1
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Wang Y, He F, Hao P, Zhang X. A fluid-structure interaction simulation on the impact of transcatheter micro ventricular assist devices on aortic valves. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2024; 254:108270. [PMID: 38878358 DOI: 10.1016/j.cmpb.2024.108270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 05/20/2024] [Accepted: 06/02/2024] [Indexed: 07/28/2024]
Abstract
BACKGROUND AND OBJECTIVE The implantation of ventricular assist devices (VADs) has become an important treatment option for patients with heart failure. Aortic valve insufficiency is a common complication caused by VADs implantation. Currently, there is very little quantitative research on the effects of transcatheter micro VADs or the intervention pumps on the aortic valves. METHODS In this study, the multi-component arbitrary Lagrange-Eulerian method is used to perform fluid-structure interaction simulations of the aortic valve model with and without intervention pumps. The effects of intervention pumps implantation on the opening area of the aortic valves, the stress distribution, and the flow characteristics are quantitatively analyzed. Statistical results are consistent with clinical guidelines and experiments. RESULTS The implantation of intervention pumps leads to the valve insufficiency and causes weak valve regurgitation. In the short-term treatment, the valve regurgitation is within a controllable range. The distribution and variation of stress on the leaflets are also affected by intervention pumps. The whirling flow in the flow direction affects the closing speed of the aortic valves and optimizes the stress distribution of the valves. In the models with whirling flow, the effects of intervention pumps implantation on valve motion and stress distribution differ from those without whirling flow. However, the valve insufficiency and valve regurgitation caused by intervention pumps still exist in the models with whirling flow. Conventional artificial bioprosthetic valves have limited effectiveness in treating the valve diseases caused by intervention pumps implantation. CONCLUSIONS This study quantitatively investigates the impact of intervention pumps on the aortic valves, and investigates the effect of blood rotation on the valve behavior, which is a gap in previous research. We suggest that in the short-term treatment, the implantation of intervention pumps has limited impact on aortic valves, caution should be exercised against valve regurgitation issues caused by intervention pumps.
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Affiliation(s)
- Yitao Wang
- Department of Engineering Mechanics, School of Aerospace Engineering, Tsinghua University, Beijing 100084, China
| | - Feng He
- Department of Engineering Mechanics, School of Aerospace Engineering, Tsinghua University, Beijing 100084, China
| | - Pengfei Hao
- Department of Engineering Mechanics, School of Aerospace Engineering, Tsinghua University, Beijing 100084, China; Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, PR China
| | - Xiwen Zhang
- Department of Engineering Mechanics, School of Aerospace Engineering, Tsinghua University, Beijing 100084, China.
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2
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Grinstein J, Cowger JA, Belkin MN, Houston BA, Tedford RJ. Hemodynamic Consequences of Long-Term Continuous Flow: The Importance of the Right Ventricular-Aortic Valve Interactions. Circ Heart Fail 2023; 16:e010713. [PMID: 37577824 DOI: 10.1161/circheartfailure.123.010713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Affiliation(s)
- Jonathan Grinstein
- Department of Medicine, Section of Cardiology, University of Chicago, IL (J.G., M.N.B.)
| | | | - Mark N Belkin
- Department of Medicine, Section of Cardiology, University of Chicago, IL (J.G., M.N.B.)
| | - Brian A Houston
- Department of Medicine, Division of Cardiology, Medical University of South Carolina, Charleston (B.A.H., R.J.T.)
| | - Ryan J Tedford
- Department of Medicine, Division of Cardiology, Medical University of South Carolina, Charleston (B.A.H., R.J.T.)
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3
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Grinstein J, Belkin MN, Kalantari S, Bourque K, Salerno C, Pinney S. Adverse Hemodynamic Consequences of Continuous Left Ventricular Mechanical Support: JACC Review Topic of the Week. J Am Coll Cardiol 2023; 82:70-81. [PMID: 37380306 DOI: 10.1016/j.jacc.2023.04.045] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 04/11/2023] [Accepted: 04/14/2023] [Indexed: 06/30/2023]
Abstract
Left ventricular assist devices (LVADs) provide lifesaving therapy for patients with advanced heart failure. The recognition of pump thrombosis, stroke, and nonsurgical bleeding as hemocompatibility-related adverse events (HRAEs) led to pump design improvements and reduced adverse event rates. However, continuous flow can predispose patients to right-sided heart failure (RHF) and aortic insufficiency (AI), especially as patients live longer with their device. Given the hemodynamic contributions to AI and RHF, these comorbidities can be classified as hemodynamic-related events (HDREs). Hemodynamic-driven events are time dependent and often manifest later than HRAEs. This review examines the emerging strategies to mitigate HDREs, with a focus on defining best practices for AI and RHF. As we head into the next generation of LVAD technology, it is important to differentiate HDREs from HRAEs so that we can continue to advance the field and improve the true durability of the pump-patient continuum.
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Affiliation(s)
- Jonathan Grinstein
- Section of Cardiology, Department of Medicine, University of Chicago, Chicago, Illinois, USA.
| | - Mark N Belkin
- Section of Cardiology, Department of Medicine, University of Chicago, Chicago, Illinois, USA
| | - Sara Kalantari
- Section of Cardiology, Department of Medicine, University of Chicago, Chicago, Illinois, USA
| | - Kevin Bourque
- Heart Failure Division, Abbott, Burlington, Massachusetts, USA
| | - Christopher Salerno
- Section of Cardiac Surgery, Department of Surgery, University of Chicago, Chicago, Illinois, USA
| | - Sean Pinney
- Section of Cardiology, Department of Medicine, University of Chicago, Chicago, Illinois, USA
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4
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Zhao X, Zhao L, Xu J, Li D, Li H, Li Y, Chen H, Zhang Y. Aortic valve opening in mock-loop with continuous-flow left ventricular assist device. Int J Artif Organs 2022; 45:809-816. [PMID: 35818176 DOI: 10.1177/03913988221111811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The appropriate opening of aortic valves is crucial for heart failure (HF) patients with left ventricular assist devices (LVADs). Nevertheless, up to the present time, aortic valve monitoring has not been performed in discharged patients. In this study, a mock-loop platform was developed to investigate the aortic valve performance in LVAD patients. An additional sluice valve was placed next to the aortic valve that when the sluice valve is manually closed, the aortic valve will remain closed; when the sluice valve is open, the aortic valve is opened or closed upon the pressures. The results showed that when the LVAD speed was below 2600 rpm, the aortic valve can be intermittently opened, while when the LVAD speed was over 2600 rpm, the aortic valve was persistently closed. The left ventricular end-systolic pressure (LVESP) was found to be an indicator of aortic valve closure that, upon the aortic valve closure LVESP suddenly decreased. The LVESP is suggested for future monitoring the status of the aortic valve for patients with implanted LVADs. The effects of heart failure (HF) degrees, circulation resistance, and aortic compliance on aortic valve closure were further studied. The results revealed that LVAD implantation in patients with early HF degrees will help to avoid persistent aortic valve closure.
