The influence of the leaflets’ curvature on the flow field in two bileaflet prosthetic heart valves

Grigioni, Mauro; Daniele, C.; D’Avenio, Giuseppe; Barbaro, V.

doi:10.1016/s0021-9290(00)00240-2

Cited by 48 publications

(42 citation statements)

References 19 publications

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“…The kinematics of this prosthesis is such that the leaflets always occupy part of the mitral channel, even when the valve is fully open (figure 23c), and this is a crucial difference with respect to the natural and biological prosthetic valves in which the flow pushes the flexible leaflets towards the channel boundary leaving the orifice completely clear ( figure 23a,b) of the valve. This produces augmented mechanical stresses on the corpuscular part of the blood which cause red blood cell damage (haemolysis) and platelet activation (Grigioni et al 2001). These phenomena both contribute to the formation of clots, whose aggregation is countered by a lifelong anticoagulant therapy, which, in turn, increases the risks of bleeding and haemorrhagic events.…”

Section: Pathological Ventricle With Natural Valvementioning

confidence: 99%

Flow structure in healthy and pathological left ventricles with natural and prosthetic mitral valves

Meschini

Tullio²,

Querzoli

et al. 2017

J. Fluid Mech.

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In this paper, the structure and the dynamics of the flow in the left heart ventricle are studied for different pumping efficiencies and mitral valve types (natural, biological and mechanical prosthetic). The problem is investigated by direct numerical simulation of the Navier-Stokes equations, two-way coupled with a structural solver for the ventricle and mitral valve dynamics. The whole solver is preliminarily validated by comparisons with ad hoc experiments. It is found that the system works in a highly synergistic way and the left ventricular flow is heavily affected by the specific type of mitral valve, with effects that are more pronounced for ventricles with reduced pumping efficiency. When the ventricle ejection fraction (ratio of the ejected fluid volume to maximum ventricle volume over the cycle) is within the physiological range (50 %-70 %), regardless of the mitral valve geometry, the mitral jet sweeps the inner ventricle surface up to the apex, thus preventing undesired flow stagnation. In contrast, for pathological ejection fractions ( 40 %), the flow disturbances introduced by the bileaflet mechanical valve reduce the penetration capability of the mitral jet and weaken the recirculation in the ventricular apex. Although in clinical practice the fatality rates in the five-year follow-ups for mechanical and biological mitral valve replacements are essentially the same, a breakdown of the deaths shows that the causes are very different for the two classes of prostheses and the present findings are consistent with the clinical data. This might have important clinical implications for the choice of prosthetic device in patients needing mitral valve replacement.

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Section: Pathological Ventricle With Natural Valvementioning

confidence: 99%

Flow structure in healthy and pathological left ventricles with natural and prosthetic mitral valves

Meschini

Tullio²,

Querzoli

et al. 2017

J. Fluid Mech.

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“…38 Thrombus formation under hemostatic conditions with potential for rapid growth after initiation is still a paramount issue even in the most advanced clinically applied devices. 16,36 A study of 1200 patients undergoing replacement with the St. Jude Medical valve revealed that the most frequent valve-related events in the early and late postoperative period were thromboembolic, including valve thrombosis associated with altered valve flow dynamics. 13 Sublytic stresses on leukocytes cause changes in cell morphology, alter cellmembrane permeability, and result in impaired chemotaxis and random migration.…”

Section: Discussionmentioning

confidence: 99%

“…16,18 In developing centrifugal blood pumps, there has been a serious problem with hemolysis at the impeller or casing edge because of flow separation and turbulence in these regions. 39 Quantification of blood component damage under turbulent flow conditions and prediction of the associated mechanical stresses will assist in optimization of prosthetic device design to minimize hemolysis and platelet activation.…”

