Velocity and turbulence measurements past mitrial valve prostheses in a model left ventricle

doi:10.1016/0021-9290(91)90288-X

Journal of Biomechanics

Volume 24, Issue 7, 1991, Pages 549-562

https://doi.org/10.1016/0021-9290(91)90288-X Get rights and content

Abstract

Thrombogenesis and hemolysis have both been linked to the flow dynamics past heart valve prostheses. To learn more about the particular flow dynamics past mitral valve prostheses in the left ventricle under controlled experimental conditions, an in vitro study was performed. The experimental methods included velocity and turbulent shear stress measurements past caged-ball, tilting disc, bileaflet, and polyurethane trileaflet mitral valves in an acrylic rigid model of the left ventricle using laser Doppler anemometry. The results indicate that all four prosthetic heart valves studied create at least mildly disturbed flow fields. The effect of the left ventricular geometry on the flow development is to produce a stabilizing vortex which engulfs the entire left ventricular cavity, depending on the orientation of the valve. The measured turbulent shear stress magnitudes for all four valves did not exceed the reported value for hemolytic damage. However, the measured turbulent shear stresses were near or exceeded the critical shear stress reported in the literature for platelet lysis, a known precursor to thrombus formation.

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Cited by (34)

In vitro hemodynamic assessment of a novel polymeric transcatheter aortic valve
2019, Journal of the Mechanical Behavior of Biomedical Materials
Citation Excerpt :
In the deceleration phase, it is clear that the HA-TAV begins to close sooner after reaching max opening than the two tissue valves, as seen by the sudden diminishing of distance between shear layers (jet width) at this time point. RSS magnitudes have an important role in determining the biocompatibility of a valve prosthesis because they can indicate regions of probable platelet activation from turbulent fluctuations of the blood velocity (Giersiepen et al., 1990; Hanle et al., 1987; Jones, 1995; Schoephoerster and Chandran, 1991; Nygaard et al., 1992). Previous in vitro studies attempted to set some thresholds that mark the onset of platelet activation (Hatoum et al., 2018d).
Transcatheter aortic valve replacement (TAVR) is a life-saving alternative to surgical intervention. However, the identification of features associated with poor outcomes, including residual paravalvular leakage (PVL), leaflet calcification, and subclinical leaflet thrombosis, are cause to be concerned about valve durablilty (Mylotte and Piazza, 2015a, 2015b; Dasi et al., 2017; Makkar et al., 2015; Kheradvar et al., 2015a). The aim of this study is to optimize the potential of a hyaluronan (HA) enhanced polymeric transcatheter aortic valve (HA-TAV) that has promised to reduce blood damage causing-turbulent flow while maintaining durability. HA-enhanced linear low-density polyethylene (LLDPE) leaflets were sutured to novel cobalt chromium stents, size 26 mm balloon expandable stents. Hemodynamic performance was assessed in a left heart simulator under physiological pressure and flow conditions and compared to a 26 mm Medtronic Evolut and 26 mm Edwards SAPIEN 3. High-speed imaging and particle image velocimetry (PIV) were performed. The HA-TAV demonstrated an effective orifice area (EOA) within one standard deviation of the leading valve, SAPIEN 3.The regurgitant fraction (RF) of the HA-TAV (11.23 ± 0.55%) is decreased in comparison the Evolut (15.74 ± 0.73%) and slightly higher than the SAPIEN 3 (10.92 ± 0.11%), which is considered trace regurgitation according to valve standards. A decreased number of higher principal Reynolds shear stresses were shown for the HA-TAV at each cardiac phase. The HA-TAV is directly comparable and in some cases superior to the leading commercially available prosthetic heart valves in in-vitro hemodynamic testing.
Transvalvular flow
2019, Principles of Heart Valve Engineering
In fluid dynamics, flow through the heart valves is considered a highly complex phenomenon due to the spatial and temporal dependency of the events. Heart valves’ prime duty is to ensure the one-way direction of the flow. However, regurgitant flow can occur to different degrees during heart valve disease. Alternatively, narrowing of the valve orifice can generate adverse flow field in the heart. Leonardo Da Vinci was the first to expect the flow through the aortic valve and portrayed leaflets being closed due to a vortex ring formed at the sinuses of Valsalva. Owing to the advances in medical imaging and computational sciences, flow through different heart valves can presently be studied with acceptable confidence. This chapter discusses the flow through different heart valves and reviews the current state of the art related to transvalvular flow.