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Affiliation(s)
- Xiang Zhao
- School of Medicine, Tsinghua University (School of Medicine) - RocketHeart Co. Ltd Joint Research Center for Artificial Heart, Tsinghua University, Beijing, China.,School of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University, Beijing, China
| | - Luxiang Zhao
- School of Medicine, Tsinghua University (School of Medicine) - RocketHeart Co. Ltd Joint Research Center for Artificial Heart, Tsinghua University, Beijing, China.,School of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University, Beijing, China
| | - Jian Xu
- School of Medicine, Tsinghua University (School of Medicine) - RocketHeart Co. Ltd Joint Research Center for Artificial Heart, Tsinghua University, Beijing, China
| | - Donghai Li
- Advanced Medical Research Institute, Shandong University, Shandong, China
| | - Heping Li
- Department of Engineering Physics, Tsinghua University, Beijing, China
| | - Yongjian Li
- School of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University, Beijing, China
| | - Haosheng Chen
- School of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University, Beijing, China
| | - Yu Zhang
- School of Medicine, Tsinghua University (School of Medicine) - RocketHeart Co. Ltd Joint Research Center for Artificial Heart, Tsinghua University, Beijing, China
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5
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Santiago A, Butakoff C, Eguzkitza B, Gray RA, May-Newman K, Pathmanathan P, Vu V, Vázquez M. Design and execution of a verification, validation, and uncertainty quantification plan for a numerical model of left ventricular flow after LVAD implantation. PLoS Comput Biol 2022; 18:e1010141. [PMID: 35696442 PMCID: PMC9232142 DOI: 10.1371/journal.pcbi.1010141] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 06/24/2022] [Accepted: 04/26/2022] [Indexed: 11/18/2022] Open
Abstract
Background
Left ventricular assist devices (LVADs) are implantable pumps that act as a life support therapy for patients with severe heart failure. Despite improving the survival rate, LVAD therapy can carry major complications. Particularly, the flow distortion introduced by the LVAD in the left ventricle (LV) may induce thrombus formation. While previous works have used numerical models to study the impact of multiple variables in the intra-LV stagnation regions, a comprehensive validation analysis has never been executed. The main goal of this work is to present a model of the LV-LVAD system and to design and follow a verification, validation and uncertainty quantification (VVUQ) plan based on the ASME V&V40 and V&V20 standards to ensure credible predictions.
Methods
The experiment used to validate the simulation is the SDSU cardiac simulator, a bench mock-up of the cardiovascular system that allows mimicking multiple operation conditions for the heart-LVAD system. The numerical model is based on Alya, the BSC’s in-house platform for numerical modelling. Alya solves the Navier-Stokes equation with an Arbitrary Lagrangian-Eulerian (ALE) formulation in a deformable ventricle and includes pressure-driven valves, a 0D Windkessel model for the arterial output and a LVAD boundary condition modeled through a dynamic pressure-flow performance curve. The designed VVUQ plan involves: (a) a risk analysis and the associated credibility goals; (b) a verification stage to ensure correctness in the numerical solution procedure; (c) a sensitivity analysis to quantify the impact of the inputs on the four quantities of interest (QoIs) (average aortic root flow Q A o a v g, maximum aortic root flow Q A o m a x, average LVAD flow Q V A D a v g, and maximum LVAD flow Q V A D m a x); (d) an uncertainty quantification using six validation experiments that include extreme operating conditions.
Results
Numerical code verification tests ensured correctness of the solution procedure and numerical calculation verification showed a grid convergence index (GCI)95% <3.3%. The total Sobol indices obtained during the sensitivity analysis demonstrated that the ejection fraction, the heart rate, and the pump performance curve coefficients are the most impactful inputs for the analysed QoIs. The Minkowski norm is used as validation metric for the uncertainty quantification. It shows that the midpoint cases have more accurate results when compared to the extreme cases. The total computational cost of the simulations was above 100 [core-years] executed in around three weeks time span in Marenostrum IV supercomputer.
Conclusions
This work details a novel numerical model for the LV-LVAD system, that is supported by the design and execution of a VVUQ plan created following recognised international standards. We present a methodology demonstrating that stringent VVUQ according to ASME standards is feasible but computationally expensive.
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Affiliation(s)
- Alfonso Santiago
- Barcelona Supercomputing Center (BSC), Barcelona, Spain
- ELEM biotech, Barcelona, Spain
| | | | | | - Richard A. Gray
- US Food and Drug Administration (FDA), Silver Spring, Maryland, United States of America
| | - Karen May-Newman
- Department of Mechanical Engineering, San Diego State University (SDSU), San Diego, California, United States of America
| | - Pras Pathmanathan
- US Food and Drug Administration (FDA), Silver Spring, Maryland, United States of America
| | - Vi Vu
- Department of Mechanical Engineering, San Diego State University (SDSU), San Diego, California, United States of America
| | - Mariano Vázquez
- Barcelona Supercomputing Center (BSC), Barcelona, Spain
- ELEM biotech, Barcelona, Spain
- * E-mail:
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6
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May-Newman K. Dynamic pressure-flow curve analysis of the native heart and left ventricular assist device for full and partial bypass conditions. Artif Organs 2021; 46:1077-1085. [PMID: 34932239 DOI: 10.1111/aor.14157] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 10/14/2021] [Accepted: 11/18/2021] [Indexed: 12/01/2022]
Abstract
BACKGROUND During left ventricular assist device (LVAD) support, the external work performed by the native heart combines with the work performed by the rotary LVAD to provide cyclic flow through the LVAD and, in some conditions, through the aortic valve. In this study, a balance of external work was developed and validated for both full and partial bypass conditions that includes valve opening and aortic compliance. METHODS The theory assumes a steady-state contribution of external work from the rotary LVAD and a dynamic portion from the heart. Cyclic flow may be ejected through either the LVAD or ascending aorta, and an energy absorption term accounts for aortic compliance. Mock loop studies were performed for LV ejection fractions of 10%-28% combined with HeartMate II LVAD support at 8 and 11 krpm to produce a range of full and partial bypass conditions. The external work of the LVAD and native heart was computed from the experimental pressure-flow (H-Q) relations and compared to the theory. RESULTS Native heart contraction produces a counterclockwise loop in the pressure-flow relation of the LVAD which increased with ejection fraction, and during full bypass conditions the external work was preserved in the total systemic flow. During partial bypass conditions, forward flow through the ascending aorta was accompanied by a reversal during aortic valve closure resulting in a reduction in energy in the downstream flow. CONCLUSIONS The study presents a balance of external work during full and partial bypass LVAD support. Experimental data validated the additional terms corresponding to forward flow and aortic compliance that contribute to the system balance. This expanded theory can be applied to LVAD design and control to improve pulsatility and aortic valve biomechanics.
