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Rocchi M, Gross C, Moscato F, Schlöglhofer T, Meyns B, Fresiello L. An in vitro model to study suction events by a ventricular assist device: validation with clinical data. Front Physiol 2023; 14:1155032. [PMID: 37560156 PMCID: PMC10407082 DOI: 10.3389/fphys.2023.1155032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 07/11/2023] [Indexed: 08/11/2023] Open
Abstract
Introduction: Ventricular assist devices (LVADs) are a valuable therapy for end-stage heart failure patients. However, some adverse events still persist, such as suction that can trigger thrombus formation and cardiac rhythm disorders. The aim of this study is to validate a suction module (SM) as a test bench for LVAD suction detection and speed control algorithms. Methods: The SM consists of a latex tube, mimicking the ventricular apex, connected to a LVAD. The SM was implemented into a hybrid in vitro-in silico cardiovascular simulator. Suction was induced simulating hypovolemia in a profile of a dilated cardiomyopathy and of a restrictive cardiomyopathy for pump speeds ranging between 2,500 and 3,200 rpm. Clinical data collected in 38 LVAD patients were used for the validation. Clinical and simulated LVAD flow waveforms were visually compared. For a more quantitative validation, a binary classifier was used to classify simulated suction and non-suction beats. The obtained classification was then compared to that generated by the simulator to evaluate the specificity and sensitivity of the simulator. Finally, a statistical analysis was run on specific suction features (e.g., minimum impeller speed pulsatility, minimum slope of the estimated flow, and timing of the maximum slope of the estimated flow). Results: The simulator could reproduce most of the pump waveforms observed in vivo. The simulator showed a sensitivity and specificity and of 90.0% and 97.5%, respectively. Simulated suction features were in the interquartile range of clinical ones. Conclusions: The SM can be used to investigate suction in different pathophysiological conditions and to support the development of LVAD physiological controllers.
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Affiliation(s)
- Maria Rocchi
- Unit of Cardiac Surgery, Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Christoph Gross
- Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Francesco Moscato
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
- Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
- Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Thomas Schlöglhofer
- Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
- Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
| | - Bart Meyns
- Unit of Cardiac Surgery, Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
- Department of Cardiac Surgery, University Hospitals Leuven, Leuven, Belgium
| | - Libera Fresiello
- Unit of Cardiac Surgery, Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
- Cardiovascular and Respiratory Physiology, University of Twente, Enschede, Netherlands
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2
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Fresiello L, Muthiah K, Goetschalckx K, Hayward C, Rocchi M, Bezy M, Pauls JP, Meyns B, Donker DW, Zieliński K. Initial clinical validation of a hybrid in silico—in vitro cardiorespiratory simulator for comprehensive testing of mechanical circulatory support systems. Front Physiol 2022; 13:967449. [PMID: 36311247 PMCID: PMC9606213 DOI: 10.3389/fphys.2022.967449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Accepted: 09/07/2022] [Indexed: 11/13/2022] Open
Abstract
Simulators are expected to assume a prominent role in the process of design—development and testing of cardiovascular medical devices. For this purpose, simulators should capture the complexity of human cardiorespiratory physiology in a realistic way. High fidelity simulations of pathophysiology do not only allow to test the medical device itself, but also to advance practically relevant monitoring and control features while the device acts under realistic conditions. We propose a physiologically controlled cardiorespiratory simulator developed in a mixed in silico-in vitro simulation environment. As inherent to this approach, most of the physiological model complexity is implemented in silico while the in vitro system acts as an interface to connect a medical device. As case scenarios, severe heart failure was modeled, at rest and at exercise and as medical device a left ventricular assist device (LVAD) was connected to the simulator. As initial validation, the simulator output was compared against clinical data from chronic heart failure patients supported by an LVAD, that underwent different levels of exercise tests with concomitant increase in LVAD speed. Simulations were conducted reproducing the same protocol as applied in patients, in terms of exercise intensity and related LVAD speed titration. Results show that the simulator allows to capture the principal parameters of the main adaptative cardiovascular and respiratory processes within the human body occurring from rest to exercise. The simulated functional interaction with the LVAD is comparable to the one clinically observed concerning ventricular unloading, cardiac output, and pump flow. Overall, the proposed simulation system offers a high fidelity in silico-in vitro representation of the human cardiorespiratory pathophysiology. It can be used as a test bench to comprehensively analyze the performance of physically connected medical devices simulating clinically realistic, critical scenarios, thus aiding in the future the development of physiologically responding, patient-adjustable medical devices. Further validation studies will be conducted to assess the performance of the simulator in other pathophysiological conditions.
