Blood Damage Quantification in Cardiovascular Flows Through Medical Devices Using a Novel Suspension Flow Method

2013 ◽  
Author(s):  
B. Min Yun ◽  
Cyrus K. Aidun ◽  
Ajit P. Yoganathan
Keyword(s):  
Mechanical Heart Valve ◽  
Alternative Methods ◽  
Suspension Flow ◽  
Spatiotemporal Resolution ◽  
Flow Solver ◽  
Jude Medical ◽  
Blood Damage ◽  
Bileaflet Mechanical Heart Valve ◽  
Damage Quantification ◽  
Baseline Case

A numerical suspension flow solver is presented that can accurately quantify blood damage in cardiovascular flows. This method is capable of high spatiotemporal resolution simulations with optimal parallel computing. In addition, the method models realistic platelets for more accurate damage quantification compared to alternative methods. The numerical tool is tested on a baseline case of a St. Jude Medical bileaflet mechanical heart valve, and blood damage results are analyzed in both Lagrangian and Eulerian viewpoints.

scholarly journals Blood Damage Through a Bileaflet Mechanical Heart Valve: A Quantitative Computational Study Using a Multiscale Suspension Flow Solver

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
B. Min Yun ◽  
Cyrus K. Aidun ◽  
Ajit P. Yoganathan
Keyword(s):  
Numerical Method ◽  
Heart Valves ◽  
Computational Study ◽  
Mechanical Heart Valve ◽  
Complex Flow ◽  
Damage Potential ◽  
Spatiotemporal Resolution ◽  
Jude Medical ◽  
Blood Damage ◽  
Flow Through

Bileaflet mechanical heart valves (BMHVs) are among the most popular prostheses to replace defective native valves. However, complex flow phenomena caused by the prosthesis are thought to induce serious thromboembolic complications. This study aims at employing a novel multiscale numerical method that models realistic sized suspended platelets for assessing blood damage potential in flow through BMHVs. A previously validated lattice-Boltzmann method (LBM) is used to simulate pulsatile flow through a 23 mm St. Jude Medical (SJM) Regent™ valve in the aortic position at very high spatiotemporal resolution with the presence of thousands of suspended platelets. Platelet damage is modeled for both the systolic and diastolic phases of the cardiac cycle. No platelets exceed activation thresholds for any of the simulations. Platelet damage is determined to be particularly high for suspended elements trapped in recirculation zones, which suggests a shift of focus in blood damage studies away from instantaneous flow fields and toward high flow mixing regions. In the diastolic phase, leakage flow through the b-datum gap is shown to cause highest damage to platelets. This multiscale numerical method may be used as a generic solver for evaluating blood damage in other cardiovascular flows and devices.

scholarly journals Effect of Hinge Gap Width of a St. Jude Medical Bileaflet Mechanical Heart Valve on Blood Damage Potential—An In Vitro Micro Particle Image Velocimetry Study

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Brian H. Jun ◽  
Neelakantan Saikrishnan ◽  
Sivakkumar Arjunon ◽  
B. Min Yun ◽  
Ajit P. Yoganathan
Keyword(s):  
Shear Stress ◽  
Mechanical Heart Valve ◽  
Shear Stresses ◽  
Leakage Flow ◽  
Damage Potential ◽  
Jude Medical ◽  
Blood Damage ◽  
Micro Particle Image Velocimetry ◽  
Flow Stasis ◽  
Gap Width

The hinge regions of the bileaflet mechanical heart valve (BMHV) can cause blood element damage due to nonphysiological shear stress levels and regions of flow stasis. Recently, a micro particle image velocimetry (μPIV) system was developed to study whole flow fields within BMHV hinge regions with enhanced spatial resolution under steady leakage flow conditions. However, global velocity maps under pulsatile conditions are still necessary to fully understand the blood damage potential of these valves. The current study hypothesized that the hinge gap width will affect flow fields in the hinge region. Accordingly, the blood damage potential of three St. Jude Medical (SJM) BMHVs with different hinge gap widths was investigated under pulsatile flow conditions, using a μPIV system. The results demonstrated that the hinge gap width had a significant influence during the leakage flow phase in terms of washout and shear stress characteristics. During the leakage flow, the largest hinge gap generated the highest Reynolds shear stress (RSS) magnitudes (∼1000 N/m2) among the three valves at the ventricular side of the hinge. At this location, all three valves indicated viscous shear stresses (VSS) greater than 30 N/m2. The smallest hinge gap exhibited the lowest level of shear stress values, but had the poorest washout flow characteristics among the three valves, demonstrating propensity for flow stasis and associated activated platelet accumulation potential. The results from this study indicate that the hinge is a critical component of the BMHV design, which needs to be optimized to find the appropriate balance between reduction in fluid shear stresses and enhanced washout during leakage flow, to ensure minimal thrombotic complications.

scholarly journals Near Valve Flows and Potential Blood Damage During Closure of a Bileaflet Mechanical Heart Valve

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
L. H. Herbertson ◽  
S. Deutsch ◽  
K. B. Manning
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
In Vitro Study ◽  
Blood Damage ◽  
Bileaflet Mechanical Heart Valve ◽  
Fluid Velocities ◽  
Design Characteristics ◽  
Valve Housing

Blood damage and thrombosis are major complications that are commonly seen in patients with implanted mechanical heart valves. For this in vitro study, we isolated the closing phase of a bileaflet mechanical heart valve to study near valve fluid velocities and stresses. By manipulating the valve housing, we gained optical access to a previously inaccessible region of the flow. Laser Doppler velocimetry and particle image velocimetry were used to characterize the flow regime and help to identify the key design characteristics responsible for high shear and rotational flow. Impact of the closing mechanical leaflet with its rigid housing produced the highest fluid stresses observed during the cardiac cycle. Mean velocities as high as 2.4 m/s were observed at the initial valve impact. The velocities measured at the leaflet tip resulted in sustained shear rates in the range of 1500–3500 s−1, with peak values on the order of 11,000–23,000 s−1. Using velocity maps, we identified regurgitation zones near the valve tip and through the central orifice of the valve. Entrained flow from the transvalvular jets and flow shed off the leaflet tip during closure combined to generate a dominant vortex posterior to both leaflets after each valve closing cycle. The strength of the peripheral vortex peaked within 2 ms of the initial impact of the leaflet with the housing and rapidly dissipated thereafter, whereas the vortex near the central orifice continued to grow during the rebound phase of the valve. Rebound of the leaflets played a secondary role in sustaining closure-induced vortices.

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