Tomographic PIV behind a prosthetic heart valve

Hasler, David; Landolt, Andrin; Obrist, Dominik

doi:10.1007/s00348-016-2158-0

Cited by 22 publications

(12 citation statements)

References 37 publications

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“…More details on the technical protocol for the TOMO PIV measurements, e.g. calibration procedure and image post-processing, are reported in earlier work by the authors [ 25 ].…”

Section: Methodsmentioning

confidence: 99%

Three-dimensional flow structures past a bio-prosthetic valve in an in-vitro model of the aortic root

Hasler

Obrist

2018

PLoS ONE

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The flow field past a prosthetic aortic valve comprises many details that indicate whether the prosthesis is functioning well or not. It is, however, not yet fully understood how an optimal flow scenario would look, i.e. which subtleties of the fluid dynamics in place are essential regarding the durability and compatibility of a prosthetic valve. In this study, we measured and analyzed the 3D flow field in the vicinity of a bio-prosthetic heart valve in function of the aortic root size. The measurements were conducted within aortic root phantoms of different size, mounted in a custom-built hydraulic setup, which mimicked physiological flow conditions in the aorta. Tomographic particle image velocimetry was used to measure the 3D instantaneous velocity field at various instances. Several 3D fields (e.g. instantaneous and mean velocity, 3D shear rate) were analyzed and compared focusing on the impact of the aortic root size, but also in order to gain general insight in the 3D flow structure past the bio-prosthetic valve. We found that the diameter of the aortic jet relative to the diameter of the ascending aorta is the most important parameter in determining the characteristics of the flow. A large aortic cross-section, relative to the cross-section of the aortic jet, was associated with higher levels of turbulence intensity and higher retrograde flow in the ascending aorta.

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“…More details on the technical protocol for the TOMO PIV measurements, e.g. calibration procedure and image post-processing, are reported in earlier work by the authors [ 25 ].…”

Section: Methodsmentioning

confidence: 99%

Three-dimensional flow structures past a bio-prosthetic valve in an in-vitro model of the aortic root

Hasler

Obrist

2018

PLoS ONE

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“…We compared two CFD simulations with moving boundaries (with and without valves) to show that the fluid dynamic field in the absence of the valves (although with the same membrane motion) substantially differs from the one with valves, in terms of both global and local hemodynamics, for example, the shear rate field and velocity fields with jet-like shape. The CFD simulation without valves is a distinctive feature of biological valves, as reported in some experimental tests (34,35).…”

Section: Discussionmentioning

confidence: 99%

Numerical Approach to Study the Behavior of an Artificial Ventricle: Fluid–Structure Interaction Followed By Fluid Dynamics With Moving Boundaries

Luraghi

Castilla

et al. 2018

Artificial Organs

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Heart failure is a progressive and often fatal pathology among the main causes of death in the world. An implantable total artificial heart (TAH) is an alternative to heart transplantation. Blood damage quantification is imperative to assess the behavior of an artificial ventricle and is strictly related to the hemodynamics, which can be investigated through numerical simulations. The aim of this study is to develop a computational model that can accurately reproduce the hemodynamics inside the left pumping chamber of an existing TAH (Carmat‐TAH) together with the displacement of the leaflets of the biological aortic and mitral valves and the displacement of the pericardium‐made membrane. The proposed modeling workflow combines fluid–structure interaction (FSI) simulations based on a fixed grid method with computational fluid dynamics (CFD). In particular, the kinematics of the valves is accounted for by means of a dynamic mesh technique in the CFD. The comparison between FSI‐ and CFD‐calculated velocity fields confirmed that the presence of the valves in the CFD model is essential for realistically mimicking blood dynamics, with a percentage difference of 2% during systole phase and 13% during the diastole. The percentage of blood volume in the CFD simulation with a shear stress above the threshold of 50 Pa is less than 0.001%. In conclusion, the application of this workflow to the Carmat‐TAH provided consistent results with previous clinical studies demonstrating its utility in calculating local hemodynamic quantities in the presence of complex moving boundaries.

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“…Out of 752 patients from children to young adults [38], the S/D ratio ranges from 0.397 to 1.62, with a mean of 0.995 ± 0.23. Therefore, based on this clinical evidence, a 1:1 ratio sinusoidal wave (50% systole) has been used in many previous fluid dynamic studies [29,30]. In all of these tests, the heart rate was fixed at 60 beats per minute (bpm), i.e., one second between two heartbeats, to enable a better synchronization between the pump and the laser system.…”

Section: Test Conditionsmentioning

confidence: 99%

“…According to Trip et al [42], when the mean Re is above 2500, the turbulent statistics of the pulsatile pipe flow become almost independent of Re and Wo. Therefore, many similar research studies using a moderately lower Re between 3000-4500 have all successfully captured the major characteristics of the pulsatile flow [25,29,43]. To evaluate the structure deformation under the pulsatile flow, two parameters, i.e., the area strain (AS) and geometric orifice area (GOA) were analyzed by digitizing the phase-averaged PIV raw images.…”

Section: Test Conditionsmentioning

confidence: 99%

“…In in vitro experimental studies, Leo et al [28] assessed the fluid dynamic characteristics downstream of polymeric prosthetic valves through PIV measurements. Hasler et al [29] performed tomographic PIV measurements on the pulsatile flow downstream of a negatively molded silicone aortic root model. Aortic valves with native tissues leaflets have also been studied through in vitro experiments to understand the changes in hemodynamics induced by morphological abnormalities, such as bicuspid aortic valves.…”

Section: Introductionmentioning

confidence: 99%

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An Experimental Study of Pulsatile Flow in a Compliant Aortic Root Model under Varied Cardiac Outputs

Zhang

2018

Fluids

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The fluid dynamics of a natural aortic valve are complicated due to the highly pulsatile flow conditions, the compliant wall boundaries, and the sophisticated geometry of the aortic root. In the present study, a pulsatile flow simulator was constructed and utilized to investigate the turbulent characteristics and structural deformation of an intact silicone aortic root model under different flow inputs. Particle image velocimetry and high-frequency pressure sensors were combined to gather the pulsatile flow field information. The results demonstrated the distributions and the variations of the jet flow structures at different phases of a cardiac cycle. High turbulence kinetic energy was observed after the peak systole phase when the flow started to decelerate. Deformations of the aortic root upstream and downstream of the valve leaflets under normal boundary conditions were summarized and found to be comparable to results from clinical studies. The cardiac output plays an important role in determining the strength of hemodynamic and structural responses. A reduction in cardiac outputs resulted in a lower post-systole turbulence, smaller circumferential deformation, a smaller geometric orifice area, and a shortened valve-opening period.

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Tomographic PIV behind a prosthetic heart valve

Cited by 22 publications

References 37 publications

Three-dimensional flow structures past a bio-prosthetic valve in an in-vitro model of the aortic root

Three-dimensional flow structures past a bio-prosthetic valve in an in-vitro model of the aortic root

Numerical Approach to Study the Behavior of an Artificial Ventricle: Fluid–Structure Interaction Followed By Fluid Dynamics With Moving Boundaries

An Experimental Study of Pulsatile Flow in a Compliant Aortic Root Model under Varied Cardiac Outputs

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