An in vitro evaluation of turbulence after transcatheter aortic valve implantation
2018, Journal of Thoracic and Cardiovascular Surgery
Citation Excerpt :
In a flexible medium, flow waves tend to be stabilized when the boundary has a compliant response to them but it was found that the effect of internal friction in the flexible medium might be destabilizing.51,52 The importance of RSS arises from its connection to platelet activation and its account of the turbulent fluctuations of the blood velocity.18-22 Reynolds stress is produced when fluid particles decelerate or accelerate while changing direction.22
This study aimed at assessment of post-transcatheter aortic valve (TAV) replacement hemodynamics and turbulence when a same-size SAPIEN 3 (Edwards Lifesciences Corp, Irvine, Calif) and Medtronic Evolut (Minneapolis, Minn) were implanted in a rigid aortic root with physiological dimensions and in a representative root with calcific leaflets obtained from patient computed tomography scans.
TAV hemodynamics were studied by placing a SAPIEN 3 26-mm and an Evolut 26-mm in rigid aortic roots and representative root with calcific leaflets under physiological conditions. Hemodynamics were assessed using high-fidelity particle image velocimetry and high-speed imaging. Transvalvular pressure gradients (PGs), pinwheeling indices, and Reynolds shear stress (RSS) were calculated.
(1) PGs obtained with the Evolut and the SAPIEN 3 were comparable among the different models (10.5 ± 0.15 mm Hg vs 7.76 ± 0.083 mm Hg in the rigid model along with 13.9 ± 0.19 mm Hg vs 5.0 ± 0.09 mm Hg in representative root with calcific leaflets obtained from patient computed tomography scans respectively); (2) more pinwheeling was found in the SAPIEN 3 than the Evolut (0.231 ± 0.057 vs 0.201 ± 0.05 in the representative root with calcific leaflets and 0.366 ± 0.067 vs 0.122 ± 0.045 in the rigid model); (3) higher rates of RSS were found in the Evolut (161.27 ± 3.45 vs 122.84 ± 1.76 Pa in representative root with calcific leaflets and 337.22 ± 7.05 vs 157.91 ± 1.80 Pa in rigid models). More lateral fluctuations were found in representative root with calcific leaflets.
(1) Comparable PGs were found among the TAVs in different models; (2) pinwheeling indices were found to be different between both TAVs; (3) turbulence patterns among both TAVs translated according to RSS were different. Rigid aortic models yield more conservative estimates of turbulence; (4) both TAVs exhibit peak maximal RSS that exceeds platelet activation 100 Pa threshold limit.
Stented valve dynamic behavior induced by polyester fiber leaflet material in transcatheter aortic valve devices
2018, Journal of the Mechanical Behavior of Biomedical Materials
Citation Excerpt :
Regarding the upward oriented jet in the DS-RT TAV and also relating the opening imaging dynamics to the orientation of the shear layers, the bottom leaflet occupies around 50% of the circular valve area making it harder for the flow to maintain it fully open at all times thus generating an upward oriented jet. The importance of RSS arises from its connection to platelet activation and its account of the turbulent fluctuations of the blood velocity (Giersiepen et al., 1990a; Hanle et al., 1987; Hatoum et al., 2018d; Jones, 1995; Nygaard et al., 1992; Schoephoerster and Chandran, 1991). Reynolds stress is produced when fluid particles decelerate or accelerate while changing direction (Jones, 1995).
This study aims at assessing the global dynamic behavior, elastic deformability, closing energy and turbulence of rigid versus deformable stented (RS vs DS) valve systems with deformable and rigid textile materials (DT vs RT) through studying the stent-valve interaction compared to a bioprosthetic material in transcatheter aortic valves (TAV).
Three 19 mm stented textile TAV designs (RS-DT, RS-RT and DS-RT) with different stent and leaflet properties were tested and compared with a control bioprosthetic TAV (RS-DB) in a left heart simulator flow loop under physiological pressure and flow. Particle Image Velocimetry and high speed imaging were performed. Pressure gradients (PG), leakage fractions (LF), Pinwheeling indices (PI), closing energy (E) and Reynolds shear stresses (RSS) were calculated.
(a) PGs and LFs were 11.86 ± 0.51 mmHg, 11.70 ± 0.34%; 8.84 ± 0.40 mmHg, 29.80 ± 0.76%; 11.59 ± 0.12 mmHg, 14.23 ± 1.64%; and 7.05 ± 0.09 mmHg, 12.08 ± 0.45% % for RS-DB, RS-DT, RS-RT and DS-RT respectively. (b) PIs were 15.79 ± 2.34%, 4.36 ± 0.84%, 2.47 ± 0.51% and 2.03 ± 0.33% for RS-DB, RS-DT, RS-RT and DS-RT respectively. (c) E is lowest for DS-RT (0.0010 ± 0.0002 J) followed by RS-RT (0.0017 ± 0.0002 J), RS-DB (0.0023 ± 0.0004 J) and highest with RS-DT (0.0036 ± 0.0007 J). (d) At peak systole lowest RSS was obtained with RS-DT (87.82 ± 0.58 Pa) and highest with DS-RT (122.98 ± 1.87 Pa).