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Affiliation(s)
- Karen May-Newman
- Bioengineering Program, San Diego State University, San Diego, California, USA
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7
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Left Ventricular Assist Device Flow Pattern Analysis Using a Novel Model Incorporating Left Ventricular Pulsatility. ASAIO J 2021; 67:724-732. [DOI: 10.1097/mat.0000000000001341] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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8
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Magkoutas K, Rebholz M, Sündermann S, Alogna A, Faragli A, Falk V, Meboldt M, Schmid Daners M. Control of ventricular unloading using an electrocardiogram-synchronized pulsatile ventricular assist device under high stroke ratios. Artif Organs 2020; 44:E394-E405. [PMID: 32321193 DOI: 10.1111/aor.13711] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 03/10/2020] [Accepted: 04/13/2020] [Indexed: 01/17/2023]
Abstract
Pulsatile ventricular assist devices (pVADs) yield a blood flow that imitates the pulsatile flow of the heart and, therefore, could diminish the adverse events related to the continuous flow provided by the ventricular assist devices that are commonly used. However, their intrinsic characteristics of larger size and higher weight set a burden to their implantation, that along with the frequent mechanical failures and thrombosis events, reduce the usage of pVADs in the clinical environment. In this study, we investigated the possibility to reduce the pump size by using high pump stroke ratios while maintaining the ability to control the hemodynamics of the cardiovascular system (CVS). In vitro and in vivo experiments were conducted with a custom pVAD implemented on a hybrid mock circulation system and in five sheep, respectively. The actuation of the pVAD was synchronized with the heartbeat. Variations of the pump stroke ratio, time delay between the pump stroke and the heart stroke, as well as duration of the pump systole in respect to the total cardiac cycle duration were used to evaluate the effects of various pump settings on the hemodynamics of the CVS. The results suggest that by varying the operating settings of the pVAD, a pulsatile flow that provides physiological hemodynamic parameters, as well as a control over the hemodynamic parameters, can be achieved. Additionally, by employing high pump stroke ratios, the size of the pVAD can be significantly reduced; however, at those high pump stroke ratios, the effect of the other pump parameters diminishes.
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Affiliation(s)
- Konstantinos Magkoutas
- Product Development Group Zurich, Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland
| | - Mathias Rebholz
- Product Development Group Zurich, Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland
| | - Simon Sündermann
- DZHK (German Center for Cardiovascular Research), Partner Site Berlin, Berlin, Germany.,Department of Cardiovascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Department of Cardiothoracic and Vascular Surgery, German Heart Center Berlin, Berlin, Germany
| | - Alessio Alogna
- DZHK (German Center for Cardiovascular Research), Partner Site Berlin, Berlin, Germany.,Department of Internal Medicine and Cardiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Campus Virchow Klinikum, Berlin, Germany
| | - Alessandro Faragli
- DZHK (German Center for Cardiovascular Research), Partner Site Berlin, Berlin, Germany.,Department of Internal Medicine and Cardiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Campus Virchow Klinikum, Berlin, Germany
| | - Volkmar Falk
- DZHK (German Center for Cardiovascular Research), Partner Site Berlin, Berlin, Germany.,Department of Cardiovascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Department of Cardiothoracic and Vascular Surgery, German Heart Center Berlin, Berlin, Germany.,Department of Health Sciences and Technology, ETH Zurich, Zurich, Switzerland
| | - Mirko Meboldt
- Product Development Group Zurich, Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland
| | - Marianne Schmid Daners
- Product Development Group Zurich, Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland
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9
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The Effect of Inflow Cannula Angle on the Intraventricular Flow Field of the Left Ventricular Assist Device-Assisted Heart: An In Vitro Flow Visualization Study. ASAIO J 2020; 65:139-147. [PMID: 29613888 DOI: 10.1097/mat.0000000000000790] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Previous studies have identified left ventricular assist device (LVAD) inflow cannula (IC) malposition as a significant risk for pump thrombosis. Thrombus development is a consequence of altered flow dynamics, which can produce areas of flow stasis or high shear that promote coagulation. The goal of this study was to measure the effect of IC orientation on the left ventricle (LV) flow field using a mock circulatory loop, and identify flow-based indices that are sensitive measures of cannula malposition. Experimental studies were performed with a customized silicone model of the dilated LV and the EVAHEART Centrifugal LVAS (Evaheart, Inc.; Houston TX). The velocity field of the LV midplane was measured for a transparent IC oriented parallel to and rotated 15° toward the septum under matched hemodynamic conditions. Vortex structures were analyzed and localized stasis calculated within the IC and combined with a map of normalized pulsatile velocity. The velocity fields revealed increased apical stasis and lower pulsatility with a small angulation of the IC. A significant change in vortex dynamics with the angled IC was observed, doubling the size of the counterclockwise (CCW) vortex while reducing the kinetic energy provided by LVAD support. A significant decrease in average and systolic velocities within the IC was found with cannula angulation, suggesting an increased resistance that affects primarily systolic flow and is worsened with increased LVAD support. These common echocardiographic indices offer the opportunity for immediate clinical application during ramp study assessment. Optimized IC positioning may be determined preoperatively using imaging techniques to develop patient-specific surgical recommendations.
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10
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Chivukula VK, Beckman JA, Prisco AR, Lin S, Dardas TF, Cheng RK, Farris SD, Smith JW, Mokadam NA, Mahr C, Aliseda A. Small Left Ventricular Size Is an Independent Risk Factor for Ventricular Assist Device Thrombosis. ASAIO J 2020; 65:152-159. [PMID: 29677037 DOI: 10.1097/mat.0000000000000798] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The prevalence of ventricular assist device (VAD) therapy has continued to increase due to a stagnant donor supply and growing advanced heart failure (HF) population. We hypothesize that left ventricular (LV) size strongly influences biocompatibility and risk of thrombosis. Unsteady computational fluid dynamics (CFD) was used in conjunction with patient-derived computational modeling and virtual surgery with a standard, apically implanted inflow cannula. A dual-focus approach of evaluating thrombogenicity was employed: platelet-based metrics to characterize the platelet environment and flow-based metrics to investigate hemodynamics. Left ventricular end-diastolic dimensions (LVEDds) ranging from 4.5 to 6.5 cm were studied and ranked according to relative thrombogenic potential. Over 150,000 platelets were individually tracked in each LV model over 15 cardiac cycles. As LV size decreased, platelets experienced markedly increased shear stress histories (SHs), whereas platelet residence time (RT) in the LV increased with size. The complex interplay between increased SH and longer RT has profound implications on thrombogenicity, with a significantly higher proportion of platelets in small LVs having long RT times and being subjected to high SH, contributing to thrombus formation. Our data suggest that small LV size, rather than decreased VAD speed, is the primary pathologic mechanism responsible for the increased incidence of thrombosis observed in VAD patients with small LVs.
