An In Vitro Study of the Hinge and Near-Field Forward Flow Dynamics of the St. Jude Medical® Regent™ Bileaflet Mechanical Heart Valve

Ellis, Jeffrey T.; Travis, Brandon R.; Yoganathan, Ajit P.

doi:10.1114/1.297

Cited by 44 publications

(50 citation statements)

References 10 publications

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“…Platelet activation and thrombus formation is reported to occur due to the leakage flow in the hinge region and much previous research has concentrated on this aspect. 21,27,39,53 The dimension of the hinge region is two orders of magnitude lower than the valve dimension and will need to be considered in the computational analysis.…”

Section: Limitations Of the Studymentioning

confidence: 99%

“…67 In bi-leaflet valves, thrombus formation is mostly observed in the hinge region and also on the valve housing. [19][20][21]28 It is hypothesized that the local flow conditions in these regions contribute to the thrombus formation. All the studies on bi-leaflet valves, experimental as well as computational, report flow separation and vortex shedding at the ends of the valve leaflets.…”

Section: Introductionmentioning

confidence: 99%

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Two-Dimensional Dynamic Simulation of Platelet Activation During Mechanical Heart Valve Closure

et al. 2006

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A major drawback in the operation of mechanical heart valve prostheses is thrombus formation in the near valve region. Detailed flow analysis in this region during the valve closure phase is of interest in understanding the relationship between shear stress and platelet activation. A fixed-grid Cartesian mesh flow solver is used to simulate the blood flow through a bi-leaflet mechanical valve employing a two-dimensional geometry of the leaflet with a pivot point representing the hinge region. A local mesh refinement algorithm allows efficient and fast flow computations with mesh adaptation based on the gradients of the flow field in the leaflet-housing gap at the instant of valve closure. Leaflet motion is calculated dynamically based on the fluid forces acting on it employing a fluid-structure interaction algorithm. Platelets are modeled and tracked as point particles by a Lagrangian particle tracking method which incorporates the hemodynamic forces on the particles. A platelet activation model is included to predict regions which are prone to platelet activation. Closure time of the leaflet is validated against experimental studies. Results show that the orientation of the jet flow through the gap between the housing and the leaflet causes the boundary layer from the valve housing to be drawn in by the shear layer separating from the leaflet. The interaction between the separating shear layers is seen to cause a region of intensely rotating flow with high shear stress and high residence time of particles leading to high likelihood of platelet activation in that region.

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Section: Limitations Of the Studymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Dynamic Simulation of Platelet Activation During Mechanical Heart Valve Closure

et al. 2006

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“…In BMHVs, thrombus formation presents a major concern and is mostly observed in the hinge region and the valve housing [80][81][82]. The exact mechanisms behind hemolysis and the cascade of thrombus formation as a result of platelet activation are not yet fully understood.…”

Section: Thrombus Formation and Hemolysismentioning

confidence: 99%

Mechanical Valve Fluid Dynamics and Thrombus Initiation

Claessens

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Vierendeels

et al. 2010

Image-Based Computational Modeling of the Human Circulatory and Pulmonary Systems

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Heart valve, and subsequently cardiac function, may be seriously compromised as a result of stenosis or regurgitation. If necessary, the native heart valve is surgically replaced with an artificial substitute, which is in about 40% of the cases a bileaflet mechanical heart valve (BMHV). While generally showing excellent hemodynamic performance in the short term, current BMHVs are not free of clinical complications, which are induced by thrombus formation and hemolysis. Computational fluid dynamic (CFD) modeling is now considered a powerful and extremely useful tool to investigate blood flow in existing BMHVs and to reduce the costs associated with the development of new prototypes. A prerequisite for performing realistic heart valve simulations is the implementation of a fluid-structure interaction (FSI) algorithm that accounts for the mechanical interaction between the valve leaflets and the ambient blood. Provided the numerical resolution is sufficiently high, three-dimensional CFD-FSI models are able to compute the complex flow structures that exist in the vicinity of a BMHV. In order to get information about the valve's potential for platelet activation and blood hemolysis, these CFD models must be accompanied by appropriate mathematical models that describe the relation between fluid dynamic variables and the damage to blood corpuscles. This chapter provides an overview on the state of the art in computational flow simulations in BMHV and discusses various approaches taken to integrate blood damage accumulation models into flow simulations.

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“…A detailed discussion of the hemodynamics of the three main bileaflet valve designs-namely the Medtronic Parallel, the St Jude Medical (SJM) and the CarboMedics (CM) valves-can be found in our previous papers. 19,26 These studies and others 10,11,15,19,26 characterizing the fluid mechanics of the hinge region have relied on point-wise velocity measurement techniques, such as Laser Doppler Velocimetry (LDV), and the emphasis was mainly on examining maximum velocity magnitudes and Reynolds shear stress (RSS) levels. Peak RSS levels ranging from 2600 to 8000 dyn/ cm 2 and peak velocity magnitudes from 1.52 to 3.17 m/s were reported, depending on the valve design and implant location.…”

Section: Introductionmentioning

confidence: 99%

Spatio-temporal Flow Analysis in Bileaflet Heart Valve Hinge Regions: Potential Analysis for Blood Element Damage

et al. 2007

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Point-wise velocity measurements have been traditionally acquired to estimate blood damage potential induced by prosthetic heart valves with emphasis on peak values of velocity magnitude and Reynolds stresses. However, the inherently Lagrangian nature of platelet activation and hemolysis makes such measurements of limited predictive value. This study provides a refined fluid mechanical analysis, including blood element paths and stress exposure times, of the hinge flows of a CarboMedics bileaflet mechanical heart valve placed under both mitral and aortic conditions and a St Jude Medical bileaflet valve placed under aortic conditions. The hinge area was partitioned into characteristic regions based on dominant flow structures and spatio-temporal averaging was performed on the measured velocities and Reynolds shear stresses to estimate the average bulk stresses acting on blood elements transiting through the hinge. A first-order estimate of viscous stress levels and exposure times were computed. Both forward and leakage flow phases were characterized in each partition by dynamic flows dependent on subtle leaflet movements and transvalvular pressure fluctuations. Blood elements trapped in recirculation regions may experience exposure times as long as the entire forward flow phase duration. Most calculated stresses were below the accepted blood damage threshold. Estimates of the stress levels indicate that the flow conditions within the boundary layers near the hinge and leaflet walls may be more detrimental to blood cells than bulk flow conditions, while recirculation regions may promote thrombus buildup.

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An In Vitro Study of the Hinge and Near-Field Forward Flow Dynamics of the St. Jude Medical® Regent™ Bileaflet Mechanical Heart Valve

Cited by 44 publications

References 10 publications

Two-Dimensional Dynamic Simulation of Platelet Activation During Mechanical Heart Valve Closure

Two-Dimensional Dynamic Simulation of Platelet Activation During Mechanical Heart Valve Closure

Mechanical Valve Fluid Dynamics and Thrombus Initiation

Spatio-temporal Flow Analysis in Bileaflet Heart Valve Hinge Regions: Potential Analysis for Blood Element Damage

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