In vitro stress measurements in the vicinity of six mechanical aortic valves using hot-film anemometry in steady flow

Hasenkam, J. Michael; Westphal, D.; Nygaard, Hans; Reul, H.; Giersiepen, M; Stødkilde‐Jørgensen, Hans

doi:10.1016/0021-9290(88)90174-1

Cited by 18 publications

(5 citation statements)

References 27 publications

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“…RNS has earlier been shown in vitro to be correlated to turbulent shear stress (TSS) according to the following formula: TSS ¼ 1 2 nRNS (Nygaard et al, 1990). The method is a perivascular approach and is less invasive than hot film anemometry which has earlier been used for turbulence measurements (Nygaard et al, 1990;Hasenkam et al, 1988bHasenkam et al, , 1989. However, the method is still invasive and can only be performed during open cardiac surgery.…”

Section: Discussionmentioning

confidence: 98%

Turbulence downstream of subcoronary stentless and stented aortic valves

Funder

Frost

Wierup

et al. 2011

Journal of Biomechanics

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Section: Discussionmentioning

confidence: 98%

Turbulence downstream of subcoronary stentless and stented aortic valves

Funder

Frost

Wierup

et al. 2011

Journal of Biomechanics

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“…In the literature it is possible to find reports in which different measurement techniques have been employed to obtain the velocity field passing through the heart valve prosthesis. The laser Doppler anemometer (LDA) (1), the hot‐wire anemometer (HWA) (2), pulsed Doppler ultrasound (PDU) (3,4), and particle image velocimetry (PIV) (5) are the most advanced techniques employed for studying an artificial heart valve prosthesis. Depending on the technique, the flow pattern may be observed in transversal planes (orthogonal to the main flow direction) when LDA, HWA, or PDU is the chosen technique or, in contrast, in axial planes (parallel to the main flow direction) when PIV is employed.…”

mentioning

confidence: 99%

Particle Image Velocimetry for Flow Analysis in Longitudinal Planes across a Mechanical Artificial Heart Valve

2004

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In the last decades a great number of in vitro studies have been conducted to improve the design and to understand the transvalvular flow patterns under steady-state and pulsating flow conditions. Steady-state tests are useful for studying the flow established upstream and downstream of the valve prosthesis in different flow conditions and, in particular, at the peak flow rate. In the present study, the particle image velocimetry (PIV) technique is employed to visualize the flow patterns in a precommercial model of a bi-leaflet mechanical heart valve prosthesis in a steady-state flow regime. The use of the PIV technique and a convenient test rig provide good conditions with which to investigate the whole flow field upstream and downstream of the valve. Velocity and vorticity maps are obtained for the flow passing through the prosthesis in different axial planes. A new and simple solution for the measurement test chamber is proposed. This innovative approach of observing the flow in staggered planes (other than diametrical planes) allows a flow analysis to be performed upstream and downstream of the valve in regions near the tube wall where it has the maximum potential for injury of the vessel's inner cell layer.

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“…The most popular and frequently implanted among this family of valves is the mechanical heart valve because of its durability. However, it suffers a major drawback due to its vulnerability to blood coagulation resulting in valve related complications such as haemolysis, platelet activation and thromboembolic events [3]. This shortcoming has been attributed to the complex flow pattern and turbulent flow that characterizes the flow downstream of this artificial heart valve [4].…”

Section: Introductionmentioning

confidence: 99%

“…The first prosthetic heart valve implant of this valve was preformed in 1960, and ever since, attention has been drawn to the study of flow dynamics past such valves and to the investigation of related physiological complications. Among the methods used to study are pulse Doppler ultrasound, laser Doppler anemometry, hot wire-film anemometry, and numerical methods such as computational fluid dynamics [CFD] [3,5]. Recently, particle image velocimetry (PIV) [6] and particle tracking velocimetry [7] were used in in vitro studies of flow dynamics downstream of prosthetic valves.…”

Section: Introductionmentioning

confidence: 99%

MRI: a tool for measuring turbulent intensities in flow systems

Adegbite¹,

Kadem²,

Newling³

2011

Environmental Health and Biomedicine

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Understanding the fluid-structure interaction and fluid dynamics downstream of an obstruction is crucial in the design and fabrication of devices that find application in both medicine and industry. It is known that the fluid flow patterns downstream of an obstruction may be very complex and are three dimensional, including the formation of vortices, recirculating flow, flow separation and the onset of turbulence. The development of any such pattern of flow might be detrimental to the optimal performance of the flow system. In this work we have used the magnetic resonance imaging (MRI) technique to investigate flow dynamics downstream of an artificial heart valve. MRI is a naturally threedimensional, non-invasive technique that finds application in clinical, biomedical research and materials research. It has the capability to visualize the internal structure of materials and also to quantify mass transport properties. In this in vitro study, we have measured the turbulent diffusivity and velocity downstream of the valve in two configurations (fully opened and partially opened). Our particular implementation of the MRI measurement (known as SPRITE imaging) is unusually robust to fast turbulent flows and has been demonstrated effective at Reynolds numbers on the order 10 5 , much higher than possible with most conventional, clinical MRI techniques. The results showed a low turbulent diffusivity downstream of the fully opened valve configuration, while the turbulent diffusivity is higher downstream of the partially opened valve coupled with a high-velocity fluid jet and recirculating flow. There are distinct differences between the downstream velocity profiles of the two configurations, which have diagnostic implications.

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In vitro stress measurements in the vicinity of six mechanical aortic valves using hot-film anemometry in steady flow

Cited by 18 publications

References 27 publications

Turbulence downstream of subcoronary stentless and stented aortic valves

Turbulence downstream of subcoronary stentless and stented aortic valves

Particle Image Velocimetry for Flow Analysis in Longitudinal Planes across a Mechanical Artificial Heart Valve

MRI: a tool for measuring turbulent intensities in flow systems

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