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Affiliation(s)
| | | | - Anthony R Prisco
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota
| | - Shin Lin
- Division of Cardiology, University of Washington, Seattle, Washington
| | - Todd F Dardas
- Division of Cardiology, University of Washington, Seattle, Washington
| | - Richard K Cheng
- Division of Cardiology, University of Washington, Seattle, Washington
| | - Stephen D Farris
- Division of Cardiology, University of Washington, Seattle, Washington
| | - Jason W Smith
- Division of Cardiothoracic Surgery, University of Washington, Seattle, Washington
| | - Nahush A Mokadam
- Division of Cardiothoracic Surgery, University of Washington, Seattle, Washington
| | - Claudius Mahr
- Division of Cardiology, University of Washington, Seattle, Washington
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11
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Left Ventricular Assist Device Inflow Cannula Insertion Depth Influences Thrombosis Risk. ASAIO J 2019; 66:766-773. [DOI: 10.1097/mat.0000000000001068] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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12
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Clifford R, Robson D, Gross C, Moscato F, Schima H, Jansz P, Macdonald PS, Hayward CS. Beat‐to‐beat detection of aortic valve opening in HeartWare left ventricular assist device patients. Artif Organs 2018; 43:458-466. [DOI: 10.1111/aor.13381] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 10/26/2018] [Indexed: 12/15/2022]
Affiliation(s)
- Rachel Clifford
- Heart and Lung Transplant Unit St. Vincent's Hospital Darlinghurst New South Wales Australia
- St. Vincent's Clinical School, University of New South Wales Sydney Australia
| | - Desiree Robson
- Heart and Lung Transplant Unit St. Vincent's Hospital Darlinghurst New South Wales Australia
| | - 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
| | - 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
| | - Paul Jansz
- Heart and Lung Transplant Unit St. Vincent's Hospital Darlinghurst New South Wales Australia
| | - Peter S. Macdonald
- Heart and Lung Transplant Unit St. Vincent's Hospital Darlinghurst New South Wales Australia
- St. Vincent's Clinical School, University of New South Wales Sydney Australia
- Victor Chang Cardiac Research Institute Darlinghurst New South Wales Australia
| | - Christopher S. Hayward
- Heart and Lung Transplant Unit St. Vincent's Hospital Darlinghurst New South Wales Australia
- St. Vincent's Clinical School, University of New South Wales Sydney Australia
- Victor Chang Cardiac Research Institute Darlinghurst New South Wales Australia
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13
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The Physiological Rationale for Incorporating Pulsatility in Continuous-Flow Left Ventricular Assist Devices. Cardiol Rev 2018; 26:294-301. [DOI: 10.1097/crd.0000000000000202] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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14
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Aortic regurgitation in patients with a left ventricular assist device: A contemporary review. J Heart Lung Transplant 2018; 37:1289-1297. [DOI: 10.1016/j.healun.2018.07.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 06/24/2018] [Accepted: 07/05/2018] [Indexed: 01/12/2023] Open
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15
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Selmi M, Chiu WC, Chivukula VK, Melisurgo G, Beckman JA, Mahr C, Aliseda A, Votta E, Redaelli A, Slepian MJ, Bluestein D, Pappalardo F, Consolo F. Blood damage in Left Ventricular Assist Devices: Pump thrombosis or system thrombosis? Int J Artif Organs 2018; 42:113-124. [PMID: 30354870 DOI: 10.1177/0391398818806162] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Introduction: Despite significant technical advancements in the design and manufacture of Left Ventricular Assist Devices, post-implant thrombotic and thromboembolic complications continue to affect long-term outcomes. Previous efforts, aimed at optimizing pump design as a means of reducing supraphysiologic shear stresses generated within the pump and associated prothrombotic shear-mediated platelet injury, have only partially altered the device hemocompatibility. Methods: We examined hemodynamic mechanisms that synergize with hypershear within the pump to contribute to the thrombogenic potential of the overall Left Ventricular Assist Device system. Results: Numerical simulations of blood flow in differing regions of the Left Ventricular Assist Device system, that is the diseased native left ventricle, the pump inflow cannula, the impeller, the outflow graft and the anastomosed downstream aorta, reveal that prothrombotic hemodynamic conditions might occur at these specific sites. Furthermore, we show that beyond hypershear, additional hemodynamic abnormalities exist within the pump, which may elicit platelet activation, such as recirculation zones and stagnant platelet trajectories. We also provide evidences that particular Left Ventricular Assist Device implantation configurations and specific post-implant patient management strategies, such as those allowing aortic valve opening, are more hemodynamically favorable and reduce the thrombotic risk. Conclusion: We extend the perspective of pump thrombosis secondary to the supraphysiologic shear stress environment of the pump to one of Left Ventricular Assist Device system thrombosis, raising the importance of comprehensive characterization of the different prothrombotic risk factors of the total system as the target to achieve enhanced hemocompatibility and improved clinical outcomes.
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Affiliation(s)
- Matteo Selmi
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milano, Italy
- Department of Surgery, Division of Cardiac Surgery, Università di Verona, Verona, Italy
| | - Wei-Che Chiu
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | | | - Giulio Melisurgo
- Anesthesia and Cardiothoracic Intensive Care, San Raffaele Scientific Institute, Milano, Italy
| | | | - Claudius Mahr
- Division of Cardiology, University of Washington, Seattle, WA, USA
| | - Alberto Aliseda
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
| | - Emiliano Votta
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milano, Italy
| | - Alberto Redaelli
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milano, Italy
| | - Marvin J Slepian
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
- Departments of Medicine and Biomedical Engineering, The University of Arizona, Tucson, AZ, USA
| | - Danny Bluestein
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Federico Pappalardo
- Anesthesia and Cardiothoracic Intensive Care, San Raffaele Scientific Institute, Milano, Italy
- Advanced Heart Failure and Mechanical Circulatory Support Program, San Raffaele Scientific Institute, Milano, Italy
- Università Vita-Salute San Raffaele, Milano, Italy
| | - Filippo Consolo
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milano, Italy
- Advanced Heart Failure and Mechanical Circulatory Support Program, San Raffaele Scientific Institute, Milano, Italy
- Università Vita-Salute San Raffaele, Milano, Italy
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Zhang Q, Gao B, Yu C. The Effects of Left Ventricular Assist Device Support Level on the Biomechanical States of Aortic Valve. Med Sci Monit 2018; 24:2003-2017. [PMID: 29618718 PMCID: PMC5900803 DOI: 10.12659/msm.906903] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Background Although aortic valve disease caused by left ventricular assist device (LVAD) support has attracted more and more attention, the precise biomechanical effects of LVAD support level on the aortic valve are still unclear. Material/Methods A structural finite element models study was conducted using an ideal aortic valve geometric model. Four different study conditions were designed, according to the reduction of the open duration of the aortic valve. The isotropic hyperelastic constitutive equation was chosen to reflect the mechanical property of the leaflets. The distribution of the stress, strain, and transient dynamics of the leaflet were calculated. Results Along with the increase of LVAD support level, the open duration of the aortic valve was also reduced by the increase of LVAD support (low support level case 0.23 seconds versus middle support level case 0.2 seconds versus high support level case 0.14 seconds). Moreover, along with the increase of support mode of LVAD, the von Mises stress in most leaflet areas was increased from the low stress level (0–0.4 MPa) to the middle region (0.4–0.8 MPa). Once the leaflets were continuously closed, the high stress level (larger than 0.8 MPa) was observed. In contrast, the support level of LVAD only had slight effects on the distribution of von Mises strain. According to the aforementioned results, maintaining the open duration of aortic valve longer than 0.2 seconds could achieve better performance of biomechanical states of leaflets. Conclusions This study could provide useful information on the determination of optimal LVAD support strategy.
