decreased. Low-frequency components progressively decreased except at 5 weeks after the pacing. A ratio of low- to high-frequency components increased in moderate heart failure and decreased in severe heart failure. Changes in the high-frequency component and low-frequency component are important for assessing heart failure in progressive heart failure. Serial follow-up measurements of HRV might be helpful for patients with such disease.
    Heart Surgery Forum 01/2008; 11(5):E295-9. · 0.63 Impact Factor
  • The Annals of thoracic surgery 12/2007; 84(5):1798-9. · 3.45 Impact Factor
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    ABSTRACT: Implantation of ventricular assist devices (VADs) is challenging in small patients with limited space in the chest. We created three-dimensional models of lambs to facilitate fitting of the PediPump, a pediatric VAD currently under development. Serial computed tomography (CT) scans were acquired at multiple time points (n = 8) for three lambs. Digital models were created using these CT datasets and three-dimensional image processing software (Mimics, Materialise). Pixels representing the heart and chest wall were rendered as three-dimensional models. Using three-dimensional model manipulation software (Magics RP, Materialise), on-screen models of extravascular and intravascular VADs were placed in right, left and biventricular support configurations to determine optimal placement. A cannulation strategy was established and in some cases three-dimensional models of the inflow and outflow grafts were created. After the final CT study, an open-chest fitting study was performed using rapid prototype models of the pediatric VAD and cannulas. The pump location and orientation predictions from the virtual fitting studies matched those determined at the time of the open-chest fitting studies. Using three-dimensional modeling, we have established a fitting protocol that facilitates animal implantations; the same modeling techniques may be useful for device fitting in humans.
    ASAIO journal (American Society for Artificial Internal Organs: 1992) 10/2007; 53(6):716-9. · 1.39 Impact Factor
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    ABSTRACT: To evaluate the effects of downsizing of the total artificial heart (TAH), we compared the anaerobic threshold (AT) values in calves with two different types of TAH (Cleveland Clinic-Nimbus TAH and the downsized MagScrew TAH). Exercise studies were performed using a treadmill in 12 calves. During the exercise, parameters to obtain the AT were measured. To evaluate the determinants of the AT, a linear regression analysis was performed between AT and potential variables. AT values from 29 studies revealed no significant differences between the two different TAHs, with no significant differences in hemodynamic or oxygen metabolic parameters. AT values correlated well with pump flow/body weight (Q) multiplied by the hemoglobin level, regardless of the TAH used. In conclusion, downsizing of the original TAH design did not reduce AT without any significant differences in hemodynamic or oxygen metabolic parameters during exercise in calves.
    Artificial Organs 10/2007; 31(9):667-76. · 1.96 Impact Factor
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    ABSTRACT: The DexAide right ventricular assist device (RVAD) has been developed to provide an implantable RVAD option to surgeons. The aim of this study was to determine the optimal cannula design and optimal implantation location of the DexAide RVAD in preparation for its clinical use. Separately, a HeartMate XVE left ventricular assist device (LVAD) and CorAide LVAD models were implanted into the preperitoneal and right thoracic space, and the anatomical fit of the DexAide RVAD was evaluated in five preserved human cadavers. The DexAide RVAD inflow cannula was inserted through the diaphragmatic surface of the right ventricle and the outflow was directed to the pulmonary artery. Right thoracic implantation of the DexAide RVAD provided an excellent fit with either the HeartMate or CorAide LVAD in all cadavers. The results of this study will guide improvements in the designs of cannulae and implantation of the DexAide RVAD in future clinical applications.
    Artificial Organs 09/2007; 31(8):646-8. · 1.96 Impact Factor

Publication Stats

692 Citations
213.61 Total Impact Points

Institutions

  • 2004–2013
    • Lerner Research Institute
      Cleveland, Ohio, United States
  • 2008
    • Cleveland Clinic Laboratories
      Cleveland, Ohio, United States
  • 2005
    • Cleveland Clinic
      Cleveland, Ohio, United States
  • 2001
    • Toyama Medical and Pharmaceutical University
      Тояма, Toyama, Japan