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Affiliation(s)
- Libera Fresiello
- Cardiovascular and Respiratory Physiology, University of Twente, Enschede, Netherlands
- Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
- *Correspondence: Libera Fresiello,
| | - Kavitha Muthiah
- Department of Cardiology, St Vincent’s Hospital, Sydney, NSW, Australia
| | - Kaatje Goetschalckx
- Department of Cardiovascular Diseases, University Hospitals Leuven, Leuven, Belgium
| | - Christopher Hayward
- Department of Cardiology, St Vincent’s Hospital, Sydney, NSW, Australia
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
| | - Maria Rocchi
- Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Maxime Bezy
- Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Jo P. Pauls
- School of Engineering, Griffith University, Southport, QLD, Australia
| | - Bart Meyns
- Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Dirk W. Donker
- Cardiovascular and Respiratory Physiology, University of Twente, Enschede, Netherlands
- Intensive Care Center, University Medical Center Utrecht, Utrecht, Netherlands
| | - Krzysztof Zieliński
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland
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3
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Ferrari G, Di Molfetta A, Zieliński K, Cusimano V, Darowski M, Kozarski M, Fresiello L. Assessment of the VAD – Native ventricle pumping system by an equivalent pump: A computational model based procedure. Biocybern Biomed Eng 2021. [DOI: 10.1016/j.bbe.2021.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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4
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Fresiello L, Gross C, Jacobs S. Exercise physiology in left ventricular assist device patients: insights from hemodynamic simulations. Ann Cardiothorac Surg 2021; 10:339-352. [PMID: 34159115 DOI: 10.21037/acs-2020-cfmcs-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Left ventricular assist devices (LVADs) assure longer survival to patients, but exercise capacity is limited compared to normal values. Overall, LVAD patients show high wedge pressure and low cardiac output during maximal exercise, a phenomenon hinting at the need for increased LVAD support. Clinical studies investigating the hemodynamic benefits of an LVAD speed increase during exercise, ended in inhomogeneous and sometimes contradictory results. The native ventricle-LVAD interaction changes between rest and exercise, and this evolution is complex, multifactorial and patient-specific. The aim of this paper is to provide a comprehensive overview on the patient-LVAD interaction during exercise and to delineate possible therapeutic strategies for the future. A computational cardiorespiratory model was used to simulate the hemodynamics of peak bicycle exercise in LVAD patients. The simulator included the main cardiovascular and respiratory impairments commonly observed in LVAD patients, so as to represent an average hemodynamic response to exercise. In addition, other exercise responses were simulated, by tuning the chronotropic, inotropic and vascular functions, and implementing aortic regurgitation and stenosis in the simulator. These profiles were tested under different LVAD speeds and LVAD pressure-flow characteristics. Simulations output showed consistency with clinical data from the literature. The simulator allowed the working condition of the assisted ventricle at exercise to be investigated, clarifying the reasons behind the high wedge pressure and poor cardiac output observed in the clinics. Patients with poorer inotropic, chronotropic and vascular functions, are likely to benefit more from an LVAD speed increase during exercise. Similarly, for these patients, a flatter LVAD pressure-flow characteristic can assure better hemodynamic support under physical exertion. Overall, the study evidenced the need for a patient-specific approach on supporting exercise hemodynamics. In this frame, a complex simulator can constitute a valuable tool to define and test personalized speed control algorithms and strategies.