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Affiliation(s)
- Qi Zhang
- School of Life Science and BioEngineering, Beijing University of Technology, Beijing, China (mainland)
| | - Bin Gao
- School of Life Science and BioEngineering, Beijing University of Technology, Beijing, China (mainland)
| | - Chang Yu
- School of Life Science and BioEngineering, Beijing University of Technology, Beijing, China (mainland)
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Mahr C, Chivukula V, McGah P, Prisco AR, Beckman JA, Mokadam NA, Aliseda A. Intermittent Aortic Valve Opening and Risk of Thrombosis in Ventricular Assist Device Patients. ASAIO J 2018; 63:425-432. [PMID: 28118265 PMCID: PMC5489364 DOI: 10.1097/mat.0000000000000512] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The current study evaluates quantitatively the impact that intermittent aortic valve (AV) opening has on the thrombogenicity in the aortic arch region for patients under left ventricular assist device (LVAD) therapy. The influence of flow through the AV, opening once every five cardiac cycles, on the flow patterns in the ascending aortic is measured in a patient-derived computed tomography image-based model, after LVAD implantation. The mechanical environment of flowing platelets is investigated, by statistical treatment of outliers in Lagrangian particle tracking, and thrombogenesis metrics (platelet residence times and activation state characterized by shear stress accumulation) are compared for the cases of closed AV versus intermittent AV opening. All hemodynamics metrics are improved by AV opening, even at a reduced frequency and flow rate. Residence times of platelets or microthrombi are reduced significantly by transvalvular flow, as are the shear stress history experienced and the shear stress magnitude and gradients on the aortic root endothelium. The findings of this device-neutral study support the multiple advantages of management that enables AV opening, providing a rationale for establishing this as a standard in long-term treatment and care for advanced heart failure patients.
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Affiliation(s)
- Claudius Mahr
- Division of Cardiology, University of Washington, Seattle, WA, USA
| | | | - Patrick McGah
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
| | - Anthony R. Prisco
- Department of Internal Medicine, University of Minnesota, Minneapolis, MN, USA
| | | | - Nahush A. Mokadam
- Division of Cardiothoracic Surgery, University of Washington, Seattle, WA, USA
| | - Alberto Aliseda
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
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Rebholz M, Amacher R, Petrou A, Meboldt M, Schmid Daners M. High-frequency operation of a pulsatile VAD - a simulation study. ACTA ACUST UNITED AC 2017; 62:161-170. [PMID: 27505081 DOI: 10.1515/bmt-2016-0052] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 07/05/2016] [Indexed: 11/15/2022]
Abstract
Ventricular assist devices (VADs) are mechanical blood pumps that are clinically used to treat severe heart failure. Pulsatile VADs (pVADs) were initially used, but are today in most cases replaced by turbodynamic VADs (tVADs). The major concern with the pVADs is their size, which prohibits full pump body implantation for a majority of patients. A reduction of the necessary stroke volume can be achieved by increasing the stroke frequency, while maintaining the same level of support capability. This reduction in stroke volume in turn offers the possibility to reduce the pump's overall dimensions. We simulated a human cardiovascular system (CVS) supported by a pVAD with three different stroke rates that were equal, two- or threefold the heart rate (HR). The pVAD was additionally synchronized to the HR for better control over the hemodynamics and the ventricular unloading. The simulation results with a HR of 90 bpm showed that a pVAD stroke volume can be reduced by 71%, while maintaining an aortic pulse pressure (PP) of 30 mm Hg, avoiding suction events, reducing the ventricular stroke work (SW) and allowing the aortic valve to open. A reduction by 67% offers the additional possibility to tune the interaction between the pVAD and the CVS. These findings allow a major reduction of the pVAD's body size, while allowing the physician to tune the pVAD according to the patient's needs.
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Affiliation(s)
- Mathias Rebholz
- pd
- z Product Development Group Zurich, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich
| | | | - Anastasios Petrou
- pd
- z Product Development Group Zurich, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich
| | - Mirko Meboldt
- pd
- z Product Development Group Zurich, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich
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Mitral Valve Regurgitation in the LVAD-Assisted Heart Studied in a Mock Circulatory Loop. Cardiovasc Eng Technol 2016; 7:139-47. [DOI: 10.1007/s13239-016-0261-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Accepted: 09/21/2015] [Indexed: 11/24/2022]
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Granegger M, Masetti M, Laohasurayodhin R, Schloeglhofer T, Zimpfer D, Schima H, Moscato F. Continuous Monitoring of Aortic Valve Opening in Rotary Blood Pump Patients. IEEE Trans Biomed Eng 2015; 63:1201-7. [PMID: 26461795 DOI: 10.1109/tbme.2015.2489188] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
GOAL Rotary blood pumps (RBPs) typically support the left ventricle by pumping blood from the ventricle to the aorta, partially bypassing the aortic valve (AV). Monitoring the AV opening during RBP support would provide important information about cardiac-pump interaction. However, currently this information is not continuously available. In this study, an algorithm to determine AV opening using available pump signals was evaluated in humans. METHODS Pump speed changes were performed in 15 RBP patients to elicit opening of the AV. Simultaneously to pump data recordings, the AV was continuously monitored using echocardiography. The algorithm, which classifies the AV state utilizing three features (skewness, kurtosis, and crest factor) calculated from the pump flow waveform, was compared to echocardiography by using cross-validation analysis. Additionally, numerical simulation was used to evaluate effects of different pump characteristics and cannula length, as well as mitral valve insufficiency on the AV opening detection method. RESULTS More than 7000 heart beats were analyzed. The correct classification rate using the developed algorithm was 91.1% (sensitivity 91.0%, specificity 91.2%). Numerical simulations showed that the flow waveform shape used for AV opening detection is preserved under the different conditions studied. CONCLUSION This study demonstrates that the AV opening can be reliably detected in RBP patients using available pump data. SIGNIFICANCE Once implemented in RBP controllers, this method will provide a novel tool to improve the management of RBP patients, particularly for adjustments of the pump speed and flow and for the evaluation of the assisted cardiac function.