PGs, LFs, PIs and E were improved with DS-RT compared to other textile TAVs and RS-DB. Despite achieving more RSS than the rest of TAVs, DS-RT still falls within the same range of RSS produced by the other 2 valves and control exceeding the threshold for platelet activation.
High-speed visualization of disturbed pathlines in axial flow ventricular assist device under pulsatile conditions
2015, Journal of Thoracic and Cardiovascular Surgery
To investigate potentially prothrombotic flow patterns within an axial flow ventricular assist device under clinically relevant pulsatile hemodynamic conditions.
A transparent replica of the HeartMate-II left ventricular assist device (Thoratec, Pleasanton, Calif) was visualized using a high speed camera at both low and high frame rates (125 and 3000 fps). Three steady-state conditions were studied: nominal (4.5 lpm), low flow (3.0 lpm), and high flow (6.0 lpm). Time-varying conditions were introduced with an external pulsatile pump that modulated the flow rate by approximately ±50% of the mean, corresponding to a pulsatility index of 1.0.
At nominal and high flow rates, the path lines within the upstream region were generally stable, well attached, and streamlined. As the flow rate was reduced below 3.8 lpm, a rapid transition to a chaotic velocity field occurred, exhibiting a large toroidal vortex adjacent to the upstream bearing. The pathlines in the downstream stator section were consistently chaotic for all hemodynamic conditions investigated. It was common to observe tracer particles trapped within recirculation bubbles and drawn retrograde, causing repeated contact with the bearing surfaces. The addition of pulsatility caused the flow field to become periodically chaotic during the diastolic portion of the cardiac cycle depending on the instantaneous flow rate and acceleration.
The contribution of pulsatility by the native heart may induce a periodic disturbance to an otherwise stable flow field within an axial flow ventricular assist device, particularly during the diastolic and decelerating portion of the cardiac cycle. Potentially prothrombotic flow features were found to occur periodically in the region of the upstream bearing.
Left ventricular flow patterns in healthy subjects and patients with prosthetic mitral valves: An in vivo study using echocardiographic particle image velocimetry
2010, Journal of Thoracic and Cardiovascular Surgery
Citation Excerpt :
To what extent this might counterbalance the disadvantages of this type of valve replacement therapy remains to be determined. It has been assumed based on numeric simulations and in vitro and in vivo experiments, as well as color Doppler and MRI measurements, that prosthetic heart valves seriously disturb intraventricular flow patterns.10,19,24-32 The application of PIV to echocardiography allows, for the first time, direct visualization and, in part, quantification of those patterns and enables estimation of energy dissipation in the left ventricle by means of a noninvasive technique.
Echocardiographic particle image velocimetry is a new feature tracking–based approach to visualize and quantify left ventricular flow patterns in vivo. We investigated the potential role of this new technique by assessing vortex formations in healthy left ventricles and the effect of different types of prosthetic valves on intraventricular flow patterns and flow-mediated energy dissipation.
We examined 19 patients (mean age, 57 ± 19 years; 10 women). Nine were healthy, and 10 had prosthetic mitral valves (5 had bileaflet valves, 4 had bioprostheses, and 1 had a tilting-disc valve). Boluses of left heart contrast were administered intravenously. Echocardiographic apical views were analyzed offline by using prototype software that allowed intracavitary flow to be explored and enabled calculations of energy dissipation (relative pulsatile vorticity strength and vortex pulsation correlation) by means of particle image velocimetry.
In healthy hearts a vortex filling the entire ventricle stores the kinetic energy of the blood and smoothly redirects the blood to the outflow tract. In patients with prosthetic valves, completely different flow patterns were identified depending on the type, orientation, and position of the valves, as well as left ventricular geometry. Patients with prosthetic valves showed significantly higher left ventricular energy dissipation than healthy subjects (relative pulsatile vorticity strength, 2.4 ± 0.7 vs 1.6 ± 0.4 [P < .001]; vortex pulsation correlation, 1.2 ± 0.5 vs 0.7 ± 0.2 [P < .001]).
Echocardiographic particle image velocimetry is feasible. It clearly distinguishes flow patterns in healthy hearts from those in hearts with different types of prosthetic valves. Echocardiographic particle image velocimetry offers new insights into cardiac function and might be of importance to optimize valve replacement therapy.