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Affiliation(s)
- Libera Fresiello
- Department of Cardiovascular Sciences, Cardiac Surgery, Katholieke Universiteit Leuven, Leuven, Belgium.,Institute of Clinical Physiology, National Research Council, Pisa, Italy
| | - Christoph Gross
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Steven Jacobs
- Department of Cardiovascular Sciences, Cardiac Surgery, Katholieke Universiteit Leuven, Leuven, Belgium
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5
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Habigt MA, Krieger M, Gesenhues J, Ketelhut M, Mechelinck M, Hein M. Non-linearity of end-systolic pressure-volume relation in afterload increases is caused by an overlay of shortening deactivation and the Frank-Starling mechanism. Sci Rep 2021; 11:3353. [PMID: 33558620 PMCID: PMC7870877 DOI: 10.1038/s41598-021-82791-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 01/19/2021] [Indexed: 11/09/2022] Open
Abstract
The linearity and load insensitivity of the end-systolic pressure-volume-relationship (ESPVR), a parameter that describes the ventricular contractile state, are controversial. We hypothesize that linearity is influenced by a variable overlay of the intrinsic mechanism of autoregulation to afterload (shortening deactivation) and preload (Frank-Starling mechanism). To study the effect of different short-term loading alterations on the shape of the ESPVR, experiments on twenty-four healthy pigs were executed. Preload reductions, afterload increases and preload reductions while the afterload level was increased were performed. The ESPVR was described either by a linear or a bilinear regression through the end-systolic pressure volume (ES-PV) points. Increases in afterload caused a biphasic course of the ES-PV points, which led to a better fit of the bilinear ESPVRs (r2 0.929 linear ESPVR vs. r2 0.96 and 0.943 bilinear ESPVR). ES-PV points of a preload reduction on a normal and augmented afterload level could be well described by a linear regression (r2 0.974 linear ESPVR vs. r2 0.976 and 0.975 bilinear ESPVR). The intercept of the second ESPVR (V0) but not the slope demonstrated a significant linear correlation with the reached afterload level (effective arterial elastance Ea). Thus, the early response to load could be described by the fixed slope of the ESPVR and variable V0, which was determined by the actual afterload. The ESPVR is only apparently nonlinear, as its course over several heartbeats was affected by an overlay of SDA and FSM. These findings could be easily transferred to cardiovascular simulation models to improve their accuracy.
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Affiliation(s)
- Moriz A Habigt
- Anaesthesiology Clinic, University Hospital RWTH Aachen, Pauwelsstr. 30, 52074, Aachen, Germany.
| | - Michelle Krieger
- Anaesthesiology Clinic, University Hospital RWTH Aachen, Pauwelsstr. 30, 52074, Aachen, Germany
| | - Jonas Gesenhues
- Institute of Automatic Control, RWTH Aachen University, Steinbachstr. 54, 52074, Aachen, Germany
| | - Maike Ketelhut
- Institute of Automatic Control, RWTH Aachen University, Steinbachstr. 54, 52074, Aachen, Germany
| | - Mare Mechelinck
- Anaesthesiology Clinic, University Hospital RWTH Aachen, Pauwelsstr. 30, 52074, Aachen, Germany
| | - Marc Hein
- Anaesthesiology Clinic, University Hospital RWTH Aachen, Pauwelsstr. 30, 52074, Aachen, Germany
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6
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Wu EL, Fresiello L, Kleinhyer M, Meyns B, Fraser JF, Tansley G, Gregory SD. Haemodynamic Effect of Left Atrial and Left Ventricular Cannulation with a Rapid Speed Modulated Rotary Blood Pump During Rest and Exercise: Investigation in a Numerical Cardiorespiratory Model. Cardiovasc Eng Technol 2020; 11:350-361. [PMID: 32557185 DOI: 10.1007/s13239-020-00471-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 06/12/2020] [Indexed: 11/28/2022]
Abstract
PURPOSE The left atrium and left ventricle are the primary inflow cannulation sites for heart failure patients supported by rotary blood pumps (RBPs). Haemodynamic differences exist between inflow cannulation sites and have been well characterized at rest, yet the effect during exercise with the same centrifugal RBP has not been previously well established. The purpose of this study was to investigate the hemodynamic effect of inflow cannulation site during rest and exercise with the same centrifugal RBP. METHODS In a numerical cardiorespiratory model, a simulated heart failure patient was supported by a HeartWare HVAD RBP in left atrial (LAC) and left ventricular cannulation (LVC). The RBP was operated at constant speed and sinusoidal co- and counter-pulse and was investigated in cardiovascular conditions of steady state rest and 80-watt bike graded exercise. RESULTS Cardiac output was 5.0 L min-1 during rest and greater than 6.9 L min-1 during exercise for all inflow cannulation sites and speed operating modes. However, during exercise, LAC demonstrated greater pressure-volume area and lower RBP flow (1.41, 1.37 and 1.37 J and 5.03, 5.12 and 5.03 L min-1 for constant speed and co- and counter-pulse respectively) when compared to LVC (pressure-volume area: 1.30, 1.27 and 1.32 J and RBP flow: 5.56, 5.71 and 5.59 L min-1 for constant speed and co- and counter-pulse respectively). CONCLUSION For a simulated heart failure patient intending to complete exercise, LVC seems to assure a better hemodynamic performance in terms of pressure-volume area unloading and increasing RBP flow.