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Programmed Speed Reduction Enables Aortic Valve Opening and Increased Pulsatility in the LVAD-Assisted Heart. ASAIO J 2015; 61:540-7. [DOI: 10.1097/mat.0000000000000241] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Abstract
Continuous-flow left ventricular assist devices (LVAD) have become standard therapy option for patients with advanced heart failure. They offer several advantages over previously used pulsatile-flow LVADs, including improved durability, less surgical trauma, higher energy efficiency, and lower thrombogenicity. These benefits translate into better survival, lower frequency of adverse events, improved quality of life, and higher functional capacity of patients. However, mounting evidence shows unanticipated consequences of continuous-flow support, such as acquired aortic valve insufficiency and acquired von Willebrand syndrome. In this review article we discuss current evidence on differences between continuous and pulsatile mechanical circulatory support, with a focus on clinical implications and potential benefits of pulsatile flow.
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Affiliation(s)
- Davor Barić
- Davor Barić, Department of Cardiac Surgery and Transplantation, Dubrava University Hospital, Avenija Gojka Šuška 6, 10000 Zagreb, Croatia,
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Cheng A, Williamitis CA, Slaughter MS. Comparison of continuous-flow and pulsatile-flow left ventricular assist devices: is there an advantage to pulsatility? Ann Cardiothorac Surg 2014; 3:573-81. [PMID: 25512897 DOI: 10.3978/j.issn.2225-319x.2014.08.24] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 08/23/2014] [Indexed: 12/16/2022]
Abstract
BACKGROUND Continuous-flow left ventricular assist devices (CFVAD) are currently the most widely used type of mechanical circulatory support as bridge-to-transplant and destination therapy for end-stage congestive heart failure (HF). Compared to the first generation pulsatile-flow left ventricular assist devices (PFVADs), CFVADs have demonstrated improved reliability and durability. However, CFVADs have also been associated with certain complications thought to be linked with decreased arterial pulsatility. Previous studies comparing CFVADs and PFVADs have presented conflicting results. It is important to understand the outcome differences between CFVAD and PFVAD in order to further advance the current VAD technology. METHODS In this review, we compared the outcomes of CFVADs and PFVADs and examined the need for arterial pulsatility for the future generation of mechanical circulatory support. RESULTS CVADs offer advantages of smaller size, increased reliability and durability, and subsequent improvements in survival. However, with the increasing duration of long-term support, it appears that CFVADs may have specific complications and a lower rate of left ventricular recovery associated with diminished pulsatility, increased pressure gradients on the aortic valve and decreased compliance in smaller arterial vessels. PFVAD support or pulsatility control algorithms in CFVADs could be beneficial and potentially necessary for long term support. CONCLUSIONS Given the relative advantages and disadvantages of CFVADs and PFVADs, the ultimate solution may lie in incorporating pulsatility into current and emerging CFVADs whilst retaining their existing benefits. Future studies examining physiologic responses, end-organ function and LV remodeling at varying degrees of pulsatility and device support levels are needed.
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Affiliation(s)
- Allen Cheng
- Department of Cardiovascular and Thoracic Surgery, University of Louisville, Louisville, Kentucky 40202, USA
| | - Christine A Williamitis
- Department of Cardiovascular and Thoracic Surgery, University of Louisville, Louisville, Kentucky 40202, USA
| | - Mark S Slaughter
- Department of Cardiovascular and Thoracic Surgery, University of Louisville, Louisville, Kentucky 40202, USA
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Bozkurt S, van de Vosse FN, Rutten MCM. Aortic Valve Function Under Support of a Left Ventricular Assist Device: Continuous vs. Dynamic Speed Support. Ann Biomed Eng 2014; 43:1727-37. [PMID: 25480480 DOI: 10.1007/s10439-014-1204-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 11/26/2014] [Indexed: 11/25/2022]
Abstract
Continuous flow left ventricular devices (CF-LVADs) support the failing heart at a constant speed and alters the loads on the aortic valve. This may cause insufficiency in the aortic valve under long-term CF-LVAD support. The aim of this study is to assess the aortic valve function under varying speed CF-LVAD support. A Medtronic freestyle valve and a Micromed DeBakey CF-LVAD were tested in a mock circulatory system. First, the CF-LVAD was operated at constant speeds between 7500 and 11,500 rpm with 1000 rpm intervals. The mean pump outputs obtained from these tests were applied in varying speed CF-LVAD support mode using a reference model for the pump flow. The peak of the instantaneous pump flow was applied at peak systole and mid-diastole, respectively. Ejection durations and in the aortic valve were the longest when the peak pump flow was applied at mid-diastole among the CF-LVAD operating modes. Furthermore, mean aortic valve area over a cardiac cycle was highest when the peak pump flow was applied at mid-diastole. The results show that changing phase of the reference flow rate signal may reduce the effects of the CF-LVADs on altered aortic valve closing behavior, without compromising the overall pump support level.
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Affiliation(s)
- Selim Bozkurt
- Department of Biomedical Engineering, Eindhoven University of Technology, Den Dolech 2, 5612 AZ, Eindhoven, The Netherlands,
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26
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Gallo M, Tarzia V, Iop L, Bejko J, Bortolussi G, Bianco R, Bottio T, Gerosa G. Cellular, molecular, genomic changes occurring in the heart under mechanical circulatory support. Ann Cardiothorac Surg 2014; 3:496-504. [PMID: 25452910 DOI: 10.3978/j.issn.2225-319x.2014.08.23] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 08/04/2014] [Indexed: 01/06/2023]
Affiliation(s)
- Michele Gallo
- Division of Cardiac Surgery, Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova 35128, Italy
| | - Vincenzo Tarzia
- Division of Cardiac Surgery, Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova 35128, Italy
| | - Laura Iop
- Division of Cardiac Surgery, Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova 35128, Italy
| | - Jonida Bejko
- Division of Cardiac Surgery, Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova 35128, Italy
| | - Giacomo Bortolussi
- Division of Cardiac Surgery, Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova 35128, Italy
| | - Roberto Bianco
- Division of Cardiac Surgery, Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova 35128, Italy
| | - Tomaso Bottio
- Division of Cardiac Surgery, Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova 35128, Italy
| | - Gino Gerosa
- Division of Cardiac Surgery, Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova 35128, Italy
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Wong K, Samaroo G, Ling I, Dembitsky W, Adamson R, del Álamo JC, May-Newman K. Intraventricular flow patterns and stasis in the LVAD-assisted heart. J Biomech 2014; 47:1485-94. [PMID: 24612721 DOI: 10.1016/j.jbiomech.2013.12.031] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 12/19/2013] [Accepted: 12/21/2013] [Indexed: 12/01/2022]
Abstract
Left ventricular assist device (LVAD) support disrupts the natural blood flow path through the heart, introducing flow patterns associated with thrombosis, especially in the presence of medical devices. The aim of this study was to quantitatively evaluate the flow patterns in the left ventricle (LV) of the LVAD-assisted heart, with a focus on alterations in vortex development and stasis. Particle image velocimetry of a LVAD-supported LV model was performed in a mock circulatory loop. In the Pre-LVAD flow condition, a vortex ring initiating from the LV base migrated toward the apex during diastole and remained in the LV by the end of ejection. During LVAD support, vortex formation was relatively unchanged although vortex circulation and kinetic energy increased with LVAD speed, particularly in systole. However, as pulsatility decreased and aortic valve opening ceased, a region of fluid stasis formed near the left ventricular outflow tract. These findings suggest that LVAD support does not substantially alter vortex dynamics unless cardiac function is minimal. The altered blood flow introduced by the LVAD results in stasis adjacent to the LV outflow tract, which increases the risk of thrombus formation in the heart.
