1
|
Vu V, Rossini L, del Alamo JC, Dembitsky W, Gray RA, May-Newman K. Benchtop Models of Patient-Specific Intraventricular Flow During Heart Failure and LVAD Support. J Biomech Eng 2023; 145:111010. [PMID: 37565996 PMCID: PMC10777504 DOI: 10.1115/1.4063147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 08/01/2023] [Accepted: 08/03/2023] [Indexed: 08/12/2023]
Abstract
The characterization of intraventricular flow is critical to evaluate the efficiency of fluid transport and potential thromboembolic risk but challenging to measure directly in advanced heart failure (HF) patients with left ventricular assist device (LVAD) support. The study aims to validate an in-house mock loop (ML) by simulating specific conditions of HF patients with normal and prosthetic mitral valves (MV) and LVAD patients with small and dilated left ventricle volumes, then comparing the flow-related indices result of vortex parameters, residence time (RT), and shear-activation potential (SAP). Patient-specific inputs for the ML studies included heart rate, end-diastolic and end-systolic volumes, ejection fraction, aortic pressure, E/A ratio, and LVAD speed. The ML effectively replicated vortex development and circulation patterns, as well as RT, particularly for HF patient cases. The LVAD velocity fields reflected altered flow paths, in which all or most incoming blood formed a dominant stream directing flow straight from the mitral valve to the apex. RT estimation of patient and ML compared well for all conditions, but SAP was substantially higher in the LVAD cases of the ML. The benchtop system generated comparable and reproducible hemodynamics and fluid dynamics for patient-specific conditions, validating its reliability and clinical relevance. This study demonstrated that ML is a suitable platform to investigate the fluid dynamics of HF and LVAD patients and can be utilized to investigate heart-implant interactions.
Collapse
Affiliation(s)
- Vi Vu
- Bioengineering Program, Department of Mechanical Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182;Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, MD 20993
| | - Lorenzo Rossini
- Mechanical and Aerospace Engineering Department, University of California, San Diego 9500 Gilman Drive, La Jolla, CA 92093
| | - Juan C. del Alamo
- Center for Cardiovascular Biology & Mechanical Engineering Department, University of Washington, 1400 NE Campus Parkway, Seattle, WA 98195
| | - Walter Dembitsky
- Cardiothoracic Surgery, Mechanical Assist Program, Sharp Memorial Hospital, San Diego 7901 Frost Street, San Diego, CA 92123
| | - Richard A. Gray
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, MD 20993
| | - Karen May-Newman
- Bioengineering Program, Department of Mechanical Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182
| |
Collapse
|
2
|
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.
Collapse
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:
| |
Collapse
|
3
|
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.
Collapse
Affiliation(s)
- Karen May-Newman
- Bioengineering Program, San Diego State University, San Diego, California, USA
| |
Collapse
|
4
|
Ortiz S, Vu V, Montes R, May-Newman K. Left Ventricular Flow Dynamics with the HeartMate3 Left Ventricular Assist Device: Effect of Inflow Cannula Position and Speed Modulation. ASAIO J 2021; 67:1301-1311. [PMID: 34261878 DOI: 10.1097/mat.0000000000001523] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Improper left ventricular assist device (LVAD) inflow cannula (IC) positioning creates areas of stasis and low pulsatility that predispose thromboembolism, but may be mitigated with LVAD speed modulation. A mock loop study was performed to assess the sensitivity of left ventricle (LV) flow architecture to IC position and speed modulation during HeartMate3 support. System pressure, flow, and the time-resolved velocity field were measured within a transparent silicone LV for three IC angles and three IC insertion depths at matched levels of cardiac function and LVAD speed. Inflow cannula angulation towards the septum increased the resistance to LVAD flow as well as increasing the size and energy of the counter-clockwise (CCW) vortex. Apical velocity was reduced compared to IC angulation towards the mitral valve, but regional pulsatility was maintained across all angles and LVAD speeds. Increased IC protrusion decreased LVAD flow resistance, increasing velocity within the IC but reducing flow and pulsatility in the adjacent apical region. Increasing LVAD flow resistance improves aortic valve opening and strengthens the CCW vortex which directs inflow towards the septum, producing higher blood residence time and shear activation potential. Despite this impact on flow architecture, pulsatility reduction with increased LVAD speed was minimal with the HeartMate3 speed modulation feature.