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Affiliation(s)
- Eric L Wu
- Innovative Cardiovascular Engineering and Technology Laboratory, Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia. .,School of Medicine, The University of Queensland, Brisbane, Queensland, Australia.
| | - Libera Fresiello
- Department of Cardiac Surgery, Katholieke Universiteit Leuven, Leuven, Belgium.,Institute of Clinical Physiology, National Research Council, Pisa, Italy
| | - Matthias Kleinhyer
- Innovative Cardiovascular Engineering and Technology Laboratory, Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia.,School of Engineering and Built Environment, Griffith University, Gold Coast, Queensland, Australia
| | - Bart Meyns
- Department of Cardiac Surgery, Katholieke Universiteit Leuven, Leuven, Belgium
| | - John F Fraser
- Innovative Cardiovascular Engineering and Technology Laboratory, Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia.,School of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Geoff Tansley
- Innovative Cardiovascular Engineering and Technology Laboratory, Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia.,School of Engineering and Built Environment, Griffith University, Gold Coast, Queensland, Australia
| | - Shaun D Gregory
- Innovative Cardiovascular Engineering and Technology Laboratory, Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia.,School of Medicine, The University of Queensland, Brisbane, Queensland, Australia.,Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Victoria, Australia.,Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
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7
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Interpretation of Physiologic and Left Ventricular Assist Device Parameters: Implications for Physical Therapist Decision-Making. Cardiopulm Phys Ther J 2020. [DOI: 10.1097/cpt.0000000000000138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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8
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Hemodynamic exercise responses with a continuous-flow left ventricular assist device: Comparison of patients' response and cardiorespiratory simulations. PLoS One 2020; 15:e0229688. [PMID: 32187193 PMCID: PMC7080259 DOI: 10.1371/journal.pone.0229688] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 02/11/2020] [Indexed: 12/24/2022] Open
Abstract
Background Left ventricular assist devices (LVADs) are an established treatment for end stage heart failure patients. As LVADs do not currently respond to exercise demands, attention is also directed towards improvements in exercise capacity and resulting quality of life. The aim of this study was to explore hemodynamic responses observed during maximal exercise tests to infer underlying patient status and therefore investigate possible diagnostics from LVAD derived data and advance the development of physiologically adaptive LVAD controllers. Methods High resolution continuous LVAD flow waveforms were recorded from 14 LVAD patients and evaluated at rest and during maximum bicycle exercise tests (n = 24). Responses to exercise were analyzed in terms of an increase (↑) or decrease (↓) in minimum (QMIN), mean (QMEAN), maximum flow (QMAX) and flow pulsatility (QP2P). To interpret clinical data, a cardiorespiratory numerical simulator was used that reproduced patients’ hemodynamics at rest and exercise. Different cardiovascular scenarios including chronotropic and inotropic responses, peripheral vasodilation, and aortic valve pathologies were simulated systematically and compared to the patients’ responses. Results Different patients’ responses to exercise were observed. The most common response was a positive change of ΔQMIN↑ and ΔQP2P↑ from rest to exercise (70% of exercise tests). Two responses, which were never reported in patients so far, were distinguished by QMIN↑ and QP2P↓ (observed in 17%) and by QMIN↓ and QP2P↑ (observed in 13%). The simulations indicated that the QP2P↓ can result from a reduced left ventricular contractility and that the QMIN↓ can occur with a better left ventricular contractility and/or aortic insufficiency. Conclusion LVAD flow waveforms determine a patients’ hemodynamic “fingerprint” from rest to exercise. Different waveform responses to exercise, including previously unobserved ones, were reported. The simulations indicated the left ventricular contractility as a major determinant for the different responses, thus improving patient stratification to identify how patient groups would benefit from exercise-responsive LVAD control.
