scholarly journals In-vitro measurement of high peak fluid pressure gradients across prosthetic heart valves at closing

1991 ◽  
Vol 17 (2) ◽  
pp. A213
Author(s):  
Ronald F. Carey ◽  
Bruce A. Herman ◽  
Matthew R. Myers
Keyword(s):  
Heart Valves ◽  
Fluid Pressure ◽  
High Peak ◽  
Prosthetic Heart Valves ◽  
Pressure Gradients

The Effect of Dipyridamole and RA 233 on Human Platelet Function in Vitro

1973 ◽  
Vol 29 (03) ◽  
pp. 694-700 ◽  
Author(s):  
Paul L. Rifkin ◽  
Marjorie B. Zucker
Keyword(s):  
Mechanism Of Action ◽  
Human Blood ◽  
Glass Bead ◽  
Heart Valves ◽  
Human Platelet ◽  
Drug Effects ◽  
Simple Relation ◽  
Prosthetic Heart Valves ◽  
Induced Aggregation

SummaryDipyridamole (Persantin) is reported to prolong platelet survival and inhibit embolism in patients with prosthetic heart valves, but its mechanism of action is unknown. Fifty jxM dipyridamole failed to reduce the high percentage of platelets retained when heparinized human blood was passed through a glass bead column, but prolonged the inhibition of retention caused by disturbing blood in vitro. Possibly the prostheses act like disturbance. Although RA 233 was as effective as dipyridamole in inhibiting the return of retention, it was less effective in preventing the uptake of adenosine into erythrocytes, and more active in inhibiting ADP-induced aggregation and release. Thus there is no simple relation between these drug effects.

Noninvasive Electromagnetic Evaluation of Bjo¨rk-Shiley Heart Valves: Lifetime Prediction

2008 ◽  
Author(s):  
Raimond Grimberg ◽  
Adriana Savin ◽  
Shiu C. Chan ◽  
Rozina Steigmann ◽  
Lalita Udpa ◽  
...  
Keyword(s):  
Eddy Current ◽  
Heart Valves ◽  
Probability Of Detection ◽  
New Method ◽  
Lifetime Prediction ◽  
Prosthetic Heart Valves ◽  
In Vitro Experiments ◽  
Current Transducer ◽  
Eddy Current Transducer

Prosthetic heart valves of the Bjork-Shiley Convexo-Concave (BSCC) type have long been used extensively in implants; however, there have been reports of cases where one component of the valves failed, leading to the demise of the patient. This paper presents a new method for noninvasive electromagnetic evaluation for this type of valve, using an eddy current transducer with orthogonal coils. In vitro experiments have shown that discontinuities of outlet strut with depths equal or larger than 0.4mm can be detected with a probability of detection (POD) of 86.4%, and in the case of discontinuities with depth equal or larger than 0.6mm with POD of 97%.

Can the Hemodynamics of Prosthetic Heart Valves be Evaluated Sufficiently by In Vitro Tests?

1986 ◽  
pp. 47-54
Author(s):  
Martin Gottwik ◽  
S. Hartung ◽  
O. Epe ◽  
S. Langsdorf ◽  
J. Thormann ◽  
...  
Keyword(s):  
Heart Valves ◽  
In Vitro Tests ◽  
Prosthetic Heart Valves

Modeling Technique of Prosthetic Heart Valves

1984 ◽  
Vol 106 (1) ◽  
pp. 83-88 ◽  
Author(s):  
T. Kitamura ◽  
T. Kijima ◽  
H. Akashi
Keyword(s):  
Real Time ◽  
Heart Valves ◽  
Time Estimation ◽  
Modeling Technique ◽  
Computational Time ◽  
Prosthetic Heart Valves ◽  
The Real ◽  
Hemodynamic State ◽  
Real Time Estimation

This paper demonstrates a modeling technique of prosthetic heart valves. In the modeling, a pumping cycle is divided into four phases, in which the state of the valve and flow is different. The pressure-flow relation across the valve is formulated separately in each phase. This technique is developed to build a mathematical model used in the real time estimation of the hemodynamic state under artificial heart pumping. The model built by this technique is simple enough for saving the computational time in the real time estimation. The model is described by the first-order ordinary differential equation with 12 parameters. These parameters can be uniquely determined beforehand from in-vitro experimental data. It is shown that the model can adapt, with sufficient accuracy, to a change in the practical pumping condition and the viscosity of the fluid in their practical range, and is also demonstrated that the estimated backflow volume by model agrees closely with the actual one.

Glutaraldehyde Fixation of Bovine Humeral Head Articular Cartilage Maintains Functional Frictional Response

2013 ◽  
Author(s):  
Brian K. Jones ◽  
Christopher S. Ahmad ◽  
Clark T. Hung ◽  
Gerard A. Ateshian
Keyword(s):  
Humeral Head ◽  
Heart Valves ◽  
Clinical Success ◽  
Fluid Pressure ◽  
Experimental Studies ◽  
The United States ◽  
Low Friction ◽  
Diarthrodial Joint ◽  
Healthy Cartilage

Hemiarthroplasty is a surgical procedure that replaces the injured half of a diarthrodial joint (such as the hip or shoulder) with a smooth impermeable metal surface, leaving the apposing healthy cartilage layer intact. In 2006, more than 260,000 hip and shoulder hemiarthroplasties were performed in the United States alone [1]. Hemiarthroplasties are often revised to total arthroplasties, due in part to premature erosion of the intact, initially healthy cartilage [2]. Recent theoretical and experimental studies [3, 4] have shown that the low friction and wear of healthy diarthrodial joints depend critically upon sustained, elevated pressure of the interstitial water within the porous cartilage. Because this fluid pressure is continuous across the porous-permeable cartilage contact interface, the impermeable bearing surface implanted in hemiarthroplasty may substantially disrupt the natural lubrication of the apposing healthy cartilage [5]. Motivated by the established clinical success of implanting glutaraldehyde-treated porcine and bovine heart valves and pericardial grafts in humans, the objective of this study was to investigate whether a novel bioprosthetic hemiarthroplasty, utilizing a glutaraldehyde-treated cartilage xenograft, can reproduce the sustained low friction of a healthy natural diarthrodial joint. The specific aim of this study was to measure and compare the 24 h in-vitro frictional response of a bovine shoulder joint with that of a bioprosthetic hemiarthroplasty consisting of a glutaraldehyde-treated humeral head and an untreated, native cartilage glenoid.

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.

Evaluation of Platelet Activation Models With Dynamic Shear Stress In Vitro Experiments

2012 ◽  
Author(s):  
Jawaad Sheriff ◽  
Michalis Xenos ◽  
João S. Soares ◽  
Jolyon Jesty ◽  
Danny Bluestein
Keyword(s):  
Platelet Activation ◽  
Heart Valves ◽  
Ventricular Assist Devices ◽  
Prosthetic Heart Valves ◽  
Shear Stresses ◽  
Ventricular Assist ◽  
Relative Paucity ◽  
Valvular Diseases ◽  
End Stage

Blood recirculating devices, which include ventricular assist devices and prosthetic heart valves, are necessary for some patients suffering from end-stage heart failure and valvular diseases. However, disturbed flow patterns in these devices cause shear-induced platelet activation and aggregation. Thromboembolic complications resulting from this platelet behavior necessitates lifelong anticoagulant therapy for patients implanted with such devices. In addition, blood recirculating device manufacturers mostly test and optimize their products for hemolysis, which occurs at shear stresses ten-fold higher than required for platelet activation. The relative paucity of optimization for flow-induced thrombogenicity is further exacerbated by the fact that there are few predictive shear-induced platelet activation models.

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