Collapse
Affiliation(s)
- Sean Ortiz
- From the Bioengineering Program, Department of Mechanical Engineering, San Diego State University, San Diego, California
| | | | | | | |
Collapse
|
5
|
Abstract
The success of left ventricular assist device (LVAD) therapy is hampered by complications such as thrombosis and bleeding. Understanding blood flow interactions between the heart and the LVAD might help optimize treatment and decrease complication rates. We hypothesized that LVADs modify shear stresses and blood transit in the left ventricle (LV) by changing flow patterns and that these changes can be characterized using 2D echo color Doppler velocimetry (echo-CDV). We used echo-CDV and custom postprocessing methods to map blood flow inside the LV in patients with ongoing LVAD support (Heartmate II, N = 7). We compared it to healthy controls (N = 20) and patients with dilated cardiomyopathy (DCM, N = 20). We also analyzed intraventricular flow changes during LVAD ramp tests (baseline ± 400 rpm). LVAD support reversed the increase in blood stasis associated with DCM, but it did not reduce intraventricular shear exposure. Within the narrow range studied, the ventricular flow was mostly insensitive to changes in pump speed. Patients with significant aortic insufficiency showed abnormalities in blood stasis and shear indices. Overall, this study suggests that noninvasive flow imaging could potentially be used in combination with standard clinical methods for adjusting LVAD settings to optimize flow transport and minimize stasis on an individual basis.
Collapse
|
6
|
Vellguth K, Sündermann S, Escher A, Bierewirtz T, Schmidt T, Alogna A, Kertzscher U, Goubergrits L, Fraser KH, Granegger M. Intraventricular flow features and cardiac mechano-energetics after mitral valve interventions – feasibility of an isolated heart model. CURRENT DIRECTIONS IN BIOMEDICAL ENGINEERING 2020. [DOI: 10.1515/cdbme-2020-0028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Abstract
The aim of this work was the development of an isolated heart setup to delineate the interactions between intraventricular flow features, hemodynamic parameters and mechano-energetics after certain mitral valve therapies. Five porcine hearts were explanted and prepared for (i) edge-to-edge mitral valve repair, (ii) implantation of a rotatable biscupid mechanical valve prosthesis. Flow structures were visualized using echocardiography while hemodynamics was recorded in terms of pressures, flow rates and ventricular volume. Hemodynamic and cardiac mechano-energetics implied a marginal effect (<5%) of alternating leaflet orientation on ventricular pre-load and stroke work. After edge-to-edge repair, substantial variations in flow structures were observed. Beside promoting profound insights into fundamental physiologic mechanisms, the setup may be used for validation of computer aided therapy planning tools.
Collapse
Affiliation(s)
| | - Simon Sündermann
- Charité – Universitätsmedizin , Berlin , Germany
- German Heart Center , Berlin , Germany
| | - Andreas Escher
- Charité – Universitätsmedizin , Berlin , Germany
- Division of Cardiac Surgery, Medical University of Vienna , Vienna , Austria
| | | | | | | | | | | | | | - Marcus Granegger
- Charité – Universitätsmedizin , Berlin , Germany
- Division of Cardiac Surgery, Medical University of Vienna , Vienna , Austria
| |
Collapse
|
7
|
Vu V, May-Newman K. Mitral Valve Orientation Affects Vortex Formation and Turbulence in the Left Ventricle. J Cardiothorac Vasc Anesth 2019; 33:3211-3213. [DOI: 10.1053/j.jvca.2019.03.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 03/12/2019] [Indexed: 11/11/2022]
|
8
|
May‐Newman K, Montes R, Campos J, Marquez‐Maya N, Vu V, Zebrowski E, Motomura T, Benkowski R. Reducing regional flow stasis and improving intraventricular hemodynamics with a tipless inflow cannula design: An in vitro flow visualization study using the EVAHEART LVAD. Artif Organs 2019; 43:834-848. [DOI: 10.1111/aor.13477] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 04/11/2019] [Accepted: 04/23/2019] [Indexed: 12/13/2022]
Affiliation(s)
- Karen May‐Newman
- Bioengineering Program, Department of Mechanical Engineering San Diego State University San Diego California
| | - Ricardo Montes
- Bioengineering Program, Department of Mechanical Engineering San Diego State University San Diego California
| | - Josue Campos
- Bioengineering Program, Department of Mechanical Engineering San Diego State University San Diego California
| | - Nikolas Marquez‐Maya
- Bioengineering Program, Department of Mechanical Engineering San Diego State University San Diego California
| | - Vi Vu
- Bioengineering Program, Department of Mechanical Engineering San Diego State University San Diego California
| | | | | | | |
Collapse
|
9
|