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Affiliation(s)
- K Wong
- Bioengineering Program, San Diego State University, Department of Mechanical Engineering, San Diego, CA 92182-1323, United States
| | - G Samaroo
- Bioengineering Program, San Diego State University, Department of Mechanical Engineering, San Diego, CA 92182-1323, United States
| | - I Ling
- Bioengineering Program, San Diego State University, Department of Mechanical Engineering, San Diego, CA 92182-1323, United States
| | - W Dembitsky
- Mechanical Circulatory Support, Cardiothoracic Surgery, Sharp Memorial Hospital, San Diego, CA 92182-1323, United States
| | - R Adamson
- Mechanical Circulatory Support, Cardiothoracic Surgery, Sharp Memorial Hospital, San Diego, CA 92182-1323, United States
| | - J C del Álamo
- Mechanical and Aerospace Engineering, U.C. San Diego, La Jolla, CA 92093-0411, United States; Institute for Engineering in Medicine, U.C. San Diego, La Jolla, CA 92093, United States
| | - K May-Newman
- Bioengineering Program, San Diego State University, Department of Mechanical Engineering, San Diego, CA 92182-1323, United States.
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Firstenberg MS, Sai-Sudhakar CB, Anyanwu A. Valvular disease in patients requiring long-term left ventricular assist devices: pathophysiology and therapeutic options. Expert Rev Cardiovasc Ther 2014; 10:205-13. [DOI: 10.1586/erc.11.189] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Amacher R, Ochsner G, Schmid Daners M. Synchronized Pulsatile Speed Control of Turbodynamic Left Ventricular Assist Devices: Review and Prospects. Artif Organs 2014; 38:867-75. [DOI: 10.1111/aor.12253] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Raffael Amacher
- Institute for Dynamic Systems and Control; Department of Mechanical and Process Engineering; ETH Zurich; Zurich Switzerland
| | - Gregor Ochsner
- Institute for Dynamic Systems and Control; Department of Mechanical and Process Engineering; ETH Zurich; Zurich Switzerland
| | - Marianne Schmid Daners
- Institute for Dynamic Systems and Control; Department of Mechanical and Process Engineering; ETH Zurich; Zurich Switzerland
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Surgical correction of aortic valve insufficiency after left ventricular assist device implantation. J Thorac Cardiovasc Surg 2013; 146:1247-52. [DOI: 10.1016/j.jtcvs.2013.05.019] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 05/15/2013] [Accepted: 05/30/2013] [Indexed: 11/19/2022]
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Investigation of hemodynamics in the assisted isolated porcine heart. Int J Artif Organs 2013; 36:878-86. [PMID: 24362896 DOI: 10.5301/ijao.5000257] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/07/2013] [Indexed: 11/20/2022]
Abstract
BACKGROUND Currently, the interaction between rotary blood pumps (RBP) and the heart is investigated in silico, in vitro, and in animal models. Isolated and defined changes in hemodynamic parameters are unattainable in animal models, while the heart-pump interaction in its whole complexity cannot be modeled in vitro or in silico. AIM The aim of this work was to develop an isolated heart setup to provide a realistic heart-pump interface with the possibility of easily adjusting hemodynamic parameters. METHODS A mock circuit mimicking the systemic circulation was developed. Eight porcine hearts were harvested using a protocol similar to heart transplantation. Then, the hearts were resuscitated using Langendorff perfusion with rewarmed, oxygenated blood. An RBP was implanted and the setup was switched to the "working mode" with the left heart and the RBP working as under physiologic conditions. Both the unassisted and assisted hemodynamics were monitored. RESULTS In the unassisted condition, cardiac output was up to 9.5 l/min and dP/dtmax ranged from 521 to 3621 mmHg/s at a preload of 15 mmHg and afterload of 70 mmHg. With the RBP turned on, hemodynamics similar to heart-failure patients were observed in each heart. Mean pump flow and flow pulsatility ranged from 0 to 11 l/min. We were able to reproduce conditions with an open and closed aortic valve as well as suction events. CONCLUSIONS An isolated heart setup including an RBP was developed, which combines the advantages of in silico/vitro methods and animal experiments. This tool thus provides further insight into the interaction between the heart and an RBP.
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Granegger M, Schima H, Zimpfer D, Moscato F. Assessment of aortic valve opening during rotary blood pump support using pump signals. Artif Organs 2013; 38:290-7. [PMID: 24102321 DOI: 10.1111/aor.12167] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
During left ventricular support by rotary blood pumps (RBPs), the biomechanics of the aortic valve (AV) are altered, potentially leading to adverse events like commissural fusion, valve insufficiency, or thrombus formation. To avoid these events, assessment of AV opening and consequent adaptation of pump speed seem important. Additionally, this information provides insight into the heart-pump interaction. The aim of this study was to develop a method to assess AV opening from the pump flow signal. Data from a numerical model of the cardiovascular system and animal experiments with an RBP were employed to detect the AV opening from the flow waveform under different hemodynamic conditions. Three features calculated from the pump flow waveform were used to classify the state of the AV: skewness, kurtosis, and crest factor. Three different classification algorithms were applied to determine the state of the AV based on these features. In the model data, the best classifier resulted in a percentage of correctly identified beats with a closed AV (specificity) of 99.9%. The percentage of correctly identified beats with an open AV (sensitivity) was 99.5%. In the animal experiments, specificity was 86.8% and sensitivity reached 96.5%. In conclusion, a method to detect AV opening independently from preload, afterload, heart rate, contractility, and degree of support was developed. This algorithm makes the evaluation of the state of the AV possible from pump data only, allowing pump speed adjustment for a frequent opening of the AV and providing information about the interaction of the native heart with the RBP.
