Effects of Valve Design and Orientation on Flow Induced Platelet Activation in Mechanical Heart Valves

2004 ◽  
Author(s):  
Wei Yin ◽  
Yared Alemu ◽  
Jolyon Jesty ◽  
Danny Bluestein
Keyword(s):  
Shear Stress ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Cumulative Effect ◽  
Left Ventricular ◽  
Platelet Activity ◽  
Ventricular Assist ◽  
Activity State ◽  
Blood Flow Patterns

A study was conducted to estimate the thromboembolic potential of different Mechanical Heart Valve (MHV) designs and the effect of valve orientation (valve axial misalignment during implantation) on it. CFD simulations of turbulent, transient, non-Newtonian blood flow patterns generated by two types of MHVs (monoleaflet and bileaflet) and the effect of valve orientation were conducted using the Wilcox k-ω turbulence model. Platelet shear stress histories (cumulative effect of shear stress and time) were calculated and averaged over a large number of platelet trajectories within the flow field, and compared with in vitro Platelet Activity State (PAS) measurements conducted in a left ventricular assist device (LVAD) model. Platelets were circulated in the LVAD with Carbomedics bileaflet and Bjork-Shiley monoleaflet MHVs correspondingly. The PAS measurement indicated that PAS induced by the tilted St. Jude bileaflet MHV and the untilted valve was very similar (P>0.1). The bileaflet MHV activated platelets at a rate of more than 2-fold than that observed with the monoleaflet MHV (P<0.05). This confirmed the CFD platelet shear stress histories, which clearly indicated a higher level of stimulation of platelets for the bileaflet MHV.

Platelet Activation and Free Emboli Formation in Flow Past Mechanical Heart Valves

2002 ◽  
Author(s):  
Danny Bluestein ◽  
Wei Yin ◽  
Jolyon Jesty ◽  
Adam E. Saltman ◽  
Irvin B. Krukenkamp ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Heart Valves ◽  
Left Ventricular ◽  
Mechanical Heart Valves ◽  
Shear Stresses ◽  
Platelet Activity ◽  
Flow Past ◽  
Activity State ◽  
Valve Implantation

Numerical studies, in vitro, and in vivo measurements were conducted, aimed at quantifying free emboli formation and procoagulant properties of platelets induced by flow past mechanical heart valves (MHV). Pulsatile turbulent flow simulation was conducted past a St. Jude medical MHV in the aortic position, to study the effects of valve implantation technique on the thromboembolic potential of the valve. A misaligned valve with subannualarly sutured pledgets produced accelerating jet flow through the valve orifices and a wider wake of shed vortices. Shear stress histories of platelets along turbulent trajectories exposed the platelets to elevated shear stresses around the leaflets, leading them to entrapment within the shed vortices. In vitro platelet studies were conducted past the MHV mounted in a recirculation flow loop and in a model of left ventricular assist device (LVAD), using an innovative platelet activity state (PAS) assay. The platelet activation significantly increased as a function of the recirculation time past the valve, and as compared to controls. Transcranial Doppler (TCD) measurements were conducted in the carotid artery of sheep with implanted MHV, showing marked increase in the number of HITS (High Intensity Transient Signals) signifying the passage of free emboli generated by the valve. The HITS were analyzed to distinguish between gaseous and thrombi emboli. Finally, platelet activity state measurements were conducted with sheep platelets, showing marked increase of platelet activation after valve implantation.

scholarly journals Validation of a CFD Methodology for Positive Displacement LVAD Analysis Using PIV Data

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
Richard B. Medvitz ◽  
Varun Reddy ◽  
Steve Deutsch ◽  
Keefe B. Manning ◽  
Eric G. Paterson
Keyword(s):  
Left Ventricular ◽  
Hydrodynamic Performance ◽  
Ventricular Assist ◽  
Shear Rates ◽  
Eddy Simulation ◽  
Positive Displacement ◽  
Image Velocimetry ◽  
Computational Fluid Dynamics Cfd ◽  
High Level

Computational fluid dynamics (CFD) is used to asses the hydrodynamic performance of a positive displacement left ventricular assist device. The computational model uses implicit large eddy simulation direct resolution of the chamber compression and modeled valve closure to reproduce the in vitro results. The computations are validated through comparisons with experimental particle image velocimetry (PIV) data. Qualitative comparisons of flow patterns, velocity fields, and wall-shear rates demonstrate a high level of agreement between the computations and experiments. Quantitatively, the PIV and CFD show similar probed velocity histories, closely matching jet velocities and comparable wall-strain rates. Overall, it has been shown that CFD can provide detailed flow field and wall-strain rate data, which is important in evaluating blood pump performance.

Design Optimization of a Mechanical Heart Valve for Reducing Valve Thrombogenicity: A Case Study With ATS Valve

2010 ◽  
Author(s):  
Gaurav Girdhar ◽  
Yared Alemu ◽  
Michalis Xenos ◽  
Jawaad Sheriff ◽  
Jolyon Jesty ◽  
...  
Keyword(s):  
Heart Valves ◽  
Thrombus Formation ◽  
Anticoagulation Therapy ◽  
Mechanical Heart Valve ◽  
Ventricular Assist Devices ◽  
Circulatory Support ◽  
Ventricular Assist ◽  
Mechanical Circulatory Support Devices ◽  
Artificial Hearts

Flow past mechanical heart valves (MHV) in mechanical circulatory support devices including total artificial hearts and ventricular assist devices, is primarily implicated in thromboembolism due to non-physiological flow conditions where the elevated stresses and exposure times are sufficiently high to cause platelet activation and thrombus formation. Mitigation of this risk requires lifelong anticoagulation therapy and less thrombogenic MHV designs should therefore be developed by device manufacturers [1].

