Multi-Laboratory Uncertainty Analysis of PIV-Measured Flow Quantities Relevant to Blood Damage in the FDA Nozzle Model

2011 ◽  
Author(s):  
Prasanna Hariharan ◽  
Matthew Giarra ◽  
Varun Reddy ◽  
Steven W. Day ◽  
Keefe B. Manning ◽  
...  
Keyword(s):  
Heart Valves ◽  
Shear Stresses ◽  
Low Velocity ◽  
Blood Damage ◽  
Flow Parameters ◽  
Image Velocimetry ◽  
Artificial Heart Valves ◽  
Post Market ◽  
Regulatory Submissions ◽  
Measured Flow

Particle image velocimetry (PIV) has been used in regulatory submissions to the FDA for pre-clinical and post-market evaluations of flow fields in medical devices, such as artificial heart valves, blood pumps, and stents. The velocity and shear fields obtained from the PIV experiments are also used to validate computational fluid dynamics (CFD) data accompanying the submissions. However, previous studies have questioned the accuracy of PIV measurements in regions of high shear and low velocity (regions prone to hemolysis and thrombosis). Currently, there is no clear estimate of the amount of uncertainty involved in measuring various flow parameters in these high-risk regions. The objective of this study was to perform an inter-laboratory PIV study in a simplified nozzle model and quantify the uncertainties involved in measuring flow quantities relevant to blood damage, such as near-wall velocity, viscous and Reynolds shear stresses, size and velocity within recirculation regions, and for estimating an index of hemolysis.

PIV Measurements of Flow in a Centrifugal Blood Pump: Steady Flow

2004 ◽  
Vol 127 (2) ◽  
pp. 244-253 ◽  
Author(s):  
Steven W. Day ◽  
James C. McDaniel
Keyword(s):  
Shear Stress ◽  
Artificial Heart ◽  
Heart Valves ◽  
Blood Pump ◽  
Reynolds Stresses ◽  
Centrifugal Blood Pump ◽  
Flow Rates ◽  
Blood Damage ◽  
Artificial Heart Valves ◽  
Stagnant Flow

Magnetically suspended left ventricular assist devices have only one moving part, the impeller. The impeller has absolutely no contact with any of the fixed parts, thus greatly reducing the regions of stagnant or high shear stress that surround a mechanical or fluid bearing. Measurements of the mean flow patterns as well as viscous and turbulent (Reynolds) stresses were made in a shaft-driven prototype of a magnetically suspended centrifugal blood pump at several constant flow rates (3–9L∕min) using particle image velocimetry (PIV). The chosen range of flow rates is representative of the range over which the pump may operate while implanted. Measurements on a three-dimensional measurement grid within several regions of the pump, including the inlet, blade passage, exit volute, and diffuser are reported. The measurements are used to identify regions of potential blood damage due to high shear stress and∕or stagnation of the blood, both of which have been associated with blood damage within artificial heart valves and diaphragm-type pumps. Levels of turbulence intensity and Reynolds stresses that are comparable to those in artificial heart valves are reported. At the design flow rate (6L∕min), the flow is generally well behaved (no recirculation or stagnant flow) and stress levels are below levels that would be expected to contribute to hemolysis or thrombosis. The flow at both high (9L∕min) and low (3L∕min) flow rates introduces anomalies into the flow, such as recirculation, stagnation, and high stress regions. Levels of viscous and Reynolds shear stresses everywhere within the pump are below reported threshold values for damage to red cells over the entire range of flow rates investigated; however, at both high and low flow rate conditions, the flow field may promote activation of the clotting cascade due to regions of elevated shear stress adjacent to separated or stagnant flow.

INFLUENCE OF FLOW RATE AND AXIAL POSITION ON SHEAR STRESSES

2004 ◽  
Vol 04 (01) ◽  
pp. 71-75
Author(s):  
ALI A. SAKHAEIMANESH
Keyword(s):  
Flow Rate ◽  
Artificial Heart ◽  
Heart Valves ◽  
Direct Relationship ◽  
Axial Position ◽  
Turbulent Shear ◽  
Shear Stresses ◽  
Close Vicinity ◽  
Velocity Gradients ◽  
Artificial Heart Valves

To locate the maximum and mean turbulent shear stresses in both time and space, and to determine how shear stresses depend on the flow rate and downstream measuring planes of the artificial heart valves, this study was carried out. Maximum and mean turbulent shear stresses estimated at 0.5D downstream of the valves showed a direct relationship with flow rate both in the Jellyfish and St. Vincent valves. The magnitude of both mean and maximum shear stresses in the Jellyfish valve was found to be higher than that of the St. Vincent valve at 0.5 and 1D downstream of the Jellyfish valve. Maximum shear stresses were found in close vicinity to the valve where highly disturbed flow with steep velocity gradients were observed.