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Affiliation(s)
- Marcus Granegger
- 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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Gregory SD, Stevens MC, Wu E, Fraser JF, Timms D. In vitro evaluation of aortic insufficiency with a rotary left ventricular assist device. Artif Organs 2013; 37:802-9. [PMID: 23901787 DOI: 10.1111/aor.12143] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Aortic insufficiency (AI) is usually repaired prior to rotary blood pump (RBP) implantation but can develop during support due, in part, to the sustained RBP-induced high pressure gradient across the aortic valve. Repair of the aortic valve before or during RBP support predisposes these critically ill patients to even higher risks. This study used an in vitro mock circulation loop to identify the severity of AI and/or left heart failure (LHF) that might benefit from valve repair while investigating RBP operating strategies to reduce the hemodynamic influence of AI. Reproduction of AI with RBP-supported LHF reduced device efficiency, particularly in the more severe cases of AI and LHF. The requirement for repair or closure of the aortic valve was demonstrated in all conditions other than those with only mild AI. When a sinusoidal RBP speed pulse was induced, small changes in systemic flow rate and regurgitant volume were observed with all degrees of AI. Variation of the pulse phase delay only resulted in minor changes to systemic flow rate, with a maximum difference of 0.17 L/min. Although the clinical implications of these small changes may be insignificant, changes in systemic flow rate and transvalvular pressure were shown when the sinusoidal RBP speed pulse was applied with no AI. In these cases, transvalvular pressure was reduced by up to 8% through sinusoidal copulsation of the RBP, which may prevent or delay the onset of AI. This in vitro study suggests that surgical intervention is required with moderate or worse AI and that RBP operating strategies should be further explored to delay the onset and reduce the harmful effects of AI.
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Affiliation(s)
- Shaun D Gregory
- School of Medicine, University of Queensland, Brisbane, Queensland, Australia; Innovative Cardiovascular Engineering and Technology Laboratory, The Prince Charles Hospital, Brisbane, Queensland, Australia; Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia
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Jahren SE, Ochsner G, Shu F, Amacher R, Antaki JF, Vandenberghe S. Analysis of Pressure Head-Flow Loops of Pulsatile Rotodynamic Blood Pumps. Artif Organs 2013; 38:316-26. [DOI: 10.1111/aor.12139] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Silje E. Jahren
- ARTORG Center for Biomedical Research; University of Bern; Bern USA
- Institute for Dynamic Systems and Control; ETH Zurich; Zurich Switzerland USA
| | - Gregor Ochsner
- Institute for Dynamic Systems and Control; ETH Zurich; Zurich Switzerland USA
| | - Fangjun Shu
- Mechanical and Aerospace Engineering Department; New Mexico State University; Las Cruces NM USA
- Department of Biomedical Engineering; Carnegie Mellon University; Pittsburgh PA USA
| | - Raffael Amacher
- Institute for Dynamic Systems and Control; ETH Zurich; Zurich Switzerland USA
| | - James F. Antaki
- Department of Biomedical Engineering; Carnegie Mellon University; Pittsburgh PA USA
| | - Stijn Vandenberghe
- ARTORG Center for Biomedical Research; University of Bern; Bern USA
- Department of Biomedical Engineering; Carnegie Mellon University; Pittsburgh PA USA
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Thromboembolism Is Linked to Intraventricular Flow Stasis in a Patient Supported with a Left Ventricle Assist Device. ASAIO J 2013; 59:452-5. [DOI: 10.1097/mat.0b013e318299fced] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Tuzun E, Pennings K, van Tuijl S, de Hart J, Stijnen M, van de Vosse F, de Mol B, Rutten M. Assessment of aortic valve pressure overload and leaflet functions in an ex vivo beating heart loaded with a continuous flow cardiac assist device. Eur J Cardiothorac Surg 2013; 45:377-83. [DOI: 10.1093/ejcts/ezt355] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Martina JR, Schipper MEI, de Jonge N, Ramjankhan F, de Weger RA, Lahpor JR, Vink A. Analysis of aortic valve commissural fusion after support with continuous-flow left ventricular assist device. Interact Cardiovasc Thorac Surg 2013; 17:616-24. [PMID: 23798641 DOI: 10.1093/icvts/ivt263] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES Continuous-flow left ventricular assist devices (cf-LVADs) may induce commissural fusion of the aortic valve leaflets. Factors associated with this occurrence of commissural fusion are unknown. The aim of this study was to examine histological characteristics of cf-LVAD-induced commissural fusion in relation to clinical variables. METHODS Gross and histopathological examinations were performed on 19 hearts from patients supported by either HeartMate II (n = 17) or HeartWare (n = 2) cf-LVADs and related to clinical characteristics (14 heart transplantation, 5 autopsy). RESULTS Eleven of the 19 (58%) aortic valves showed fusion of single or multiple commissures (total fusion length 11 mm [4-20] (median [interquartile range]) per valve), some leading to noticeable nodular displacements or considerable lumen diameter narrowing. Multiple fenestrations were observed in one valve. Histopathological examination confirmed commissural fusion, with varying changes in valve layer structure without evidence of inflammatory infiltration at the site of fusion. Commissural fusion was associated with continuous aortic valve closure during cf-LVAD support (P = 0.03). LVAD-induced aortic valve insufficiency developed in all patients with commissural fusion and in 67% of patients without fusion. Age, duration of cf-LVAD support and aetiology of heart failure (ischaemic vs dilated cardiomyopathy) were not associated with the degree of fusion. CONCLUSIONS Aortic valve commissural fusion after support with cf-LVADs is a non-inflammatory process leading to changes in valve layer structure that can be observed in >50% of cf-LVAD patients. This is the first study showing that patients receiving full cf-LVAD support without opening of the valve have a significantly higher risk of developing commissural fusion than patients on partial support.
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Affiliation(s)
- Jerson R Martina
- Department of Cardiothoracic Surgery, University Medical Center Utrecht, Utrecht, Netherlands
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Modified central closure technique for treatment of aortic insufficiency in patients on left ventricular assist device support. ASAIO J 2013; 58:626-8. [PMID: 23103701 DOI: 10.1097/mat.0b013e318271bc49] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Development of aortic insufficiency (AI) in a patient with a continuous flow left ventricular assist device (CF-LVAD) represents a serious complication. The circulatory loop that is created by the AI can lead to cardiogenic shock, malperfusion, and multisystem organ failure. The central closure technique has been well described and is a popular method of repairing the aortic valve in CF-LVAD patients with AI. Because of an early failure using this technique, we developed a modification of this technique that we describe in this report that can be particularly useful when the aortic valve leaflet tissue is relatively normal or thin, as opposed to thickened/fibrosed, as the strength of the repair is not solely provided by the central coaptation point of the leaflets, but is rather, distributed more diffusely across the leaflets.
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Sansone F. Aortic regurgitation and extracorporeal membrane oxygenation: An undiscussed topic. JOURNAL OF ACUTE DISEASE 2012. [DOI: 10.1016/s2221-6189(13)60015-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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