Section: Introductionmentioning

confidence: 99%

The Cumulative and Sublethal Effects of Turbulence on Erythrocytes in a Stirred-Tank Model

et al. 2007

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Mechanical forces generated by prosthetic heart devices (artificial valves, artificial hearts, ventricular assist devices) have been known to cause damage and destruction of erythrocytes. Turbulent flow within such devices generates shear stresses and can induce cell damage. Current models of cell damage rate utilize only the power input per unit mass as a modeling parameter. A stirred-tank reactor provides for a more extensive characterization of turbulence through eddy scale calculations. Through a simplified model, turbulence can be characterized by evaluating the Kolmogorov microscale. Our analysis of erythrocyte rupture in a stirred tank reactor suggests that parameters such as eddy wavelength and eddy velocity may better characterize and model the turbulent damage. Further, hemolysis of red blood cells by turbulent effects has been shown to have a fixed rate for constant levels of power input. Damage inflicted on the remaining, intact erythrocytes (sublethal damage) was evaluated by exposure to turbulence followed by osmotic fragility (OF) testing. Logistic models were fit to the OF data indicating a significant osmotic sensitivity in the sublethal damaged population between control and turbulence-exposed cells (chi(2) test; p < 0.001). This susceptibility indicates a significant cell population more susceptible to destruction as a result of turbulent exposure. This work has therefore helped identify optimization parameters for evaluating cell damage potential when engineering cardiovascular prosthetic devices.

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“…Numerous experimental studies have been performed to investigate regions of high shear stress, and better understand the fluid mechanics downstream of an aortic BiMHV (Yoganathan et al 1982, Chandran 1985, Hanle et al 1988, 1989, Fatemi and Chandran 1989, Giersiepen et al 1989, Brucker 1997, Barbaro et al 1998, Fontaine et al 1996, Bluestein et al 2000, Browne et al 2000, Ellis et al 2000, Liu et al 2000, Grigioni et al 2001, Leo et al 2002, Balducci et al 2004, Marassi et al 2004, Ge et al 2005, Dasi et al 2007, Kaminsky et al 2007a, 2007b. Although in vivo techniques such as pulsed Doppler ultrasound (Travis et al 2004) and magnetic resonance imaging (MRI) (Hasenkam 1999) show promise, spatial resolution and accuracy are still too low for detailed flow mapping .…”

Section: Literature Reviewmentioning

confidence: 99%

“…Complex three dimensional vortex dynamics has been modelled by Dasi et al (2007), and the ability to perform inexpensive parametric studies with different valve geometries using CFD has enormous potential. Grigioni et al (2001) used 2C-LDA to compare leaflet geometry of two BiMHVs and found that leaflet curvature was an important parameter in BiMHV design. The computational resources for such simulations are significant, and only small sample sizes have been obtained (N = 10 cycles for Dasi et al 2007).…”

Section: Literature Reviewmentioning

confidence: 99%

Stereoscopic PIV of Steady Flow Through a Bileaflet Mechanical Heart Valve

Hutchison

Sullivan

Ethier

2008

ASME 2008 Summer Bioengineering Conference, Parts a and B

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The Reynolds number based on inlet diameter was 7600, and the measurement plane was perpendicular to the leaflet axes at the centerline of the aortic sinus. The typical formation of three jets was observed: the upper and lower lateral orifice jets, and the central jet. Flow separation from the valve ring was seen, and large scale vortices were identified in both the upper and lower sinus regions. An asymmetry in the reverse flow was found, and possible causes were discussed. All three jets were seen to decay similarly to free rectangular jets, with zero decay initially, followed by a 'linear' decay rate in which U max 2 ∝ X. The central jet was also seen to be self similar in the linear decay region. Analysis of the out-of-plane velocity yielded two alternate explanations of streamwise vortex (i.e. Ω x ) structure, with either a four-cell or an eight-cell streamwise vortex structure being present in the mean velocity field. Organization of large scale three dimensional flow structures was thus apparent. Calculation of in-plane Reynolds stresses showed that values were highest in the outer shear layers of the lateral orifice jets. Elevated Reynolds shear stress values were also found in the leaflet wake regions, and the shear layers of the central jet.iii

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The influence of the leaflets’ curvature on the flow field in two bileaflet prosthetic heart valves

Cited by 48 publications

References 19 publications

Flow structure in healthy and pathological left ventricles with natural and prosthetic mitral valves

Flow structure in healthy and pathological left ventricles with natural and prosthetic mitral valves

The Cumulative and Sublethal Effects of Turbulence on Erythrocytes in a Stirred-Tank Model

Stereoscopic PIV of Steady Flow Through a Bileaflet Mechanical Heart Valve

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