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9
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Gross C, Moscato F, Schlöglhofer T, Maw M, Meyns B, Marko C, Wiedemann D, Zimpfer D, Schima H, Fresiello L. LVAD speed increase during exercise, which patients would benefit the most? A simulation study. Artif Organs 2019; 44:239-247. [DOI: 10.1111/aor.13569] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 09/03/2019] [Indexed: 01/20/2023]
Affiliation(s)
- Christoph Gross
- Center for Medical Physics and Biomedical Engineering Medical University of Vienna Vienna Austria
- Ludwig‐Boltzmann‐Cluster for Cardiovascular Research Vienna Austria
| | - Francesco Moscato
- Center for Medical Physics and Biomedical Engineering Medical University of Vienna Vienna Austria
- Ludwig‐Boltzmann‐Cluster for Cardiovascular Research Vienna Austria
| | - Thomas Schlöglhofer
- Center for Medical Physics and Biomedical Engineering Medical University of Vienna Vienna Austria
- Ludwig‐Boltzmann‐Cluster for Cardiovascular Research Vienna Austria
- Department of Cardiac Surgery Medical University of Vienna Vienna Austria
| | - Martin Maw
- Center for Medical Physics and Biomedical Engineering Medical University of Vienna Vienna Austria
- Ludwig‐Boltzmann‐Cluster for Cardiovascular Research Vienna Austria
- Department of Cardiac Surgery Medical University of Vienna Vienna Austria
| | - Bart Meyns
- Department of Cardiac Surgery Katholieke Universiteit Leuven Leuven Belgium
| | | | - Dominik Wiedemann
- Department of Cardiac Surgery Medical University of Vienna Vienna Austria
| | - Daniel Zimpfer
- Ludwig‐Boltzmann‐Cluster for Cardiovascular Research Vienna Austria
- Department of Cardiac Surgery Medical University of Vienna Vienna Austria
| | - Heinrich Schima
- Center for Medical Physics and Biomedical Engineering Medical University of Vienna Vienna Austria
- Ludwig‐Boltzmann‐Cluster for Cardiovascular Research Vienna Austria
- Department of Cardiac Surgery Medical University of Vienna Vienna Austria
| | - Libera Fresiello
- Department of Cardiac Surgery Katholieke Universiteit Leuven Leuven Belgium
- Institute of Clinical Physiology National Research Council Pisa Italy
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10
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Chang BY, Keller SP, Edelman ER. Leveraging Device-Arterial Coupling to Determine Cardiac and Vascular State. IEEE Trans Biomed Eng 2019; 66:2800-2808. [PMID: 30703007 PMCID: PMC6661194 DOI: 10.1109/tbme.2019.2895752] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
OBJECTIVE Limitations in available diagnostic metrics restrict the efficacy of managing therapies for cardiogenic shock. In current clinical practice, cardiovascular state is inferred through measurement of pulmonary capillary wedge pressure and reliance on linear approximations between pressure and flow to estimate peripheral vascular resistance. Mechanical circulatory support devices residing within the left ventricle and aorta provide an opportunity for both determining cardiac and vascular state and offering therapeutic benefit. We leverage the controllable mode of operation and transvalvular position of an indwelling percutaneous ventricular assist device to assess vascular and, in turn, cardiac state through the effects of device-arterial coupling across different levels of device support. METHODS Vascular state is determined by measuring changes in the pressure waveforms induced through intentional variation in the device generated blood flow. We evaluate this impact by applying a lumped parameter model to quantify state-specific vascular resistance and compliance and calculate beat-to-beat stroke volume and cardiac output in both animal models and retrospective patient data without external calibration. RESULTS Vascular state was accurately predicted in patients and animals in both baseline and experimental conditions. In the animal, stroke volume was predicted within a total root mean square error of 3.71 mL (n = 482). CONCLUSION We demonstrate that device-arterial coupling is a powerful tool for evaluating patient and state specific parameters of cardiovascular function. SIGNIFICANCE These insights may yield improved clinical care and support the development of next generation mechanical circulatory support devices that determine and operate in tandem with the supported organ.
