An Experimental Study of the Flow-Induced Mass Transfer Distribution in the Vicinity of Prosthetic Heart Valves

1981 ◽  
Vol 103 (1) ◽  
pp. 1-10 ◽  
Author(s):  
F. L. Galanga ◽  
J. R. Lloyd
Keyword(s):  
Mass Transfer ◽  
Experimental Study ◽  
Heart Valves ◽  
Electrochemical Techniques ◽  
Reynolds Numbers ◽  
In Vivo Studies ◽  
High Mass ◽  
Prosthetic Heart Valves ◽  
Disk Valve

An experimental study of the flow-induced mass transfer distribution in the vicinity of a model disk valve and a ball valve was conducted using electrochemical techniques. Reynolds numbers ranged from 1000 to 6000, which are characteristic of physiologic conditions. Local instantaneous and time average data are presented. It was found that the flow-induced mass transfer distribution was high in regions of both low and high shear. It was also demonstrated that the fluctuations in the mass transfer to the wall of the test section around the valve are significantly affected by valve design. The regions of high mass transfer measured in this study were found to correlate very closely to regions where thrombus formations have been documented in in-vivo studies.

Experimental Measurements of the Flow-Induced Shear Stress Distribution in the Vicinity of Prosthetic Heart Valves

1981 ◽  
Vol 103 (4) ◽  
pp. 267-274 ◽  
Author(s):  
W. H. Herkes ◽  
J. R. Lloyd
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Test Section ◽  
Heart Valves ◽  
Reynolds Numbers ◽  
Shear Stress Distribution ◽  
Electrochemical Technique ◽  
Prosthetic Heart Valves ◽  
Disk Valve ◽  
Flow Through

The present study examines the local shear stress distribution occurring during flow through prosthetic valves. The electrochemical technique is a powerful tool for the study of mass transfer related phenomena and was selected for this investigation. The present investigation attempts to establish the viability of the particular application of the technique. Three test section geometries were analyzed: a straight tube, a ball-in-cage valve, and a model disk-in-cage valve, and the tests were conducted at six Reynolds numbers ranging from 1000 to 6000 under steady-state conditions. The model disk valve provided a base-case check on the validity of the technique since it has been employed in several previous studies and the flow through it is well documented. High shear and low shear regions are clearly evident and their locations can be pinpointed. The ball-in-cage valve was tested over the full range of Reynolds numbers. The shear profiles demonstrate a double peak in the region of the ball, a result which was unexpected. Careful study revealed that this was a result of the test section geometry and provides another demonstration of the importance of test section geometry. The frequency of the fluctuations in wall shear for the ball valve were found to be different than those for the disk valve indicating that the environment at the aortic wall is definitely affected by valve design. This study showed the electrochemical technique to be a valuable tool for the study of the flow through prosthetic heart valves.

The Effect of Angle and Flow Rate Upon Hemodynamics in Distal Vascular Graft Anastomoses: A Numerical Model Study

1994 ◽  
Vol 116 (3) ◽  
pp. 331-336 ◽  
Author(s):  
Ding-Yu Fei ◽  
James D. Thomas ◽  
Stanley E. Rittgers
Keyword(s):  
Numerical Model ◽  
Stagnation Point ◽  
Arterial Wall ◽  
Artery Bypass ◽  
Three Dimensional ◽  
Separated Flow ◽  
Reynolds Numbers ◽  
In Vivo Studies ◽  
Stagnation Points

Flow in distal end-to-side anastomoses of iliofemoral artery bypass grafts was simulated using a steady flow, three-dimensional numerical model. With the proximal artery occluded, anastomotic angles were varied over 20, 30, 40, 45, 50, 60 and 70 deg while the inlet Reynolds numbers were 100 and 205. Fully developed flow in the graft became somewhat skewed toward the inner wall with increasing angle for both Reynolds numbers. Separated flow regions were seen along the inner arterial wall (toe region) for angles ≥ 60 deg at Re = 100 and for angles ≥ 45 deg at Re = 205 while a stagnation point existed along the outer arterial wall (floor region) for all cases which moved downstream relative to the toe of the anastomosis with decreasing angles. Normalized shear rates (NSR) along the arterial wall varied widely throughout the anastomotic region with negative values seen in the separation zones and upstream of the stagnation points which increased in magnitude with angle. The NSR increased with distance downstream of the stagnation point and with magnitudes which increased with the angle. Compared with observations from chronic in vivo studies, these results appear to support the hypothesis of greater intimal hyperplasia occurring in regions of low fluid shear.

Modeling of Tissue Fatigue Damage in Bio-Prosthetic Heart Valve

2011 ◽  
Author(s):  
Caitlin Martin ◽  
Wei Sun
Keyword(s):  
Fatigue Damage ◽  
Heart Valve ◽  
Anticoagulant Therapy ◽  
Heart Valves ◽  
Prosthetic Heart Valve ◽  
Bovine Pericardium ◽  
Prosthetic Heart Valves ◽  
Mechanical Valves ◽  
In Vivo Degradation

Bio-prosthetic heart valves (BHVs) with leaflets made of glutaraldehyde-treated bovine pericardium (GLBP), have been used extensively to replace diseased heart valves. BHVs display superior hemodynamics to mechanical valves and eliminate the need for anticoagulant therapy; however, they exhibit poor durability resulting from in vivo degradation and fatigue damage of the leaflets.

scholarly journals SIBS triblock copolymers in cardiac surgery: in vitro and in vivo studies in comparison with ePTFE

