The Influence of the Aortic Root Geometry on Flow Characteristics of a Prosthetic Heart Valve

Barannyk, Oleksandr; Oshkai, Peter

doi:10.1115/1.4029747

Cited by 20 publications

(18 citation statements)

References 39 publications

(39 reference statements)

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“…However, these values are based on a simple laminar profile approximation resulting in the effect of turbulence being ignored. Using particle image velocimetry (PIV) on different aortic root geometries (normal, dilated, constricted), Barannyk and Oshkai investigated the turbulence stresses and found the peak turbulence stress to be ~1200 dyne/cm 2 . Gunning et al found the similar level of turbulent stress (up to 2300 dyne/cm 2 ) from their heart valve study.…”

Section: Discussionmentioning

confidence: 99%

Stress and Exposure Time on von Willebrand Factor Degradation

Jhun

Siedlecki

et al. 2018

Artificial Organs

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Despite the prevailing use of the continuous flow left ventricular assist devices (cf-LVADs), acquired von Willebrand syndrome (AvWS) associated with cf-LVADs still remains a major complication. As AvWS is known to be dependent on shear stress ( ) and exposure time (t exp ), this study examined the degradation of high molecular weight multimers (HMWM) of von Willebrand factor (vWF) in terms of τ and t exp . Two custom apparatus, i.e., capillary-tubing-type degrader (CTD) and Taylor-Couettetype degrader (TCD) were developed for short-term (0.033 sec ≤ t exp ≤ 1.05 s) and long-term (10 s ≤ t exp ≤ 10 min) shear exposures of vWF, respectively. Flow conditions indexed by Reynolds number (Re) for CTD were 14 ≤ Re ≤ 288 with corresponding laminar stress level of 52 ≤ CTD ≤ 1042 dyne/ cm 2 . Flow conditions for TCD were 100 ≤ Re ≤ 2500 with corresponding rotor speed of 180 ≤ ω o ≤ 4000 RPM and laminar stress level of 50 ≤ TCD ≤ 1114 dyne/cm 2 . Due to transitional and turbulent flows in TCD at Re > 1117, total stress (i.e., total = laminar + turbulent) was also calculated using a computational fluid dynamics (CFD) solver, Converge CFD. Inhibition of ADAMTS13 with different concentrations of EDTA (5 mM and 10 mM) was also performed to investigate the mechanism of cleavage in terms of mechanical and enzymatic aspects. Degradation of HMWM with CTD was negligible at all given testing conditions. Although no degradation of HMWM was observed with TCD at Re < 1117 ( total = 1012 dyne/cm 2 ), an increase in degradation of HMWM was observed beyond Re of 1117 for all given exposure times. At Re ~ 2500 ( total = 3070 dyne/ cm 2 ) with t exp = 60 s, a severe degradation of HMWM (90.7 ± 3.8%, abnormal) was observed, and almost complete degradation of HMWM (96.1 ± 1.9%, abnormal) was observed with t exp = 600 s. The inhibition studies with 5 mM EDTA at Re ~ 2500 showed that loss of HMWM was negligible (<10%, normal) for all given exposure times except for t exp = 10 min (39.5 ± 22.3%, borderline-abnormal).

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Section: Discussionmentioning

confidence: 99%

Stress and Exposure Time on von Willebrand Factor Degradation

Jhun

Siedlecki

et al. 2018

Artificial Organs

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“…The peak inflow velocity was ~1.2 m/s and the density of blood was set to ρ = 1080 kg/ m 3 . The blood also was considered to be both Newtonian with the viscosity of 0.0035 kg/(m.s) and non-Newtonian based on generalized Carreau-Yasuda model [14]. This lead to an inlet peak Reynolds number…”

Section: Models and Methodsmentioning

confidence: 99%

Hemodynamics of a Bileaflet Mechanical Heart Valve with Different Levels of Dysfunction

Khalili

Ppt

2017

JABB

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Heart disease is one of leading causes of mortality worldwide. Healthy heart valves are key for proper heart function. When these valves dysfunction, a replacement is often necessary in severe cases. The current study presents an investigation of the pulsatile blood flow through a bileaflet mechanical heart valve (BMHV) where one leaflet is healthy and can fully open and the other leaflet cannot fully open with different levels of dysfunction. To better understand the implications that a dysfunctional leaflet has on the blood flow through these valves, analysis of flow characteristics such as velocity, pressure drop, wall shear stress and vorticity profiles was performed. Results suggested that leaflet dysfunction caused increased local velocities, separation regions and wall shear stresses. For example, the maximum velocity increased from 2.53 m/s to 4.9 m/s when dysfunction increased from 0% to 100%. The pressure drop increased (by up to 300%) with dysfunctionality. Results suggested that leaflet dysfunction also caused increased wall shear stresses on the valve frame where higher stresses developed around the hinges (at 75% and 100% dysfunctions). Analysis also showed that increased dysfunctionality of one leaflet led to higher net shear forces on both the healthy and dysfunctional leaflets (by up to 200% and 600%, respectively).

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“…The current computational study provides new quantitative information on blood flow characteristics, plus forces and moments acting on the leaflets of bileaflet mechanical heart valves at different levels of leaflet dysfunctionality during peak systolic flow. Model improvements compared to previous studies include: A more realistic aortic sinuses geometry (compared to References [ 41 , 42 ]), addition of the valve ring to the model (compared to References [ 43 , 44 ]), and creation of a 3-D model instead of a 2-D model (compared to References [ 2 , 13 , 45 ]). The study quantified important hemodynamic characteristics (such as principle stresses) that are not measurable using currently available standard diagnostic tools.…”

Section: Introductionmentioning

confidence: 99%

Adverse Hemodynamic Conditions Associated with Mechanical Heart Valve Leaflet Immobility

et al. 2018

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Artificial heart valves may dysfunction, leading to thrombus and/or pannus formations. Computational fluid dynamics is a promising tool for improved understanding of heart valve hemodynamics that quantify detailed flow velocities and turbulent stresses to complement Doppler measurements. This combined information can assist in choosing optimal prosthesis for individual patients, aiding in the development of improved valve designs, and illuminating subtle changes to help guide more timely early intervention of valve dysfunction. In this computational study, flow characteristics around a bileaflet mechanical heart valve were investigated. The study focused on the hemodynamic effects of leaflet immobility, specifically, where one leaflet does not fully open. Results showed that leaflet immobility increased the principal turbulent stresses (up to 400%), and increased forces and moments on both leaflets (up to 600% and 4000%, respectively). These unfavorable conditions elevate the risk of blood cell damage and platelet activation, which are known to cascade to more severe leaflet dysfunction. Leaflet immobility appeared to cause maximal velocity within the lateral orifices. This points to the possible importance of measuring maximal velocity at the lateral orifices by Doppler ultrasound (in addition to the central orifice, which is current practice) to determine accurate pressure gradients as markers of valve dysfunction.

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The Influence of the Aortic Root Geometry on Flow Characteristics of a Prosthetic Heart Valve

Cited by 20 publications

References 39 publications

Stress and Exposure Time on von Willebrand Factor Degradation

Stress and Exposure Time on von Willebrand Factor Degradation

Hemodynamics of a Bileaflet Mechanical Heart Valve with Different Levels of Dysfunction

Adverse Hemodynamic Conditions Associated with Mechanical Heart Valve Leaflet Immobility

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