Argatroban and bivalirudin compared to unfractionated heparin in preventing thrombus formation on mechanical heart valves

2009 ◽  
Vol 101 (06) ◽  
pp. 1163-1169 ◽  
Author(s):  
Torsten Linde ◽  
Thomas Michel ◽  
Kathrin Hamilton ◽  
Ulrich Steinseifer ◽  
Ivar Friedrich ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Unfractionated Heparin ◽  
Continuous Infusion ◽  
Valve Replacement ◽  
Heart Valves ◽  
Thrombus Formation ◽  
Mechanical Heart Valve ◽  
Mechanical Heart Valves ◽  
Valve Prostheses

SummaryPrevention of valve thrombosis in patients after prosthetic mechanical heart valve replacement and heparin-induced thrombocytopenia (HIT) is still an open issue. The aim of the present in-vitro study was to investigate the efficacy of argatroban and bivalirudin in comparison to unfractionated heparin (UFH) in preventing thrombus formation on mechanical heart valves. Blood (230 ml) from healthy young male volunteers was anticoagulated either by UFH, argatroban bolus, argatroban bolus plus continuous infusion, bivalirudin bolus, or bivalirudin bolus plus continuous infusion. Valve prostheses were placed in a newly developed in-vitro thrombosis tester and exposed to the anticoagulated blood samples. To quantify the thrombi, electron microscopy was performed, and each valve was weighed before and after the experiment. Mean thrombus weight in group 1 (UFH) was 117 + 93 mg, in group 2 (argatroban bolus) 722 + 428 mg, in group 3 (bivalirudin bolus) 758 + 323 mg, in group 4 (argatroban bolus plus continuous infusion) 162 + 98 mg, and in group 5 (bivalirudin bolus plus continuous infusion) 166 + 141 mg (p-value <0.001). Electron microscopy showed increased rates of thrombus formation in groups 2 and 3. Argatroban and bivalirudin were as effective as UFH in preventing thrombus formation on valve prostheses in our in-vitro investigation when they were administered continuously. We hypothesise that continuous infusion of argatroban or bivalirudin are optimal treatment options for patients with HIT after mechanical heart valve replacement for adapting oral to parenteral anticoagulation or vice versa.

scholarly journals Effects of a Short-Term Left Ventricular Assist Device on Hemodynamics in a Heart Failure Patient-Specific Aorta Model: A CFD Study

2021 ◽  
Vol 12 ◽  
Author(s):  
Yu Wang ◽  
Junwei Wang ◽  
Jing Peng ◽  
Mingming Huo ◽  
Zhiqiang Yang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pressure Difference ◽  
Left Ventricular ◽  
Patient Specific ◽  
Short Term ◽  
Ventricular Assist ◽  
Left Ventricular Assist ◽  
Wall Shear ◽  
Hemodynamic Performance

Patients with heart failure (HF) or undergoing cardiogenic shock and percutaneous coronary intervention require short-term cardiac support. Short-term cardiac support using a left ventricular assist device (LVAD) alters the pressure and flows of the vasculature by enhancing perfusion and improving the hemodynamic performance for the HF patients. However, due to the position of the inflow and outflow of the LVAD, the local hemodynamics within the aorta is altered with the LVAD support. Specifically, blood velocity, wall shear stress, and pressure difference are altered within the aorta. In this study, computational fluid dynamics (CFD) was used to elucidate the effects of a short-term LVAD for hemodynamic performance in a patient-specific aorta model. The three-dimensional (3D) geometric models of a patient-specific aorta and a short-term LVAD, Impella CP, were created. Velocity, wall shear stress, and pressure difference in the patient-specific aorta model with the Impella CP assistance were calculated and compared with the baseline values of the aorta without Impella CP support. Impella CP support augmented cardiac output, blood velocity, wall shear stress, and pressure difference in the aorta. The proposed CFD study could analyze the quantitative changes in the important hemodynamic parameters while considering the effects of Impella CP, and provide a scientific basis for further predicting and assessing the effects of these hemodynamic signals on the aorta.

A Systemic Mock Circulation for In-Vitro Testing of a Pneumatically Operated Left Ventricular Assist Device

2014 ◽  
Vol 47 (3) ◽  
pp. 8409-8414 ◽  
Author(s):  
A. Karabegovic ◽  
M. Hinteregger ◽  
C. Janeczek ◽  
W. Reichenfelser ◽  
V. Soragnese ◽  
...  
Keyword(s):  
Left Ventricular Assist Device ◽  
Ventricular Assist Device ◽  
Left Ventricular ◽  
In Vitro Testing ◽  
Assist Device ◽  
Ventricular Assist ◽  
Mock Circulation ◽  
Left Ventricular Assist
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