Benito Y, Martinez-Legazpi P, Rossini L, Pérez del Villar C, Yotti R, Martín Peinador Y, Rodríguez-Pérez D, Desco MM, Medrano C, Antoranz JC, Fernández-Avilés F, del Álamo JC, Bermejo J. Age-Dependence of Flow Homeostasis in the Left Ventricle. Front Physiol 2019; 10:485. [PMID: 31105588 PMCID: PMC6498893 DOI: 10.3389/fphys.2019.00485] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 04/08/2019] [Indexed: 11/29/2022] Open
Abstract
Background: Intracardiac flow homeostasis requires avoiding blood stasis and platelet activation during its transit through the cardiac chambers. However, the foundations of intraventricular blood washout and its exposure to shear stresses have been poorly addressed. We aimed to characterize and quantify these features in a wide population of healthy subjects and assess the relationships of these indices with age. Methods: We used color-Doppler echocardiography and custom post-processing methods to study 149 healthy volunteers from 26 days to 80 years old. From the intraventricular flow-velocity fields we obtained personalized maps of (1) the residence time of blood in the LV, and (2) the shear index, a metric accounting for the strongest occurrence of shear stresses inside the chamber. From these maps we derived quantitative indices of the overall intraventricular blood washout and shear exposure. We addressed the age-dependence of these indices and analyzed their relationship with age-related changes in filling-flow. Results: The entire intraventricular blood pool was replaced before 8 cycles. Average residence time of blood inside the LV was <3 cycles in all subjects and followed an inverse U-shape relationship with age, increasing from median (IQR) of 1.0 (0.7 to 1.2) cycles in the 1st year of life to 1.8 (1.4-2.2) cycles in young adults (17-30 years old), becoming shorter again thereafter. Shear index showed no relation with age and was bounded around 20 dyn·s/cm2. Regions with the longest residence time and highest shear index were identified near the apex. Differences in the degree of apical penetration of the filling waves and the duration of the late-filling phase explained the age-dependence of residence time (R adj 2 = 0.48, p < 0.001). Conclusions: In average, blood spends 1 to 3 beats inside the LV with very low shear stress rates. The apical region is the most prone to blood stasis, particularly in mid-aged adults. The washout of blood in the normal LV is age-dependent due to physiological changes in the degree of apical penetration of the filling waves.
Collapse
Affiliation(s)
- Yolanda Benito
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón and CIBERCV, Madrid, Spain
| | - Pablo Martinez-Legazpi
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón and CIBERCV, Madrid, Spain
| | - Lorenzo Rossini
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA, United States
| | - Candelas Pérez del Villar
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón and CIBERCV, Madrid, Spain
| | - Raquel Yotti
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón and CIBERCV, Madrid, Spain
| | - Yolanda Martín Peinador
- Centro de Salud Goya, Dirección Asistencial Centro, Atención Primaria de Madrid, Madrid, Spain
| | - Daniel Rodríguez-Pérez
- Department of Mathematical Physics and Fluids, Facultad de Ciencias, Universidad Nacional de Educación a Distancia, Madrid, Spain
| | - M. Mar Desco
- Department of Mathematical Physics and Fluids, Facultad de Ciencias, Universidad Nacional de Educación a Distancia, Madrid, Spain
| | - Constancio Medrano
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón and CIBERCV, Madrid, Spain
| | - Jose Carlos Antoranz
- Department of Mathematical Physics and Fluids, Facultad de Ciencias, Universidad Nacional de Educación a Distancia, Madrid, Spain
| | - Francisco Fernández-Avilés
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón and CIBERCV, Madrid, Spain
| | - Juan C. del Álamo
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA, United States
- Institute for Engineering in Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Javier Bermejo
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón and CIBERCV, Madrid, Spain
| |
Collapse
|
10
|
Vu V, May-Newman K. Bileaflet Prosthesis Design and Orientation Affect Fluid Shear, Residence Time, and Thrombus Formation. J Cardiothorac Vasc Anesth 2019; 33:2870-2872. [PMID: 31060942 DOI: 10.1053/j.jvca.2019.03.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 03/08/2019] [Accepted: 03/09/2019] [Indexed: 11/11/2022]
Abstract
The orientation and design of bileaflet valve prosthesis in the mitral position affects the intraventricular blood flow and exposure to shear. The combination of the anatomic orientation and a small gap size of the St. Jude Medical valve produces an increase in shear exposure and blood residence time, which both predispose the formation of thrombus in the high shear gaps of the valve hinges.
Collapse
Affiliation(s)
- Vi Vu
- Bioengineering Program, Dept. of Mechanical Engineering, San Diego State University, San Diego, CA
| | - Karen May-Newman
- Bioengineering Program, Dept. of Mechanical Engineering, San Diego State University, San Diego, CA.
| |
Collapse
|