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Journal of Biomechanics

Abstract

References (23)

Laser anemometry measurements of pulsatile flow past aortic valve prostheses

J. Biomechanics

Pulsatile flow past aortic valve bioprostheses in a model human aorta

J. Biomechanics

In vitro pulsatile flow velocity and shear stress measurements in the vicinity of mechanical mitral heart valve prosthesis

J. Biomechanics

Thromboembolic complications of prosthetic valves

Cardiovasc. Clinics

Mean flow velocity patterns within a ventricular assist device

ASAIO Trans.

In vitro comparison of velocity profiles and turbulent shear distal to polyurethane trileaflet and pericardial prosthetic valves

Artif. Organs

Effect of prosthetic mitral valve geometry and orientation on flow dynamics in a model human ventricle

J. Biomechanics

Rheological approach to thrombosis and atherosclerosis

Angiology

Experimental investigation of the turbulent flow development in the entrance region of a curved tube using laser anemometry

Shear induced aggregation and lysis of platelets

Trans. ASAIO

Evaluation of prosthetic heart valves by Doppler flow imaging

Echocardiography

Cited by (34)

In vitro hemodynamic assessment of a novel polymeric transcatheter aortic valve

Transvalvular flow

An in vitro evaluation of turbulence after transcatheter aortic valve implantation

Stented valve dynamic behavior induced by polyester fiber leaflet material in transcatheter aortic valve devices

High-speed visualization of disturbed pathlines in axial flow ventricular assist device under pulsatile conditions

Left ventricular flow patterns in healthy subjects and patients with prosthetic mitral valves: An in vivo study using echocardiographic particle image velocimetry