Flow Characteristics Inside a Transpatent Flexible Left Ventricle With Anatomical and Antianatomical Valve Orientation

2001 ◽  
Author(s):  
Olga Pierrakos ◽  
Pavlos P. Vlachos ◽  
Demetri P. Telionis
Keyword(s):  
Heart Valves ◽  
Particle Image ◽  
Flow Characteristics ◽  
Shear Stresses ◽  
Pathological Conditions ◽  
Image Velocimetry ◽  
Flow Through ◽  
Blood Elements ◽  
The Ideal

Abstract Mechanical heart valves (MHV) and the operation of heart valve replacement have evolved to a level of universal acceptance and yet, MHV implantation is not always the ideal solution. Apparently the flow through pivoted leaflets of MHVs induces a combination of flow characteristics, which are clearly conducive to clot formation and can initiate many other pathological conditions. Most in vitro studies of the flow downstream of a MHV have been conducted with the valve in the aortic position (i.e. Reul et al., 1986). Bluestein et al., (2000) used a numerical simulation and Digital Particle-Image Velocimetry (DPIV) to reveal intricate patterns of interacting shed vortices downstream of the aortic valve and demonstrated that blood elements exposed to the highest shear stresses in the immediate proximity of the MHV could be trapped within the vortices that form in the wake of the valve.

In Vitro Blood Damage by High Shear Flow: Human versus Porcine Blood

2002 ◽  
Vol 25 (4) ◽  
pp. 306-312 ◽  
Author(s):  
S. Klaus ◽  
S. Körfer ◽  
K. Mottaghy ◽  
H. Reul ◽  
B. Glasmacher
Keyword(s):  
Human Blood ◽  
Heart Valves ◽  
High Shear ◽  
Blood Damage ◽  
Shear Rates ◽  
Porcine Blood ◽  
High Shear Rates ◽  
Blood Pumps ◽  
Artificial Heart Valves

Devices for modern heart support are minimized to reduce priming blood volume and contact area with foreign surfaces. Their flow fields are partly governed by very high velocity gradients. In order to investigate blood damage, porcine and human blood was passed through a narrow Couette type shear gap applying defined high shear rates within the typical range for devices such as blood pumps or artificial heart valves (γ = 1800/s to 110,000/s for 400 ms). Traumatization profiles of both blood species were recorded in terms of hemolysis and platelet count. Sublethal damage in terms of platelet (PF4) and complement activation (C5a) was additionally measured for human blood. Results for porcine and human blood were very similar. Hemolysis was not started until critical shear rates of about 80,000/s. Impact on platelets was severe with drops in cell count of up to 65% (at γ = 55,000/s to 110,000/s) likely to set stronger limits to the design layout of devices than hemolysis. Concentrations of PF4 and C5a clearly increased with shear rate exhibiting stronger gradients where hemolysis started. Due to the similar results of porcine and human blood for hemolysis and platelet drop, porcine blood seems to be suitable for device testing. Selection of blood species would thus depend on handling, availability and analysis demands.

scholarly journals Analysis of leaflet flutter in biological prosthetic heart valves using PIV measurements

2019 ◽  
Vol 42 ◽  
pp. e41746
Author(s):  
Artur Henrique de Freitas Avelar ◽  
Mairon Assis Guimaris Eller Stófel ◽  
Glenda Dias Vieira ◽  
Jean Andrade Canestri ◽  
Rudolf Huebner
Keyword(s):  
High Speed ◽  
Heart Valves ◽  
Particle Image ◽  
Prosthetic Heart Valves ◽  
Shear Stresses ◽  
Lower Velocity ◽  
Piv Measurements ◽  
Prosthetic Valves ◽  
Image Velocimetry ◽  
Experimental Bench

