Free emboli formation in the wake of bi-leaflet mechanical heart valves and the effects of implantation techniques

Bluestein, Danny; Li, Y.M.; Krukenkamp, Irvin B.

doi:10.1016/s0021-9290(02)00093-3

Cited by 101 publications

(89 citation statements)

References 24 publications

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“…This phase in the flow cycle was chosen because during deceleration a turbulent jet develops through the valve orifices, followed by a wake of shed vortices, which entrain and activate platelets, and perhaps contribute to the formation of free emboli. 1,2 At low shear rates, such as occur in the recirculation zones and the shed vortices in the valve's wake, the nonNewtonian properties of blood may overwhelm its Newtonian properties. Accordingly, the blood was modeled as a non-Newtonian viscoelastic fluid with a density of 1.2 g/ml and a yield shear of 0.1 s −1 .…”

Section: Computational Fluid Dynamicsmentioning

confidence: 99%

“…Briefly, the cumulative effect of shear stress (τ ) and exposure time ( t) was computed by summation of the product of their instantaneous absolute values in each computational node along the platelet path, i.e., (τ × t). 1 The total stress, laminar plus turbulent, was computed using the Boussinesq approximation 12 and multiplied by the instantaneous exposure time to this stress ( t i ), according to the following formulation:…”

Section: Computational Fluid Dynamicsmentioning

confidence: 99%

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Flow-Induced Platelet Activation in Bileaflet and Monoleaflet Mechanical Heart Valves

Yin

Alemu

Affeld

et al. 2004

Annals of Biomedical Engineering

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Abstract-A study was conducted to measure in vitro the procoagulant properties of platelets induced by flow through Carbomedics bileaflet and Bjork-Shiley monoleaflet mechanical heart valves (MHVs). Valves were mounted in a left ventricular assist device, and platelets were circulated through them under pulsatile flow. Platelet activation states (PAS) were measured during circulation using a modified prothrombinase method. Computational fluid dynamics (CFD) simulations of turbulent, transient, and nonNewtonian blood flow patterns generated by the two valve designs were done using the Wilcox k − ω turbulence model, and platelet shear-stress histories (the integral of shear-stress exposure with respect to time) through the two MHVs were calculated. PAS measurements indicated that the bileaflet MHV activated platelets at a rate more than twice that observed with the monoleaflet MHV. Turbulent flow patterns were evident in CFD simulations for both valves, and corroborated the PAS observations, showing that, for particles close to the leaflet(s), shear-stress exposure in the bileaflet MHV can be more than four times that in the monoleaflet valve.

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Section: Computational Fluid Dynamicsmentioning

confidence: 99%

Section: Computational Fluid Dynamicsmentioning

confidence: 99%

Flow-Induced Platelet Activation in Bileaflet and Monoleaflet Mechanical Heart Valves

Yin

Alemu

Affeld

et al. 2004

Annals of Biomedical Engineering

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“…In vitro studies have shown that valves with different orientations and designs vary with regard to their valve outlet configuration, downstream turbulence, and rate of embolization. 28,29 It is therefore reasonable to suppose that the design of MHVs is important for both the degree of cavitation and platelet activation. MHVs with a high local shear stress may lead to both the stabilization of gas bubbles and the promotion of inflammation, which may contribute to the formation of solid emboli.…”

Section: Discussionmentioning

confidence: 99%

Solid Cerebral Microemboli and Cerebrovascular Symptoms in Patients With Prosthetic Heart Valves

Skjelland

Michelsen

Brosstad

et al. 2008

Stroke

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Background and Purpose-Although cerebral microemboli are often detected by transcranial Doppler ultrasonography in mechanical heart valve patients, the clinical significance of such microemboli is unclear. The aim of this study was to determine the frequency and composition of cerebral microemboli in a prosthetic heart valve population and to correlate these findings to cerebrovascular symptoms, blood inflammation, and coagulation parameters. Methods-Seventy-six consecutive patients with a total of 81 prosthetic (54 mechanical, 27 biologic) heart valves were monitored for cerebral microemboli by multifrequency transcranial Doppler ultrasonography 1 year after valve replacement. Cerebrovascular events in the first year were recorded by a neurologist. Inflammation and coagulation markers were measured by immunoassays. Results-Microemboli were detected in mechanical heart valve patients only (28 patients, 56%). Twelve percent were solid, occurring in 17 (34%) of the mechanical heart valve population. The presence of solid cerebral microemboli was the only variable that was associated with cerebrovascular symptoms after a final regression analysis (Pϭ0.026). The plasma monocyte chemotactic protein-1 level was raised in patients with solid microemboli (Pϭ0.014). Conclusions-Solid cerebral microemboli were detected by multifrequency transcranial Doppler ultrasonography in 35% of a mechanical heart valve population, and the frequency was higher in patients who experienced cerebrovascular events during the first year after valve replacement. The results suggest that the detection of solid cerebral microemboli may be helpful in predicting the risk of ischemic stroke in mechanical heart valve patients.

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“…Secondly, regions of flow separation, recirculation, and stagnation promote the deposition of damaged blood cells and increase the formation of thrombi (Yoganathan et al, 2004). Finally, the shear layers surrounding the leaflets and the wake also expose the platelets to elevated shear stresses and lead them towards entrapment in the shed vortices of the wake (Bluestein et al, 2002). Several studies used numerical methods to calculate the accumulated platelet activation when the blood flows through a BMHV.…”

Section: Blood Damage and Bmhvsmentioning

confidence: 99%

“…Several studies used numerical methods to calculate the accumulated platelet activation when the blood flows through a BMHV. In the past, the valve leaflets were kept in a fixed position throughout the cardiac cycle due to the computational cost (Bluestein et al, 2002;Alemu et al, 2007;Dumont et al, 2005Dumont et al, , 2007. More recently, however, Morbiducci et al (2009) combined numerical FSI simulations with a numerical blood damage model.…”

Section: Blood Damage and Bmhvsmentioning

confidence: 99%

State-Of-The-Art Methods for the Numerical Simulation of Aortic BMHVs

Annerel¹,

Claessens²,

Ransbeeck³

et al. 2011

Aortic Valve

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Free emboli formation in the wake of bi-leaflet mechanical heart valves and the effects of implantation techniques

Cited by 101 publications

References 24 publications

Flow-Induced Platelet Activation in Bileaflet and Monoleaflet Mechanical Heart Valves

Flow-Induced Platelet Activation in Bileaflet and Monoleaflet Mechanical Heart Valves

Solid Cerebral Microemboli and Cerebrovascular Symptoms in Patients With Prosthetic Heart Valves

State-Of-The-Art Methods for the Numerical Simulation of Aortic BMHVs

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