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11
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Chang BY, Keller SP, Bhavsar SS, Josephy N, Edelman ER. Mechanical circulatory support device-heart hysteretic interaction can predict left ventricular end diastolic pressure. Sci Transl Med 2019; 10:10/430/eaao2980. [PMID: 29491185 DOI: 10.1126/scitranslmed.aao2980] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 09/12/2017] [Accepted: 01/25/2018] [Indexed: 11/02/2022]
Abstract
The full potential of mechanical circulatory systems in the treatment of cardiogenic shock is impeded by the lack of accurate measures of cardiac function to guide clinicians in determining when to initiate and how to optimally titrate support. The left ventricular end diastolic pressure (LVEDP) is an established metric of cardiac function that refers to the pressure in the left ventricle at the end of ventricular filling and immediately before ventricular contraction. In clinical practice, LVEDP is typically only inferred from, and poorly correlates with, the pulmonary capillary wedge pressure (PCWP). We leveraged the position of an indwelling percutaneous ventricular assist device and advanced data analysis methods to obtain LVEDP from the hysteretic operating metrics of the device. We validated our hysteresis-derived LVEDP measurement using mock flow loops, an animal model of cardiac dysfunction, and data from a patient in cardiogenic shock to show greater measurement precision and correlation with actual pressures than traditional inferences via PCWP. Delineation of the nonlinear relationship between device and heart adds insight into the interaction between ventricular support devices and the native heart, paving the way for continuous assessment of underlying cardiac state, metrics of cardiac function, potential closed-loop automated control, and rational design of future innovations in mechanical circulatory support systems.
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Affiliation(s)
- Brian Y Chang
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Steven P Keller
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. .,Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | | | - Noam Josephy
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.,Abiomed Inc., Danvers, MA 01923, USA
| | - Elazer R Edelman
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.,Division of Cardiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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12
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Graefe R, Henseler A, Körfer R, Meyns B, Fresiello L. Influence of left ventricular assist device pressure-flow characteristic on exercise physiology: Assessment with a verified numerical model. Int J Artif Organs 2019; 42:490-499. [PMID: 31104554 DOI: 10.1177/0391398819846126] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Current left ventricular assist devices are designed to reestablish patient's hemodynamics at rest but they lack the suitability to sustain the heart adequately during physical exercise. Aim of this work is to assess the performance during exercise of a left ventricular assist device with flatter pump pressure-flow characteristic and increased pressure sensitivity (left ventricular assist device 1) and to compare it to the performance of a left ventricular assist device with a steeper characteristic (left ventricular assist device 2). The two left ventricular assist devices were tested at constant rotational speed with a verified computational cardiorespiratory simulator reproducing an average left ventricular assist device patient response to exercise (EXE↑) and a left ventricular assist device patient with no chronotropic and inotropic response (EXE→). According to the results, left ventricular assist device 1 pumps a higher flow than left ventricular assist device 2 both at EXE↑ (6.3 vs 5.6 L/min) and at EXE→ (6.7 vs 6.1 L/min), thus it better unloads the left ventricle. Left ventricular assist device 1 increases the power delivered to the circulation from 0.63 W at rest to 0.67 W at EXE↑ and 0.82 W at EXE→, while left ventricular assist device 2 power shows even a minimal decrease. Left ventricular assist device 1 better sustains exercise hemodynamics and can provide benefits in terms of exercise performance, especially for patients with a poor residual left ventricular function, for whom the heart can hardly accommodate an increase of cardiac output.