The use of biological prosthetic valves has increased considerably in recent decades since they have several advantages over mechanical ones, but they still possess the great disadvantage of having a relatively short lifetime. An understudied phenomenon is the flutter effect that causes oscillations in the cusps, which is associated with regurgitation, calcification and fatigue, which can reduce even more the lifetime of bioproteses. In an experimental bench that simulates the cardiac flow, the behavior of a porcine and a bovine pericardium valves was recorded by a high-speed camera to quantify the oscillations of the cusps and an experiment using particle image velocimetry was conducted to study the velocity profiles and shear stresses and their relations with flutter. Results showed that the pericardial valve has lower values of frequencies and amplitudes compared to the porcine valve. Lower velocity values were found in the cusps that did not have flutter, but no relationship was observed between shear stress values and leaflet vibrations. These results may assist in future projects of biological prosthetic valves that have less flutter and longer lifespan.

The Influence of Open Leaflet Geometry on the Haemodynamic Flow Characteristics of Polyurethane Trileaflet Artificial Heart Valves

1996 ◽  
Vol 210 (4) ◽  
pp. 273-287 ◽  
Author(s):  
J Corden ◽  
T David ◽  
J Fisher
Keyword(s):  
Axial Velocity ◽  
Heart Valves ◽  
Flow Characteristics ◽  
Manufacturing Method ◽  
Blood Damage ◽  
Flow Recirculation ◽  
Maximum Value ◽  
Artificial Heart Valves

In vitro velocity data were obtained downstream of two versions of the Leeds polyurethane trileaflet heart valve in a simulated pulsatile flow regime using laser Doppler velocimetry. The main difference between the two valves studied was the manufacturing method used to create the valves. The film-fabricated valve was constructed from solvent-cast sheets of polyurethane, thermally formed into the correct leaflet geometry. The dip-cast valve used a stainless steel mould which was dipped into a polyurethane solution to produce the valve leaflets. Significant differences were visible between the fully open leaflet shape of each valve. The distribution of mean axial velocity and Reynolds normal stress (RNS) was shown to be dependent on the shape of the fully open valve orifice. For the film-fabricated valves, flow recirculation and high values of RNS were present downstream of the frame posts. The maximum value of RNS obtained downstream of the film-fabricated valve at peak systole was 147 N/m2. Results for the dip-cast valve showed a more uniform distribution of mean axial velocity and RNS resulting from the more circular central orifice produced by the dip-cast leaflets. The maximum value of RNS obtained downstream of the dip-cast valve at peak systole was 109 N/m2. These results demonstrate the effect of the open valve geometry on the flow characteristics downstream of trileaflet valves and that minor changes to the open leaflet geometry can significantly affect the flow characteristics and the possibility of flow-related blood damage occurring in vivo.

Reduction of Flow-Induced Blood Damage in Bileaflet Mechanical Heart Valves Through Passive Flow Control

2008 ◽  
Author(s):  
David W. Murphy ◽  
Lakshmi P. Dasi ◽  
Ari Glezer ◽  
Ajit P. Yoganathan
Keyword(s):  
Shear Stress ◽  
Platelet Activation ◽  
Heart Valves ◽  
Vortex Generators ◽  
Mechanical Heart Valves ◽  
Shear Stresses ◽  
Valve Closure ◽  
Passive Flow Control ◽  
Blood Damage ◽  
Passive Flow

Bileaflet mechanical heart valves (BMHVs), though a life-saving device in treating heart valve disease, are often associated with several complications including a high risk of hemolysis, platelet activation, and thromboembolism. To address this risk, patients must undergo prophylactic anticoagulation therapy. One likely cause of this hyper-coagulative state is the nonphysiologic levels of stress experienced by the erythrocytes and platelets flowing through the BMHVs. Research has shown that the combination of shear stress magnitude and exposure time found in the highly transient leakage jet emanating from the b-datum gap during valve closure is sufficient to cause hemolysis and platelet activation [1–3]. Reducing the shear stresses experienced by the blood flowing through the b-datum gap during valve closure may therefore reduce the prevalence of valve-related blood damage. Such shear stress reduction could be achieved by passive flow control, in particular vortex generators, incorporated onto the BMHV leaflet surface. Vortex generators have been used to control shear flows in various aerodynamic applications, and it is thus thought that their application to mechanical heart valve leaflet surfaces may reduce shear stresses by creating streamwise vortices that will serve to dissipate the regurgitant jet originating from the b-datum gap at the time of valve closure.

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