2020 ◽  
Vol 21 (4) ◽  
pp. 67-80
Author(s):  
M. A. Rezvova ◽  
E. A. Ovcharenko ◽  
P. A. Nikishev ◽  
S. V. Kostyuk ◽  
L. V. Antonova ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Heart Valves ◽  
Ex Vivo ◽  
Calcium Content ◽  
Positive Control ◽  
Prosthetic Heart Valves ◽  
Solution Casting Method ◽  
Cell Adhesion And Proliferation

Implantation of polymeric heart valves can solve the problems of existing valve substitutes – mechanical and biological. Objective: to comprehensively assess the hemocompatibility of styrene-isobutylene-styrene (SIBS) triblock copolymer, synthesized by controlled cationic polymerization in comparison with expanded polytetrafluoroethylene (ePTFE) used in clinical practice. Materials and methods. SIBS-based films were made by polymer solution casting method; in vitro biocompatibility assessment was performed using cell cultures, determining cell viability, cell adhesion and proliferation; tendency of materials to calcify was determined through in vitro accelerated calcification; in vivo biocompatibility assessment was performed by subcutaneous implantation of rat samples; hemocompatibility was determined ex vivo by assessing the degree of hemolysis, aggregation, and platelet adhesion. Results. The molecular weight of synthesized polymer was 33,000 g/mol with a polydispersity index of 1.3. When studying cell adhesion, no significant differences (p = 0.20) between the properties of the SIBS polymer (588 cells/mm2) and the properties of culture plastics (732 cells/mm2) were discovered. Cell adhesion for the ePTFE material was 212 cells/mm2. Percentage of dead cells on SIBS and ePTFE samples was 4.40 and 4.72% (p = 0.93), respectively, for culture plastic – 1.16% (p < 0.05). Cell proliferation on the ePTFE surface (0.10%) was significantly lower (p < 0.05) than for the same parameters for SIBS and culture plastic (62.04 and 44.00%). Implantation results (60 days) showed the formation of fibrous capsules with average thicknesses of 42 μm (ePTFE) and 58 μm (SIBS). Calcium content in the explanted samples was 0.39 mg/g (SIBS), 1.25 mg/g (ePTFE) and 93.79 mg/g (GA-xenopericardium) (p < 0.05). Hemolysis level of red blood cells after contact with SIBS was 0.35%, ePTFE – 0.40%, which is below positive control (p < 0.05). Maximum platelet aggregation of intact platelet-rich blood plasma was 8.60%, in contact with SIBS polymer – 18.11%, with ePTFE – 22.74%. Conclusion. In terms of hemocompatibility properties, the investigated SIBS polymer is not inferior to ePTFE and can be used as a basis for development of polymeric prosthetic heart valves.

scholarly journals In-Vivo Studies of the Angiogenic Potential of Mandur Bhasma

2021 ◽  
pp. 79-84
Author(s):  
Ekta Tomar ◽  
Sonali Wairagade ◽  
Arachana Gharote ◽  
Ranjit S. Ambad ◽  
Dhruba Hari Chandi
Keyword(s):  
Experimental Study ◽  
Analytical Study ◽  
Chorioallantoic Membrane ◽  
In Vivo Studies ◽  
Classical Literature ◽  
Standard Drug ◽  
Angiogenic Potential ◽  
Egg Shell ◽  
Cam Model

Background: Mandur Bhasma is a herbo-mineral compound. It is prepared by Putapaka method. It is described as Raktasanjanan. In the current study, Mandur Bhasma was prepared with a standardized method w.s.r to Rasatarangini and an experimental study was done to observe the Angiogenic property of Mandur Bhasma. The current study will analyze angiogenic potential of Mandur Bhasma using chick CAM model. This research is intended to study the possible role of Mandur Bhasma on angiogenesis and establishing properties of Mandur Bhasma as an angiogenic by newer means. The experimental study inside the egg shell will be carried out on a membrane known as “chorioallantoic membrane”. Objectives: To Prepare Mandur Bhasma Physicochemical and Analytical study of Mandur Bhasma To verify the angiogenic potential of Mandur bhasma using the chicken chorioallantoic membrane (CAM) model. To compare Angeogenic potential of Mandur bhasma with standard drug progesterone Methodology: Relevant classical literature regarding Mandur will be reviewed and the data will be collected. Mandur Shodhan with Gomutra and Mandur Maran with Triphala decoction will be done. Analytical Study like Organoleptic Test for Rasa, Gandha, Varna, Sparsha, Physicochemical Tests and other analytical test like ICP-AES /ICPMS, XRD structure of Bhasma, EDAX-NANO Particle Size will be done. Expected Results: Changes will be observed in objective outcomes. Conclusion: Conclusion will be drawn by suitably analyzing data.

scholarly journals MASS TRANSFER CORRELATION FOR THE REMOVAL OF COPPER IONS FROM WASTEWATER

2010 ◽  
Vol 9 (1-2) ◽  
pp. 63
Author(s):  
N. M. S. Kaminari ◽  
M. J. J. S. Ponte ◽  
H. A. Ponte
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Copper Ions ◽  
Mass Transfer Rate ◽  
Reynolds Numbers ◽  
Electrochemical Reactor ◽  
High Mass ◽  
Ore Processing ◽  
Lead Nickel ◽  
Copper Lead

One of the biggest problems with ore processing in extractive metallurgical industries is the high toxicity of the heavy metals waste content (e.g., copper, lead, nickel and chrome). This work investigates the copper (II) íons removal from aqueous solutions in concentrations up to 1000 ppm. Therefore, a fluidized bed electrolytic reactor was used with flow-by configuration considered as a hopeful method due to the large specific surface area and the high mass transfer rate. The performance of the electrochemical reactor was investigated by using different porosities. Dimensionless Sherwood and Reynolds numbers were correlated to characterize the mass transport properties of the reactor, and they were fitted to the equation Sh = a.Reb.Sc1/3.

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