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Affiliation(s)
| | | | | | - Bart Meyns
- 2 Cardiac Surgery, Katholiek Universiteit Leuven, Leuven, Belgium
| | - Libera Fresiello
- 2 Cardiac Surgery, Katholiek Universiteit Leuven, Leuven, Belgium.,3 Institute of Clinical Physiology of the National Research Council, Pisa, Italy
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13
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Gross C, Marko C, Mikl J, Altenberger J, Schlöglhofer T, Schima H, Zimpfer D, Moscato F. LVAD Pump Flow Does Not Adequately Increase With Exercise. Artif Organs 2018; 43:222-228. [PMID: 30155903 PMCID: PMC6589923 DOI: 10.1111/aor.13349] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 07/27/2018] [Accepted: 08/20/2018] [Indexed: 12/26/2022]
Abstract
Left ventricular assist devices (LVADs) restore cardiovascular circulatory demand at rest with a spontaneous increase in pump flow to exercise. The relevant contribution of cardiac output provided by the LVAD and ejected through the aortic valve for exercises of different intensities has been barely investigated in patients. The hypothesis of this study was that different responses in continuous recorded pump parameters occur for maximal and submaximal intensity exercises and that the pump flow change has an impact on the oxygen uptake at peak exercise (pVO2 ). Cardiac and pump parameters such as LVAD flow rate (QLVAD ), heart rate (HR), and aortic valve (AV) opening were analyzed from continuously recorded LVAD data during physical exercises of maximal (bicycle ergometer test) and submaximal intensities (6-min walk test and regular trainings). During all exercise sessions, the LVAD speed was kept constant. Cardiac and pump parameter responses of 16 patients for maximal and submaximal intensity exercises were similar for QLVAD : +0.89 ± 0.52 versus +0.59 ± 0.38 L/min (P = 0.07) and different for HR: +20.4 ± 15.4 versus +7.7 ± 5.8 bpm (P < 0.0001) and AV-opening with 71% versus 23% of patients (P < 0.0001). Multi-regression analysis with pVO2 (R2 = 0.77) showed relation to workload normalized by bodyweight (P = 0.0002), HR response (P = 0.001), AV-opening (P = 0.02), and age (P = 0.06) whereas the change in QLVAD was irrelevant. Constant speed LVADs provide inadequate support for maximum intensity exercises. AV-opening and improvements in HR show an important role for higher exercise capacities and reflect exercise intensities. Changes in pump flow do not impact pVO2 and are independent of AV-opening and response in HR. An LVAD speed control may lead to adequate left ventricular support during strenuous physical activities.
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Affiliation(s)
- Christoph Gross
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig-Boltzmann-Cluster for Cardiovascular Research, Vienna, Austria
| | - Christiane Marko
- PVA Center for Ambulatory Rehabilitation Vienna, Vienna, Austria
| | - Johann Mikl
- Rehabilitation Center Felbring, Felbring, Austria
| | - Johann Altenberger
- Rehabilitation Center Großgmain, Großgmain, Austria.,Paracelsus Medical University, Salzburg, Austria
| | - Thomas Schlöglhofer
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig-Boltzmann-Cluster for Cardiovascular Research, Vienna, Austria.,Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Heinrich Schima
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig-Boltzmann-Cluster for Cardiovascular Research, Vienna, Austria.,Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Daniel Zimpfer
- Ludwig-Boltzmann-Cluster for Cardiovascular Research, Vienna, Austria.,Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Francesco Moscato
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig-Boltzmann-Cluster for Cardiovascular Research, Vienna, Austria
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